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ASME Conference Presenter Attendance Policy and Archival Proceedings

2011;():i. doi:10.1115/POWER2011-NS2.
FREE TO VIEW

This online compilation of papers from the ASME 2011 Power Conference collocated with JSME ICOPE 2011 (POWER2011) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in the ASME Digital Library and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Plant Operations and Maintenance

2011;():1-6. doi:10.1115/POWER2011-55012.

Today’s energy market demands flexible operation of power plant units from plant operators. Frequent shutdowns of power plant units combined with the requirement for fast restoration of power output are now standard requirements for many power plants. Daily startups and shutdowns are now a common occurrence. This increases the economic significance of a short startup process with an extensively optimized and automated startup sequence for hot starts. This paper describes the progress which has been made in recent years with respect to the startup times of combined-cycle power plants. It describes the process changes which have been implemented for hot starts paying special attention to their impact on the steam turbine.

Commentary by Dr. Valentin Fuster
2011;():7-12. doi:10.1115/POWER2011-55059.

In order to develop efficient control and to predict a steam turbine’s power output precisely, it is desirable to have a linear relationship between controller output, RA, and steam mass flow. Unfortunately, steam mass flow through a turbine is not only determined by the control valve stroke but also by the pressure in front of these valves. Even at constant pressure the relation between valve stroke and steam flow through the turbine is extremely non linear. The complexity is increased by the fact that a turbine is generally operated by two or four control valves which do not necessarily work parallel over the complete operational range. Additionally, the pressure in front of the control valve changes with the admitted steam mass flow. A counterbalancing method was developed that allows to include individual process data, such as pressure in front of the valves and at the turbine inlet in dependence of steam mass flow and valve throttle characteristics, as well as process engineering constraints, like valve staggering, for example. The developed method is applicable to new steam power plants as well as to retrofits. With the developed method it is also possible to predict individual valve strokes at valve testing or at deviating exterior conditions. The later feature is extremely useful for retrofit applications. Firstly, the correctness of the implementation with respect to the ‘old’ set-up can be verified, and then, secondly, the characteristics of the retrofitted components and thermodynamic conditions, respectively, can be substituted. The developed method was successfully applied for several power plants. A comparison of predicted data and commissioning data will be provided.

Commentary by Dr. Valentin Fuster
2011;():13-18. doi:10.1115/POWER2011-55091.

The efficient handling of coal on belt conveyors is essential to coal-fired power plants. The conveying of coal is prone to problems including the escape of spillage and airborne dust. These problems lead to excessive, expensive, and sometimes hazardous maintenance requirements. The failure to provide this essential maintenance leads to more fugitive material and more problems in material handling. The key to efficient conveyors are the implementation of advanced systems to improve performance and prevent fugitive material including dust, combined with the training of plant personnel in the operation and maintenance of these sophisticated systems. This presentation looks at “new generation” conveyor architecture that combines better control of fugitive material with improved serviceability and increased employee safety. These systems feature engineered chutes that channel the material stream to reduce the entrainment of air into the material flow, and so minimize the release of dust. And this next generation system feature a modern architecture with improved belt support and sealing systems that reduce maintenance requirements and allow maintenance work to be performed from safely outside enclosures and away from moving parts. An important consideration in these advanced systems is the training of plant personnel on the operations and maintenance of these systems. This presentation will also consider this essential training, and propose several methods to achieve these training requirements.

Commentary by Dr. Valentin Fuster
2011;():19-23. doi:10.1115/POWER2011-55147.

Selective catalytic reduction (SCR) technology is being increasingly applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. For many power plants, temperature control becomes an essential challenge to ensure optimal SCR performance and to keep the material integrity of the SCR structure. Progress Energy MAYO Plant has a tandem boiler design with a Gross Power Generation Capacity of 2 × 400 MW. The plant decided to change their coal source to a lower HHV type PRB coal and integrated Clyde Bergemann’s SmartClean technology to deal with the changes in the coal quality and ensure a stable flue gas temperature going into the SCR. The new SmartClean technology optimized the cleaning to control the Economizer Exit Gas Temperature (EEGT) at a desired set temperature. The results of the performance tests showed that the EEGT control was successful and the temperature profile stabilized after implementing the new SmartClean technology. The new technology derives decisions and changes the cleaning strategy based on the effect of the sootblowers on the heat transfer performance rather than the traditional approach of targeting a static cleanliness level in the boiler. The performance data of the closed loop tests are presented as well as the economical justification of the project.

Commentary by Dr. Valentin Fuster
2011;():25-33. doi:10.1115/POWER2011-55164.

Cold Reheat Piping in power plants has received little attention for many years. Carbon Steel piping that handles steam at 500 F to 700 F has only had problems when not properly supported or water hammered on start up. Most recorded failures have been mechanical fatigue at a girth weld. Excessive attemperation in both coal fired plants and combined cycle ones, has become a routine practice. Consequently the number of failures (catastrophic or non-catastrophic) in Cold Reheat Piping have occurred in recent years. Most of these recent failures can be traced back to water hammer or a thermal shock due to changes in the operation of attemperator sprays. This paper shows how a Cold Reheat Piping system, that was included in a nondestructive test program, failed in a short period of time due to thermal fatigue, from a change in spray operation.

Commentary by Dr. Valentin Fuster
2011;():35-46. doi:10.1115/POWER2011-55192.

The use of insitu methods to rehabilitate buried or inaccessible piping systems is an emerging technology which has received recognition as an ASME XI Code approved alternate to traditional repair practices. This type repair requires the insertion of a carrier tube, containing thermosetting resins and reinforcement fillers into the host pipe. The length of the carrier tube is only limited by the pot life of the resin and restrictions of piping geometry. Once the insertion is completed, the resin is cured using hot water, air or steam, which is circulated through the host pipe. After curing, the resultant product is a form-fitted structurally reinforced resin pipe within the existing host piping. The Cured-In-Place Pipe (CIPP) has mechanical properties similar to those of fiberglass piping. The savings of this type repair, in both system downtime and replacement cost, is substantial. This methodology provides utilities with a technically sound, economically feasible solution to buried piping repairs and the ASME Section XI Code Case N-589 provides the requirements for materials, design and installation.

Topics: Pressure , Pipes
Commentary by Dr. Valentin Fuster
2011;():47-54. doi:10.1115/POWER2011-55193.

AREVA Solar, Inc. constructed, commissioned and operated the first-of-its-kind Once Through Solar Steam Generator (OTSG SSG), SSG4 at the Kimberlina Solar Thermal Power Station. The construction and commissioning of SSG4 was completed in September 2010, culminating in the successful execution of a series of performance tests. This was the first SSG that AREVA Solar, Inc. designed, manufactured and constructed to comply with ASME Section I, and registered with the National Board. SSG4 is the first in its class that produces high-pressure, superheated steam in a once through configuration. Some aspects of the system presented unique commissioning and operational challenges that are not commonly found in conventional fired boilers. These include: i) the use of a first-in-class model predictive control (MPC) system; ii) a steam integration system to blend steam from the once-through superheated SSG4 and the previous-generation, saturated steam SSGs; iii) a steam handling system that delivers the steam to a turbine generator or to a dump condenser; iv) precision optical tracking that is required for optimal boiler performance; v) 1310ft (400 meter) long boiler tube bundle. Unique for field erected boilers, the SSG4 tube bundle was welded at grade. After being inspected, the receiver and tube bundle support structure was placed over the bundles, secured and the entire receiver structure, with boiler tubes, was hoisted to its operating position, 60ft (18m) above grade. Following final connections of feedwater and steam piping, the boiler was inspected by Hartford Steam Boiler Insurance Company, which included hydrostatic test pressurization to 2002.5 psi (13.8MPa), and the stamps were applied to the boiler nameplate (see Figure 1 for a photo of the SSG4 boiler nameplate). Commissioning included standard boiler flushing and tube cleaning program and a comprehensive set of pre-operational tests. There were additional requirements that are unique to Compact Linear Fresnel Reflector (CLFR) solar thermal systems such as reflector alignment and tuning. These and other commissioning activities were scheduled around a constraint unique to solar systems — the availability of sunlight. A comprehensive set of procedures was followed to enable safe and successful integration and commissioning of the model predictive control system. Upon completion of commissioning, the plant was turned over to operations for continued testing. Stable superheated steam delivery was achieved within one week of Mechanical Completion, and Acceptance Testing was completed two weeks later at levels that exceeded the guarantee. This paper will describe the details of the integration, construction and commissioning milestones, distinctive aspects of commissioning solar thermal systems, and organization of the commissioning team to achieve success.

Topics: Boilers , Solar energy
Commentary by Dr. Valentin Fuster
2011;():55-63. doi:10.1115/POWER2011-55195.

Flow Accelerated Corrosion (FAC) is a fundamental problem for nuclear, fossil, and combined cycle power plants which can result in the loss of power generation, damage to equipment, and personnel injury. These documented events and failures have attracted the attention of utilities, industry groups, and regulatory agencies. The economic impact of FAC in terms of lost power, lost revenue, damaged equipment and components, and personnel injury has gained increased attention. The mechanism of FAC involves the formation and removal of the protective oxide layer from the inside surface of the pipe or equipment. This process occurs in carbon steel piping systems, tanks, and vessels. The FAC process is influenced by flow rate, pH, oxygen content, operating temperature, material of construction, and piping configuration. To oversee and manage Flow Accelerated Corrosion (FAC) in power plants, utilities have assigned personnel the responsibility to manage the FAC program either at the corporate level or a site representative or both. One of the keys in managing FAC is the relationship, interface, and communication with the other disciplines within the organization. Some of these disciplines include Management, Operations, Maintenance, Design Engineering, System Engineering, Water Chemistry, Plant Documentation, and Non-Destructive Examination (NDE). Their responsibilities within the organization and to each other are critical in keeping the plant on-line and minimizing personnel injury. In addition, it is the foundation for maintaining an effective Flow Accelerated Corrosion Program. These relationships and responsibilities within the FAC Program will be discussed in this paper.

Commentary by Dr. Valentin Fuster
2011;():65-70. doi:10.1115/POWER2011-55203.

High energy piping in power plants and industrial installations have a limited life due to creep and fatigue. Creep in steam pipes and headers are a collection of diffusion processes, driven by temperature and mechanical stress, which cause permanent strain. The surface strain is an objective measure for creep and these can be measured using nondestructive examinations. KEMA developed an inspection technique SPICA (Speckle Pattern Image Correlation Analysis) which makes it possible to measure on stream deformation due to creep in critical areas like the heat-affected zone (HAZ) in welds. This paper discusses the measurement method and results of tests on different scales. Also, a procedure for the application of strain measurements in power plants and creep strain criteria for end of life are discussed.

Topics: Creep , Pipes
Commentary by Dr. Valentin Fuster
2011;():71-86. doi:10.1115/POWER2011-55222.

Flow accelerated corrosion (FAC) is a combined form of erosion, corrosion and Cavitation. This is prominent in steam condensate lines which results in fast reduction of thickness in piping, piping components and valves. It is estimated that this problem is faced by majority of plants. There has been an increased emphasis on correcting these problems due to fatal accidents that occurred in 1986, 1995, 1996 and 2004 at various locations around the world. [3] After commissioning of the plant, Steam condensate system erosion/corrosion problem started appearing within one year of operation. To ensure uninterrupted plant running on line sealing was done and monitoring was done by proper thickness checking. These on line sealing points were replaced during available opportunity. In some cases plant shutdown was taken to replace leaking piping components & these incidents resulted into revenue loss to company. Aggressive inspection programs were taken up for thickness measurement on condensate lines and as a proactive measure, elbows were encapsulated with higher size elbows, reducers by on line welding/furmaniting with special clamps. Similarly gate and globe valves in condensate service also started failing as a result of erosion of body seat rings. Globe valves installed on bypass lines of control valves were found passing. Once these valves were operated for maintenance of control valves they could not be closed. In some cases valve body developed leak due to high velocity erosion. Various studies conducted for replacing these components by higher schedule fittings & pipes but it did not improve the situation except for slight increase in life of these components. Velocities were calculated at various locations and higher velocity, condensate impingement/cavitation was found as root cause of problems. This problem was solved by various methods like using higher metallurgy P11, P22 material, line size increase with increase in control valve sizing, lay out changes etc. This helped in improving reliability of condensate system and reducing risk associated with failure of piping. This paper presents a variety of cases where single-phase and two-phase steam flows, caused erosion-corrosion damage mainly at turn points of elbows and valves. It was observed that the presence, even of a small amount of the vapor phase can significantly increase the velocity of the condensate. This paper describes the mechanism of failures by study of the failed components, operating conditions & piping lay out. In this study velocity of steam /condensate at reducing section was found to be very high. Other various contributing factors like control valve / piping sizing, metallurgical requirements, effectiveness of steam traps, flow velocity and valve design (globe & gate) were also studied. The main causes of the failures are discussed and recommendations are provided to rectify the root cause of the problems & avoid similar problems in the future.

Commentary by Dr. Valentin Fuster
2011;():87-94. doi:10.1115/POWER2011-55227.

McGuire Nuclear Station and Alden Research Laboratory recently completed an extensive computational and experimental study characterizing the operating fluid mechanics and debris clean-out behavior of a rotating-drum strainer. The strainers are used in the plant for raw water (RN) and are installed on the suction side of the RN system pumps. The study served a twofold purpose. The first part of the study identified the requirements for flow withdrawal from the strainer to ensure adequate cleaning performance. It also identified the maximum debris loading rate at which the strainer could reject debris into the outlet channel [1]. The findings defined input to the second part of the study, the backwash pump performance evaluation, which is the focus of this paper. The backwash pumps will be installed to backwash the strainers with performance requirements based on the results of part one of the study. MPR Associates joined the effort to evaluate different pumps for performance under normal operating and design basis conditions. A test loop was constructed that allowed controlled debris injection at atmospheric and vacuum conditions. Vacuum condition performance is required since some operating conditions generate pressures inside the strainer near 9 ft abs. This paper summarizes the performance differences by pump type and discusses the characteristics of debris-laden performance relative to standard performance and the influence of degraded conditions on debris handling.

Commentary by Dr. Valentin Fuster
2011;():95-102. doi:10.1115/POWER2011-55315.

A generic real-time hydroelectric plant simulator has been implemented and validated. The simulator has the capability to run entirely in a simulation mode or to use actual control components running in parallel with simulated components. This flexibility results in a wide range of applicability, for example, it may be used for training of I&C personnel, tuning of turbine governors or testing the performance of actual control equipment. A further important feature of the simulator is its generic nature. A user-friendly interface is employed to parameterize any particular hydroelectric unit that uses a Pelton, Kaplan, or Francis turbine. The simulator includes mathematical models for the major systems in a hydroelectric plant, namely, hydraulic system (dam, water conduits, and turbine), electric generation (synchronous generator and excitation system) and power system (electrical grid). The simulator has been implemented on a GNU/Linux operative system with a Fedora Core 6 distribution and within a complete simulation environment, which includes real-time conditions management, graphical interfaces to operate the simulator, databases to store variables, and post-processing tools to visualize results. For control equipment testing applications an I/O data system is employed for the interaction between the simulator and the control equipment being tested. Comprehensive tests have been conducted and results compared with available plant data as validation. Three hydroelectric plants have been selected for tests: a 55 MW Pelton turbine plant, a 105 MW Kaplan turbine plant, and a 180 MW Francis turbine plant. A wide range of tests can be simulated, for example: turbine startup, disturbances in turbine speed or load, load rejection, electrical or mechanical trips, etc. Comparisons between calculations and plant data show in general relatively good agreement. A few selected tests are presented.

Commentary by Dr. Valentin Fuster
2011;():103-116. doi:10.1115/POWER2011-55330.

Today’s Heat Recovery Steam Generators are exposed to more severe operation than just running at a base load. The deregulation of the electric generation industry has resulted in an increase of merchant plants that are required to supply electrical power to the grid as needed and when needed. The plants will be coming on line with minimal notice. This puts a strain on the HRSG and unless properly designed and operated to withstand the quick start-ups and shut downs, the integrity will be compromised. Fast starts result in achieving full load revenues much sooner including the cost of high start-up emission reduction. Basic definition of a fast start is to have about 66% of the plant power available in 30–50 minutes and full plant power available in 60–75 minutes with a hot or warm steam turbine. This paper describes various mechanisms which affect the integrity of the boilers. These include the damage mechanisms, their effect on various parts and how to control them. The causes and the end results of these damage mechanisms are not the same for all components of the boiler. This analysis results in deciding which components need further review of the critical components. Detailed analysis of the critical components under the specified operating conditions can lead the nature and origin of the forces causing adverse impact on the life of the component. Once the failure mechanism is determined, means to eliminate or reduce the impact can be developed. This paper also describes the Life Consumption Estimation software which uses the data directly retrieved from the plant data acquisition system, thus eliminating the tedious task of manual data transmission. Based on the correlations developed by Vogt Power International Inc. (VPI) with the detailed dynamic simulation, Finite Element Analysis and various codes the component consumption is estimated and displayed with the calculated replacement and start-up costs on a continual basis. This gives the plant owners and operators an on line tool to gauge the economic benefits of the aggressive operations in real time.

Commentary by Dr. Valentin Fuster
2011;():117-122. doi:10.1115/POWER2011-55347.

During ferroalloy production, a large quantity of waste gas can be utilized to generate steam and electric power. In this paper, 4 detailed thermodynamic models of single-pressure (SP) and dual-pressure (DP) waste heat recovery power generation systems are presented, to analyze the impact of the steam pressure, steam temperature and pinch temperature difference on power generating capacity. By comparing the performance of typical systems, more reasonable thermodynamic models and their parameters are proposed. It is found that the power generation capacity of dual-pressure system is higher than that of the single-pressure system, but SP system is much simpler. Using superheated steam in deaerator reduces the efficiency of heat recovery power generation systems by 1.8%. The fluctuation of waste gas source affects the power generation greatly. It should be considered when more reasonable ranges for the main parameters are required. With the improvement of thermodynamic system and parameter optimization, the gross power is increased by 15% for SP system and 17% for DP system, corresponding to the steam parameters of 3.0MPa/400°C and 6.0MPa/400°C.

Commentary by Dr. Valentin Fuster
2011;():123-128. doi:10.1115/POWER2011-55397.

Oxygenated treatment (OT) is an excellent choice for supercritical (SC) and ultrasupercritical (USC) fossil units to alleviate flow accelerated corrosion (FAC). Unfortunately, many large utility boilers had suffered series bursts caused by exfoliation of duplex scale in steam path after adopting OT measures. It has been hopeful always about that OT should be independent of scale exfoliation, but many tube failures in fossil power plants go by contraries. Ecocide hypothesis which has been verified reveals the secret of the causal relationship between OT and exfoliation. Ecocide is the abbreviation of “Evaporating Consumption of Chromium Induced Disastrous Exfoliation” and that’s the essence of our hypothesis. We can explain the mechanism of exfoliation of duplex scale in oxygenated steam path with the help of ecocide hypothesis, and furthermore we can predict the risk of OT. Concerned with operating utility boilers which intend to apply OT, the longer the operating history, the greater the risk; the higher the concentration of oxygen in steam, the greater the risk; the higher the parameters of steam, the greater the risk. To avoid the risk of exfoliation, OT should be synchronously scheduled in commissioning.

Topics: Steam
Commentary by Dr. Valentin Fuster
2011;():129-132. doi:10.1115/POWER2011-55407.

This paper analyzes the applications and prospects of supercritical/ultra-supercritical power generation technology, integrated coal gasification cycle combination (IGCC) power generation technology, double reheat supercritical power generation technology, large-scale air-cooled power generation technology and modern thermal power system integration and optimization technology in China’s coal-fired power conservation.

Commentary by Dr. Valentin Fuster
2011;():133-140. doi:10.1115/POWER2011-55424.

The efficiency and reliability of thermal power plant directly depends on conditions of the condensation-steam system. The key of energy-saving and optimal operation in condensation-steam system is to adjust the circulating cooling water flow with different operation conditions to get the optimal vacuum. This paper presents the optimal mathematical model of circulating water flow of a 600MW supercritical thermal power plant using Matlab/Simulink. And this model has comprehensively considered the coupling influence of many parameters on the optimal vacuum, including circulating cooling water temperature, cooling water flow, vacuum pump output, condenser cleanness, and makeup water. This model can not only simulate the thermodynamic parameters of the condensation-steam system on operation conditions, but also simulate the influence of the health status of condensation-steam equipments on the operating performance. The accuracy of this model is validated by comparing the simulation results with design parameters under different conditions. We studied the optimal vacuum on off-design conditions using the model. The research shows that the change of the vacuum pump output will affect the results of the optimum circulating water flow, so the net power of the unit should be calculated with consideration of the change of the vacuum pump output in order to get the more practical optimal circulating water flow. The cleanliness of heat transfer surface has a great influence on the optimum circulating water flow. When the cleanliness is poor, the unit needs larger circulating flow to maintain the optimal vacuum. We should estimate the cleanliness of heat transfer surface to arrange suitable cleaning interval time according to the operation conditions of the unit.

Commentary by Dr. Valentin Fuster
2011;():141-144. doi:10.1115/POWER2011-55434.

In this paper, the combustion monitoring system at different inputs of burners in a reheating furnace by choosing the second heating section as the research subjects based on flame image processing technology has been discussed, and a linear temperature model has been developed for practical combustion control. In the linear model, the gas and air flow of burners in each section are mainly taken into account. The reheating furnace combustion control coefficients of the linear model from in-situ furnace combustion process by date acquisition system have been resolved.

Topics: Combustion , Furnaces
Commentary by Dr. Valentin Fuster
2011;():145-150. doi:10.1115/POWER2011-55442.

The inference of strong background noise and reflected by the wall and tube rows surface makes it impossible that justify accurately leakage position employing the characteristic received by multi-channel sensors. It is the ‘bottleneck’ for promoting the accuracy of boiler tube leakage location. The 600MW supercritical boiler model was established, the leakage source propagation process of reflection and attenuation in boiler furnace was simulated by EASE. The approximate signal to noise ratio (SNR) was obtained and the reverberation time was calculated with the squared impulse response integration method on the foundation of simulation. The time delay estimation algorithm PTN, SWITCH derived from PHAT and ML, respectively, are proposed and experiments results revealed the superiority over the classical generalized cross correlation (GCC) method in reverberant and noisy boiler background. Although SWITCH is outperformed by PTN slightly, but the prior knowledge of reverberant energy to direct energy ratio may be hard to obtain in practice and frequencies onset detection is required in PTN method, so the implementation of SWITCH is much easier.

Commentary by Dr. Valentin Fuster

Reliability, Availability and Maintainability

2011;():151-158. doi:10.1115/POWER2011-55028.

This paper will address the application of Guided Wave Radar [GWR], also known as Time Domain Reflectometry [TDR], in your steam loop. Included will be discussions of how this technology functions and differs from more traditional forms of level indication. Real world applications will be discussed that highlight technology features, subsequent benefits and other relevant information.

Topics: Waves , Radar , Steam
Commentary by Dr. Valentin Fuster
2011;():159-171. doi:10.1115/POWER2011-55114.

Cleaning of air heaters in power plants or recovery boilers has been traditionally done with high pressure water, chemicals or steam. These techniques, while effective on moderate air-side fouling of heat exchange surfaces, are usually ineffective on more tenacious deposits that can develop in coal-fired plants with buildup of fly ash, dust and oil. If these deposits are not cleaned periodically, the heat transfer in the heaters is reduced, which in turn reduces boiler efficiency and increases a unit’s heat rate. Severe fouling on air preheaters and air heaters can even reduce a unit’s Mw output. This paper discusses the recent introduction of a highly effective method of cleaning air heaters utilizing pressurized liquid nitrogen (LN2 ). A success story at PPL Generation’s Brunner Island plant illustrates the effectiveness of this new technology.

Topics: Nitrogen
Commentary by Dr. Valentin Fuster
2011;():173-176. doi:10.1115/POWER2011-55142.

Steam turbines have numerous applications in various sectors of industry and it is known by experience that blade failures are the most common origin of breakdown in these machines, causing significant economic losses in turbomachinery industry. The turbines are designed to work in stable conditions of operation; nevertheless, failure in blades could appear after a short time of work. Failures are attributed to resonance of the blades to certain excitation frequencies. The vibration stresses reached by resonance conditions and the combination of other random variables could determine the useful life of the blades. In the deterministic design of turbines, the failure possibility is reduced in acceptable small levels by means of safety factors based on the good judgment. However, the possibility of failure could be reduced by using probabilistic methods. In the probabilistic approach, the variability in the properties of the material, tolerances in manufacture and uncertainties in the load are considered with statistical methods. The probabilistic method allows to evaluate the uncertainty or randomness present in some variables which translates in a high level of reliability in the results and a better operation analysis of the turbines. There are a lot of variables in the operation of the turbomachineries, in its design and construction. These variables are conceived under a certain degree of uncertainty, that is to say, these cannot be totally controlled. Generally, repeated measurements of mechanical phenomena generate a lot of input variables each one with certain instability in their magnitude that contributes to increase the probability of failure before the estimated time. In this work the reliability and useful life of blade steam turbines of 110 MW of the L-0 stage are analyzed using deterministic numerical methods and a probabilistic approach. Curves of the useful life for both cases are obtained. The probabilistic approach shows that failure occurs when a combination of variables and the presence of failure are combined.

Commentary by Dr. Valentin Fuster
2011;():177-191. doi:10.1115/POWER2011-55298.

Field measurements of the steamside oxide thickness for high temperature (> 850F) boiler tubing subject to the accumulation of creep damage often are made to support deterministic assessments of the remaining life. Most often, these inspections are undertaken to understand the condition of the tubing at some particular location along a circuit, often as a result of a tube failure. The life assessment is based on relationships that have been developed between oxide growth kinetics and temperature. Unfortunately, because of variability in the oxide-temperature relationships reflecting different original data sets, and because of the inherent uncertainty in materials properties where heat-specific test data is not available, there typically exists a broad range of uncertainty in the deterministic assessment results. Large utility-type boilers typically contain a number of high temperature sections, including various stages of superheat and reheat, each of which will contain miles of tubing. Since the temperature derived from an oxide thickness measurement is relevant only to the specific location where the measurement was made, the deterministically derived life calculation is also specific to that location. As a result, the attempt to draw conclusions regarding the condition of an entire superheater or reheater section from measurements made at only one or two locations in those sections is fraught with difficulties. It is for this reason that the Probabilistic Gas Touched Length Analysis model has been developed. This model makes it possible to calculate creep damage accumulation/remaining life at any point along the steam path. Oxide thickness data and operating data are the primary operating inputs into the model, which performs heat transfer calculations at user-defined locations along the length of the tube circuit. The model applies statistical methods to evaluate variations in operating conditions as well as in physical and mechanical properties using a Monte Carlo simulation to generate values for the probability of failure at selected locations. This paper will discuss the limitations of the existing approach to estimating the remaining life of high temperature boiler tubing and present the underpinning theory of the gas touched length analysis model. A case study showing the analysis results is included.

Commentary by Dr. Valentin Fuster
2011;():193-200. doi:10.1115/POWER2011-55316.

Nowadays the refining sector in Mexico needs to increase the quantity and quality of produced fuels by installing new process plants for gasoline and ultra low sulphur diesel. These plants require the provision of electricity and steam, among other services to function properly, which can be supplied by the power plants currently installed in each refinery through an expansion of their generation capacity. These power plants need to increase its production of electricity and steam at levels above their installed capacity, which involves the addition of new power generating equipment (gas or steam turbo-generators) as well as the raise of the electrical loads. Currently, the Mexican Petroleum Company (PEMEX) is planning to restructure their electrical and steam systems in order to optimally supply the required services for the production of high quality fuels. In this paper the present status of the original electrical power systems of the refineries is assessed and the electrical integration of new process plants in the typical schemes is analyzed. Also this paper shows the conceptual schemes proposed to restructure the electrical power system for two refineries and the strategic planning focused on implement the modifications required for the integration of new process plants that will demand about 20 MW for each refinery by 2014. The results of the analysis allowed to identify the current conditions of the electrical power systems in the oil refining industry or National Refining Industry (NRI), and thereby to offer technical solutions that could be useful to engineers facing similar projects.

Commentary by Dr. Valentin Fuster
2011;():201-210. doi:10.1115/POWER2011-55324.

The modeling of dependent failures, specifically Common Cause Failures (CCFs), is one of the most important topics in Probabilistic Risk Analysis (PRA). Currently, CCFs are treated using parametric methods, which are based on historical failure events. Instead of utilizing these existing data-driven approaches, this paper proposes using physics-based CCF modeling which refers to the incorporation of underlying physical failure mechanisms into risk models so that the root causes of dependencies can be “explicitly” included. This requires building a theoretical foundation for the integration of Probabilistic Physics-Of-Failure (PPOF) models into PRA in a way that the interactions of failure mechanisms and, ultimately, the dependencies between the multiple component failures are depicted. To achieve this goal, this paper highlights the following methodological steps (1) modeling the individual failure mechanisms (e.g. fatigue and wear) of two dependent components, (2) applying a mechanistic approach to deterministically model the interactions of their failure mechanisms, (3) utilizing probabilistic sciences (e.g. uncertainty modeling, Bayesian analysis) in order to make the model of interactions probabilistic, and (4) developing appropriate modeling techniques to link the physics-based CCF models to the system-level PRA. The proposed approach is beneficial for (a) reducing CCF occurrence in currently operating plants and (b) modeling CCFs for plants in the design stage.

Commentary by Dr. Valentin Fuster
2011;():211-220. doi:10.1115/POWER2011-55325.

Reliability and availability modeling of complex mechanical systems such as power plants in a single model, considering binary/tertiary states of individual components, using Markov approach is difficult due to state space explosion problem. Inclusion of various types of dependencies in the model further aggravates it. Moreover, the Markov approach is applicable when failure and repair time distributions are exponential. As the time to failure of mechanical components in most of the cases follows Weibull distribution, the Markov approach cannot be realistically applied for such systems. To overcome this, Stochastic Petri net (SPN) hierarchical modeling is proposed in this paper. The model is based on three aspects of the system: hierarchical level, basic structure and dependency. The three hierarchical levels are considered in the model. Individual component (level ‘3’) SPN model is developed assuming Weibull failure distribution, while the individual subsystem (level ‘2’) SPN model is developed considering the arrangement of components within the subsystem. The individual model at level ‘2’ is reduced to an equivalent single net model and its equivalent transition rate is derived from its basic structure assuming the independence of components. The assumption of independence is relaxed for the system model (level ‘1’) and the dependencies (e.g. repair, standby redundancy, load sharing) are incorporated. The repair distribution in the system model is assumed exponential and repairs are considered at the subsystem level. Reachable markings are generated for the system model to obtain the reduced state space model. The proposed methodology provides realistic assessment of reliability and availability values. The suggested methodology is demonstrated for the ‘Cooling Tower System’.

Topics: Reliability , Modeling
Commentary by Dr. Valentin Fuster
2011;():221-226. doi:10.1115/POWER2011-55329.

Power generation has the goal of maximizing power output while minimizing operations and maintenance cost. The challenge for plant manager is to move closer to reliability limits while being confident the risks of any decision are understood. To attain their goals and meet this challenge they are coming to realize that they must have frequent, accurate assessment of equipment operating conditions, and a path to continued innovation-. At a typical plant, making this assessment involves the collection and effective analysis of reams of complex, interrelated production system data, including demand requirements, load, ambient temperature, as well as the dependent equipment data. Wind turbine health and performance data is available from periodic and real-time systems. To obtain the timeliest understanding of equipment health for all the key resources in a large plant or fleet, engineers increasingly turn to real-time, model-based solutions. Real-time systems are capable of creating actionable intelligence from large amounts and diverse sources of current data. They can automatically detect problems and provide the basis for diagnosis and prioritization effectively for many problems, and they can make periodic inspection methods much more efficient. Technology exists to facilitate prediction of when assets will fail, allowing engineers to target maintenance costs more effectively. But, it is critical to select the best predictive analytics for your plant. How do you make that choice correctly? Real-time condition monitoring and analysis tools need to be matched to engineering process capability. Tools are employed at the plant in lean, hectic environments; others are deployed from central monitoring centers charged with concentrating scarce resources to efficiently support plants. Applications must be flexible and simple to implement and use. Choices made in selection of new tools can be very important to future success of plant operations. So, these choices require solid understanding of the problems to be solved and the advantages and trade-offs of potential solutions. This choice of the best Predictive Analytic solution will be discussed in terms of key technology elements and key engineering elements.

Commentary by Dr. Valentin Fuster
2011;():227-234. doi:10.1115/POWER2011-55375.

In order to operate thermal power plants safely, early detection of equipment failure signs is one of the most important issues. To detect the signs before an alarm is issued in the existing monitoring system, we developed a fault diagnosis system based on the Adaptive Resonance Theory (ART). The vigilance parameter, which is a design parameter in the ART model, was shown to influence the diagnosis accuracy. Fixing the value of the vigilance parameter also had problems: we needed to use time-consuming trial and error, and we needed to have empirical knowledge of the parameter tuning. In this paper, using simulations we demonstrated the relationship between the vigilance parameter and diagnosis accuracy. Furthermore, to overcome the problems of the vigilance parameter tuning, we have proposed an auto tuning algorithm to make the parameter the optimum value. The performance of the proposed algorithm was evaluated in several case studies using gas turbine plant data. The effectiveness of the proposed algorithm was confirmed by the obtained results.

Commentary by Dr. Valentin Fuster
2011;():235-240. doi:10.1115/POWER2011-55410.

The mathematical model and the methodology of the reliability prediction of generating units are presented. Based on statistical analysis of operation reliability past data for generating units, statistical values of the repair factor and the mathematical model’s parameters of the repair factor are determined. According to plan repair outage days and the mathematical model for the repair factor of some generating unit, equivalent availability factor (EAF) of the generating unit can be predicted in future three years. The reliability prediction examples for sub-critical 300MW, supercritical 600MW and sub-critical 600MW fossil units are given together with reliability prediction results of 550MW hydro units and 984MW, 990MW nuclear units. The relative error’s range for equivalent availability factor prediction values of the generating units is between −1.48% and 2.69% which indicates that reliability prediction precision is higher. By using reliability prediction method, prediction values for the reliability indexes of generating units can be quantitatively calculated, which provides a basis for reliability objective management and optimization repair of generating units.

Topics: Reliability
Commentary by Dr. Valentin Fuster
2011;():241-246. doi:10.1115/POWER2011-55411.

A method for the reliability and the availability prediction of main stop valve and control valve systems of steam turbines is presented. The calculation models for the reliability and the availability of series, parallel and series-parallel systems of main stop valves and control valves are introduced. The reliability block diagrams, the availability block diagrams, formulas for the reliability prediction and the availability prediction of systems with 2 main stop valves and 2 control valves, 2 main stop valves and 4 control valves, 2 main stop valves and 6 control valves, 4 main stop valves and 4 control valves are given together with some examples. The mathematical model for the reliability and the availability prediction method of main stop valve and control valve systems of steam turbine is simple and the physical meaning is definite. The reliability and availability of main stop valve and control valve systems can be quantitatively already calculated and improved during the design stage. A basis is thus provided for the reliability and the availability design of main stop valve and control valve systems of steam turbines.

Commentary by Dr. Valentin Fuster
2011;():247-253. doi:10.1115/POWER2011-55430.

Accurate risk assessment is an important scientific basis for maintenance decision making. Based on the reliability analysis, prediction technology and fault dialogue technology, this paper defines a risk index, run vulnerability, which considers factors of equipment status, consequences of potential failures and run trend, thus, it reflects equipment risk more comprehensive than that of traditional risk index do. This paper presents a new risk evaluation model based on run vulnerability for power generation equipment. The model process all factors affecting run vulnerability with the quantification of fuzzy rules, and constructs a three-dimensional surface run vulnerability map to achieve the risk assessment of power generation equipment. The example of feed water pump’s risk evaluation validates the model.

Commentary by Dr. Valentin Fuster

Plant Systems, Structures, Components and Materials Issues

2011;():255-259. doi:10.1115/POWER2011-55099.

Pumps in nuclear power plants are periodically tested to ensure their performance and readiness to meet a variety of design basis conditions. As with any component, a pump’s performance will degrade over time. A nuclear pump’s initial performance should always be established by the manufacturer during a shop test that is run over the pump’s entire range of operability. Following installation, periodic testing is typically performed at a single reference point. This paper provides a methodology for establishing a centrifugal pump performance curve based on both its performance when new and its level of degradation documented by in-service test data. In the extreme, this method can be used to establish a pump’s minimum performance curve by using the pump’s acceptance criteria as the data point.

Commentary by Dr. Valentin Fuster
2011;():261-265. doi:10.1115/POWER2011-55338.

Cooling water pipe systems are a critical part of a power generation plant. If the cooling water pipe fails, the whole plant may shut down. Due to its high tensile strength steel pipe has been used for cooling water pipe since the beginning of power generation. High density polyethylene (HDPE) has emerged as a reliable and sustainable replacement for steel pipe primarily due to its corrosion resistance. The Hazen-Williams C-factor of steel pipe decreases during the service period because of corrosion and buildup while HDPE pipe has a stable C-factor. The build up inside steel pipe reduces not only the C-factor but also the inside diameter. Steel pipe may fail in the ductile mode as a result of corrosion-related pipe strength reduction combined with the pressure surge related to the reduction of inside diameter. Ductile failure is not observed in the field for HDPE pipe. HDPE pipe is virtually maintenance-free while corrosion protection measures are used for steel pipe. HDPE pipe has advantage over metal pipe in total life cycle costs including material, installation, maintenance, and replacement costs. With these outstanding performance attributes, HDPE pipe has been used in power plants over the last 15 years to transport cooling water pipe for non-safety related applications. In November 2008, Ameren’s Callaway Nuclear Power Plant successfully completed the installation of a 36″ HDPE cooling water pipe system; the first safety related HDPE water pipe in North America for the ASME category 3 cooling pipe application. This safety related PE 4710 cooling water pipe has delivered exceptional performance since its installation.

Commentary by Dr. Valentin Fuster
2011;():267-274. doi:10.1115/POWER2011-55348.

The aim of this paper is to study the effect of flow conditions on nanoparticle fraction suspending in base fluid, using water-based TiO2 nanofluids under laminar flow conditions as an example. With the same initial concentration of nanoparticle (about 0.5% mass fraction), significant deterioration of stability is observed and the deterioration depends on the flow conditions (Reynolds number 500–2000, circulating time). The nanoparticle fraction in nanofluids flowing through bend tube with multi elbows is obviously lower than straight tube with fewer elbows, especially for that at higher Reynolds number. After 8 h, compared with the initial concentration (about 0.5% mass fraction), the relative concentration of nanofluids is 71.5% and 68.5% at Re = 500, for straight tube and bend tube, respectively. Whereas, that is 96.9% and 89.3% at Re = 2000 for straight tube and bend tube, respectively. Sample of nanoparticles in base fluid flowing through bend tube obviously appears the agglomeration (shown in TEM images), larger particle size (measured by laser particle size analyzer) compared with that flowing through straight tube. Moreover, the precipitation of particles can be apparently observed at the out curvature of elbows. These results imply that higher nanoparticle fraction can be maintained for nanofluids at higher Reynolds number and fewer elbows. It maybe helpful for better understanding heat transfer behavior of nanofluids.

Commentary by Dr. Valentin Fuster
2011;():275-280. doi:10.1115/POWER2011-55354.

In a piping system of power plant, pipe wall thinning by Flow Accelerated Corrosion, FAC, Liquid Droplet Impingement Erosion, LDI, and Cavitation Erosion, C/E, are very serious problems because they give a damage and lead to the destructtion of the piping system[1]–[6] . In this study, the pipe wall thinning by FAC in the downstream of orifice nozzle, flow meter, is examined. Namely, the characteristics of FAC, generation mechanism, and prediction of the thinning and the reduction are made clear by experimental analysis. As a results, it was made clear that (1) the thinning is occurred mainly according to the size of the pressure fluctuation p′ on the pipe wall and the thinning can be estimated by it, and (2) the suppression of p′ can be realized by replacing the orifice to a taper shaped one having an angle to the upstream.

Commentary by Dr. Valentin Fuster
2011;():281-286. doi:10.1115/POWER2011-55374.

Power plant design using digital engineering based on 3-D computer-aided design has become a mainstream technology because of possessing higher speed and improvement in design accuracy. To take a coal-fired boiler building as an example, it has many complex structures with several million parts including the boiler itself, large fans, steel structures, and piping in varying sizes. Therefore, it is not easy to maintain integrity of the whole design throughout all the many engineering processes. We have developed a smart design system for coal-fired boiler buildings to solve the integrity problem. This system is capable of creating and allocating 3-D models automatically in accordance with various technical specifications and engineering rules. Lately, however, there has been a growing demand for more effectiveness of the developed system. We have begun to look into the feasibility of further improvements of the system function. The first point to note, when considering effectiveness, is the piping path routing process in the coal-fired boiler building. The quantity of piping is large, and it has a considerable impact on performance of the whole plant because hot steam is fed into the steam turbine and cold steam is taken from it through the piping. A considerable number of studies have been made on automatic searching methods of piping path routing. Although, the decision of piping path routing by using the Dynamic Programming method is most commonly, a previously decided routing becomes an interference object because of the single searching method. Therefore, basically, the later the order of the routing becomes, the longer the length of the routing becomes. To overcome this problem, in this paper we have proposed a new searching method based on the Genetic Algorithm (GA). The GA is a multipoint searching algorithm based on the mechanics of natural selection and natural genetics. Virtual prohibited cells are introduced into the proposed search method as a new idea. The virtual prohibited cells are located in a search space. The different paths are generated by avoiding the virtual prohibited cells while searching for the piping path routing. The optimum locations of the prohibited cells which are expressed in a genotype are obtained by using the GA in order to get a lot of paths independent of the order of the routing. The proposed method was evaluated using a simple searching problem. The results showed that many effective paths are generated by making the virtual prohibited cells.

Commentary by Dr. Valentin Fuster
2011;():287-291. doi:10.1115/POWER2011-55443.

Based on the developed three-dimensional computation model of natural draft wet cooling towers, the effect of crosswind on circumferential distribution of air radial pressure gradient and velocity at tower air inlet was studied, and the effect of crosswind on total air inflow rate, transverse mass flow rate, vertical mass flow rate and water temperature drops of the three zones (i.e. spray zone, filling zone and rain zone) were also analyzed. Analysis of crosswind effect on air flow field in heat and mass transfer zone indicates that the induced longitudinal eddy causes reduction of effective ventilation area in filling zone. Results showed that crosswind destroys the uniform air inflow, reducing the total air inflow mass rate and the effective ventilation area of filling zone, resulting in cooling performance deterioration of natural draft wet cooling towers.

Commentary by Dr. Valentin Fuster
2011;():293-297. doi:10.1115/POWER2011-55446.

The circumferential inflow air distributing rules on the bottom of wet cooling tower are studied by thermal state model experiment under crosswind conditions. Researches showed the axisymmetric distribution of circumferential inlet wind is destroyed under crosswind conditions. And this phenomenon is very obvious when environmental crosswind velocity is more than 0.2m/s. Compared with windless conditions, when environmental wind velocity is about 0.4m/s, the circumferential inlet wind velocity in windward side is about 1.8 times of windless conditions, but the circumferential inlet wind velocity in leeward side is about 0.3 times of windless conditions. Thus, the environmental crosswind affects airflow rate entering into the cooling tower, and deteriorating the heat and mass transfer performance. In addition, the relationship of air gravity wind velocity and crosswind is received that can be acted as the theoretical basis of deep research.

Commentary by Dr. Valentin Fuster
2011;():299-305. doi:10.1115/POWER2011-55447.

For the air-cooled thermal power generating unit, specific climatic conditions exert fast and great impact on the condenser pressure. When equipping turbine driven feed water pumps (TDFWP), as the exhaust steam leaving the boiler feed pump turbine (BFPT) is directly discharged into the air-cooled system, the change of environmental conditions such as air temperature and wind speed will result in the distinct change of BFPT back-pressure both in scope and magnitude. For once-through boilers, such changes will cause disturbance to feed water, and further lead to the change of fuel and air feeding. The back-pressure of main steam turbine is much higher in summer climatic condition. In order to maintain rated or certain power load, steam supplied into the main steam turbine has to be increased. Meanwhile, it is necessary to increase the steam flux in the driving turbine to maintain the needed power for feed water pumps, so there is a conflict that the driving turbine for feed water pumps will compete for steam with the main steam turbine. A dynamical mathematical model of a 600MW direct air-cooled thermal power generating unit is built in this paper. The focus is on the transient analysis of the effect of TDFWP on main equipments when the back-pressure changes in the manners of slope and step mutations. Simulation results show that when the disturbance is smaller, the unit can be quickly adjusted to the operational status at given steam and feed water flow rates. The greater the magnate of back-pressure mutation, the greater the changing range of the parameters, and the longer time is needed for adjusting. Under the condition of the same change magnitude of back-pressure, when the back-pressure rise time is longer, the parameters fluctuation is smaller. When the disturbance is larger, the steam flow of TDFWP is gradually increased to its maximum value. With further increase in the back-pressure, the steam flux in the turbine of TDFWP is gradually decreased, so it is difficult to ensure the feed water flow in this case. The results in this study provide important theoretical significance and engineering reference for the implementation of utilizing direct cooling steam feed pump technology in the actual unit.

Commentary by Dr. Valentin Fuster
2011;():307-313. doi:10.1115/POWER2011-55457.

It is well known that the wetness of steam flow sometimes causes measurement errors of the steam flow meter. However, it is difficult to clarify a particular error quantitatively in actual plants and factories, and thus far, there has been no established method for estimating the error caused by the wetness of steam flow. Therefore, wet steam flow rate measurement experiments were conducted to clarify the measurement error caused by the wetness of steam flow in a plant and a factory. In this study, as the first step, the orifice flow meter was applied because it is the main flow meter in actual plants. Experiments were conducted with the steam flow apparatus by changing the flow rate, pressure and wetness. As a result, the correlation between the measurement error and the flow condition was clarified. Moreover, for the correction of the error, a new correction method was applied and was confirmed to be better than existing methods now being used.

Commentary by Dr. Valentin Fuster
2011;():315-324. doi:10.1115/POWER2011-55471.

Advanced ultra supercritical (A-USC) steam power generation, in which high-pressure steam is raised to beyond 700°C, is being studied internationally. The creep strength of Ni-based super alloys evaluated at these high temperatures in an air environment makes these materials promising candidates for the material to be used for the structural components of these generators. Since they are exposed to high temperature steam, it is important that the effect of the environment on the degradation of these materials is investigated. In this investigation, the crack growth rate under cyclic loading in a 750°C steam environment using a compact tension specimen was evaluated. Crack length monitoring using the direct current potential drop technique was applied to the growing crack in a high temperature environment in order to evaluate the time-dependent behavior of the crack growth. The dependence of the loading rate and amplitude in terms of the stress intensity factor was obtained. The crack growth rate increased with decreasing loading rate and increasing amplitude. Multiple loading patterns were applied to a single specimen during crack length monitoring. When the loading pattern was changed to a different pattern, in most of the cases, the crack growth rate started to change and then became stable aftera transition period. The influence of intermetallics and different phases on the crack growth behavior is discussed based on the oxidation rate of these phases.

Commentary by Dr. Valentin Fuster

Advanced Energy Systems

2011;():325-334. doi:10.1115/POWER2011-55018.

The ability of modern power plant data acquisition systems to provide a continuous real-time data feed can be exploited to carry out interesting research studies. In the first part of this study, real-time data from a power plant is used to carry out a comprehensive heat balance calculation. The calculation involves application of the first law of thermodynamics to each powerhouse component. Stoichiometric combustion principles are applied to calculate emissions from fossil fuel consuming components. Exergy analysis is carried out for all components by the combined application of the first and second laws of thermodynamics. In the second part of this study, techniques from the field of System Identification and Linear Programming are brought together in finding thermoeconomically optimum plant operating conditions one step ahead in time. This is done by first using autoregressive models to make short-term predictions of plant inputs and outputs. Then, parameter estimation using recursive least squares is used to determine the relations between the predicted inputs and outputs. The estimated parameters are used in setting up a linear programming problem which is solved using the simplex method. The end result is knowledge of thermoeconomically optimum plant inputs and outputs one step ahead in time.

Topics: Power stations
Commentary by Dr. Valentin Fuster
2011;():335-343. doi:10.1115/POWER2011-55019.

In this paper, two new combined cycle systems with/without CO2 capture based on methanol indirect combustion are developed, which have significantly higher efficiency than methanol fueled conventional combined cycle. The performance of the new systems is compared with conventional combined cycle to identify the potentials of methanol indirect combustion. The systems are modeled by using Aspen Plus™ and GTPro™. Exergy analysis and the principle of cascade utilization of chemical exergy reasonably explain the improved efficiency of the new systems. Other merits of the combined cycle system based on methanol indirect combustion are discussed and its promising commercial application aspects are pointed out.

Topics: Combustion , Cycles , Methanol
Commentary by Dr. Valentin Fuster
2011;():345-352. doi:10.1115/POWER2011-55097.

Efficient and sustainable methods of clean fuel and energy production are needed in all countries of the world in the face of depleting oil reserves and the need to reduce carbon dioxide emissions. Some countries are developing technologies that could be named zero carbon technologies. The presented article will show how hydrogen technologies could be implemented with renewable technologies and nuclear technology. Nuclear technology produce very cheap electricity and could produce also cheap energy like heat and vapour. This technology should be used in nuclear power plants to develop other products like hydrogen, biofuels or district heating. One of the biggest opportunities for nuclear energy technology is to produce hydrogen. Some countries like Canada and US are in preparation to build hydrogen villages. However, a key missing element is a large-scale method of hydrogen production [1–5]. As a carbon-based technology, the predominant existing process (steam-methane reforming (SMR)) is unsuitable. This paper focuses on a production of hydrogen in connection with a nuclear power plant. We will show the technologies which allow the coupling between a nuclear power plant and hydrogen technologies.

Commentary by Dr. Valentin Fuster
2011;():353-362. doi:10.1115/POWER2011-55267.

We must soon “run the world on renewables” but cannot, and should not try to, accomplish this entirely with electricity transmission. We need to supply all energy, not just electricity, from diverse renewable energy (RE) resources, both distributed and centralized, where the world’s richest RE resources — of large geographic extent and high intensity — are stranded: far from end-users with inadequate or nonexistent gathering and transmission systems to deliver the energy. Electricity energy storage cannot affordably firm large, intermittent renewables at annual scale, while carbon-free gaseous hydrogen (GH2) and liquid anhydrous ammonia (NH3) fuels can: GH2 in large solution-mined salt caverns, NH3 in surface tanks, both pressurized and refrigerated. “Smart Grid” is emerging as primarily a DSM (demand side management) strategy to encourage energy conservation. Making the electricity grid “smarter” does not: 1. Increase physical transmission capacity; 2. Provide affordable annual-scale firming storage for RE; 3. Solve grid integration problem for large, time-varying RE; 4. Alleviate NIMBY objections to new transmission siting; 5. Reduce the high O&M costs of overhead electric lines. The “smarter” grid may be more vulnerable to cyberattack. Adding storage, control, and quality adjunct devices to the electricity grid, to accommodate very high renewables content, may be technically and economically inferior to GH2 and NH3 RE systems. Thus, we need to look beyond “smart grid”, expanding our concept of “transmission”, to synergistically and simultaneously solve the transmission, firming storage, and RE integration “balancing” problems now severely constraining our progress toward “running the world on renewables”.

Commentary by Dr. Valentin Fuster
2011;():363-367. doi:10.1115/POWER2011-55308.

Methane hydrate dissociation is studied using numerical and experimental approaches for a low carbon dioxide (CO2 ) emission power generation system utilizing methane hydrate. A novel power generation system has been proposed by authors, in which methane gas produced from oceanic methane hydrate reservoir by thermal stimulation method is used as fuels. The performance of the power generation system and the heat loss during the injection of hot seawater to the methane hydrate layer were investigated in previous study. However, the estimation of the methane gas production rate from the methane hydrate reservoir is necessary to evaluate the performance of whole system. In this study, we conducted the numerical simulation of methane hydrate reservoir. In order to evaluate the reaction rate of methane hydrate dissociation, the methane hydrate formation and dissociation experiment was conducted. The result of numerical simulation indicates the necessity of improvement of the production process to supply the heat of hot water effectively. From the experimental result, it comes to see that consideration of the scale effect of the methane hydrate construction is necessary to describe the dissociation rate.

Commentary by Dr. Valentin Fuster
2011;():369-377. doi:10.1115/POWER2011-55317.

The connection between combined power and heat generation, and the concept of distributed generation is a relevant issue viz. improvement of the overall efficiency of energy conversion and distribution. In this context, the use of biomass may be of particular interest due to its potentially very low CO2 emissions as well as low kWh production cost with respect to other renewable energy sources. Traditional methods to convert biomass involve micro-turbines or steam power plants. However, both electrical and overall efficiencies may not be particularly high for both technological and thermodynamic reasons; the latter being hard to supersede. High temperature Solid Oxide Fuel Cells (SOFCs) offer an attractive solution because they are characterized by electrical efficiencies in the range of 35% to 48% [1], and present a significant potential for integrating with the biomass gasification process; thus, exploiting advantages of high operating temperatures. Moreover, thermal integration is of prime importance. In fact, optimal management of thermal integration may allow operation with high moisture content feedstocks and with high water concentration in the SOFC; thus, promoting further hydrogen production via the water gas shift reaction [2]. In this paper, an integrated solid oxide fuel cell-gasifier system is modeled to identify the main effects on fuel cell performance under several operating conditions in terms of biomass flow rates and moisture contents. The SOFC and the gasifier are modeled by a zero dimensional approach to perform a sensitivity analysis with a numerical tool which requires less computational effort compared to those previously presented. The thermochemical phenomena are taken into account with a high degree of detail, and model validation is also showed via comparison with literature available data. Results highlight the impact of biomass feedstock and its moisture content on the electrical current density value. Final performance depends on the interaction among gasifier thermal sustainability, SOFC operating temperature and chemical equilibrium concentrations, via water gas shift reactions. In particular, it has been shown that thermal integration allows operation with higher moisture content biomass, thereby further exploiting H2 O conversion into H2 via water gas shift reactions and high fuel utilization operating conditions. The importance of thermal integration and advanced control of SOFC based biomass fueled systems is demonstrated by this study, as well as the use of a fast and reliable zero-dimensional modeling for system design and control purpose.

Commentary by Dr. Valentin Fuster
2011;():379-386. doi:10.1115/POWER2011-55355.

This paper reports application study of newly developed turbo heat pump for 130 degrees Celsius (°C) water for an industrial process in an actual factory. The heat pump is characterized by high efficiency and large heat output, by using a state-of-the-art turbo compressor. The heat pump requires a low temperature heat source in order to achieve high efficiency. The heat demand is for several drying furnaces in the factory, which requires producing hot air of 120 °C. The heat exchanger was designed to produce the hot air. Experiments were conducted to confirm the performance of the heat exchanger under a reduced size of the heat exchanger. Low temperature heat sources are from both exhaust gas of the drying furnaces and that of an annealing furnace. The heat exchangers were also designed to recover heat of the exhaust gas from the two types of furnace. A thermal storage tank was prepared for the low temperature heat source, and for adjusting the time difference between the heat demand and the low temperature heat source. The size of the tank was determined by considering the schedule of furnaces operations. As a result of the present study, it was confirmed that the heat pump was able to satisfy the present heat demand while retaining high efficiency. Primary energy consumption and CO2 emission of the heat pump were calculated on the basis of the present results in order to compare them with those of the boilers.

Topics: Heat pumps , Water
Commentary by Dr. Valentin Fuster
2011;():387-392. doi:10.1115/POWER2011-55356.

Variety researches and developments have been performed in order to decrease the emission of carbon dioxides as known of major cause on global warming. The SMART study group has proposed a concept of the solution for the low carbon dioxides emission and the disaster-proof community cooperating with industries, academics and municipal offices. This concept is based on the distributed energy network as known as SMART grid technology proposed in 2004. The system consists of the micro-grid system with distributed energy and IT network securing the power supply apart from the power utility in case of emergency and disasters. The proposed SMART system has major three functions. The first is to provide the ability to use the renewable energy generated in the local community. The renewable energy is most expected one but the output is too fluctuating to use usually. The second is to provide the tools to cooperate with citizens. The advanced demand-side control can contribute to save the energy. The third is to prepare for the disaster as mentioned above.

Commentary by Dr. Valentin Fuster
2011;():393-402. doi:10.1115/POWER2011-55357.

Efficient utilization of biomass by a cogeneration system (CGS) is a promising technology for promoting sustainable energy development. Sewage treatment plants are facilities that have been continuously producing biogas by anaerobic digestion. Thus, the potential of a biogas-fuelled CGS in a sewage treatment plant is estimated to be very high. However, there have been few reports on the performance of a biogas-fuelled CGS, particularly regarding the effect of ambient temperature on its performance, and the most efficient arrangement of a biogas-fuelled CGS remains unknown. In this study, performance of a biogas-fuelled CGS was simulated under three typical ambient temperature (low, medium and high) conditions using actual data for a CGS with a micro gas turbine. In the beginning of this study, the relation of energy balance of the plant and ambient temperature was clarified. It was found that the amount of heat demand is ambient temperature-dependent but that the amount of biogas fuel produced is almost constant throughout the year. When a boiler is replaced with a biogas-fuelled CGS to utilize the biogas, under a high temperature condition, the CGS is not able to fully utilize all of the biogas produced, and therefore another pathway of biogas utilization is needed. Under a medium temperature condition, a gas storage system is needed for using biogas efficiently. However, some of the biogas still cannot be utilized efficiently. Under a low temperature condition, since ambient temperature varies greatly between summer and winter, the amount of heat demand of the plant also varies greatly throughout the year. This leads to an imbalance in biogas production and heat demand, and therefore attention must be given to energy management in this condition. The combination of other auxiliary equipment such as a boiler, heat pump and gas storage with the CGS is required in order to cover the total heat demand throughout the year. Four possible arrangements of the CGS with different auxiliary components were proposed and their performances were compared. It was found that all of the proposed CGS arrangements can sufficiently cover the total heat demand by only using biogas produced in the facility. Compared to the conventional system, all proposed CGS arrangements can reduce electrical power demand by 23∼28%, recover 74∼77% of the energy of biogas produced, and utilize almost 100% of the biogas produced. The arrangement with a heat pump is more efficient than the arrangement with a boiler. It was also found that excess biogas in summer can be used in winter by storing the biogas. Thus, a CGS arrangement that includes a gas storage system will enable efficient utilization of biogas and recovered exhaust heat.

Commentary by Dr. Valentin Fuster
2011;():403-408. doi:10.1115/POWER2011-55363.

We propose a novel concept for power generation that involves the combination of a low-condition heat generator (LCHG), such as a light water nuclear reactor or a biomass combustion boiler, with an advanced closed-cycle oxy-fuel combustion gas turbine—a type of complex and efficient oxyfuel gas turbine plant, in accordance with our previous studies in combination with a simple oxy-fuel gas turbine plant. In this study, a LCHG is designed to heat water to saturated steam of a few MPa, to assist in the generation of the main working fluids, instead of a compressor used in the advanced oxy-fuel gas turbine. This saturated steam can have a lower pressure and temperature than those of an existing nuclear power plant or biomass-fired power plant. We estimated plant performances from a heat balance model based on a conceptual design of a plant for different gas turbine inlet pressures of 2.5–6.5 MPa and temperatures of 1300 and 1500°C, taking into account the work to produce O2 and capture CO2 . While the net power generating efficiencies of a reference advanced oxy-fuel gas turbine plant are estimated to be about 52.0% and 56.0% at 1300 and 1500°C, respectively, and conventional steam power generation is assumed to have an efficiency of about 35% or less for pressures of 2.5–6.5 MPa, the proposed hybrid plant achieved 42.8–44.7% at 1300°C and 47.8–49.2% for 1500°C. In the proposed plant, the power output contributed by a LCHG may be obtained by subtracting the LNG contribution from the whole net power output. Even supposing that the generation efficiency of the LNG system in the proposed plant remains equal to that of the reference plant (56.0% at 1500°C), some components used in the reference plant are omitted by installation of the LCHG. The efficiency of LCHG system can be estimated 37.4% for 6.5 MPa and 33.2% for 2.5 MPa, even though the LHCG system may be regarded as consisting of fewer plant facilities than a conventional LCHG power plant.

Commentary by Dr. Valentin Fuster
2011;():409-416. doi:10.1115/POWER2011-55366.

In order to spread economically viable distributed generation systems for apartment buildings, it is essential to develop an efficient and low-cost heat supply system. We are developing a new cogeneration system (Neighboring CoGeneration system: NCG). The key concept of this system is to install a heat storage unit with a hot water supply and a room heating function at each household and to connect heat storage units by a single-loop hot water pipe. In this study, a simulator was developed to reproduce the dynamic performance of the NCG system that combined cogeneration with solar heat for 50 households, and the environmental load reduction effects of the system were evaluated on the condition that heat supply to all households was ensured. It showed that the gas engine system reduced the primary energy use by 18% in a year. Meanwhile, the SOFC system reduced the primary energy use by 29%.

Commentary by Dr. Valentin Fuster
2011;():417-425. doi:10.1115/POWER2011-55372.

Combined heat and power (CHP) systems are widely used considering the prevention of global climate change and the reduction of energy costs. In distributed CHP systems, both high efficiency of elements and good coordination of the systems are considered as the points to solve. We had been researched and demonstrated the micro gas turbine CHP system with heat storage at Sapporo City University from April 2006 to March 2010. At first, the start times of microturbine (MGT) and heat storage system (HST) was set up by schedule timers. In 2008 the schedule timers were substituted to a new programmable logic controller (PLC) and the start times of MGT and HST were calculated as the function of temperature outside and room temperature. Setting the start time of MGT at maximum 5 hours before 8:00 and interlocking relays of HST on MGT, the start times were calculated from temperature outside and room temperature at 21:00 the day before. Control of start time using PLC was demonstrated from Feb. 21, 2009 to June 1 and from Nov. 16 to Jan. 7, 2010. It is shown the time series data of temperature and analysis of the CHP with the original boiler heating system.

Commentary by Dr. Valentin Fuster
2011;():427-432. doi:10.1115/POWER2011-55376.

Visualization of dynamic three-dimensional water behavior in a PEFC stack was carried out by neutron CT using a neutron image intensifier for clarifying water effects on performances of a Polymer Electrolyte Fuel Cell (PEFC) stack. Neutron radiography system at JRR-3 in Japan Atomic Energy Agency was used. An operating stack with three cells based on Japan Automobile Research Institute standard was visualized. A consecutive CT reconstruction method by rotating the fuel stack continuously was developed by using a neutron image intensifier and a C-MOS high speed video camera. The dynamic water behavior in channels in the operating PEFC stack was clearly visualized 15 sec in interval by the developed dynamic neutron CT system. From the CT reconstructed images, evaluation of water amount in each cell was carried out. It was shown that the water distribution in each cell was correlated well with power generation characteristics in each cell.

Commentary by Dr. Valentin Fuster
2011;():433-438. doi:10.1115/POWER2011-55379.

The green house effect by carbon dioxide issue would make better recognizing the importance of efficient use of energy in terms of high energy conservation measures. Accordingly, attention is drawn to the Stirling cycle machine, which is a perfect Freon free and efficient machine. Most Stirling engines operate in temperature ranges in which the temperature difference between the heat source and heat sink is between 100 K and 700 K, with the room temperature being at the lower end of the operating temperature range. However, information available on engines that utilize the room temperature as the heat source and the ultra-low temperature of liquid nitrogen as the heat sink is scarce. Engines that operate within such temperature ranges are called cryogenic heat engines. If their practical applications are realized, energy that has hitherto been wasted during the use of ultra-low-temperature media can be recovered in the form of electrical energy. We have designed and developed a 500 W class Stirling machine as a cryogenic engine. This paper presents some operating characteristics.

Commentary by Dr. Valentin Fuster
2011;():439-445. doi:10.1115/POWER2011-55381.

Recently, cutting the CO2 emissions has been the worldwide problem. In order to reduce the CO2 emissions, it is important to promote the energy conservation and introduce the sustainable natural energy. In this paper, we have been studied to develop a combination energy system of the energy conservation and the natural energy in the Okayama Prefectural University. We have a result that it is possible to cut off the 36% or more CO2 emission with the combination of (1) replacing the air-conditioner from the absorption type to a heat pump type, (2) introducing photovoltaic power generation and (3) changing the car that is used for commute from the internal-combustion engine type to an electric vehicle (EV). In addition to cut the CO2 emission, the studied combination energy system can be presented the high economically method.

Commentary by Dr. Valentin Fuster
2011;():447-452. doi:10.1115/POWER2011-55393.

A catalyst plays an important role in fuel cell because of promotion of chemical reaction for room temperature type fuel cell. In general, platinum is adopted as a catalyst even though it is very expensive. An ascorbic acid aqueous solution is able to react without catalyst for the oxidation reaction. At first, authors made sure of generation of the electric output using ascorbic acid for fuel without the catalyst. Next, we were able to increase the electric output with adding to metal ions to ascorbic acid aqueous solution. Finally, high and stable electric output was obtained by using the chelating agent.

Topics: Ions , Copper , Fuel cells
Commentary by Dr. Valentin Fuster
2011;():453-459. doi:10.1115/POWER2011-55394.

Reduction of global carbon dioxide emissions is one of the most critical challenges for realizing sustainable society. In order to reduce carbon dioxide emissions, energy efficiency must be improved. Waste heat recovery with external combustion engine is expected to be one of the promising technologies for efficient energy utilization. However, the temperature of waste heat is getting lower with the progress of energy technologies. For example, in Japan which is known as one of the most energy-efficient countries in the world with advanced technologies such as cogeneration and hybrid automobiles, total amount of disposed heat below 300 °C is as much as 10% of the total amount of primary energy supply. Conventional external combustion engines, such as Stirling, thermoacoustic1 and steam engines2 show significant decrease in their efficiency at low temperatures below 300 °C. Utilization of high-temperature heat sources, however, requires relatively expensive materials and advanced processing technologies to achieve high reliability. In order to overcome these issues, a novel liquid-piston steam engine is developed, which achieves high efficiency as well as high reliability and low cost using low temperature heat below 300 °C. Present liquid-piston steam engine demonstrated a thermal efficiency of 12.7% at a heating temperature of 270 °C and a cooling temperature of 80 °C, which was about 40% of the Carnot efficiency operating at same temperatures. The liquid-piston steam engine operated even with wet steam, without requiring steam to be superheated. This low temperature operation yielded relatively little deformation of components, which leads to high reliability of the engine. In addition, present liquid piston engine can achieve both high efficiency and low cost compared to conventional external combustion engines, because it has only one moving part whereas both Stirling and Rankin engines have at least two moving parts. The developed liquid piston engine is thus expected to possess large possibility of recovering energy from waste heat.

Topics: Engines , Pistons , Steam
Commentary by Dr. Valentin Fuster
2011;():461-466. doi:10.1115/POWER2011-55400.

Based on the mode of off-grid and supplying power for a 10,000 Chicken Farm, there is a experimental study and energy efficiency analysis on a biogas CHP. The results indicate that, the biogas CHP system can satisfy the demand on heating of biogas digester and electricity of farm’s. Reusing the gas-fired remaining heating powered in the internal engine to heat the digester, it can guarantee the temperature in the biogas digester between 32°C and 34°C, even if the climate is very cold. The power load vary obviously in 24 hours, power efficiency and energy efficiency of the biogas CHP plant increase with increasing of the power load of the farm. In low power load operation, the power generation efficiency and energy efficiency of entire system is very low, respectively 4.3%–19%, with the increasing of the load, the measured power efficiency is up to 19.2% when energy efficiency up to 47%, which is lower than that of the fossil CHP. By analyzing the main reason, it is found that the off-grid mode restricts the power load to vary with that of the farm passively, the heat efficiency exchanging is low between the cylinder water and the flue gas heat exchanger of the system, need to be reconstructed and installed gear change iso-frequency mechanism for decreasing the in-gas-fired quantity.

Commentary by Dr. Valentin Fuster
2011;():467-474. doi:10.1115/POWER2011-55453.

Silicon cell is one of the promising technologies which can convert the incident solar radiation into electric power directly. Meanwhile, PV conversion is a highly spectrally dependent quantum process and most silicon PV cells have good spectral response from 400nm to 1100nm. In this paper, a solar beam splitting technology is introduced, which uses an optical thin-film filter that can be applied to hybrid solar system such as photovoltaic/thermal (PV/T) systems. In addition, we summarize the filter design theory and the performance of optical dielectric thin-film interference filter. The next parts of this paper involve the calculation of the cell temperature and efficiency including the analyze models and results. The final conclusion is that, at the same condition of incident solar radiation and cooling effect, the cell efficiency is higher in the solar splitting system compared to that without splitter.

Commentary by Dr. Valentin Fuster
2011;():475-483. doi:10.1115/POWER2011-55456.

Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) is expected to be the most efficient power generation system in coal fired power generation systems [1,2]. We have been analyzing the processes of Advanced IGFC (A-IGFC) [3] which is expected to be realized in 2040. The Advanced IGFC (A-IGFC) system can reduce the exergy loss resulting from combustion, and its ‘exergy recuperation’ [4] is appealing. The waste heat exhausted from the fuel cells is recycled to the gasifier for steam reforming in an endothermic reaction with a low exergy loss and a high cold gas efficiency. Our current study focuses on the optimization of the unit configurations of the A-IGFC including gasifier, compressor, solid oxide fuel cell (SOFC), combustor, gas turbine, heat recovery steam generator (HRSG), and steam turbine. The process simulator HYSYS®.Plant (Aspen technology Inc.) is employed in order to express the gasifier, the SOFC and the other units. The process of reforming with steam means recycled steam stream in the HYSYS® model. In the previous study [3] we found that many recycled material streams and recycled steam in the AIGFC process prevent convergence of solver. It is shown that comparison of simulation program, a trial analysis of the AIGFC process using HYSYS.Plant and the problems about convergence of solver.

Commentary by Dr. Valentin Fuster
2011;():485-492. doi:10.1115/POWER2011-55458.

To cope with global warming problem, utility companies are required to reduce CO2 emission from pulverized coal fired power plants. Japanese utility companies are advancing various measures to improve plant thermal efficiency and to promote utilization of biomass as a fuel. In Europe and America, CO2 capture and storage (CCS) technology is regarded as one effective approach, and various demonstration projects are planned all over the world. However, the introduction of conventional CO2 capture system to power station causes a decrease in the plant thermal efficiency and an increase in the power generating cost. In this reason, it is necessary to develop a new power generating system with high thermal efficiency. Therefore, Central Research Institute of Electric Power Industry (CRIEPI) proposed an innovative integrated coal gasification combined cycle power generating system (IGCC) with CO2 capture whose plant thermal efficiency is very high, and is working on the research and development of the new system. This is a system to combine a new oxygen-CO2 blown coal gasifier in that captured CO2 is used with the closed gas turbine in which coal gas from the gasifier is burned with the gas mixed oxygen and recycled exhaust CO2 . The system has the following features. The gasification performances improve greatly. The processes of concentrating and separating CO2 are unnecessary. It is estimated that the carbon conversion efficiency (CCE) and the cold gas efficiency (CGE) in oxygen-CO2 blown gasifier improve more than conventional oxygen blown gasifiers by the effect of the gasification reaction promotion of CO2 by gasifying coal with oxygen and CO2 . As a result, the gasifier and the char recycling system can make to compact, and the equipment cost can be reduced. This paper reports on examination of CO2 promotion effect on the gasification performances by gasification test using a bench scale gasifier facility.

Commentary by Dr. Valentin Fuster

Renewables (Wind, Solar and Geothermal)

2011;():493-499. doi:10.1115/POWER2011-55070.

The reduction in cost of energy from wind turbines requires many technical contributions from all areas of Wind Energy Conversion Systems. The concept of a telescopic blade has been analyzed to improve rotor blade performance. The effect of a step change is significant for any extension. The current simulation model in WT Perf with a Prandtl tip and hub loss model over-predicts the rotor performance. The correlations developed herein for telescopic blades with step change in the blade chord are in good agreement with the experimental data. The maximum loss for a rotor blade with a step change occurs when the extension is equal to the root blade chord.

Commentary by Dr. Valentin Fuster
2011;():501-505. doi:10.1115/POWER2011-55200.

In the last five years the electric grid worldwide has seen increasing amounts of installed wind generation capacity. Over the last five years, North America (USA and Canada) has witnessed wind capacity grow at an annual rate of over 30%. At the same time, increasing investments in smart grid technologies have enabled improvements in energy products such as Demand Response (DR). The utility industry, system operators and regulators are investing heavily to understand and determine the impacts of increasing wind penetration on the power system. As explored below, an often neglected, but important point of interest to the authors has been the effect of increased cycling of large fossil, formerly base loaded power plants due to increasing penetration of variable wind or solar power. Various types of DR programs have been implemented by utilities and system operators and these DR programs may be classified based on the time it takes to call upon a DR event or the energy market that the programs are allowed to participate within. Hence, we may have a “slow” DR that participates in a Day-Ahead market and the events are called upon well in advance. On the other hand, “fast” DR programs would participate in Real-Time and Ancillary Services markets. DR from a power dispatch perspective can be considered a “virtual power plant” providing energy, ancillary service and capacity in energy markets. Energy benefits of DR have been explored extensively, especially in terms of reduced fuel costs due to reduction in demand. In this paper we explore the conceptual use and value of DR in providing benefits associated with reduced damage to a fleet of fossil-fueled power plants if it is used to reduce startups and/or load following/cycling.

Topics: Smart grids , Wind
Commentary by Dr. Valentin Fuster
2011;():507-516. doi:10.1115/POWER2011-55226.

The aerodynamics of a straight edged and a swept edged blade are investigated using a commercial CFD code. RANS equations with SST k-ω equation were utilized to study the flow separation along the blades span in a stall region. The analysis results will be used to provide inputs to future designs to improve and to enable better prediction of the stall region. The computations were carried out in a narrow wind speed range of 14 m/s to 16 m/s which as per earlier analysis was near the stall point to further understand the locations of flow separations along the blade span. The study provides some insights in to the flow physics in the region around the wind turbine blade. An FE Analysis was also performed to further understand the maximum stress and displacement regions to further provide inputs to future designs. A comparison of maximum stress, deformation and structural vibration modes for the two blades were also done.

Commentary by Dr. Valentin Fuster
2011;():517-522. doi:10.1115/POWER2011-55243.

Monitoring of photovoltaic (PV) systems is essential for achieving reliable and, maximum yield from solar PV plants. This paper proposes PV plant hierarchy, and a novel near real-time monitoring system combined with a solar tracking controller for utility scale PV installations. Currently, most PV installations employ monitoring at the inverter level, lacking sufficient resolution. Furthermore, the solar tracking and performance monitoring systems are isolated from one another. The proposed design increases monitoring resolution, allowing PV malfunctions to be addressed immediately, effectively optimizing a plant’s power generation. Moreover, the tracker control and monitoring are fused into an inclusive hardware design. Incorporating state-of-the-art electronic sensors, coupled with wireless communication protocols, the resulting system is a robust, accurate sensor and control network. Accessible through the internet, the system will provide a way to monitor and control multiple installations from a centralized location. The collected data enables efficient maintenance scheduling, and long-term performance analysis for utility scale PV plants. The developed system includes string level power measurement sensors, sun tracking actuators, a network of microprocessors and a central processing unit (CPU) for application in utility-scale central inverter PV plants. The basic designs and feasibility of the system are presented in this paper.

Commentary by Dr. Valentin Fuster
2011;():523-529. doi:10.1115/POWER2011-55248.

The movement for energy independence coupled with aggressive renewable energy goals and government investment incentives has led the power industry to develop efficient and reliable sources of renewable power. In a power tower system a central Solar Receiver Steam Generator (SRSG) is surrounded by a field of mirrors (heliostats) that focus and concentrate sunlight onto the receiver tubes. The energy from the sunlight is used to generate and superheat steam for electric production. The Ivanpah Solar Electric Generating System (ISEGS) project, located in Ivanpah, CA, consists of three 126 MWg units, to power approximately 140,000 homes. The Ivanpah SRSG’s are forced circulation drum-type boilers with single reheat; located on top of a 400 ft (122 m) steel tower [1]. This paper will discuss the development, constraints, and unique design challenges of the Riley Power Inc. (RPI) SRSG selected for the Ivanpah project. Process descriptions and predicted unit performance are presented, along with comparisons to typical fossil boilers. First of kind concepts and engineering design achievements are discussed for what will be the largest power tower project in the world.

Commentary by Dr. Valentin Fuster
2011;():531-535. doi:10.1115/POWER2011-55358.

A series of laboratory experiments on self-circulating thermosyphon (SCT) was carried out. The thermosyphon system consists of heating section, condenser, reservoir, and heat exchanging section. The basic performance was elucidated. The present thermosyphon system works by itself under certain conditions of tilting angle of the condenser, the water filling rate, and the input power. The startup time of the present system is remarkably improved. The effect of the buoyancy on the driving force is indicated through the tilting angle of the condenser.

Commentary by Dr. Valentin Fuster
2011;():537-543. doi:10.1115/POWER2011-55364.

In this paper, a hydroelectric power generator that can extract the water flow energy from the hydroelastic response of an elastically supported rectangular wing is experimentally investigated. An electric motor is used to excite pitching oscillations of the wing. The wing and the electric motor are supported by leaf springs that are designed to function both as a linear guide for the sway oscillations and as elastic elements. The wing mass in the sway direction necessary to achieve a hydroelastic response is obtained by utilizing a mechanical snubber mechanism. The load to generate electricity is provided equivalently by magnetic dampers. In a previous paper, the power generation rate and the efficiency of a single-wing model were examined through experiments, and the feasibility of a flapping wing hydroelectric power generator was verified. In this paper, the influence of neighboring wings is examined by using two experimental apparatuses with the intention of achieving a practical cascade-wing generator. Tests showed that a cascade moving in-phase with neighboring wings with smaller gaps between the wings has a higher rate of electric power generation.

Commentary by Dr. Valentin Fuster
2011;():545-549. doi:10.1115/POWER2011-55369.

As more and more wind turbines and farms are constructed in Japan, utility companies have introduced a grid code, which is effective in controlling the grid frequency. We designed a hybrid system by combining charge/discharge properties of lead-acid batteries with long life, and a power control of wind turbines to ensure the code. We also constructed a wind farm with this system in Shiura, Japan, which went into operation in January 2010. This system showed reduction in wind farm power fluctuation, and that battery capacity can be maintained for 17 years.

Commentary by Dr. Valentin Fuster
2011;():551-555. doi:10.1115/POWER2011-55373.

Geothermal energy is considered a comparatively abundant renewable energy resource. The geothermal power generation system has negligible environmental impact (approximately 0.015kg-CO2 /kWh), and it is expected to help prevent carbon dioxide emissions to the atmosphere. On the other hand, in our institute, we have developed general purpose software (EnergyWin™) to analyze the thermal efficiencies of power generation systems easily and rapidly. Such software can not only analyze the plant performance but also investigate the effect of the performance-deteriorated equipment or air condition change on power output quantitatively. Using this software, we have developed a new plant performance analysis system based on actual operation data for geothermal power plants. Then, applying the system to existing facilities, we have analyzed the plant performance and evaluated the effectiveness of the plant maintenance strategy during periodic inspection for consistency.

Commentary by Dr. Valentin Fuster
2011;():557-561. doi:10.1115/POWER2011-55385.

This paper describes the wind direction characteristics of the wind collector used for our 8th model of the vertical axis wind turbine using the mechanism of a bird’s wing. The 8th model is divided into two sections top and bottom. Each section looks like a Savonius wind turbine. The blade is divided into seven rows of plates. Each 0.18mm stainless plate has only one side attached to the frame. Wind from the outside enlarges the space between the blades, and passes through. However, wind from the inside closes the space. In the wind collector, four wind collection boards are located every 90 degrees around this wind turbine. In an earlier paper, it was confirmed that these collection boards collected 1.6 times the wind and resulted in twice the output. In this paper, the variations in the wind collector characteristics due to the wind direction are clarified experimentally. A wind tunnel experiment using six different wind directions shows that the output increases for four wind directions and decreases for one wind direction. Additionally, the computer simulation confirms the wind direction and the wind speed distribution around the wind turbine when the wind collection boards are in place.

Commentary by Dr. Valentin Fuster
2011;():563-568. doi:10.1115/POWER2011-55408.

In this paper, in order to solve the problem of intensified heat dissipation in high power electronic devices, a fast transient and intensified heat dissipation technology was put forward by comparing many heat transfer modes based on the analytical study on the existing technologies about heat dissipation at high heat flux density and about fast heat transport. This technology combined spray cooling technology with fast endothermic chemical reaction processes; we summarized the characteristics of media applicable to an environment with transient high heat flux density by comparing various parameters of many sprayed media in the spray cooling process. According to the energy balance of endothermic chemical reactions of relevant media, we determined the media (mainly carbon dioxide hydrate) applicable to the fast transient and intensified heat dissipation technology and presented the conditions for the chemical reactions. We analyzed the methods controlling the instantaneous chemical reaction rate and proposed the structural characteristics of the chemical reactor so as to ensure that the time for heat removal will be control to around 0.01 second. Thus, the problem of fast transient heat dissipation in high power electronic devices, etc. would be radically solved.

Commentary by Dr. Valentin Fuster
2011;():569-573. doi:10.1115/POWER2011-55428.

As the single unit capacity has been increased, the length of wind turbine blade is becoming longer, and the blade vibration fatigue damage caused by impact of wind turbines has become an important issue of wind turbine security. Therefore, modal analysis and study on the impact of crack on the natural frequency of the wind turbine blade are of great significance. The finite element software ANSYS was used to establish a finite element model of a 1.5MW composite wind turbine blade, with a structure of twisted variable cross-section and hollow core in the first place of this paper. Modal analysis of the model established in this paper showed that the blade vibrates in 3 different forms, they are flap within the rotating plane, flutter vibration perpendicularity to the rotating plane and torsional vibration around the blade shaft. Among all the orders, flap and flutter vibration are predominent in low modes, while torsional vibration appears only in high modes (above the fifth order). Then blade models with cracks in the root were established to analyze the regularity of the blade natural frequencies with the crack location, depth and the variation of the angle. The results showed that: as the location of the crack changed in wingspan direction, the change of frequencies showed two basic trends: one was declining gradually; the other was decreasing and then increasing before decreasing again, and the minimum the maximum value appeared at location around 32.5% and 87.5% of the blade root respectively. As crack depth increased gradually, the frequencies reduced continuously, and compared to crack location, influence of crack depth was more prominent. For slant crack, when the crack angle, that is the angle between the crack section chord line and the foliosine plane, increased, all orders of frequencies gradually increased, indicating that the influence of the crack on the blade stiffness decreases as the angle increases.

Commentary by Dr. Valentin Fuster
2011;():575-579. doi:10.1115/POWER2011-55439.

In this paper, building simulation software Energy Plus was used to simulate thermal performance, and PV electricity generation of five kinds of glazing system install on the office building in four cities of China, Harbin, Beijing, Shanghai, and Shenzhen, which represent severe cold zone, cold zone, hot summer and cold winter zone, hot summer and warm winter zone respectively. According to the simulation results, the best glazing system for the severe cold zone Harbin and the cold zone Beijing is double PV system, while natural ventilated PV system for the hot summer and cold winter zone Shanghai, the hot summer and warm winter zone Shenzhen. The energy saving rates of the optimal PV glazing system compared to the local SC at Harbin, Beijing, Shanghai, and Shenzhen are 12.3%, 4.9%, 4.8%, 10% respectively.

Topics: China
Commentary by Dr. Valentin Fuster
2011;():581-586. doi:10.1115/POWER2011-55459.

The increased integration of wind power into the electric grid poses new challenges due to its fluctuation and volatility. Short term wind power forecasting is one of the most effective ways to deal with it. Various individual non-linear models are proposed to meet the data requirement to forecast short term wind power. However, as every model has its advantage and weakness, when these models are applied to different wind farms, the forecasting accuracy of every model varies because of distinct data character. This paper analyzes individual forecast models like Wavelet Transform and Support Vector Machine (SVM), and then puts forward a complex-valued forecasting model which is based on Artificial Natural Network in accordance with forecasting data provided by National Climatic Data Center in U.S. The existing individual models are matched and trained according to certain means by Natural Network to propose a multistage model. For variable data from different wind farms, the model can adjust and optimize portion of individual models. Compared with each single model, the multistage model has more robust adaptation and faster calculation speed, which can improve the forecasting precision and have more engineering value.

Commentary by Dr. Valentin Fuster

Thermal Hydraulics and CFD

2011;():587-596. doi:10.1115/POWER2011-55033.

For efficient cooling applications in power plants, the use of small two-phase natural circulation loops becomes attractive. An experimental study was carried out to examine how thermal hydraulic stability and operation conditions of these devices are affected by nucleation sites. A very smooth glass tube with artificial nucleation sites have been employed as boiling channel. The mass flow rate has been determined as function of heat flux and nucleation site location. Particular for low heat flux levels, the nucleation sites have a strong impact to the stability behavior. The observed flow instabilities have been analyzed with regard to non-linear effects and chaotic behavior.

Commentary by Dr. Valentin Fuster
2011;():597-609. doi:10.1115/POWER2011-55077.

During the startup of a new fossil power plant, a high level of fly ash accumulation (higher than predicted) was encountered in the flue gas ducting upstream of a fluidized bed scrubber. The level of fly ash accumulation made it necessary to manually withdraw fly ash using a vacuum truck after short periods of operation, at less than 80% maximum continuous rating (MCR). This paper presents a simple method for rapid assessment of fly ash accumulation in flue gas ducts using steady state single phase Computational Fluid Dynamics (CFD) simulation of flue gas flow. The propensity for fly ash accumulation in a duct is predicted using calculated wall shear stresses from CFD coupled with estimates for the critical shear stresses required for mobilization of settled solids. Critical values for the mobilization stresses are determined from the Shields relations for incipient motion of particles in a packed bed with given fly ash particle size and density as inputs. Solids accumulation is possible where the wall shear stress magnitude is less than the critical shear stress for mobilization calculated from the Shields relations. Predictions of incipient fly ash accumulation based on the coupled CFD/Shields relations model correlate well with plant startup field observations. Fly ash accumulation was not observed in a related physical scale model test. A separate CFD/Shields relation analysis of the scale model physical tests show that the wall shear stresses in the scale model are several times larger than the critical value required for the mobilization of the fly ash simulant. This study demonstrates that a simple steady state, single phase CFD analysis of flue gas flow can be used to rapidly identify and address fly ash accumulation concerns in flue gas duct designs. This approach is much simpler and computationally inexpensive compared to a transient Eulerian multiphase simulation of particle laden flow involving handling the dense phase in regions of ash accumulation. Further, this study shows that physical model tests will be accurate for predicting fly ash accumulation, only if, the scaling maintains the proper ratio of wall shear stress to critical remobilization stress.

Commentary by Dr. Valentin Fuster
2011;():611-618. doi:10.1115/POWER2011-55110.

A computational model is developed in order to investigate pollutant emissions from power plant boilers to the atmosphere. A well-known method of pollutant reduction is the modification of the combustion conditions to prevent their formation, and 3D computational fluid dynamics (CFD) codes provide an effective tool for the analysis of the combustion process. In this paper CFD calculations were performed to analyze the effect of the amount of combustion air on the production and emission of nitrogen oxides, one of the main pollutants produced during the combustion process. For this analysis the appropriate modeling of the chemical and physical phenomena involved is important, because the production and transport of pollutant species strongly depend on the flow and temperature distributions in the furnace. Two case studies are presented: a pulverized coal-firing tangential boiler and a fuel-oil frontal boiler. The CFD calculations adopt a 3D-formulation of the mean flow equations in combination with the standard high-Reynolds-number k-ε turbulence model. The model domain consists of the whole boiler, from the burner nozzles up to the exit of the economizer. Due to their complex geometrical features and computational limitations bank tubes are not modeled individually, but are grouped in a total volume. A porous media region approach is then undertaken to model gas flow and heat transfer in each heat exchanger. Model validation is a difficult task due to the lack of available data from commercial utilities. Validation has been done using routinely measured global parameters. Relatively good agreement is obtained. Results show that increasing the amount of air reduce nitrogen oxides formation for the case of the tangential boiler, however for the frontal boiler case this behavior is not as evident. These results demonstrate that CFD simulations are a viable tool to study the effect some combustion parameters have on the production of pollutants. CFD results may help to establish trends that, in turn, may help to reduce pollutant emissions from power plant boilers.

Commentary by Dr. Valentin Fuster
2011;():619-625. doi:10.1115/POWER2011-55124.

The thermal-structural analysis of the super-heater tubes for a 158 MW unit, applying FLUENT® (CFD) and ANSYS® (FEA), is presented. The analysis includes the spacers (union piece between tubes), welding and tubes. The failures of these elements are related with the operation of the unit and the selection of the weld and materials involved in the affected zone. The distribution of temperature in each metal depends of the thermal conductivity and coefficient of thermal expansion, provoking stress concentration in the rigid zones. The CFD study considers a three-dimensional model where the conjugate heat transfer, including internal flow (steam) and external flow (gases), was analyzed to full load of the unit in steady state. In the FEA study, the thermal-structural stresses were analyzed considering the temperature distribution obtained from the CFD study. The results obtained show that the spacer is of greater temperature than the tubes, provoking gradients of temperature through tube walls, spacers and welds. The highest stress located on the interior tube wall (on the direction of plane where the spacer is welded) is attributed to the different thermal dilatation and pressure expansion of the tube, spacer and weld. The study includes the analysis of some geometries of the union piece (spacer) to release the thermal-structural stresses.

Topics: Superheaters
Commentary by Dr. Valentin Fuster
2011;():627-637. doi:10.1115/POWER2011-55202.

In 2006, the first Computational Fluid Dynamics (CFD) simulations of the ventilation of specific hydro-generator components were performed at the Hydro-Québec Research Institute (IREQ) and lately the entire ventilation circuit is being investigated. Due to the complexity of flow calculations, a validation process is necessary and for this reason a 1:4 scale model of a hydro-generator has been built at IREQ to get experimental data by means of particle image velocimetry (PIV). This paper presents 2D and 3D simulation results for the scale model obtained with a commercial CFD code and addresses the challenges associated with the application of CFD to hydro-generators. In particular, the effect of rotor-stator interface (RSI) types and configuration is analyzed to determine the approach that best suits this application. Two-dimensional calculations show that the steady state multiple frames of reference (MFR) solution is highly sensitive to the type (frozen rotor (FR) vs. mixing plane (MP)) and location of the RSI. A parametric study is performed where each interface configuration is compared to the transient case results. The MFR-FR interface model produces results that may vary significantly depending on the relative rotor position and the radial location of the RSI in the air gap. The MFR-MP interface model appears to be more coherent with reference values obtained from a transient case, since the radial velocity profiles in the stator are similar. Furthermore with an appropriate radial positioning of the interface, the windage losses are within 20%. Simulations of the complete 3D ventilation circuit revealed a maximum variation of 10% in both total ventilation flow rate and total windage losses, between the RSI configurations studied. However, the relative flow distributions, normalized with respect to the total flow rate, are unaffected by changes in RSI configuration. This paper focuses mainly on sensitivity studies to numerical settings, but this comparison still requires experimental validation before any final conclusions can be made.

Commentary by Dr. Valentin Fuster
2011;():639-644. doi:10.1115/POWER2011-55398.

Axial microfan is widely used as cooling equipment for electronic devices such as PCs. Currently, the PC size becomes smaller and smaller while their operating speed becomes faster and faster, which calls for better cooling performance of axial microfan. As an important and effective design approach, the similitude design has been widely used in the design of large and medium fans, but not yet in the design of axial microfan. The traditional similitude design approach may work well in self-similitude area for Reynolds number, such as the flow inside the large and medium fans, where simple geometric similitude can promise the aerodynamic similitude. But the flow inside the microfan locates in non self-similitude area for Reynolds number, where the traditional similitude design for large and medium fans may be out of work on microfans, which results in poor performance of the microfan designed by the traditional similitude approach. In this paper, the aerodynamic similitude conditions for axial microfan are presented according to the similitude principle for aerodynamics. Compared to large and medium fans in self-similitude area, a new criterion called ‘Chord Reynolds Number Criterion’ suitable to the flow in non self-similitude area is proposed and is numerically validated with discussions on its applicability and limitation. Results indicate that ‘Chord Reynolds Number Criterion’ can well realize the aerodynamic similitude for the axial microfan but it requires that the revolution speed of the impeller should be in direct proportion to the squared minification of the model impeller, so the reduced scale of model impeller shall not be too large, otherwise new non similitude factors may occur again due to too high revolution speed.

Commentary by Dr. Valentin Fuster
2011;():645-652. doi:10.1115/POWER2011-55435.

The present paper is devoted to clarify the effect of buoyancy on the flow and heat transfer of supercritical pressure water flowing in horizontal pipes at supercritical pressures. A series of experiments have been designed and carried out in Xi’an Jiaotong University, Xi’an, China to obtain data in relation to flow and heat transfer of supercritical pressure water in pipes with different arrangements. The experimental parameters are as follows: pressures ranging from 23 to 28MPa, heat flux being up to 600 kW/m2 , and the fluid mass fluxes being in the range from 100 to 1000kg/(m2 s). In this study, distributions of the local wall temperatures and the local heat transfer coefficients around the circumference of the tube are measured at different cross-sections along the flowing direction. On the basis of the experimental data obtained in the study, some criteria available in open literatures, including Gr/Re2.7 , Gr/Re2 , and Grq/Grth, are employed to estimate the magnitude of buoyancy and the effect of buoyancy on the flow and heat transfer behavior of the supercritical fluid. It is showed that buoyancy is of particular importance for horizontal flows, but play significantly different role in different regions having different characteristics of the specific heat capacity. Strong buoyancy effect exists in the large specific heat region, but in the enthalpy region which is far away from the LSHR, the discrepancy between the temperature of the top wall and that of the bottom wall is small, indicating that the buoyancy effect can be negligible. Based on the present study, it was found that the criteria Grq/Grth is better than others in terms of the capability of evaluating the effect of the buoyancy on the flow and heat transfer of supercritical water.

Commentary by Dr. Valentin Fuster
2011;():653-660. doi:10.1115/POWER2011-55437.

Based on the single blow technique, experimental research was conducted for the performance of heat transfer and flow drop for six test cores with cross corrugated (CC) or corrugated undulated (CU) primary surfaces for different geometries. After the mathematical model was established for heat transfer under the condition of single blow, a matching numerical solution was obtained for different NTU. The correlations of hear transfer factor j and friction factor f were obtained for three types of cross corrugated primary surfaces (crossed angle 45∼75°) with a range of Re = 120∼800 and three types of corrugated undulated primary surfaces (crossed angle 52.5∼67.5°) with a range of Re = 200∼1200. Hydraulic diameters of all heat transfer surfaces are from 1.2∼1.48mm. Analysis on the flow and heat transfer for cross corrugated and corrugated undulated primary surfaces was made based on the comprehensive evaluating factor j/f. The experimental results were compared to references with good consistency. The regressive errors of correlations were less than 16%.

Commentary by Dr. Valentin Fuster

Performance Testing and Performance Test Codes

2011;():661-668. doi:10.1115/POWER2011-55123.

Many modern power plants feature gas turbines with advanced control systems that allow a greater level of performance enhancements, over a broader range of the combined-cycle plant’s operating environment, compared to conventional systems. Control system advancements tend to outpace a plant’s construction and commissioning timescale. Often, the control algorithms and settings in place at the final guarantee performance test will differ significantly from those envisioned during the contract agreement phase. As such, the gas turbine’s actual performance response to changes in boundary conditions, such as air temperature and air humidity, will be considerably different than the response illustrated on the initial correction curves. For the sake of technical accuracy, the performance correction curves should be updated to reflect the as-built, as-left behavior of the plant. By providing the most technically accurate curves, the needs of the new plant performance test are satisfied. Also, plant operators receive an accurate means to trend performance over time. The performance correction curves are intended to provide the most technically accurate assurance that the corrected test results are independent of boundary conditions that persist during the performance test. Therefore, after the gas turbine control algorithms and/or settings have been adjusted, the performance correction curves — whether specific to gas turbines or overall combined-cycle plants — should be updated to reflect any change in turbine response. This best practice maintains the highest level of technical accuracy. Failure to employ the available advanced gas turbine control system upgrades can limit the plant performance over the ambient operating regime. Failure to make a corresponding update to the correction curves can cause additional inaccuracy in the performance test’s corrected results. This paper presents a high-level discussion of GE’s recent gas turbine control system advancements, and emphasizes the need to update performance correction curves based on their impact.

Commentary by Dr. Valentin Fuster
2011;():669-676. doi:10.1115/POWER2011-55137.

ASME Performance Test Code PTC 4 for “Fired Steam Generators” superseded previous Code PTC 4.1 in 1998[1][2] . PTC 4 corrects many of the deficiencies in PTC 4.1 and makes testing more accurate and easy to integrate into plant performance tests. PTC 4.1 however continues to be used in many parts of the industry mainly due to its simplicity and ease of use. The use of both PTC 4 and PTC 4.1 has caused confusion. Direct comparison of testing results obtained in accordance with the two Codes may lead to wrong conclusions. Fundamentally, PTC 4 is a more technically sound and comprehensive Code than PTC 4.1 was. The calculation procedures of PTC 4 are intended to produce more accurate loss results and reduce the uncertainty. For example, the surface radiation and convection losses are measured instead of estimated, and the un-measured minor losses must be estimated individually if not measured, with appropriate uncertainty values. Therefore, the level of uncertainty associated with the estimate of unmeasured losses commonly assumed by a lump sum value in PTC 4.1 would normally be greater than that associated with the individually estimated losses by PTC 4. This paper presents a study of steam generator efficiency and fuel flow for a 700MW net coal-fired power plant with the application of both PTC 4 and PTC 4.1 Codes. Without considering the differences in uncertainty analysis, radiation / convection losses, and un-measured losses / credits, it is found that the results of tests conducted by the two methods vary marginally, given that the gross efficiency in the scope of PTC 4.1 is converted into the fuel efficiency as defined by PTC 4. The difference between the PTC 4 and 4.1 efficiencies is principally due to the energy credits associated with auxiliary equipment power consumption. The paper also discusses differences in efficiency definitions, efficiency conversions, and fuel flow calculations between the two Codes.

Topics: Boilers , Coal
Commentary by Dr. Valentin Fuster
2011;():677-686. doi:10.1115/POWER2011-55148.

The publication of ASME Performance Test Code 6.2-2004 provided the industry with a Code document dedicated to calculating the performance of a steam turbine in a combined cycle power plant. Power output at specified steam flows and conditions was chosen as the Code’s primary performance parameter. That choice was based on the operating and cycle characteristics of a combined cycle plant operating, where the steam turbine is part of the bottoming cycle operating in a sliding pressure mode that follows ambient conditions and the gas turbine operating profile. This steam turbine generator output, corrected to reference heat consumption, is called Output Performance and is a measurement of steam turbine efficiency. Accompanying this new Code was a new correction methodology that focused on correcting the steam turbine generator output to the reference heat consumption of the cycle. In the development of the overall correction methodology, the corrections associated with high-pressure (HP) steam inlet conditions were given careful attention. The committee developing the Code and methodology concluded that three correction formulations were required to accurately and fairly correct back to the reference heat input of the high-pressure turbine inlet, and to account for changes in the as-built flow capacity versus the design flow capacity. The new correction formulations chosen were: • HP Steam Flow; • HP Steam Temperature; • HP Turbine Flow Capacity. Applying these three corrections on a sliding pressure steam turbine ensures that the output performance is corrected to the true reference high pressure steam heat input to the cycle. If any of these three corrections is excluded the calculated output performance will not be a true representation of the steam turbine efficiency.

Commentary by Dr. Valentin Fuster
2011;():687-692. doi:10.1115/POWER2011-55149.

Since its publication in 1996, ASME PTC 46 Performance Test Code on Overall Plant Performance has established itself as the premier test code for conducting overall plant performance within the power industry, especially for combined cycle power plants. The current text within ASME PTC 46, which is currently under revision by the ASME PTC 46 Committee, describes in Section 5.3.4 Specified Measured Net Power that “This test is conducted for a combined cycle power plant with duct firing or other form of power augmentation, such as steam or water injection when used for that purpose.” Further, the only example problem for a combined cycle with duct firing is provided in Appendix B of the code utilizing the Specified Measured Net Power Test Method. Though the text and example are correctly presented within the code, it resulted in misinterpretation within the industry that the only correct way to test a combined cycle plant with duct firing was to conduct a Specified Measured Net Power Test. Though the Specified Measured Net Power Test Method is an acceptable and accurate method in determining the performance of a combined cycle plant with duct firing in operation, it lends to being inflexible to the weather conditions for the plant operation. When the weather is too cold, the exhaust energy from the combustion turbines may be at such a magnitude as to not allow the duct burners to be fired due to limitations within the heat recovery steam generator and steam turbine systems to take the load, thus limiting the plant testing to take place when the weather is warm enough to allow the plant to be operated with duct firing. The opposite condition can also exist where the ambient conditions are too hot so that the duct burner capacity is unable to achieve the specified measured net power allowing the test to be conducted. The limitations stated herein are the reasons that an alternative approach with more flexibility is necessary. This paper will present an alternative approach referred to as the Fixed Duct Burner Heat Input Test Method to testing combined cycle plants where the duct burner heat input (Fuel Flow) is held fixed while the plant net power and heat rate are left to float with ambient conditions. Corrections for both power and heat rate will be developed for ambient conditions per ASME PTC 46 guidelines. This paper will further present a comparison between the Specified Measured Net Power Test Method and the Fixed Duct Burner Heat Input Test Method in the areas of the flexibility of the methods for various ambient conditions, and the method uncertainty associated with each method’s ability to correct to reference conditions.

Commentary by Dr. Valentin Fuster
2011;():693-697. doi:10.1115/POWER2011-55160.

The ASME Performance Test Code PTC-51 “Gas Turbine Inlet Air Conditioning Equipment” (PTC-51) [1] is currently in its final editing phase prior to publication. This paper will give a brief introduction to the code and outline some examples of how to apply PTC-51 to actual testing scenarios. Many plants are designed for hot summer peak ambient temperatures, but need to be tested in early spring for substantial completion and commercial contractual requirements. PTC-51 puts limits on the ambient conditions in which you can test inlet air conditioning equipment. Understanding these limits during the contract and design phase is critical if code-level testing will be a requirement for final completion.

Commentary by Dr. Valentin Fuster
2011;():699-706. doi:10.1115/POWER2011-55178.

The Kimberlina Solar Thermal Power Station in Bakersfield, California, is AREVA Solar’s first North American solar thermal energy facility and an important showcase of AREVA’s Compact Linear Fresnel Reflector (CLFR) technology. Construction of a fourth solar steam generator (SSG4) was completed at Kimberlina in August 2010. At the time SSG4 represented AREVA Solar’s most current commercial technology, designed for direct superheat steam generation. SSG4 incorporates technology advancements that significantly enhance the AREVA Solar technology’s controllability, steam temperature and pressure capabilities as well as overall performance. After SSG4 was commissioned, AREVA Solar carried out an extensive performance test program on this advanced technology to formally evaluate and quantify its measured performance and compare that to the model-predicted performance. The performance testing included two specific tests. The first was the Steady State Performance Test (SSPT), which evaluated the technology’s steady-state performance over a two-hour period on multiple days. The second test was the Entire Day Performance Test (EDPT), which evaluated the technology’s performance throughout an entire day, including overnight losses, startup, mid-day performance (including steady-state, quasi steady-state and transients) and shutdown. The third test demonstrated the technology’s response to a simulated direct normal insolation (DNI) transient. AREVA Solar took great care to design and perform this testing in a standardized manner that would stand up to independent, expert observation and was consistent with established ASME performance test codes (PTC), where applicable. AREVA Solar plans to implement this testing methodology in future commercial plants and technology demonstrations. This paper documents in detail the performance testing methodology used to evaluate AREVA Solar’s new technology, including: • Test prerequisites; • Performance (both measured and modeled) calculation equations; • Environmental and optical surface measurement techniques; • Measurement test success criteria; • Uncertainty calculation and implementation. This paper also documents the measured testing results relative to the AREVA Solar internal modeled results including follow-up model validation.

Commentary by Dr. Valentin Fuster
2011;():707-719. doi:10.1115/POWER2011-55216.

This paper examines the effects of particle size on the calorific value of hydrocarbons, shedding light on the thermodynamics of pulverizing coal in a commercial power plant. Both laboratory testing results and energy balances around an actual pulverizer are presented. Although tacitly known to any power plant engineer, efficient combustion is seen in two parts: preparation of the material’s surface/mass ratio, and then its combustion with the proper air/fuel mix and associated mechanics. This work attempts to put a thermodynamic face on the first part. A theory is presented which demonstrates that a hydrocarbon’s surface/mass ratio affects its potential to release its full chemical energy. This theory has been generally supported in this work by laboratory testing of pure substances; however this testing was not conclusive and should be repeated. If an optimum surface/mass is not achieved, unburned combustibles will result — and this regardless of subsequent air/fuel mixtures and/or burner sophistications. This work is suggests that a unique optimum surface/mass ratio exists for each hydrocarbon substance (and coal Rank); that once its full potential is reached, a higher ratio provides no further benefit. Since surface tension describes a material’s free energy, an aspect of surface tension, termed hydrogen bonding free energy, was shown to relate to the Äcalorific value penalty associated with non-optimum surface/mass ratio. A correlation was developed relating surface/mass ratio to observed an Äcalorific value penalty and hydrogen bonding free energy. This correlation’s form may be applied to coal if supported with additional research. The impetus for this work was the ASME Performance Test Code 4’s allowance of pulverizer shaft power to influence boiler efficiency’s “credit” term, thus affecting efficiency. It was demonstrated that surface/ mass affects calorific value and thus efficiency. However, there is no observable difference between grinding a hydrocarbon to a given surface/mass ratio, versus manufactured spheres. Although laboratory preparation of coal samples should emulate pulverizer action, this work suggests that a renewed and careful review of laboratory procedures is required. Recommendations are provided for critique and debate.

Topics: Boilers , Coal
Commentary by Dr. Valentin Fuster
2011;():721-726. doi:10.1115/POWER2011-55333.

Performance Test Codes (PTC) for gas turbines are about to experience a happy convergence of revisions to three principal documents. Several aspects of gas turbines are under consideration in ASME PTC 22 Gas Turbines, ASME PTC 36 Gas Turbine Installations Sound Emissions and ASME PTC 51 Gas Turbine Inlet Air Conditioning Equipment, all of which are in various stages of final development. These PTCs can be used to specify equipment and to perform verification testing to ensure conformance to performance requirements. This overview of the three PTCs will address the key concerns driving the development of the standards, the general issues addressed and the application and significance of uncertainties relevant to each.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
2011;():727-732. doi:10.1115/POWER2011-55417.

Steam seal is an important part in steam turbine, the leakage performance of seal has a significant impact on turbine efficiency. Research of seal is greatly emphasized with the development of design and manufacture technology, more professionals committed to the research and develop of new-type seal. Researchers from Shanghai power equipment research institute have conducted leakage performance test of different kinds of steam seal on the seal test bed. This paper introduce result of four kinds of seal, including labyrinth seal, honeycomb seal, touched seal and brush seal. The test analyzed blocked performance of different kinds of seals and concluded the suited scope of different seals.

Topics: Steam , Leakage
Commentary by Dr. Valentin Fuster
2011;():733-738. doi:10.1115/POWER2011-55449.

The importance of on line measurement of ultrafine particulates in pulverized coal flames is mainly due to the detection of ultrafine particulate in the effluent for pollution control, and the quantification of fuel burnout in real time within a boiler for improved understanding of the flame heat transfer soot modeling as well. A method has been investigated using laser-heated emission within an O2 -free flame which provides a continuous in situ measurement of ultrafine particles during high-temperature pulverized coal pyrolysis. Bituminous coal particles are entrained by nitrogen along the centerline of a laminar flow flat flame burner, where a hydrogen-air flame under fuel-rich condition is used as a heat source. The temperatures of the hydrogen flame were measured by a finite-wire silica-coated Platinum-Rhodium type B Thermocouple. Volatiles released during the coal pyrolysis form a cloud of ultrafine particles at high temperature. A pulse laser sheet introduced to the flame heats the ultrafine particles to incandescent temperatures. The time-resolved laser-induced emission signals with different incident laser-pulse fluences were evaluated. The volume faction of ultrafine particles was associated with the peak value of the signals, and the mean particle size characterized by a time constant of the exponential signal decay. A strong dependence of the characteristic peak value and emission time constant during laser-heated particle cooling from the measured coal particle class could be determined. Specialties in signal evaluation due to residence time in the hydrogen flame for two sizes of coal particles are discussed.

Commentary by Dr. Valentin Fuster

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