ASME Conference Presenter Attendance Policy and Archival Proceedings

2015;():V06BT00A001. doi:10.1115/IMECE2015-NS6B.

This online compilation of papers from the ASME 2015 International Mechanical Engineering Congress and Exposition (IMECE2015) 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to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Energy: Energy-Related Multidisciplinary

2015;():V06BT07A001. doi:10.1115/IMECE2015-50434.

U.S. Department of Energy affirms that HVAC systems consume approximately 40% of the total energy used in commercial-building sector. These types of systems are complex because they are composed of a large number of interconnected subsystems. The analysis shown in this paper is established on a building geographically located at the Caribbean coast region of Colombia in a region with tropical savanna climate and it is exposed to constant thermal load changes associated to high wall temperatures and direct sunlight incidence. Under this perspective, an energetic analysis is performed for the HVAC in order to implement a Model Predictive Control (MPC) strategy to enhance the system efficiency under the previously mentioned external conditions. The model predictive strategy is implemented as a system supervisor in order to minimize a cost function that measures the ratio of water consumption to air temperature change in the cooling coil. The strategy manipulates the required temperature of supply water to cooling coil from the chiller, perceiving as input perturbation the outdoor temperature, the desired temperatures for the classrooms and the desired temperature of the air supply to the different zones. The comparison and selection of thermodynamical states for analysis are conducted according to the dynamic characteristics of the entire system and individual components, and the energy assessment is performed including the system transient response. The accomplishment of the supervisory control strategy has demonstrated that dynamic energetic analysis and assessment is an auxiliary tool for HVAC performance management. The analysis performed shows that the supervisory strategy can reduce properly the energy performance index as a consequence, the energy consumption of the fan has a reduction of a 0.65%, while the water required shows a reduction of 66.93%.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A002. doi:10.1115/IMECE2015-50521.

Low power adsorption chillers with low desorption temperatures deserve particular attention, because of the possibility of driving them with a solar thermal system integrated with buildings. The monitoring of a recent solar cooling installation in Turin, Italy, has pointed out the opportunity of developing a dynamic mathematical model, in order to simulate the transient performances of this plant. Focusing on the aforementioned low power-low temperature adsorption chiller category, this work proposes a numerical model of the systems, that include a novel zeolite as the adsorbent and water as the refrigerant fluid. The simulation results have been verified by means of the nominal values of one of the very few commercial chillers of this typology available on the market, and have compared with experimental data found in the literature for similar plants.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A003. doi:10.1115/IMECE2015-50630.

Energy consumption from buildings is a major component of the overall energy consumption by end-use sectors in industrialized countries. In the United States of America (USA), the residential sector alone accounts for half of the combined residential and commercial energy consumption. Therefore, efforts toward energy consumption modeling based on statistical and engineering models are in continuous development. Statistical approaches need measured data but not buildings characteristics; engineering approaches need building characteristics but not data, at least when a calibrated model is the goal. Among the statistical models, the linear regression analysis has shown promising results because of its reasonable accuracy and relatively simple implementation when compared to other methods. In addition, when observed or measured data is available, statistical models are a good option to avoid the burden associated with engineering approaches. However, the dynamic behavior of buildings suggests that models accounting for dynamic effects may lead to more effective regression models, which is not possible with standard linear regression analysis. Utilizing lag variables is one method of autoregression that can model the dynamic behavior of energy consumption. The purpose of using lag variables is to account for the thermal energy stored/release from the mass of the building, which affects the response of HVAC equipment to changes in outdoor or weather parameters. In this study, energy consumption and outdoor temperature data from a research house are used to develop autoregressive models of energy consumption during the cooling season with lag variables to account for the dynamics of the house. Models with no lag variable, one lag variable, and two lag variables are compared. To investigate the effect of the time interval on the quality of the models, data intervals of 5 minutes, 15 minutes, and one hour are used to generate the models. The 5 minutes time interval is used because that is the resolution of the acquired data; the 15 minutes time interval is used because it is a common time interval in electric smart meters; and one hour time interval is used because it is the common time interval for energy simulation in buildings. The primary results shows that the use of lag variables greatly improves the accuracy of the models, but a time interval of 5 minutes is too small to avoid the dependence of the energy consumption on operating parameters. All mathematical models and their quality parameters are presented, along with supporting graphical representation as a visual aid to comparing models.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A004. doi:10.1115/IMECE2015-50741.

This article presents the dynamic behaviors of two bed adsorption chiller utilizing the composite adsorbent “immobilization of NH2, -NO2, -OH groups to MiL-101(Cr)” as adsorbent and water as adsorbate, which is based on the experimentally confirmed adsorption isotherms and kinetics data. The experimentally measured MOFs + water based isotherms and kinetics data are fitted with adsorption isotherm models and linear driving force kinetics equations. Compared with the experimental data of conventional adsorption chiller based on zeolites/silica gel-water system, we found that the newly working pair provides better cooling capacity and performances in terms of COP and adsorption bed size. From numerical simulation, it is also found that the cooling capacity can be increased up to 20 percent of the parent silica gel-water adsorption chiller and the COP can be improved up to 25% more at optimum conditions.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A005. doi:10.1115/IMECE2015-50751.

As promising material for gas storage applications, MIL-101(Cr) can further be modified by doping with alkali metal (Li+, Na+, K+) ions. However, the doping concentration should be optimized below 10% to improve the methane adsorption. This article presents (i) the synthesis of MIL-101 (Cr) Metal Organic Frameworks, (ii) the characterization of the proposed doped adsorbent materials by X-ray Diffraction, Scanning Electron Microscopy, N2 Adsorption, Thermo-Gravimetric Analyzer, and (iii) the measurements of methane uptakes for the temperatures ranging from 125 K to 303 K and pressures up to 10 bar. It is found that the Na+ doped MIL-101(Cr) exhibits CH4 uptake capacity of (i) 295 cm3/cm3 at 10 bar and 160 K and (ii) 95 cm3/cm3 at 10 bar at 298 K. This information is important to design adsorbed natural gas (ANG) storage tank under ANG-LNG (liquefied natural gas) coupling conditions.

Topics: Methane , Storage
Commentary by Dr. Valentin Fuster
2015;():V06BT07A006. doi:10.1115/IMECE2015-51168.

Ventilation is a process of changing air in an enclosed space. Air should continuously be withdrawn and replaced by fresh air from a clean external source to maintain internal good air quality, which may referred to air quality within and around the building structures. In natural ventilation the air flow is due through cracks in the building envelope or purposely installed openings. Its can save significant amount of fossil fuel based energy by reducing the needs for mechanical ventilation and air conditioning. Numerical predictions of air velocities and the flow patterns inside the building are determined. To achieve optimum efficiency of natural ventilation, the building design should start from the climatic conditions and orography of the construction to ensure the building permeability to the outside airflow to absorb heat from indoors to reduce temperatures. Effective ventilation in a building will affects the occupant health and productivity. In this work, computational simulation is performed on a real-sized box-room with dimensions 5 m × 5 m × 5 m. Single-sided ventilation is considered whereby openings are located only on the same wall. Two opening of the total area 4 m2 are differently arranged, resulting in 16 configurations to be investigated. A logarithmic wind profile upwind of the building is employed. A commercial Computational Fluid Dynamics (CFD) software package CFD-ACE of ESI group is used. A Reynolds Average Navier Stokes (RANS) turbulence model & LES turbulence model are used to predict the air’s flow rate and air flow pattern. The governing equations for large eddy motion were obtained by filtering the Navier-Stokes and continuity equations. The computational domain was constructed had a height of 4H, width of 9H and length of 13H (H=5m), sufficiently large to avoid disturbance of air flow around the building. From the overall results, the lowest and the highest ventilation rates were obtained with windward opening and leeward opening respectively. The location and arrangement of opening affects ventilation and air flow pattern.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A007. doi:10.1115/IMECE2015-51552.

The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. GHEs is commonly sized according to short time (one year or less) simulation algorithms. Variation of soil temperature in long time period is more important and, therefore, long term simulation is required to be assure the performance of the GSHP system. In this study, long time (10 years) simulation for parallel pipe GHE of a GSHP system was performed numerically with dynamical boundary conditions. In the numerical study ANSYS CFD package was used. This package uses a technique based on control volume theory to convert the governing equations to algebraic equations so they can be solved numerically. The control volume technique works by performing the integration of the governing equations about each control volume, and then generates discretization of the equations which conserve each quantity based on control volume. Thermal boundary conditions can be defined in four different types in ANSYS Fluent: Constant heat flux, constant temperature, convection-radiation and convection. In this study, periodic variation of air temperature boundary at upper surface condition is applied, the lateral and bottom surface of the solution domain are defined as adiabatic wall type boundary condition; the pipe inner surface is taken as wall with a constant heat flux. In order to provide the periodic variation of air temperature boundary at upper surface condition a User Defined Function (UDF) was written and interpreted in ANSYS Fluent. Likewise, a UDF was also written to give constant heat flux intermittently for the pipe inner surface.

Constant heat flux of 10, 20, 30 W per unit length of pipe used for calculations. Effects of distance between pipes and thermal conductivity on temperature distribution in the soil were investigated. Heat transfer in the soil is time dependent three dimensional heat conduction with dynamical boundary conditions. Temperature distribution in soil were obtained and storage effect of the soil has also been investigated. An optimization methodology based on long term simulation of GHE was suggested.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A008. doi:10.1115/IMECE2015-51689.

The industrial sector is the largest consumer of produced electric energy worldwide. Electric motor systems account for about 70 percent of the total industrial electricity demand and possess a great cost and energy saving potential. The paper provides an overview of global and regional efforts to create awareness for potential cost drivers in the industry. Various software and excel-based tools for a preliminary estimation of the energy consumption of electric motor systems are available in the market, but a holistic approach is missing. Therefore a framework and a systematic process for the estimation of potential energy savings in motor systems running on alternating current are illustrated in this paper. Moreover a new software tool is discussed, that allows a holistic view on all motor systems within a company without cost-intensive measurements or the use of external consultants.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A009. doi:10.1115/IMECE2015-52624.

The traditional refrigerants used in the vapor compression cycles have significant environmental impacts due to their high global warming potential. To address this challenge, solid-sate cooling technologies without using any aforementioned fluids have been developed rapidly during the past decades. Thermoelastic cooling, a.k.a. elastocaloric cooling, is a new concept, and thus no systematic studies of it have been conducted to date. Heat recovery plays an important role in the performance of the cooling systems, affected by the parasitic internal latent heat loss inside the cycle. A novel heat recovery (HR) scheme was been proposed in our previous study to minimize such parasitic internal latent heat loss. The objective of this study is to further investigate the performance improvement potential of the proposed heat recovery method by introducing the optimization study using the previously validated heat recovery model. The dynamic model details are revisited. The assumptions behind the model are re-examined by using the real thermoelastic cooling prototype geometries and materials properties of nickel-titanium tubes. A multi-objective optimization problem was formulated for the model and solved by MatLab. The heat recovery efficiency and the heat recovery duration were used as optimization objectives. A well-spread Pareto solutions were obtained, and a final solution was chosen with a 6.7% penalty in HR efficiency but six times faster cycle.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A010. doi:10.1115/IMECE2015-52957.

In this present paper, an advanced model of a ground source heat pump (GSH) system coupled with thermal energy storage (TES) is simulated and performed under a developed load management control strategy in order to supply a residential complex by taking the advantage of cheap excess electricity of the grid network during off-peak hours, where demand is in its lowest rate. Analyzing the performance of the system under different time and weather conditions leads to recognizing the effective parameters on thermal performance of the system which leads to achieve the optimal system efficiency and output energy. The proposed system with off-peak control scenario produces flexible heat supply profile which covers peak load consumptions whilst can smooth the electricity production peaks, caused by introduction of renewable energies, and prevents high rates of energy loss consequently.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A011. doi:10.1115/IMECE2015-53161.

Residential air conditioning consumes a huge amount of the produced electrical power from fossil fuel power plants in Kuwait. Energy availability and the consequences on Kuwait’s expenditure associated with producing electricity is a hot topic in this oil producing country. The predominant air conditioning type in Kuwait’s residential sector is packaged direct expansion. An intention to shift to chilled water air conditioning system for future’s houses was announced as a promising solution to save energy. This work is presented to demonstrate how lifecycle cost analysis can be performed to underline tentative issues before shifting to a new air conditioning system for houses in Kuwait. No previous attempts have been made to assess the feasibility of chilled water air conditioning system for houses in Kuwait based on lifecycle cost analysis. The work considered the air conditioning requirements for a block of six typical houses as a baseline for the evaluation. The total cooling load of the studied block of houses was used to estimate the annual electrical energy associated with each air conditioning alternative. This was made by the help of DOE EnergyPlus thermal simulation engine through its interface with DesignBuilder software. Actual financial inputs were penetrated in the analysis; which includes installation, operation and maintenance costs for each studied air conditioning alternative. It was found that chilled water system can conserve about 40% of the annual electrical energy required to operate packaged direct expansion air conditioning. But, due to high installation cost, chilled water system is not cost effective for consumers. The outcomes from the lifecycle cost analysis indicated that it would be cost effective for the government to subsidy the installation of chilled water systems for consumers. This will help to conserve electrical energy associated with conventional systems that are currently in use.

Commentary by Dr. Valentin Fuster

Energy: Engineering Thermodynamics

2015;():V06BT07A012. doi:10.1115/IMECE2015-51079.

Modeling of engine-out heat release is of great importance for engine combustion research. Variations in fuel properties bring about changing combustion behavior within the cylinder, which may be captured by modeling of the rate of heat release. This is particularly true for biodiesel fuels, where changes in fuel behavior are linked to viscosity, density, and energy content. Heat release may also be expanded into an analysis using the 2nd Law of Thermodynamics, which may ascertain the pathways through which availability is either captured as useful work, unused as thermal availability of the exhaust gas, or wasted as heat transfer. In specific, the 2nd Law model identifies the period of peak availability, and thus the ideal period to extract work, and is of use for power optimization.

A multi-zone (fuel, burned, and unburned) diagnostic model using a 1st Law of Thermodynamics analysis is utilized as a foundation for a 2nd Law analysis, allowing for a simultaneous energy and exergy analysis of engine combustion from a captured pressure trace. The model calibrates the rate and magnitude of combustion through an Arrhenius equation in place of a traditional Wiebe function, calibrated using exhaust emission measurements.

The created model is then utilized to categorize combustion of diesel and palm biodiesel fuels, as well as their blends. The 2nd Law analysis is used to highlight the effects of increasing biodiesel usage on engine efficiency, particularly with respect to fuel viscosity and combustion temperature. The 2nd Law model used is found to provide a more clear understanding of combustion than the original 1st Law model, particularly with respect to the relationships between biodiesel content, viscosity, temperature, and diffusion-dominated combustion.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A013. doi:10.1115/IMECE2015-51835.

Transitioning from R134a refrigerant to a low global warming potential (GWP) refrigerant is a current issue of global importance. Although any refrigerant still has set; there are a few options to replace it such as the R1234yf. In this paper is presented a semi-empirical model to assess the energy performance of mixtures with R134a and its possible substitute R1234yf. The inputs variables to the computational model are: suction conditions (pressure and temperature), discharge pressure and rotation speed. With these variables the model must compute the following parameters: mass flow rate, discharge temperature and energy consumption. The model is validated with data obtained from an experimental facility; calculations are obtained within a relative error band of ±10% for mass flow rate and energy consumption, and an error of ±1 K for discharge temperature. Finally, the model is carried out to an energy simulation in order to predict the behavior of different mass fractions of R1234yf. Energy savings are found when R1234yf mass fraction is reduced from 1 to 0.9. Knowing that the mixture with y=0.9 may be used as its GWP is 150.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A014. doi:10.1115/IMECE2015-52317.

In this study, constraint potential and constraint forms of the Rate-Controlled Constrained-Equilibrium (RCCE) method have been investigated in terms of accuracy and performance. Although the two formulations are equivalent mathematically, they show quite different performances from the computational standpoint. The main objective of this work is to determine the most efficient implementation of RCCE to be used in turbulent combustion simulations. Simulations are conducted of an adiabatic, isobaric stirred reactor. The kinetics includes methane oxygen combustion using 133 reaction steps and 29 species. RCCE calculations are performed by 12 constraints. The simulations are carried out over a wide range of initial temperatures for stoichiometric gas mixtures. Performance studies of the two RCCE formulations are carried out and the results are compared with those obtained by direct integration of detailed kinetics.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A015. doi:10.1115/IMECE2015-53581.

Conventional first principle approaches for studying non-equilibrium or far-from-equilibrium processes all depend on the mechanics of individual particles or quantum states and as a result, require too many details of the mechanical features of the system to easily or even practically arrive at the value of a macroscopic property. In contrast, thermodynamics, which has been extremely successful in the stable equilibrium realm, provides an approach for determining a macroscopic property without going into the mechanical details. Nonetheless, such a phenomenological approach is not generally applicable to a non-equilibrium process except in the near-equilibrium realm and under the limiting local equilibrium and continuum assumptions, both of which prevent its application across all scales. To address these drawbacks, steepest-entropy-ascent quantum thermodynamics (SEAQT) can be used. It provides an ensemble-based, thermodynamics, first principles approach applicable to the entire non-equilibrium realm even that far-from-equilibrium and does so with a single kinematics and dynamics able to cross all temporal and spatial scales. Based on prior developments by the authors, this paper applies SEAQT to the study of mass and heat diffusion. Specifically, the study focuses on the thermodynamic features of far-from-equilibrium state evolution. Two kinds of size effects on the evolution trajectory, i.e., concentration and volume effects, are discussed.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A016. doi:10.1115/IMECE2015-53726.

Oxygen reduction in a solid oxide fuel cell (SOFC) cathode involves a non-equilibrium process of coupled mass and heat diffusion and electrochemical and chemical reactions. These phenomena occur at multiple temporal and spatial scales, from the mesoscopic to the atomistic level, making the modeling, especially in the transient regime, very difficult. Nonetheless, multi-scale models are needed to improve an understanding of oxygen reduction and guide fuel cell cathode design. Existing methods are typically phenomenological or empirical in nature so their application is limited to the continuum realm and quantum effects are not captured.

Steepest-entropy-ascent quantum thermodynamics (SEAQT) can be used to model non-equilibrium processes (even those far-from equilibrium) from the atomistic to the macroscopic level. The non-equilibrium relaxation is characterized by the entropy generation, and the study of coupled heat and mass diffusion as well as electrochemical and chemical activity are unified into a single framework. This framework is used here to study the transient and steady state behavior of oxygen reduction in an SOFC cathode system. The result reveals the effects on performance of the different timescales of the varied phenomena involved and their coupling. In addition, the influence of cathode microstructure changes on performance is captured.

Commentary by Dr. Valentin Fuster

Energy: Exergo- and Techno-Economics

2015;():V06BT07A017. doi:10.1115/IMECE2015-50519.

Combined Heat and Power (CHP) is a technology that has been proven to be very effective in the industrial sector, when both thermal and electrical energy are required, as it allows a more rational use of the input primary energy. However, CHP technology is not limited to industrial uses, as it can also be effectively exploited in the civil sector, such as in District Heating (DH) applications. Moreover, in recent years the opportunity to develop hybrid systems, in which traditional and renewable energy sources are integrated, is gaining more and more consideration. For these reasons, the most recent European Standards propose a set of newly conceived indices whose aim is easily assessing the energetic performances of DH networks, but the effectiveness of these indices in the study of DH networks coupled with CHP and renewable energy systems has not yet been thoroughly investigated.

This paper presents a comparative study, based on these indices, of different electrical and thermal generation technologies, with the aim of assessing their effectiveness when hybrid systems are analyzed. A CHP-DH application, actually installed and in operation in Turin, Italy, has also been considered in the analysis, in order to have a comparison with a real case. The results of the study are presented and discussed in detail in the following sections.

Topics: Central heating
Commentary by Dr. Valentin Fuster
2015;():V06BT07A018. doi:10.1115/IMECE2015-51652.

This paper presents the development of an exergy and thermoeconomic analysis of a wheat flour agro-industrial plant, which was aimed to evaluate the energy use and establish the operation cost of its components, and to understand the cost formation process and the cost flow. It was found that throughout the production process exists an exergy destruction ratio of 95,08 %. It identified improvement opportunities in relation to cost, has recommended alterations with regard matter flows or an economic investment for change some components with low exergoeconomic factors: 2% planer of wheat bran, 3% knurled roller grinding benches and 5% smooth roller grinding benches.

Topics: Thermoeconomics
Commentary by Dr. Valentin Fuster
2015;():V06BT07A019. doi:10.1115/IMECE2015-51888.

In electronics assembly, the convection based soldering technologies in the production lines consumes massive resources and energy. The recent advancements in soldering technologies consume comparatively higher resources and needs to be optimized for resource efficient production which is also the motivation for the present work. This study is devoted to quantify the resource consumption and qualify this consumption through exergy flows in an over-pressure reflow technology as an energy intensive process in electronics manufacturing.

The analysis implies on a big saving potential for energy consumption specifically during the over-pressure process which also defines the void reduction quality of solder joints. Exergy efficiency is the fraction of the work potential of the heat that is converted to work, and it illustrates the quality of consumed resources during the soldering oven process. Shortening the production lead-time, and increasing the production rate increase the efficiency of exergy and prevents wastage of usable energy. Furthermore, the set-up improvements for the temperature profiles are necessary, and the changes toward developing new technologies in pre-heating and over-pressure chamber zones are mandatory if a high efficiency of resources used is expected.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A020. doi:10.1115/IMECE2015-52051.

Borehole thermal energy storage (BTES) is an option to provide large-scale seasonal storage of cold and heat in natural underground sites. Boreholes are used to transfer heat from the working fluid to the ground in charging phase and vice versa in discharging.

The design of boreholes influences system efficiency, installation costs and the charging time required to reach the design temperature in the ground. The latter can result too long but may be reduced significantly through the selection of an optimal design and a storage temperature that maximizes the efficiency. Nevertheless high performances are usually accompanied by high purchase and installation costs of the borehole exchangers. The increase in efficiency and the decrease of investment costs are two conflicting objectives that must be considered in the design stage to select the best configuration.

This work is focused on the optimal configuration of BTES in which the boreholes are used to charge the ground to the design temperature and to supply the thermal energy demand during the operation. Several designs are explored at two different levels of temperature in the storage.

A novel design strategy, based on energy, exergy and thermoeconomic analysis, is proposed to select the optimal configuration that guarantees a balance between expenditure on capital costs and exergy efficiency. This constitutes a novel approach which ensures high performances of BTES systems for long periods of operation, which is an interesting area of research that is currently not sufficiently explored.

Commentary by Dr. Valentin Fuster

Energy: Fuel Cell Systems Design and Applications

2015;():V06BT07A021. doi:10.1115/IMECE2015-50651.

Efficient removal of liquid-water from gas-diffusion layer (GDL) media in polymer-electrolyte fuel cells (PEFC) is critical to achieving reliable, high power operation. Studies have shown that PEFC systems exposed to vibration suffer from performance loss; however, fundamental understanding as to why is lacking. This work investigates vibrations ranging from 1–100 Hz and their effect on wetting behavior as well as liquid adhesion to the GDL surfaces. Vibrations are found to redistribute water in a way that raises its barrier to removal. An increased frequency reduced droplet contact area and height while expanding the wetting diameter. Moreover, while vibrations did not change the adhesion force, the increased wetting diameter resulted in a larger net force required to achieve droplet detachment.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A022. doi:10.1115/IMECE2015-51723.

A direct methanol fuel cell can convert chemical energy in the form of a liquid fuel into electrical energy to power devices, while simultaneously operating at low temperatures and producing virtually no greenhouse gases. Since the direct methanol fuel cell performance characteristics are inherently nonlinear and complex, it can be postulated that artificial neural networks represent a marked improvement in performance prediction capabilities. Artificial neural networks have long been used as a tool in predictive modeling. In this work, an artificial neural network is employed to predict the performance of a direct methanol fuel cell under various operating conditions. This work on the experimental analysis of a uniquely designed fuel cell and the computational modeling of a unique algorithm has not been found in prior literature outside of the authors and their affiliations. The fuel cell input variables for the performance analysis consist not only of the methanol concentration, fuel cell temperature, and current density, but also the number of cells and anode flow rate. The addition of the two typically unconventional variables allows for a more distinctive model when compared to prior neural network models. The key performance indicator of our neural network model is the cell voltage, which is an average voltage across the stack and ranges from 0 to 0:8V. Experimental studies were carried out using DMFC stacks custom-fabricated, with a membrane electrode assembly consisting of an additional unique liquid barrier layer to minimize water loss through the cathode side to the atmosphere. To determine the best fit of the model to the experimental cell voltage data, the model is trained using two different second order training algorithms: OWO-Newton and Levenberg-Marquardt (LM). The OWO-Newton algorithm has a topology that is slightly different from the topology of the LM algorithm by the employment of bypass weights. It can be concluded that the application of artificial neural networks can rapidly construct a predictive model of the cell voltage for a wide range of operating conditions with an accuracy of 10−3 to 10−4. The results were comparable with existing literature. The added dimensionality of the number of cells provided insight into scalability where the coefficient of the determination of the results for the two multi-cell stacks using LM algorithm were up to 0:9998. The model was also evaluated with empirical data of a single-cell stack.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A023. doi:10.1115/IMECE2015-51913.

This paper presents, an open cathode fuel cell dynamic model and an advanced control system design that allows to study the transient response of the system and its nonlinearities. The model can be used to design control strategies and design test benches to test fuel cells stacks. A dynamic performance characterization is performed (transient response to disturbances or setpoint changes), and the information is used to propose the structure of a control system capable of incorporating expert information and transition in non-linear regions. The model used in the simulation takes account of three different phenomena: (a) mass transfer, (b) thermodynamics and (c) electrochemical. The fuel cell uses hydrogen and air to generate electricity. The hydrogen is supplied to the fuel cell anode and the air is supplied to the fuel cell cathode. This model allows the calculation of the pressure and mass flow circulating in the cell. Balances are presented for cathode, anode and membrane. The energy balance proposed includes the electrochemical reaction that is exothermic and the heat transfer to the air flowing through the cathode which has to supply the electrochemical reaction with the oxygen required and regulate the stack temperature. The ideal electric potential of a fuel cell is defined by the Nernst equation. The Nernst equation alone is not enough to describe the electrical potential during the actual operation of the system. The main sources of voltage loss are presented: Activation, electrical resistance and concentration. PEM control system is designed and simulated. A model–based algorithm is used to achieve different objectives than could lead to an improvement in the system performance. Results demonstrate that the predictions in voltage and current in the fuel cell stack are close to experimental data obtained from manufacturer. Constraints in the algorithm allow avoiding hazardous operational conditions and a decrease in controlled variable variance.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A024. doi:10.1115/IMECE2015-52478.

In recent years, there has been increased interest in fuel cells as a promising energy storage technology. The environmental impacts due to the extensive fossil fuel consumption is becoming increasingly important as greenhouse gas (GHG) levels in the atmosphere continue to rise rapidly. Furthermore, fuel cell efficiencies are not limited by the Carnot limit, a major thermodynamic limit for power plants and internal combustion engines. Therefore, hydrogen fuel cells could provide a long-term solution to the automotive industry, in its search for alternate propulsion systems. Two most important methods for hydrogen delivery to fuel cells used for vehicle propulsion were evaluated in this study, which are fuel processing and hydrogen storage. Moreover, the average fuel cost and the greenhouse gas emission for hydrogen fuel cell (H2 FCV) and gasoline fuel cell (GFCV) vehicles are compared to that of a regular gasoline vehicle based on the Argonne National Lab’s GREET model. The results show that the average fuel cost per 100 miles for a H2 FCV can be up to 57% lower than that of regular gasoline vehicles. Moreover, the obtained results confirm that the well to wheel greenhouse gas emission of both H2 FCV and GFCV is significantly less than that of regular gasoline vehicles. Furthermore, the investment return period for hydrogen storage techniques are compared to fuel processing methods. A qualitative safety and infrastructure dependency comparison of hydrogen storage and fuel processing methods is also presented.

Commentary by Dr. Valentin Fuster

Energy: Nuclear Power Plants: Design, Analysis and Safety

2015;():V06BT07A025. doi:10.1115/IMECE2015-52377.

A prevalent issue within extended long term dry storage units for spent nuclear fuel has always been fuel and cask contamination. This contamination can be the result of the helium within the cask leaking into the atmosphere or inadequate vacuum drying techniques. Once the cask integrity has been compromised, the helium starts to leak, and the resulting space once occupied by helium in the casks is replaced with ambient air. One of the other prominent gases found within ambient air besides oxygen is water vapor which can be a result of both helium leaking and poor vacuum drying techniques. Contact between water and the fuel rods/assemblies for a prolonged amount of time can result in corrosion of the fuel cladding, and the canister if exposed. The potential of corrosion of the fuel cladding increases risk of radioactive fission fragments contaminating the environment, increases the radioactive period of spent nuclear fuel, and decreases the potential for fuel rod repurposing within the future if U.S. law permits.

With literary findings showing liquid water within the inner cask in a long term storage unit of fifteen years or longer, proper drying techniques have not been fully developed. There are a number of projected theories about how water is entering the cask without an external crack or imperfection within the inner cask walls. This case study aims to solve this issue by inspecting the vacuum drying process of the fuel rods/assemblies from the temporary on-site storage pools to their respective long term dry storage casks.

The purpose of this case study is to conduct a laboratory experiment of a scale replica of one dry storage cask and the vacuum drying process before long term storage. The experiment will be focused around the process of applying several cycles of vacuum and backfilling the cask with Helium. The purpose of several cycles of backfilling gas is to simultaneously introduce more of a pressure gradient for water evaporates to depart the pressure vessel and to avoid thermodynamic temperatures that would otherwise freeze the top layer of water. To do this, the vacuuming process must be properly understood, as pulling a vacuum drops pressures instantaneously. There are possibilities of freezing water vapor into its solidified form due to its thermodynamic triple point during this vacuum process. Once water is trapped under a layer of ice within the vessel, water will remain throughout storage time due to restrictions to its own geometries. The importance of developing a scale model and improving the drying process that precedes long term storage of spent nuclear fuel is a necessary solution to existing contamination results for practical future applications within the United States and other countries moving towards long term storage of spent nuclear fuel.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A026. doi:10.1115/IMECE2015-52504.

Commercial light water reactor fuel UO2 has a low thermal conductivity that leads to the development of a large temperature gradient across the fuel pellet, limiting the reactor operational performance due to the effects that include thermal stresses causing pellet cladding interaction and the release of fission product gases. This study presents the development of a modeling and simulation for enhanced thermal conductivity UO2-BeO fuel behavior in a light water reactor, using self-defined multiple physics models fully coupled based on the framework of COMSOL Multiphysics. Almost all the related physical models are considered, including heat generation and conduction, species diffusion, thermomechanics (thermal expansion, elastic strain, densification, and fission product swelling strain), grain growth, fission gas production and release, gap heat transfer, mechanical contact, gap/plenum pressure with plenum volume, cladding thermal and irradiation creep and oxidation. All the phenomenal models and materials properties are implemented into COMSOL Multiphysics finite-element platform with a 2D axisymmetric geometry of a fuel pellet and cladding. UO2-BeO high thermal conductivity nuclear fuel would decrease fuel temperatures and facilitate a reduction in pellet cladding interaction from our simulation results through lessening thermal stresses that result in fuel cracking, relocation, and swelling, so that the safety of the reactor would be improved.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A027. doi:10.1115/IMECE2015-52990.

The design and the analysis of nuclear power plants (NPPs) require computational codes to predict the behavior of the NPP nuclear components and other systems (i.e., reactor core, primary coolant system, emergency core cooling system, etc.). Coupled calculations are essential to the conduct of deterministic safety assessments.

Inasmuch as the physical phenomena that govern the performance of a nuclear reactor are always present simultaneously, ideally computational modeling of a nuclear reactor should include coupled codes that represent all of the active physical phenomena. Such multi-physics codes are under development at several institutions and are expected to become operational in the future. However, in the interim, integrated codes that incorporate modeling capabilities for two to three physical phenomena will remain useful. For example, in the conduct of safety analyses, of paramount importance are codes that couple neutronics and thermal-hydraulics, especially transient codes. Other code systems of importance to safety analyses are those that couple primary system thermal-hydraulics to fission product chemistry, neutronics to fuel performance, containment behavior and structural mechanics to thermal-hydraulics, etc. This paper surveys the methods used traditionally in the coupling of neutronic and thermal-hydraulics codes.

The neutron kinetics codes are used for computing the space-time evolution of the neutron flux and, hence, of the power distribution. The thermal-hydraulics codes, which compute mass, momentum and energy transfers, model the coolant flow and the temperature distribution. These codes can be used to compute the neutronic behavior and the thermal-hydraulic states separately. However, the need to account with fidelity for the dynamic feedback between the two sets of properties (via temperature and density effects on the cross section inputs into the neutronics codes) and the requirement to model realistically the transient response of nuclear power plants and to assess the associated emergency systems and procedures imply the necessity of modeling the neutronic and thermal-hydraulics simultaneously within a coupled code system. The focus of this paper is a comparison of the methods by which the coupling between neutron kinetics and thermal-hydraulics treatments has been traditionally achieved in various code systems. As discussed in the last section, the modern approaches to multi-physics code development are beyond the scope of this paper.

From the field of the most commonly used coupled neutron kinetic-thermal-hydraulics codes, this study selected for comparison the coupled codes RELAP5-3D (NESTLE), TRACE/PARCS, RELAP5/PARCS, ATHLET/DYN3D, RELAP5/SCDAPSIM/MOD4.0/NESTLE. The choice was inspired by how widespread the use of the codes is, but was limited by time availability. Thus, the selection of codes is not to be construed as exhaustive, nor is there any implication of priority about the methods used by the various codes.

These codes were developed by a variety of institutions (universities, research centers, and laboratories) geographically located away from each other. Each of the research group that developed these coupled code systems used its own combination of initial codes as well as different methods and assumptions in the coupling process. For instance, all these neutron kinetics codes solve the few-groups neutron diffusion equations. However, the data they use may be based on different lattice physics codes. The neutronics solvers may use different methods, ranging from point kinetics method (in some versions of RELAP5) to nodal expansion methods (NEM), to semi-analytic nodal methods, to the analytic nodal method (ANM). Similarly, the thermal-hydraulics codes use several different approaches: different number of coolant fields, homogenous equilibrium model, separate flow model, different numbers of conservation equations, etc. Therefore, not only the physical models but also the assumptions of the coupled codes and coupling techniques vary significantly. This paper compares coupled codes qualitatively and quantitatively. The results of this study are being used both to guide the selection of appropriate coupled codes and to identify further developments into coupled codes.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A028. doi:10.1115/IMECE2015-52991.

High-fidelity and accurate nuclear system codes play a key role in the design and analysis of complex nuclear power plants, which consist of multiple subsystems, such as the reactor core (and its fuel, burnable poisons, control elements, etc.), the reactor internal structures, the vessel, and the energy conversion subsystem and beyond to grid demand. Most commonly the interplay between these various subsystems is modeled using coupled codes, each of which represents one of the subsystems. And the most common direct coupling is that of thermal-hydraulics and neutronics codes.

The subject of this paper is the coupling of codes that model not only thermal-hydraulics and neutronics, but also structural components damage. Furthermore, the neutronic component is not limited to the sole core solver. The coupled code system encompasses thermal-hydraulics, material performance of the fuel, neutronic solver, and neutronic data preparation. Thus, this paper presents a framework for coupling RELAP5/SCDAPSIM/MOD4.0 with a suite of neutron kinetics codes that includes NESTLE, DRAGON and a version of the ENDF library.

The version of the RELAP5/SCDAPSIM/MOD4.0 code used in this work is one developed by Innovate System Software (ISS) as part of the international SCDAP Development and Training Program (SDTP) for best-estimate analysis to model reactor transients including severe accident phenomena. This RELAP5/SCDAPSIM/MOD4.0 code version is also capable of predicting nuclear fuel performance. It uses nodal power distributions to calculate mechanical and thermal parameters such as heat-up, oxidation and meltdown of fuel rods and control rods, the ballooning and rupture of fuel rod cladding, the release of fission products from fuel rods, and the disintegration of fuel rods into porous debris and molten material. On the neutronics side, this work uses the NESTLE and DRAGON codes. NESTLE is a multi-dimensional static and kinetic neutronic code developed at North Carolina State University. It solves up to four energy groups neutron diffusion equations utilizing the Nodal Expansion Method (NEM) in Cartesian or hexagonal geometry. The DRAGON code, developed at Ecole Polytechnique de Montreal, performs lattice physics calculations based on the neutron transport equation and is capable of using very fine energy group structures.

In this work, we have developed a coupling approach to exchange data among the various modules. In the coupling process, the generated nuclear data (in fine multigroup energy structure) are collapsed down into two- or four-group energy structures for use in NESTLE. The neutron kinetics and thermal-hydraulics modules are coupled at each time step by using the cross-section data. The power distribution results of the neutronic calculations are transmitted to the thermal-hydraulics code. The spatial distribution of coolant density and the fuel-moderator temperature, which result from the thermal-hydraulic calculations, are transmitted back to the neutron kinetics codes and then the loop is closed using new neutronics results. Details of the actual data transfers will be described in the full length paper.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A029. doi:10.1115/IMECE2015-53050.

Effects of initial stress-strain states on irradiation performance of monolithic fuel plates were studied. The monolithic fuel plates consist of a high density low enrichment U-Mo fuel that is encapsulated in an Aluminum cladding. Because the fabrication involves multiple stages, there are concerns, if the irradiation performance of the plates is affected by the pre-irradiation stress-strain states. To investigate these concerns, a representative plate was evaluated for distinct initial stress-strain states. First, the foil preparation stage by co-rolling process was simulated. For this, a scaled version of the process was simulated to calculate the stress-strain profiles. These profiles were then used to incorporate initial states for the HIP process. Additional HIP simulations were also considered to evaluate the cases with stress-free foils prior HIP bonding. For the simulation of HIP process with initially stress-free co-rolled foils, several bonding temperatures were considered. Finally, the irradiation processes were simulated for all cases with distinct pre-irradiation stress-strain states. The stress-strain fields from the fabrication process were used to incorporate the initial states for the irradiation simulations. The resulted distortions, stress-strain fields and temperature profiles were extracted at the selected locations. Finally, a comparative evaluation was made to determine the sensitivity of the plate’s performance to the pre-irradiation stress-strain states. The irradiation simulations have revealed that the fabrication stresses in the fuel would be relieved relatively fast in reactor. The fuel foil would be essentially stress-free during irradiation. The stresses however, would develop at the shutdown stage. For the cladding material, the stresses continue to increase and additional plastic strains are generated as a result of fuel swelling. The study indicated that the stress-strain fields of the plates during irradiation are not affected by the initial stress state of the plates.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A030. doi:10.1115/IMECE2015-53142.

The DOE/NNSA Conversion [1] Program in the US aims to minimize the use of high enrichment uranium in civilian applications. This initiative is being approached by converting research and test reactors from the use of highly enriched uranium (HEU) to low enrichment uranium (LEU, <20% 235U) with high density of uranium to achieve stable operation of converted reactors. Among variety of fuel materials investigated to serve in the conversion process, U-Mo based alloys have shown stable and acceptable swelling response under typical operation conditions of research and test reactors.

For the conversion of high performance research reactors, a large number of irradiation experiments were conducted to evaluate the mechanical behavior of the U-10Mo monolithic mini-plate; however, it is difficult to investigate all design and operation variables with potential impact on the irradiation behavior of the fuel experimentally.

Thus, this study performed Finite Element Analyses (FEA) on a 3-D monolithic plate by changing material properties of components. The material properties considered in this study included thermal, mechanical, and irradiation specific properties of the fuel, cladding, and liner. Among FEA results, higher Young’s modulus of cladding material caused a significant decrease in all stress values in the three sections of the monolithic mini-plate. On the other hand, variation in the Young’s modulus of Zr-liner showed the minimal effect on the overall mechanical response of the monolithic mini-plate. Results showed that increasing the yield stress of the cladding material directly caused a increase in the maximum stress observed in the cladding section by almost 40 %. Considering the thermal properties of materials in the monolithic plate, maximum and minimum stress in fuel foil were found to either increase or decrease in proportional with the coefficient of thermal expansion of the fuel material. However, variation in the coefficient of thermal expansion in the cladding section caused a remarkable increase in peak stresses in the fuel foil.

While mechanical and thermal properties of the foil, liner, and cladding sections are known, other irradiation-dependent properties such as coefficient of irradiation creep of U-10Mo are not firmly determined to date. The mechanical response of L1P756 is being simulated with different values of the coefficient of irradiation creep and the observed “bulging” in the plate will be compared to available post-irradiation measurements. Thus, it will be possible to determine an accurate value of irradiation creep coefficient of U-10Mo which in turn would allow predicting its mechanical behavior under different irradiation conditions.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A031. doi:10.1115/IMECE2015-53209.

During postulated design-basis or beyond-design-basis accident at nuclear power plant with PWR or BWR, the high temperature oxidation of Zr-based fuel claddings in H2O-O2-N2 gas atmosphere could take place.

Recent experimental observations showed that the oxidation of those claddings in the air (or, more generally, in oxygen-nitrogen and steam-nitrogen mixtures) behaves in much more aggressive way (linear or enhanced parabolic kinetics) compared to oxidation in pure steam (standard parabolic kinetics).

This is why an advanced model of Zr-based cladding oxidation was developed. For calculations of cladding oxidation in oxygen-nitrogen and steam-nitrogen mixtures, the effective oxygen diffusion coefficient in ZrO2+ZrN layer formed in cladding is used. The diffusion coefficient enhancement factor depends on ZrN content in ZrO2+ZrN layer.

A numerical scheme was realized to determine ZrO2+ZrN/α-Zr(O) and α-Zr(O)/β-Zr layers boundaries relocation and layers transformations in claddings.

The model was implemented to the SOCRAT best estimate computer modeling code. The SOCRAT code with advanced model of oxidation was successfully used for calculations of separate effects tests and air ingress integral experiments QUENCH-10, QUENCH-16 and PARAMETER-SF4.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A032. doi:10.1115/IMECE2015-53544.

A temperature sensitivity evaluation has been performed on a thermal model for the AGR-3/4 fuel experiment on an individual capsule. The experiment was irradiated in the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL). Four TRISO fuel irradiation experiments are planned for the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program which supports the development of the Very High Temperature Gas-cooled Reactor under the Next-Generation Nuclear Plant project.

AGR-3/4 is the third TRISO-particle fuel test of the four planned and is intended to test tri-structural-isotropic (TRISO)-coated, low-enriched uranium oxy-carbide fuel. The AGR-3/4 test was specifically designed to assess fission product transport through various graphite materials. The AGR-3/4 irradiation test in the ATR started in December 2011 and finished in April 2014. Forty-eight (48) TRISO-particle fueled compacts were inserted into 12 separate capsules for the experiment (four compacts per capsule).

The purpose of this analysis was to assess the sensitivity of input variables for the capsule thermal model. A series of cases were compared to a base case by varying different input parameters into the ABAQUS finite element thermal model. These input parameters were varied by ±10% to show the temperature sensitivity to each parameter. The most sensitive parameter was the compact heat rates, followed by the outer control gap distance and neon gas fraction. Thermal conductivity of the compacts and thermal conductivity of the various graphite layers vary with fast neutron fluence and exhibited moderate sensitivity. The least sensitive parameters were the emissivities of the stainless steel and graphite, along with gamma heat rate in the non-fueled components. Separate sensitivity calculations were performed varying with fast neutron fluence, showing a general temperature rise with an increase in fast neutron fluence. This is a result of the control gas gap becoming larger due to the graphite shrinkage with neutron damage. A smaller sensitivity is due to the thermal conductivity of the fuel compacts with fast neutron fluence.

Heat rates and fast neutron fluence were input from a detailed physics analysis using the Monte Carlo N-Particle (MCNP) code. Individual heat rates for each non-fuel component were input as well. A steady-state thermal analysis was performed for each sensitivity calculation. ATR outer shim control cylinders and neck shim rods along with driver fuel power and fuel depletion were incorporated into the physics heat rate calculations. Surface-to-surface radiation heat transfer along with conduction heat transfer through the gas mixture of helium-neon (used for temperature control) was used in the sensitivity calculations.

Commentary by Dr. Valentin Fuster

Energy: Posters

2015;():V06BT07A033. doi:10.1115/IMECE2015-50212.

Cu2Zn0.8Cd0.2SnS4 quinternary alloy nanostructures were prepared with different copper (Cu) concentrations; 0.3, 0.5, 0.7 and 0.9 mol/L using the spin coating technique. The direct band gap energy of Cu2Zn0.8Cd0.2SnS4 quinternary alloy nanostructures is investigated to decrease as Cu increases. The transmittance value in the range 63–49% is depending on Cu content.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A034. doi:10.1115/IMECE2015-50513.

Solid manure handling is a major environmental issue confronting animal facilities in the United States. One difficulty in using dairy manure as a fuel source is the presence of sand bedding used for lactating dairy cows. More than 30% of dairy farms use sand beds for a dry and clean environment that prevents bacterial growth [1]. In this study, dairy animal manure obtained directly from waste lagoons was used for the air gasification process. The manure was dried to reduce the moisture down to 5% and a sand separating system was designed to remove some sand bedding materials. Preliminary air gasification experiments showed that the direct use of dairy manure containing 75% ash content, that reflect high sand content, reduced the temperature of the reactor. The study is also aimed at handling unprocessed dairy manure and generating electric power for the on-site use. A high heating value manure is needed to run the gasifier and the produced synthesis gas (or syngas) is fed to an engine coupled with a generator. Some dairy manure gasification work were done using fresh dairy manure. The highest heating value from the dairy manure biomass was found to be 4.5MJ/kg in a fixed-bed gasifier [2]. Another gasification study using a fluidized-bed reactor could produce syngas heating value as high as 4.7MJ/m3 from dairy manure [3]. A bench-scale fluidized bed containing a 3-inch diameter reactor tube with a cyclone and a scrubber was used to gasify dairy manure using air at different temperatures. The sand separated dairy manure used in this study contained approximately 45% ash content. The maximum heating value of the synthesis gas was 3.8MJ/m3 at an operating temperature of 750°C. The syngas will need to be upgraded. To upgrade the synthesis gas heating value, sludge pellets of 18.7MJ/kg were mixed with the dairy manure in different ratios of 10% and 30%. The syngas heating values from mixed manure with sludge pellet were increased to 5MJ/m3 with 10% sludge, and 5.7MJ/m3 with 30% sludge. The sludge used has higher heating value resulting in higher gas HV. The cold gasification efficiency was achieved as high as 36±5% with dairy manure mixed with sludge pellet. At a higher operating temperature, higher efficiency was obtained with increased gas composition of hydrogen and carbon monoxide. This syngas may then be used for power generation as well as possible input gas for the Fisher Tropsch process for liquid biofuel production. The result of the experiments will be a cornerstone for the widespread application of low heating value animal waste for producing high heating value syngas that may be used for electric power generation as a result of various upgrading processes.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A035. doi:10.1115/IMECE2015-52259.

This paper reports advancement in bringing flexible piezoelectric nanogenerators (NGs) closer to being realized in a commercial market. We have adopted a method to synthesize piezoelectric ZnO nanorods (NRs) on any electrically conductive surface without a seed layer or a specially selected substrate with matching lattice spacing. By contacting a metal with a dissimilar electro-negativity, a galvanic cell is created in the electrolyte growth medium. We have demonstrated the performance of the as grown NRs on a thin NG using common PET film. The device produced voltages in excess of three times higher than a parallel fabricated reference sample under bending loads.

Commentary by Dr. Valentin Fuster

Energy: Renewable Energy

2015;():V06BT07A036. doi:10.1115/IMECE2015-50191.

Tidal current energy is regarded as one of the most promising alternative energy resources for its minimal environmental footprint and high-energy density. The device used to harness tidal current energy is the tidal current turbine, which shares similar working principle with wind turbines. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation. There is a paucity of information regarding various key aspects of system design encountered in this relatively new area of research. Not much work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship’s propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. A tidal current turbine rated at 1–3 m/s in water can result in four times as much energy per year/m2 of rotor swept area as similarly rated power wind turbine. Areas with high marine current flows commonly occur in narrow straits, between islands, and around. There are many sites worldwide with current velocities around 2.5 m/s, such as near the UK, Italy, the Philippines, and Japan. In the United States, the Florida Current and the Gulf Stream are reasonably swift and continuous currents moving close to shore in areas where there is a demand for power. In this study tidal current turbines are designed for several high tidal current areas around USA for a tidal current speed range from 1 m/s to 2.5 m/s. Several locations around USA are considered, e.g. the Gulf Stream; Mississippi River, St. Clair’s river connecting Lake Huron to Lake St. Clair’s; Colorado River within Cataract Canyon etc. Tidal current turbines can be classified as either horizontal or vertical axis turbines. In this study several designs from both the classifications are considered and modeled using SolidWorks. Hydrodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and ultimate power generation capacity. From flow simulations, forces on the tidal current turbine blades and structures are calculated, and used in subsequent stress analysis using SolidWorks Simulation software to confirm structural integrity. The comparative results from this study will help in the systematic optimization of the tidal current turbine designs at various locations.

Topics: Turbines , Tides
Commentary by Dr. Valentin Fuster
2015;():V06BT07A037. doi:10.1115/IMECE2015-50311.

A SUNTRACKER (illustrated in figure1), is a Concentrating Solar Power (CSP) unit, in the category of solar dish engines. The novel solar dish engine module (shown in figure 2) is designed to provide 10.1kW electric power (measured at the engine output electric power lugs), from a conversion of 21kW solar energy from the solar dish reflective sun light to the high temperature receiver focal point. Total electric power output from the solar dish engine module is attributed to combined cycles, closed brayton cycle (CBC) and a organic rankine cycle (ORC), both of which are hermetically sealed to atmosphere. The CBC engine receives 21kW solar energy from a solar dish, estimated to have 27 square meters (291 square feet) reflective surface area. However, unlike the photovoltaic (PV) units, the SUNTRACKER will provide increased use of available solar energy from sunlight. Concentrated sunlight from the dish will focus on the CBC engine receiver, which in turn heats the working fluid media to as much as 1600F, pending the ratio of solar dish to receiver areas. A specific gas mixture of xenon/helium, with excellent thermodynamic properties is used for the high temperature application. Turbomachinery in the CBC engine has one moving part / assembly (compressor impeller, alternator rotor and turbine rotor), mounted on compliant foil bearings. Reference figure 4 as an example. The engine operates with a compressor impeller stage pressure ratio 1.6, and is recuperated. Electric power, measured at the CBC engine electric power lugs, is 6.4kW. The CBC engine is not new, (a closed Brayton cycle, sealed to atmosphere) [1], [4], [8], [18], [19]. However, the application to extract thermal energy from the sunlight and provide electric power in commercial and residential use is (patented). In addition, to increase the efficiency of solar energy conversion to electric power, waste heat from the CBC engine provides thermal energy to an ORC engine, to generate an additional electrical output of 3.7kW (measured at the output electric power lugs). With use of an ORC system, the size of the radiator (CBC unit) for heat rejection is reduced significantly. Working fluid HFC-RC245fa [10] was selected for the ORC unit, based on the low temperature application. Also, as with the CBC turbomachinery, the ORC rotor assembly has one moving part, comprised of a pump impeller, alternator rotor and turbine rotor. With the two engines combined, total system thermal efficiency is 48% (10.1kW electric power out / 21kW solar energy in). However, power electronics are needed for conversion of high frequency voltage at the engine output electric power leads to 60/50 Hz power, for customer use. Power electronics losses for this machine, debits the power 0.5 kW. Thus total electric power to the customer, as measured at power electronics output terminals, is 9.6kW. With solar energy, from the reflective sunlight solar dish 21kW and measured output power from the power electronics 9.6kW, the conversion of solar energy to useful electric power an efficiency 46% (i.e. 9.6kW / 21kW). In addition, the design does not require external water / liquid for cooling.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A038. doi:10.1115/IMECE2015-50478.

In this work, a novel Ground-Level Integrated Diverse Energy Storage (GLIDES) system which can store energy via input of electricity or heat and deliver dispatchable electricity is presented [1]. The proposed system is low-cost and hybridizes compressed air and pumped-storage approaches that will allow for the off-peak storage of intermittent renewable energy for use during peak times. A detailed control-volume energy analysis of the system is carried out, yielding a set of coupled differential equations which are discretized using a finite difference scheme and used to model the transient response during charging and discharging. The energy analysis includes coupled heat transfer and pressure drop analysis used to predict system losses for more accurate round trip efficiency (RTE) calculations and specific energy density (ED) predictions. Preliminary analysis of the current prototype indicates an electric-to-electric RTEE of 66% (corresponding to shaft-to-shaft mechanical RTEM of 78%) and ED of 2.5 MJ/m3 of air, given initial air volume and pressure of 2 m3 and 70 bar. The electric power output ranges from a max of 2.5 kW to a min of 1.2 kW and the output current ranges from a max of approximately 21 amps to approximately 10 amps at 120 V, 60 Hz dispatchable electricity, over a period of approximately 50 minutes. Additionally, it is shown that heat transfer enhancement to the point of a 5-fold increase in air heat transfer rates results in a near 5% improvement in RTEE (70% considering all component losses). Additional component efficiency improvements and efficiency gains due to system scale-up could see higher achievable RTEs.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A039. doi:10.1115/IMECE2015-50652.

In this paper a novel method is presented to store energy in order to overcome the intermittent power supply problems caused by the use of conventional wind turbines. This novel method is based on the recognition that the winds over the oceans can be harnessed by means of sailing ships equipped with hydrokinetic turbines whose electric output can be used to charge electric batteries or to convert the seawater into hydrogen. It is shown that small off-grid communities can be supplied with stable year-round power by means of a small fleet of remotely controlled ships which operate in high-wind ocean areas. A prelimina1y cost analysis indicates that this energy ship concept is economically competitive with land-based wind-hydrogen systems. Also, it is shown that the Hawaiian Islands can be provided with stable year-round power by the use of large-scale energy ships operating in high-wind areas to produce hydrogen and by the use of energy ships operating in Hawaiian waters to charge the batteries of plug-in hybrid electric vehicles.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A040. doi:10.1115/IMECE2015-50683.

Over the past decade wind turbines have been proven to be a competitive contender to produce cheap electricity. Their output electrical power went from few dozens of watts to several megawatts, and this trend is continuing to increase as they become larger in size. Most of these wind turbines are typically regulated through a set of controls acting on the electricity generator workload. These controls are achieved through the use of power electronics controlling the electrical load on the generator for variable speed wind turbine. This paper explores the possibility of implementing an alternative control system in variable wind speed turbines using a special gearbox with a high number of close consecutive discrete gear ratios. The proposed gear based Quasi-Continuous Variable Transmission, called QCVT, allows a variable speed at the input shaft and delivers a quasi-constant speed at the output shaft of the gearbox. The system consists of a special drivetrain assembly of spur gears run and controlled automatically through a set of clutch power shifters. The clutches are used to shift a set of compound gears, thus modifying the drivetrain total gear ratio. The designed system can produce up to 625 gear ratios and acts as a quasi-continuously variable transmission between the wind turbine hub and the electricity generator which requires a constant entry speed delivering a frequency of 60 Hz. The gearing transmission system has been designed using the SolidWorks CAD software for modeling and simulation and the gearing design theory has been used to dimension the special drivetrain assembly of spur gears. The kinematic gearing theory has been used to establish the multitude of close consecutive discrete gearing ratios of the transmission system. A wind driven rotor model for the wind turbine power coefficient has been used to determine the power absorbed by the wind turbine from the blowing wind and the power delivered to the electricity generator. The wind turbine torque generated by the wind and the torque produced at the electricity generator have also been determined using the multitude of gear ratios of the designed drivetrain. A new control law is established to keep the wind turbine generator running at a quasi-constant speed while producing maximum power. Considering the QCVT with its numerous close and consecutive gear ratios as the main torque regulator, the wind turbine system is expected to deliver the right needed torque for a specified electrical load. A set of results featuring how the electricity generator power and torque can be controlled by shifting the ratios of drivetrain transmissions are delivered. A particular emphasis is put on maximizing the generator delivered power using controlled gear ratios while the speed of the wind is changing. A small scale prototype of the QCVT powertrain transmission has been designed and built for concept demonstration and testing purposes.

Topics: Gears , Wind turbines
Commentary by Dr. Valentin Fuster
2015;():V06BT07A041. doi:10.1115/IMECE2015-50739.

The ongoing advanced space exploration requires the novel energy sources that can generate power for extreme duration without need of refill. The long duration betavoltaic devices are presented using conjugated polymer with scintillators. The Monte Carlo simulations are used to study the interaction of electron beam with two different scintillators, Cerium doped Yttrium Aluminum Garnet (Ce:YAG) and Thallium doped Cesium Iodide (CsI:Tl). The catholuminescence profiles from simulation showed that CsI:Tl is more-efficient to generate photons when hit by electron beam compared to Ce:YAG. The semiconductive conjugated polymer device stack of ITO/PEDOT:PSS/P3HT:ICBA/Al are then fabricated and tested with Ce:YAG and CsI:Tl scintillators under different electron beam energies. The electrical current is successfully extracted from these betavoltaic devices when illuminated with electron beams. As expected, the betavoltaic devices with CsI:Tl scintillator performed better compared with Ce:YAG. The maximum power conversion efficiency (PCE) of 0.24% is obtained at 10 kV electron beam with CsI:Tl, while PCE in device with Ce:YAG is 0.16%. The short circuit current in devices with CsI:Tl is about 57%, greater than in devices with Ce:YAG. The experimental result showed that output electrical power increased with increase in incident electron beam energy.

Topics: Polymers
Commentary by Dr. Valentin Fuster
2015;():V06BT07A042. doi:10.1115/IMECE2015-50793.

There is an important need for improvement in both cost and efficiency of photovoltaic cells. For improved efficiency a better understanding of solar cell performance is required. In this paper we propose an analytical kinetic model of thin-film silicon solar cell, which can provide an intuitive understanding of the effect of illumination on its charge carriers and electric current. The separate cases of homogeneous and inhomogeneous charge carrier generation rates across the device are investigated. Our model also provides for the study of the carrier transport within the quasi-neutral and depletion zones of the device, which is of importance for thin-film solar cells. Two boundary conditions based on (i) fixed surface recombination velocity at the electrodes and (ii) intrinsic conditions for large size devices are explored. The device short circuit current and open circuit voltage are found to increase with the decrease of surface recombination velocity at electrodes. The power conversion efficiency of thin film solar cells is observed to strongly depend on impurity doping concentrations. The developed analytical kinetic model can be used to optimize the design and performance of thin-film solar cells without involving highly complicating numerical codes to solve the corresponding drift-diffusion equations.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A043. doi:10.1115/IMECE2015-50809.

The dynamic motion of tethered undersea kites (TUSK) is studied using numerical simulations. TUSK systems consist of a rigid-winged kite moving in an ocean current. The kite is connected by tethers to a platform on the ocean surface or anchored to the seabed. Hydrodynamic forces generated by the kite are transmitted through the tethers to a generator on the platform to produce electricity. TUSK systems are being considered as an alternative to marine turbines since the kite can move in high speed motions to increase power production compared to conventional marine turbines. The two-dimensional Navier-Stokes equations are solved on a regular structured grid that comprises the ocean current flow, and an immersed boundary method is used for the rigid kite. A two-step projection method along with Open Multi-Processing (OpenMP) is employed to solve the flow equations. The reel-out and reel-in velocities of the two tethers are adjusted to control the kite angle of attack and the resultant hydrodynamic forces. A baseline simulation was studied where a high net power output was achieved during successive kite power and retraction phases. System power output, vorticity flow fields, tether tensions, and hydrodynamic coefficients for the kite are determined. The power output results are in good agreement with established theoretical results for a kite moving in two dimensions.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A044. doi:10.1115/IMECE2015-50959.

The use of renewable energy with storage systems is particularly important in small and unreliable grids, such as islands. This paper reports sizing of a photovoltaic (PV) power plant with storage system for Middle East Technical University Northern Cyprus Campus through technical and economic analyses. PV system was modeled considering fixed tilted, one-axis and two-axis tracking systems using hourly data. Energy storage system was included in the model to overcome the temporal mismatch between the electricity demand of the campus and the electricity supplied by the PV system. The reduction in CO2 emissions by deploying these systems was studied. The results showed that although it would not be economically feasible to meet the entire demand of the campus, a PV system of 4.5 MW with 15 MWh of storage size would generate enough electricity to meet the demand for 83% of the time in a year, yielding the cost of 0.25 USD/kWh.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A045. doi:10.1115/IMECE2015-51157.

Large offshore renewable energy investments require the use of maintenance boats to keep them in operable conditions. Unfortunately, due to rough seas in some of the project locations, the transferring of crew members from vessel to turbine or platform is no easy task. Thus, the research presented is focused at further looking into add on stability systems for marine vessels to further ease the process of offshore platform maintenance and crew member safety.

The rolling and pitching of ships and boats induced by the ocean waves results in undesirable motion. In an effort to increase the stability of the deck/platform and human comfort and safety, various add-on stability systems have been developed. Of interest in the research presented are internal active systems, specifically the active gyroscopic stabilizer.

Previous research and industrial use of active gyroscopic roll stabilizers has shown and proven the effectiveness of the system to reduce rolling motion. The research presented here is focused on developing a more detailed mathematical analysis of a marine vessel installed with active gyroscopic roll stabilizer(s). Through the use of the moving frame method developed by the second author, a novel approach has been developed to derive a mathematical model for two different cases: 1) a marine vessel with a single gyroscopic roll stabilizer and 2) a marine vessel with two gyroscopic roll stabilizers. The moving frame method allows for a systematic derivation despite the increase in complexity of the system as the number of stabilizers is increased. Lastly, the nonlinear equations of motion of a ship with a gyroscopic roll stabilizer are derived.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A046. doi:10.1115/IMECE2015-51163.

Global attempts to increase generation of clean and reproducible natural energy have greatly contributed to the progress of solar, wind, biomass, and geothermal energy generation. To meet the goal set by the Renewable Portfolio Standards (RPS) in the United States, it is advisable for several of the coastal states to tap into the least explored resource: ocean-wave energy. There are many advantages to ocean-wave energy generation. First, the energy per unit area is 20 to 30 times larger compared with solar and five to ten times larger when compared to wind energy. Second, waves are more easily predicted than wind. Currently, there are several challenges with capturing ocean energy: With respect to the environment, noise pollution and effects on marine life need to be taken into consideration; with respect to design, ocean-wave power generators need to withstand large waves due to hurricanes and be designed to lessen visual pollution.

There are various methods and devices used to capture ocean wave energy. Point absorbers, such as PowerBuoy, can harness vertical or heaving motion into electricity while attenuators like Pelamis use the induced movement of its joints from the incoming waves. Unfortunately, many have few parameters that can be varied to optimize power generation and or suffer from the various challenges mentioned above. The gyroscopic ocean wave energy converter harnesses the rocking or pitching motion induced by the ocean waves and converts it into rotary motion that is then fed to a generator. Furthermore, it is a fully enclosed floating device that has several parameters that can be varied to optimize power output. Previous work has demonstrated the viability of such a device, but the theoretical modeling of these converters is still in its infancy compared to that of other ocean wave energy converters. The objective of the research presented is to fully understand the mechanisms of power generation in the gyroscopic ocean wave energy converter. Using the moving frame method, a mathematical model of the device is developed. The nonlinear equations of motion are derived through the use of this novel method and then solved numerically. The results are then used to optimize the system and identify key parameters and their effect on the output power generated. Additionally, the resulting equations serve as a tool for identifying an appropriate control strategy for the system. Finally, a scale model of a gyroscopic ocean wave energy converter is developed to validate the equations of motion that have been derived.

Topics: Wave energy
Commentary by Dr. Valentin Fuster
2015;():V06BT07A047. doi:10.1115/IMECE2015-51461.

One of the best ways of making efficient use of energy in residential units is to use heat pump. Heat pump performance can be further enhanced by integrating a solar thermal unit to provide hot water and subsidize space heating. This paper presents numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence, where a flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solar fluid heat transfer coefficient has been conducted to determine the required solar collector heat transfer characteristics in this system. Solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator availability was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achievement of this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solar fluid heat transfer coefficient (U-value) with a factor of 6 to 8 compared to the base case with only natural convection heat exchange between solar collector cover and ambient.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A048. doi:10.1115/IMECE2015-51477.

In the present work the authors propose a solar powered cascaded multilevel inverter which can be integrated with the grid. To connect the solar photovoltaic system to the grid a dc to ac conversion of power is required which is made possible using a multilevel inverter, but the power electronic switches introduces harmonics during the switching process. Thus the investigators propose a selective harmonic elimination technique using Genetic Algorithm and Differential Evolution Optimization Techniques. The performance comparisons of the proposed techniques will be carried out by comparing the Total Harmonic Distortion (THD) and the selective harmonics such as 5th, 7th,11th and 13th using FFT analysis in MATLAB/SIMULINK. The authors anticipate that the comparative analysis presented in this work will be very useful for further research.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A049. doi:10.1115/IMECE2015-51498.

Fossil fuels have been the main supply of power generation for use in manufacturing, transportation, residential and commercial sectors. However, environmentally adverse effects of fossil fuel conversion systems combined with pending shortage raise major concerns. As a promising approach to tackle these challenges, this paper presents a novel energy conversion system comprising of a solar thermal reactor coupled with hydrogen fuel cell and carbon fuel cell for electricity generation. The system uses concentrated solar energy for high temperature heat which upgrades the calorific value of the feedstock by 8%. The paper describes the components and characteristics of the proposed concept and models the energy flow of this system. A comparison based on unit mass feedstock supply is made with conventional Brayton cycles for electricity production. The results show that the extent of acetylene byproduct conversion in the solar reactor is of crucial importance to ensure competitiveness. Depending on the fuel cells efficiency and even more on the extent of byproduct formation, the results show that the overall chemical-to-electrical efficiency of this combined system ranges from 35 to 58%.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A050. doi:10.1115/IMECE2015-51650.

A renewable energy harvesting system is designed and tested for micro power generation. Such systems have applications ranging from mobile use to off-grid remote applications. This study analyzed the use of micro power generation for small unmanned aerial vehicle (UAV) flight operations. The renewable energy harvesting system consisted of a small wind turbine, flexible type PV panels and a small fuel cell. Fuel cell is considered the stable source while PV and wind turbine produced varying power output. The load of around 250 W is simulated by a small motor. The micro wind turbine with the total length of 4.5 m and the disk diameter of 1.8 m is tested. The micro wind turbine dimensions make it big enough to be used to charge batteries yet small enough to be installed on rooftops or easily transportable. The wind turbine blades are installed at an angle of 22°, with respect to the disk plane, as it gives the highest rotation. The voltage and current output for the corresponding RPM and wind speeds are recorded for the wind turbine. Two 2 m and a single 1 m long WaveSol Light PV panels are tested. The PV tests are conducted to get the current and voltage output with respect to the solar flux. The variation in solar flux represented the time of day and seasons. A 250 W PEM fuel cell is tested to run the desired load. Fuel cell’s hydrogen pressure drop is recorded against the output electrical power and the run time is recorded. System performance is evaluated under different operating and environmental conditions. Data is collected for a wide range of conditions to analyze the usability of renewable energy harvesting system. This energy harvesting method significantly improves the usability and output of the renewable energy sources. It also shows that small renewable energy systems have existing applications.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A051. doi:10.1115/IMECE2015-51745.

Today a large-scale wind turbine blade can be 70 m long and 5 m in root chord length, and it is fabricated in a single piece. This feature leads to high initial costs, as transportation of a large blade requires special trucks, escorts, and road adaptations. These constraints can account for approximately 6–7% of the total investment for the blade. In addition, the manufacturing process commonly used is a hand lay-up configuration of thermoset composite sheets. These materials are not reusable after fabrication, which is a non-renewable feature of existing systems. The project consists of manufacturing thermoplastic composite blades in segments, which are joined before installation at the turbine site. This paper addresses the preliminary research results when conducting design and fabrication of a small blade with this innovative approach. Three segmented blades are manufactured for a horizontal-axis wind turbine, with each blade having a 50 cm span and a 4 cm tip chord length. The blade size and profile are designed based on the idealized Betz limit condition. The material used for manufacturing is a glass fiber reinforced thermoplastic composite system with a polypropylene matrix that melts at 200 °C. Each blade is fabricated in 4 independently manufactured pieces, consisting of top/bottom, and tip/root segments, via a vacuum assisted thermoforming technique. The parts will be assembled afterwards by a joining process, forming the final part for site testing.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A052. doi:10.1115/IMECE2015-51865.

In conventional solar water heaters, the thermal energy storage is accomplished by increasing the sensible heat in a fluid. Therefore, the accumulation capacity of sensible heat is proportional to the mass storage and the increase of temperature, so that an increase in the requirements involves a bigger tank volume. Phase change materials (PCM) stored energy at constant temperature (or at least in a fairly narrow range of temperature) while the phase change is produced, they are presented as an alternative to compensate the solar heat supply periods and the thermal demand with a better heat accumulation per volume unit. In contrast, these systems require more complicated thermal analysis and designs than the traditional systems by sensible heat with a single phase. The selection of PCM, its content and location on the device will have a determining effect on the overall performance of the solar collector. This implies that the heat exchanger must be designed for each specific application.

Currently, there are no commercial devices for heating water by solar energy using thermal accumulation with PCM. However, preliminary studies in lab scale have shown significant increases in efficiencies and supply capacity. Several authors have been performed experimental and numerical studies in solar collectors including PCM technology, but, due to the complexity of the phenomena and the high consumptions of resources for both approaches, it has not been possible to evaluate different configurations that lead to optimized designs for selection, location and amount of PCM. This fact shows the need to develop simplified models that consider the main physical phenomena in the operation, in order to support the experimental and numerical techniques to determine the comprehensive thermal behavior. This kind of models can be used to estimate the performance for different configurations and boundary conditions in a fast way, to make possible in a posterior stage a detailed evaluation with numerical analysis or an experimental technique.

In this paper, a simplified comprehensive model for assessing thermal performance of a flat-plate solar collector with PCM is presented with incorporation of specialized semi-empirical correlations. The model takes into account the main thermodynamic and heat transfer processes in the device, including the internal and external convection effects, conduction, solar radiation analysis, radiation, losses and interactions between surfaces, material solid-liquid phase change and conjugated problems in gas-liquid-solid zones.

Due to the numerous existing design alternatives, consideration of an excessive number of options in the final design can lead to long development times and process inefficiencies. Therefore, a methodology of design that includes fast calculations of the main thermal parameters is highly regarded, since this can reduce the number of study cases and thus obtain optimal configurations from the simplified models.

The performance of the reduced model, including a sensibility analysis of several input data, is compared qualitatively with results obtained in a traditional collector for a typical cycle available in bibliography. Integrated simplified models are developed to perform a coarse preliminary design of flat solar collectors with incorporation of PCM technology, and thus serve as a pre-evaluator of the different configurations.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A053. doi:10.1115/IMECE2015-51904.

In this paper, we introduce a symmetric five-bar compliant mechanism for the displacement amplification of mechanical vibration. When the proposed mechanism is connected to an energy harvester, input excitation vibrations to the mechanism are amplified, which leads to an increase in harvested power. The mechanism is composed of both rigid links and flexure hinges, which enable deflection. The flexure hinges we use are either of the right-circular, or the corner-filleted types. The mechanism is analyzed using a pseudo-rigid-body-model, where flexure hinges are substituted with rotational springs. We developed an analytical model of the displacement amplification, which was validated both experimentally and numerically using a finite element model. Our model reveals that the displacement amplification is a function in design parameters, such as the geometry of the mechanism, the flexure hinges stiffness, in addition to the load caused by the harvester. The effects of the flexure hinge dimensions on the flexure hinges stiffness, and thus on displacement amplification were investigated. Preliminary experiments indicate the success of our proposed mechanism in amplifying small excitation harmonic inputs and generation of power.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A054. doi:10.1115/IMECE2015-51973.

The last decade has seen the increase of solar and wind generation systems which has led to high grid penetration of such technologies. Currently, the issue of grid stability and reliability with increased levels of such non-dispatchable generation is of great fundamental concern. This paper reports on the results of analyzing 15 min monitored data over a whole year from a large university campus with over 50% solar penetration of one of its four sub-stations. Net loads or electric purchases are the differences between the campus electric load and the electricity production of the solar system. These net loads are analyzed both in terms of diurnal “duck curves” and as load duration curves in order to determine the frequency and magnitude of different ramping up and down events experienced during the on-peak and off-peak periods. The extent to which such events can be tempered by installing combined heat and power (CHP) systems is studied, and it is found that increases in levels of net load stability vary non-linearly with size of the installed CHP system. Though the results are specific to this case study, the methodology adopted and some of the results and conclusions reached would be useful to those performing similar evaluations in other parts of the world.

Topics: Stress , Solar energy
Commentary by Dr. Valentin Fuster
2015;():V06BT07A055. doi:10.1115/IMECE2015-52082.

The optimum design of stationary flat-plate solar collectors is considered using the game theory approach for multiple objectives. The clear day solar beam radiation and diffuse radiation at the location of the solar collector are estimated. Three objectives are considered in the optimization problem formulation: maximization of the annual average incident solar energy, maximization of the lowest month incident solar energy and minimization of the cost. The game theory solution represents the best compromise in terms of the supercriterion selected. Because some design parameters such as solar constant, altitude, typical day of each month and most of the design variables are not precisely known, a probabilistic approach is also proposed in this work. The results obtained by the determinist and probabilistic approaches are compared. It is found that the absolute value of each objective function decreases with an increase in either the probability of constraint satisfaction or the coefficient of variation of the random variables. This work represents the first work aimed at the application of multi-objective optimization strategy, particularly the game theory approach, for the solution of the solar collector design problem.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A056. doi:10.1115/IMECE2015-52093.

The robust design of horizontal axis wind turbines, including both parameter and tolerance designs, is presented. A simple way of designing robust horizontal axis wind turbine systems under realistic conditions is outlined with multiple design variables, multiple objectives, and multiple constraints simultaneously by using the traditional Taguchi method and its extensions. The performance of the turbine is predicted using the axial momentum theory and the blade element momentum theory. In the parameter design stage, the energy output of the turbine is maximized using the Taguchi method and an extended penalty-based Taguchi method is proposed to solve constrained parameter design problems. Using an appropriate set of tolerance settings of the parameters, the tolerance design problem is formulated so as to yield an economical design while ensuring a minimal variability in the performance of the wind turbine. The present work provides a simple and economical approach for the robust optimal design of horizontal axis wind turbines.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A057. doi:10.1115/IMECE2015-52521.

Heat-driven ejector refrigeration system is one of the fastest emerging technologies in cooling applications for years. This is due to the fact that it can harness cooling capacity from waste heat sources at above 80 °C. Low coefficient of performance (compared to commercial vapor compression systems) is the major disadvantage of the said system, and thus it became a topic of research studies in the field of cooling. The work required by the compressor in a vapor compression cycle (VCC) can be eliminated by using waste heat from any available heat source. Although a relatively lower COP was obtained, the savings using the ejector refrigeration system can cover all the disadvantages and proved that this system can be actually helpful if implemented in the real working systems with waste heat.

In this study, a mathematical model for determining ejector parameters and performance was developed and applied to a system where shock was tried to be avoided. The model was coded into a computer program to allow easier computation of the ejector geometric and thermo-fluid dynamic parameters with varying input data such as the refrigerant to be used, evaporator and condensing temperatures, entrainment ratio, and velocity of the fluid flows. An ejector refrigeration system using ammonia, propane, R22, R134a, R1234yf, and R245fa as refrigerants was simulated using the said model. A boiler or generator temperature of 90 °C, a condenser temperature of 40 °C, and a refrigerating capacity of 35kW were maintained for all the refrigerants; however, the evaporator temperature was varied within the range of −10 °C to 10 °C, depending on the behavior of the system. A combination of a short straight section and then a converging-diverging profile was used for the combined mixing section and diffuser to smoothly decelerate the fully mixed supersonic flow exiting the short mixing section and thereby avoid shock waves in the section. The resulting parameters including the ejector dimensions, pressure and Mach number were determined along the length of the ejector. For all the simulation runs, the fluids respond as expected and the expansion energy was utilized from the high pressure side of the ejector as shown in the trend of pressure along the length of the ejector. Ejector size varies a little for different refrigerants; the calculated range of length is from 0.14 m to 0.36 m — this range shows the compactness of the resulting ejectors.

The results show that a VCC refrigeration system can be replaced by a heat-driven ejector refrigeration system with the ejector that was designed from the simulations. Since the two systems are designed to have the same refrigerating capacity and working temperatures, it can be projected that savings can be made by using the ejector system. The compactness of the ejector produced in the simulations show a good potential for this kind of refrigerating system to be manufactured and mass produced.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A058. doi:10.1115/IMECE2015-52857.

According to the World Energy Council (WEC) the estimated energy of the wave power in the world is in the range of 8,000 to 80,000 TWh/year to depths of 100 meters or higher and actually the utilization of wave energy resource it is possible because it has been implemented in countries like Australia, Indonesia, Nigeria, United Kingdom, Norway, Portugal and Colombia evaluating different types of marine technologies that take the advantage of the kinetic energy in the ocean waves.

Mexico according to the National Institute of Statistics and Information (INEGI) has a land area of 1,972,550 km2 of which has a coastline of 11,150 km having potential for the use of their coasts. Baja California with a land area of 71,445 km2 (3.6% of the country) is located on a peninsula in northwest Mexico and has 720 km of coastline on the Pacific Ocean (6.4% nationally) with a range of depths of 25.6 m to 650 m at a distance of the coastline of 15 km, which makes it suitable to evaluate the use of wave energy at local sites.

With the completion of this work will contribute to the characterization of the sites that will present the best technical and economic conditions for its implementation, considering the physical characteristics of the site as well as connection points on the transmission lines operated by the Federal Electricity Commission (CFE).

For the preparation of this study was carried out in three stages: a) Site Selection, b) Evaluation of Wave Energy and c) Economic evaluation of sites using RETScreen.

Based on the characteristics of the coast of Baja California the results obtained are the following: 1) 18 sites were selected with a sea depth averaged of 50 m, the annual density power was 7.5 kW/m, this represents a potential of 210 MW considering an average length of 2 km in each site, 2) The economic evaluation of this type of project was for a period of 30 years in RETScreen, considers an annual inflation rate of 5% and obtains an investment cost of 9,538 US $/kW for this type of generation. We conclude that this source of energy will reduce dependence on fossil fuels and contribute to the generation of electricity in the state of Baja California diversifying the energetic matrix state by the use of clean and renewable sources, which represents an investment opportunity between the public and private sector.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A059. doi:10.1115/IMECE2015-52865.

3D wind field construction is important in many aspects, such as wind energy assessment, wind turbine siting and weather forecasting. The development of Computational Fluid Dynamics (CFD) 3D wind flow over complex terrain and boundary conditions in simulation has been studied intensively over past thirty years. However, the topographical effects has seldom been considered in the 3-D wind field construction in suburban environment. In this paper, 3-D wind field is constructed with consideration of terrain effects. 3-D terrain flowing mesh is built from digital elevation data (DEM) by in house codes. The Reynolds-averaged Navier-Stokes equations are solved by the standard k-ε turbulence model with Ansys Fluent©. The integration between the topographical effects and 3D wind field in suburban environment is investigated. Simulation results of 3-D wind field, wind velocity distributions, turbulence intensity distributions, wind power density distributions and wind profiles are obtained around Purdue University Calumet (PUC) campus. Additionally, the surround building effect and topographical effect are discussed. The simulation results are validated against measurements data.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A060. doi:10.1115/IMECE2015-52898.

In this present paper, nanoparticles are dispersed into a base fluid, their effect on the thermophysical properties and overall heat transfer coefficient of the fluid inside a circular tube representing an absorber tube of a Parabolic Trough Solar Collector (PTSC) is studied. Different models are used to predict the effective density, specific heat capacity, viscosity and thermal conductivity of the nanofluids. For the analytical analysis, Alumina (Al2O3), Copper (Cu) and Single Wall Carbon Nanotubes (SWCNT) nanoparticles are dispersed into Therminol VP-1 oil. The resulting nanofluids are compared in terms of their thermophysical properties, their convective heat transfer characteristics and their overall heat transfer coefficient. Moreover, the effect on increasing the volume fraction on the properties and the heat transfer coefficient is studied. The computational analysis results show that the thermal conductivity increases with the increase of the volume fraction. In addition Therminol/SWCNT showed the highest thermal conductivity enhancement of 98% for a volume fraction of 3%. Further, the overall heat transfer coefficient increases with the increase of volume fraction, and Therminol/SWCNT showed the highest enhancement with 72% compared to Al2O3/Therminol and Cu/Therminol that showed an enhancement of 29% and 43% respectively.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A061. doi:10.1115/IMECE2015-53455.

A suite of nonlinear dynamical simulations of in-stream hydrokinetic devices has been developed and this paper discussed the linearization of these models for control system development. One of these numerical simulations represents a small 3 meter rotor diameter, 35 kW turbine with fixed pitch blades, and the other a 20 meter, 700 kW turbine with variable pitch blades. Each turbine simulation can be operated to represent a bottom mounted tidal turbine or a moored ocean current turbine. These nonlinear dynamical models can serve as stepping stones toward control system design using linear or nonlinear, time or frequency-domain methodologies. A common step further toward controller synthesis is to obtain linearized models of the system dynamics. Towards this end, two linearization techniques are presented. The first is based straightforward analytical and numerical linearization of the full nonlinear state-space equations of the plant; this method has been applied for the underwater flight dynamics of the 700 kW plant. The second is a phenomenological system identification approach consisting of data analysis performed on time series obtained through simulations; it has been used to model the system of systems in the case of the 35 kW plant. In the first approach, the linearized model is valid for specific operating conditions around equilibrium values of the state variables. In the second approach, the plant dynamical model is used as a black-box in order to obtain the simulated response of the system to a variety of test input signals, like e.g. sinusoids of relatively small amplitudes and various frequencies superimposed to steady-state offsets; in effect, a phenomenological model is derived describing the plant dynamics. The outcomes of both approaches are assessed and several conclusions are drawn from the analysis.

Commentary by Dr. Valentin Fuster
2015;():V06BT07A062. doi:10.1115/IMECE2015-53821.

The State of Kuwait is considering diversifying its energy sector and not entirely depend on oil. This desire is motivated by Kuwait commitment to reducing its share of pollution, as a result of burning fossil fuel, and to extend the life of its oil and gas reserves. The potential for solar energy in Kuwait is quite obvious; however, it is not the case when it comes to wind energy. The aim of this work was to analyze wind data from several sites in Kuwait and assess their suitability for building large-scale wind farms. The analysis of hourly averaged wind data showed that some sites can have an average wind speed as high as 5.3 m/s at 10 m height. The power density using Weibull distribution function was calculated for the most promising sites. The prevailing wind direction for these sites was also determined using wind-rose charts. The power curves of several Gamesa turbines were used in order to identify the best turbine model in terms of specific power production cost. The results showed that the area of Abraq Al-Habari has the highest potential for building a large-scale wind farm. The payback period of investments was found to be around 7 years and the cost of electricity production was around US Cent 4/kWh.

Commentary by Dr. Valentin Fuster

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