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The solar energy converter in Concentrated Solar Power (CSP) system, applies the solid frame structure of the ceramic foams to receive the concentrated solar radiation, convert it into thermal energy, and heat the air flow through the ceramic foams by convection heat transfer. In this paper, first, the pressure drops in the studied ceramic foams were measured under all kinds of flow condition. Based on the experimental results, an empirical numerical model was built for the air flow through ceramic foams. Second, a 3-D numerical model was built, for the receiving and conversion of the solar energy in the ceramic foams of the solar energy converter. Third, applying two aforementioned numerical models, the numerical studies of the thermal performance were carried out, for the solar energy converter filled with the ceramic foams, and results show that the structure parameters of the ceramic foams, the effective reflective area and the solar radiation intensity of the solar concentrator, have direct impacts on the absorptivity and conversion efficiency of the solar energy in the solar energy converter. And the results of the numerical studies are found to be in reasonable agreement with the experimental measurements. This paper will provide a reference for the design and manufacture of the solar energy converter with the ceramic foams.Copyright © 2011 by ASME

An exergoeconomic analysis identifies the location, magnitude and sources of thermodynamic inefficiencies and costs in an energy conversion system. This information is used for improving the thermodynamic and the economic performance and for comparing various systems. A conventional exergy-based analysis does not consider the interactions among the components of a system nor the real potential for improving the system. These shortcomings can be addressed and the quality of the conclusions obtained from an exergoeconomic evaluation is improved, when for each important system component the values of exergy destruction and costs are split into endogenous/exogenous and avoidable/unavoidable parts. We call the analyses resulting from such splittings advanced exergy-based analyses. The paper demonstrates how an advanced exergoeconomic analysis provides the user with information on the formation processes of thermodynamic inefficiencies and costs and with suggestions for their minimization. In the first part of the paper, the advanced exergy-based analyses are applied to an air refrigeration machine. In the second part of the paper, we demonstrate that the information obtained in the first part can be used to modify the values of the decision variables to reduce the cost of the final product (cold) of the overall system.Copyright © 2011 by ASME

Alternative energy storage systems (AESS) are receiving considerable interest today for low-cost mild-hybrid vehicles where the electrical system is substituted with mechanical or hydraulic energy storage. As these technologies are being explored, simulation tools become helpful to predict the behavior of the energy storage system during vehicle use, as well as to conduct comparative studies evaluating the energy and power density, fuel economy improvement, system weight and costs. This paper presents an energy-based modeling approach to characterize the low-frequency dynamic behavior of alternative energy storage systems for hybrid vehicle applications, with the ability to predict the energy flows and sources of energy loss during driving operations. The model aims at evaluating the potential, in terms of efficiency and fuel economy improvement, offered by non-electrified energy storage systems, such as mechanical (flywheels) or hydraulic (accumulators). The modeling tool developed is able to provide a characterization of the performance of each of the two systems starting from a characterization of the components energy conversion behavior. The paper includes a simulation study where the performance of a mechanical and hydraulic energy storage system are compared on a forward-oriented hybrid vehicle simulator, with the objective of characterizing and comparing the energy recuperation process and the energy efficiency of the two systems.Copyright © 2011 by ASME

This paper explores the theoretical and computational challenges associated with modeling of flow, momentum transport, and energy conversion processes in disk rotor drag turbine expanders. This category of expander devices, also known as Tesla turbines, has distinct advantages for Rankine power generation using low temperature heat from renewable source such as solar, waste heat, or geothermal steam or hot water. Specifically, the nozzle and rotor designs and the overall expander can be simple to manufacture, low cost, and durable, making this type of expander an attractive option in green energy technology applications where low maintenance costs and rapid capital investment payback are important qualities. Efficient energy conversion performance in rotor disk drag expanders requires that the nozzle efficiently convert flow exergy to fluid kinetic energy, and the rotor be designed to efficiently convert fluid angular momentum to shaft torque and power. To achieve these goals, modeling and analysis tools must provide the designer with a means to predict the performance of these components that accurately represents the physics, and can be effectively used to illuminate the parametric trends in performance. Two categories of modeling are examined in this paper: (1) computational fluid dynamics (CFD) modeling, and (2) more idealized one- and two-dimensional analysis frameworks. The advantages and disadvantages of these two approaches are examined here for the specific flows of interest in this type of expander design. The implications of model predictions for optimal design of disk rotor expanders for green energy applications are also discussed.Copyright © 2010 by ASME

This paper will examine the wheel loader as a system with two parallel energy conversion systems that show a complex interaction with each other and with the power source. Using a systematic design approach, several principle design solutions for hybridization can be found. Furthermore, the human operator with his/her control actions needs to be considered as part of the total system. This paper will therefore also connect to results from ongoing and previous research into operator workload and operability.

Fuel cell technology based on natural gas is a kind of promising and cleaning energy conversion technology under development. The generation mechanism of fuel cell is different from the traditional power generation device, and the efficiency of fuel cell is not restricted to Carnot cycle, therefore, it has almost the highest efficiency in most of the power generation device. Fuel cell as the motor of building cogeneration system is the integration of high efficiency energy conversion type with high efficiency energy utilization method. In this paper, a Solid oxide fuel cell (SOFC)-based Building Combined Cooling, Heating and Power (BCHP) system is simulated, and it can meet the basically electrical and heating (cooling) load of the end users. The peak power load could be supplied by power grid, and the peak heating (cooling) load could be supplied by the backup equipments. In this paper, the restricted nonlinear optimization model is built in order to solve the economic load balancing problem of the system, and the sequential quadratic programming (SQP) is used to successfully solve the optimal equipment capacity for the production costs minimization on the equality constraint of customer’s heat and power requirement, and the other inequality constraint of equipment capacity. The computation results show that it is a good method to size SOFC power generation capacity meet the electrical base load of a building. The model can be used to provide guidance in the SOFC based BCHP system design and optimization.Copyright © 2009 by ASME

This paper deals with integrated conventional and advanced exergetic, exergoeconomic and exergoenvironmental analyses. Such an advanced analysis evaluates the interactions among components of the overall system, and the real potential for improving a system component. Splitting the exergy destruction, the capital investment cost and the component-related environmental impact associated with each single component of an energy conversion system into endogenous/exogenous and avoidable/unavoidable parts enhances these analyses and improves the quality of the conclusions obtained from them. The paper consists of two parts. In the first one, the theoretical development is presented, whereas in the second part an application to a gas-turbine-based cogeneration system is discussed.Copyright © 2008 by ASME

This paper deals with integrated conventional and advanced exergetic, exergoeconomic and exergoenvironmental analyses. Such an advanced analysis evaluates the interactions among components of the overall system, and the real potential for improving a system component. Splitting the exergy destruction, the capital investment cost and the component-related environmental impact associated with each single component of an energy conversion system into endogenous/exogenous and avoidable/unavoidable parts enhances these analyses and improves the quality of the conclusions obtained from them. The paper consists of two parts. In the first one, the theoretical development is presented, whereas in the second part an application to a gas-turbine-based cogeneration system is discussed.Copyright © 2008 by ASME

Due to its high efficiency and good environmental performance, solid oxide fuel cell (SOFC) system is very attractive for future power generation, especially integrated with the conventional power generation system. However, how to effectively integrate SOFC with the conventional thermal power system and build the hybrid system with high efficiency is still a research focus. This paper studies a novel SOFC-IGCC (integrated gasification combined cycle) hybrid power system with high efficiency. On the base of the integration idea of total energy system, a novel SOFC-IGCC hybrid power system is proposed in this paper. The energy conversion mechanism of SOFC from chemical energy to electrical energy is analyzed. The maximum potential of improving the total system performance is also analyzed. The system characteristics of the hybrid system have been studied. The optimal rules of main parameters of hybrid system are revealed. The research results obtained in this paper show that integration with SOFC system will result in a significant performance improve of the total hybrid system. The integration degree of SOFC with IGCC greatly influences the system performance of the hybrid system. Compared with the base IGCC system (the system thermal efficiency is 46%), the efficiency of SOFC-IGCC hybrid system is greatly improved and increased to approximately 52%. The achievements acquired results from this paper will provide a feasible way to develop hybrid power system and valuable information for further study on IGCC system with high efficiency.

Nanoscale thermal management (NSTM) will become imperative as power density of IC’s increases further or as 3-dimensional IC’s are introduced. Such NSTM solutions must be integrated with the IC’s to be effective. It can be envisioned that an ideal NSTM solution will involve two-phase flow, liquid flow and gas flow. This paper focuses on gas flow, both as a fundamental thermal management technique in any future NSTM solution, and also as a basis for understanding more complex liquid and two-phase flow techniques that may also be involved in any NSTM solution. Heat removal by gaseous flow in any NSTM solution may be broken up in four fundamental processes: (1) bulk flow through micro-scale ducts where there may or may not be any heat transfer through the side-walls, (2) interaction of gaseous molecules with duct walls which may be at the same or a different temperature, (3) interaction between gas molecules and any enhanced surfaces such as carbon nanotubes (CNTs) as pin fins, and (4) thermal conduction and distribution in the device substrate. This paper touches upon all four fundamental process of heat removal by gaseous flow in an NSTM solution. Preliminary results from the first three processes are presented whereas a preliminary design and fabrication solution is presented for the fourth process. Preliminary computational results for pressure-driven flow of helium as the coolant gas through a micro-channel duct with a backward facing step are presented as an example for the first process. Backward facing step simulates any change in flow cross-section that may be unavoidable or desirable in any practical NSTM solution. Computation is based on direct simulation Monte Carlo (DSMC), where statistical noise due to low-speed flow is greatly eliminated through the use of the IP technique. Pressure boundary conditions are used in this simulation as they would be more realistic to represent an NSTM application. Preliminary results for computation of tangential momentum accommodation coefficient (TMAC) for helium-wall collisions are presented as an example for the second process. Molecular dynamics (MD) simulation of collisions between helium atoms and copper atoms in a crystallographically perfect copper wall are performed for different ratios between kinetic energy of helium atoms and Lenard-Jones energy of He-Cu interactions. The results are compared to limited experimental results that are available. Preliminary computational results for energy transfer between hydrogen molecules/atoms and a single wall carbon nanotube (SWNT) are presented as an example for the third process. Here MD simulation is employed where high temperature hydrogen molecules are allowed to collide with a SWNT that is initially at a lower temperature. As time progresses, the amount of net energy transfer from the hydrogen molecules to the SWNT is monitored. The result is normalized with the nominal surface area of the SWNT and the driving temperature differential to form coefficient for thermal energy transport (CTET). The values obtained are compared against macroscopic correlations. Deposition of nano-crystalline diamond is proposed as a solution for thermal spreading in the fourth process. Some examples of deposition and the corresponding atomic structure are presented.Copyright © 2007 by ASME

Any device aiming to harness the abundant clean and renewable energy from ocean and other water resources must have high energy density, be unobtrusive, have low maintenance, be robust, meet life cycle cost targets, and have a 10–20year life. The vortex induced vibration aquatic clean energy (VIVACE) converter—invented by Bernitsas and Raghavan, patent pending through the University of Michigan—satisfies those criteria. It converts ocean/river current hydrokinetic energy to a usable form of energy such as electricity using VIV successfully and efficiently for the first time. VIVACE is based on the idea of maximizing rather than spoiling vortex shedding and exploiting rather than suppressing VIV. It introduces optimal damping for energy conversion while maintaining VIV over a broad range of vortex shedding synchronization. VIV occurs over very broad ranges of Reynolds (Re) number. Only three transition regions suppress VIV. Thus, even from currents as slow as 0.25m∕s, VIVACE can extract energy with high power conversion ratio making ocean/river current energy a more accessible and economically viable resource. In this paper, the underlying concepts of the VIVACE converter are discussed. The designs of the physical model and laboratory prototype are presented. A mathematical model is developed, and design particulars for a wide range of application scales are calculated. Experimental measurements on the laboratory prototype are reported in the sequel paper and used here for preliminary benchmarking.

Lighthouses and other navigational aids are situated near tumultuous seas and thus may be good candidates for early applications of wave energy conversion technologies. The U.S. Coast Guard First District is converting lighthouses’ electrical systems to solar power to divest itself of electrical submarine cables and overhead costs associated with cable maintenance. However, in some lighthouses solar conversion is impractical or may compromise historic preservation. Unless alternative energy sources become available for these locations, they will continue to use submarine cables to run on shore power. Lighthouse sites for which shoreline and wave characteristics are suitable would be good candidates for a wave energy demonstration project. This paper describes gravity wave physics and the characteristics of mechanical radiation (growth, propagation, diffraction, and shoaling). A simple expression for energy content of a wave train with a two-parameter Bretschneider spectrum is applied to spectral wave density data collected from 15 buoys to evaluate wave energy resource potential at 31 candidate lighthouse sites in New England. Annual average wave power per meter of wavecrest varied from 3.9 to 21.7 kW/m at the buoys, and from 3.9 to 9.2 kW/m (with an average of 5.0 kW/m) at the lighthouses (buoys with maximum wave power are far out to sea, but still influence the correlation). The performance characteristics of two types of wave energy conversion technologies are used to calculate annual energy delivery by way of example. The paper concludes with a discussion of economics and environmental and permitting issues. It identifies Seguin Island light off a point in Maine and Nauset Beach, Chatham, Nantucket, and Sankaty Head lights (on Nantucket Island and along the outer shore of Cape Cod) as the best sites to begin more detailed evaluations, based on a comparison of wave power and utility rates. Subsequent studies would include demand profile for lighthouses, supply profiles, and resulting storage requirements.Copyright © 2005 by ASME

The Idaho National Engineering and Environmental Laboratory (INEEL) has investigated a Brayton cycle efficiency improvement on a high temperature gas-cooled reactor (HTGR) as part of Generation-IV nuclear engineering research initiative. In this study, we are investigating helium Brayton cycles for the secondary side of an indirect energy conversion system. Ultimately we will investigate the improvement of the Brayton cycle using other fluids, such as supercritical carbon dioxide. Prior to the cycle improvement study, we established a number of baseline cases for the helium indirect Brayton cycle. The baseline cases are based on a 250 MW thermal pebble bed HTGR. In this study, we used the HYSYS computer code for optimization of the helium Brayton cycle and the balance of plant (BOP). In addition to the HYSYS process optimization, we performed parametric study to see the effect of important parameters on the cycle efficiency. For these parametric calculations, we also used a cycle efficiency model that was developed using the Visual Basic computer language. The results from this study are applicable to other reactor concepts such as a very high temperature gas-cooled reactor (VHTR), fast gas-cooled reactor (FGR), supercritical water reactor (SWR), and others. As part of this study we are currently investigated single-shaft vs. multiple shaft arrangement for cycle efficiency and comparison, which will be published in the next paper. The ultimate goal of this study is to use supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency to values great than that of the helium Brayton cycle. This paper includes preliminary calculations of the steady state overall Brayton cycle efficiency based on the pebble bed reactor reference design (helium used as the working fluid) and compares those results with an initial calculation of a CO2 Brayton cycle.Copyright © 2004 by ASME

This study is about a much discussed and recommended application of a nuclear gas turbine and was undertaken at the request of many visitors to the Nuclear Gas Turbine stand at the ASME IGTI 2002 in Amsterdam. Apparently, the specifications of the NEREUS plant led their thoughts to small-scale energy production combined with fresh water production. This thought fits well into the basic idea that: Energy equals Electricity, Heat and Fresh Water. The NEREUS project is a non-profit organisation seeking to expand the use of Small Scale Nuclear Power Generation. This paper discusses the possibilities to produce fresh water with a NEREUS inherently safe nuclear power plant. The acronym NEREUS describes very well the goals of this project and stands for: A Natural safe, Efficient, Reactor, Easy to operate, Ultimately simple and Small . Fresh water can be produced using any fossil fuelled energy conversion unit, but this study works out how the advantages of a gas turbine in combination with an inherently safe and well-proven nuclear heat source combines the advantages of a gas turbine with the logistic advantages of nuclear power. The paper starts with an introduction on why the energy conversion branch should pay more attention to fresh water production. Secondly the paper gives an overview of the main characteristics of the nuclear heat source. Thirdly the paper briefly explains the most common methods used for fresh water produced. Finally the paper will discuss the conclusion of this study, which was: The ENERGY demand of 27648 people can be fully and affordably satisfied in both quantity and quality, with a well-proven, inherently safe, self controlling nuclear pebble-bed 20 MWth reactor. Such a reactor is suitable for unmanned operation with a three year refuelling and maintenance cycle, and with the dimensions of 10 × 10 × 10 meters.Copyright © 2004 by ASME

Gas turbines in combination with a nuclear heat source have been subject for study for some years. This paper is a logical follow up on previous papers regarding small scale nuclear power generation using gas turbines with a well-proven, inherently safe nuclear heat source. In the Netherlands the NEREUS project has been working on this concept since 1993. The acronym NEREUS describes very well the goals of this project. (Ref 1, 2, 3, 4, 5). NEREUS stands for: a N atural safe, E fficient, R eactor, E asy to operate, U ltimately simple and S mall. Current studies focus on the gas turbine part of the installation. After three years of studying the possibilities of the closed cycle helium gas turbine, the NEREUS project returned in 2000 to its original thought of using an existing open-cycle gas turbine or components of such an engine, as energy conversion unit. The paper starts with an introduction on why nuclear power should get more attention, basically explaining “the reasons why” of the NEREUS project. Secondly the paper gives an overview of the main characteristics of the nuclear heat source. Thirdly the paper will discuss the current study to determine the specifications of an open-cycle gas turbine for the NEREUS installation. Attention is given to the way such an open-cycle gas turbine can be controlled. The nuclear heat source is controlled by the laws of physics and it is not recommended to intervene under any circumstances with this very important safety feature.Copyright © 2004 by ASME

This paper continues our effort to study the dynamics of deterministic stresses in a multistage turbomachine using experimental data. Here we focus on the tip and hub regions and compare them to midspan data obtained in previous studies. The analysis is based on data obtained in particle image velocimetry (PIV) measurements performed in the second stage of a two-stage turbomachine. A complete data set is obtained using blades and fluid with matched optical index of refraction. Previous measurements at midspan have shown that at midspan and close to design conditions, the deterministic kinetic energy is smaller than the turbulent kinetic energy. The primary contributor to the deterministic stresses at midspan is the interaction of a blade with the upstream wakes. Conversely, we find that the tip vortex is the dominant source of phase-dependent unsteadiness and deterministic stresses in the tip region. Along the trajectory of the tip vortex, the deterministic kinetic energy levels are more than one order of magnitude higher than the levels measured in the hub and midspan, and are of the same order of magnitude as the turbulent kinetic energy levels. Reasons for this trend are explained using a sample distribution of phase-averaged flow variables. Outside of the region affected by tip-vortex transport, within the rotor-stator gap and within the stator passages, the turbulent kinetic energy is still 3–4 times higher than the deterministic kinetic energy. The deterministic and turbulent shear stress levels are comparable in all spanwise locations, except for the wakes of the stator blades, where the turbulent stresses are higher. However, along the direction of tip-vortex transport, the deterministic shear stresses are about an order of magnitude higher than the turbulent shear stresses. The decay rates of deterministic kinetic energy in the hub and midspan regions are comparable to each other, whereas at the tip the decay rate is higher. The decay rates of turbulent kinetic energy are much smaller than those of the deterministic kinetic energy. The paper also examines terms in the deterministic kinetic energy transport equation. The data indicate that “deterministic production” and a new term, here called “dissipation due to turbulence,” are the dominant source/sink terms. Regions with alternating signs of deterministic production indicate that the energy transfer between the phase-averaged and average-passage flow fields can occur in both directions. The divergence of the pressure-velocity correlation, obtained from a balance of all the other terms, is dominant and appears to be much larger than the deterministic production (source/sink) term. This trend indicates that there are substantial deterministic pressure fluctuations in the flow field, especially within the rotor-stator gap and within the stator passage.

The Starting up and Shutting down of a closed cycle gas turbine power plant needs special attention due to the inter-dependable nature of the components. Achieving self-sustainability in a fast and efficient way within the mechanical constraints is the challenge in the start-up of a closed cycle. The Nuclear reactor as the heat source will add more complexity to the system. The paper looks into the various options available for the start up and shutdown of a closed cycle Helium turbine using a gas cooled reactor as the heat source. A comparative analysis of these options is carried out by simulating various operating scenarios using a Transient Simulation Computer Programme especially prepared for an HTGR Project called PBMR (Pebble Bed Modular Reactor), which is being carried out in South Africa. The simulation was focused on the power conversion side of the plant, which includes all the Turbocompressors, Turbogenerator, Heat exchangers, Valves etc. Based on the analysis and its findings, an outline of a start up and shutdown procedure for a 3-shaft Closed Cycle Turbine Power Plant using hot gas injection is proposed in the paper.

The paper discusses uranium as a new fuel for gas turbines used as energy conversion installations for the markets of: stand-alone heat production, combined heat and power generation, stand-alone electricity production and as prime mover on board ships. This development is a logical step in a historical trend in energy conversion. The paper discusses the availability of the fuel, uranium and the construction of the fuel which makes this combination of gas turbine and uranium suitable for the non-utility markets.Copyright © 2002 by ASME

The United States Department of Energy, Nuclear Energy Research Initiative (NERI) Direct Energy Conversion project has as its goal the development of direct energy conversion (DEC) processes suitable for commercial development. DEC is defined as any fission process that returns usable energy with no intermediate thermal process. This project includes the study of the fission electric cell (FEC). In the FEC, fission fragments exit the fuel element cathode and are collected by the cell anode. Previous work [1] has shown the potential of FECs, with theoretical efficiencies up to 60%. Inspection of this work indicates the need for additional system modeling prior to any conclusions regarding the final FEC reactor configuration. This paper builds on the previous work and outlines the development of models to facilitate design decisions. The models address criticality, design life, reactor configuration, and current-voltage characteristics. In addition, this paper proposes future work to complete the design model.Copyright © 2002 by ASME

The United States Department of Energy, Nuclear Energy Research Initiative (NERI) Direct Energy Conversion (DEC) project has as its goal the development of a direct energy conversion process suitable for commercial development. We define direct energy conversion as any fission process that returns usable energy without an intermediate thermal process. Enough of the project has been completed, roughly two thirds, to indicate that a viable direct energy device is possible. This paper reports on the progress of the DEC project. Three concepts are under development: Fission Electric Cell using magnetic insulation, Magnetic Collimator using magnetic fields to direct fission fragments to collectors, and Gas Vapor Core Reactor using magnetohydrodynamics to generate electrical current. Included in this paper area a short project description, an abbreviated summary of the work completed to date, a description of ongoing and future project activities, and a discussion of the potential for future research and development.Copyright © 2002 by ASME

The U.S. Department of Energy’s Nuclear Energy Research Initiative Direct Energy Conversion project has a goal of developing direct energy conversion (DEC) processes suitable for commercial development. DEC is any fission process that returns usable energy with no intermediate thermal process. This project includes the study of the fission electric cell (FEC). In the FEC, fission fragments exit the fuel element cathode and are collected by the cell anode. Previous work [1] has shown the potential of FECs with theoretical efficiencies up to 60%. Inspection of this work indicates the need for additional system criticality studies prior to any conclusions regarding the final FEC reactor configuration. This paper outlines the development of models to facilitate reactor criticality design decisions. The models address criticality, design life, and reactor configuration. In addition, this paper proposes future work to complete the criticality model. The direct energy conversion concept converts nuclear energy to electrical energy without the use of a Carnot cycle based system. Kinetic energy of the highly charged fission fragments is converted directly into electrical potential using strong magnetic fields to separate the positive fission fragments from the electrons that are also produced during the fission process. A parametric analysis is performed using Monte Carlo N-Particle (MCNP) [2] simulations to calculate criticality for exact geometric models. The effect on criticality of changing enrichment, number of cells, size of cells, fuel thickness, and reactor size is determined. Heavy water, helium, and beryllium are each considered for a reflector design.Copyright © 2002 by ASME

The United States Department of Energy, Nuclear Energy Research Initiative (NERI) Direct Energy Conversion (DEC) project has as its goal the development of a direct energy conversion process suitable for commercial development. Direct energy conversion is defined as any fission process that returns usable energy without using an intermediate thermal process. This project includes the study of the fission electric cell (FEC). Inherent to the FEC is a cathode insulated from the rest of the cell by a vacuum. This arrangement has the potential to trap energy on the cathode, increasing temperatures and potentially causing structural problems and gas emissions. This paper describes the project efforts to address this and similar thermal issues. This paper describes the development of a Thermal Model that integrates thermodynamic and heat transfer considerations into an overall Design Model. The Thermal Model begins with the basic energy balance. It then applies heat transfer methods to these models to develop a general relationship between temperature and system operating parameters. Finally, the model uses published correlations to relate the general parameters to specific geometric configurations. The Thermal Model demonstrates that the low energy densities typical of fission electric cells result in assemblies whose available heat transfer mechanisms efficiently transport any waste heat the systems generate. This results in a design at this conceptual level with significant opportunities to optimize system operations and economics using operating temperature. The model also demonstrates that for the same reasons, heat buildup has a weak correlation with system operating voltage.Copyright © 2002 by ASME

This paper analyses the operational aspects of a temperature Gas Reactor using direct Helium Cycle for power conversion. As an engineering project, the complexity in the operational aspects of HTGR’s is more severe than that of its design and installation. Its transient stability is achieved in a different manner compared to conventional power plants. An efficient and steady operation is a must for its successful realization. The paper looks into the start-up, shutdown and part load performance of helium power conversion system. The study is based on an ongoing developmental project in South Africa called Pebble Bed Modular Reactor (PBMR).Copyright © 2002 by ASME

Exergy-based analyses are useful means for the evaluation and improvement of energy conversion systems. A life cycle assessment (LCA) is coupled with an exergetic analysis in an exergo-environmental analysis. An advanced exergo-environmental analysis quantifies the environmental impacts estimated in the LCA into avoidable/unavoidable parts and into endogenous/exogenous parts, depending on their source. This analysis reveals the potential for improvement of plant components/processes and the component interactions within a system. In this paper, the environmental performance of an advanced zero emission plant (AZEP) with CO2 capture is evaluated based on an advanced exergoenvironmental analysis. The plant uses oxy-fuel technology and incorporates an oxygen-separating mixed conducting membrane (MCM). To evaluate the operation of the system, a similar plant (reference plant) without CO2 capture is used. It has been found that the improvement potential of the AZEP concept is restricted by the relatively low avoidable environmental impact of exergy destruction of several plant components. Moreover, the endogenous environmental impacts are for the majority of the components significant, while the exogenous values are, generally, kept at low levels. Nevertheless, a closer inspection reveals that there are strong interactions among the components of the MCM reactor and the components constituting the CO2 compression unit. Such results are valuable, when the improvement of the environmental performance of the plant is targeted and they can only be obtained through advanced exergy-based methods.

Recent developments of high-performance nano-structured thermoelectric (TE) materials show that these materials have much higher conversion efficiencies than the state-of-the-art (SOTA) thermoelectrics. In these new quantum well (QW) materials, the carrier and barrier materials (in this case SiGe and Si) are confined in alternating layers less than 10 nm thick, and this confinement has been shown to result in greatly improved TE properties (Seebeck coefficient, electrical resistivity and thermal conductivity) leading to higher TE Figure of Merit, ZT, conversion efficiencies and Coefficient of Performance (COP) for cooling applications than for SOTA bulk thermoelectrics. From the most recent QW test data, ZTs greater than 3 at room temperature have been obtained which constitutes a significant improvement over the SOTA bulk thermoelectrics which have ZTs less than 1. The QW TE materials with ZTs greater than 3 lead to conversion efficiencies greater than 20 percent and higher COPs than for the SOTA vapor-compression cooling systems, which allow for much wider commercial applications, particularly in the applications such as the waste-heat recovery from truck engines and power plants, refrigeration and air conditioning, where the SOTA bulk TE modules were shown to be technically feasible but economically unjustified due to low conversion efficiencies. With higher efficiency QW materials, these applications become economically attractive. In a recent QW test, a conversion efficiency corresponding to 60 percent of the Carnot efficiency was measured and this is believed to be the highest such value ever measured for a TE material. For power generation applications, QW TE generators can be designed for capacities ranging from milliwatts to kilowatts and for cooling applications with capacities ranging from watts to several tons of refrigeration. This involves the transition from the nano scale QW thin films to macro scale TE devices. This paper discusses the status of the prototype QW TE generators and coolers being designed and fabricated, and the latest test results.

Wave breaking has different physics from the potential flow wave motion. The roller model introduced by Svendsen [1] illustrates the separation of the wave motion and the roller. The roller propagation speed, therefore, is a very important factor for the energy calculation of the bore. The wave celerity data collected at the wave tank displays that the maximum roller propagation speed occurs when the wave has already decayed due to the breaking. This fact clearly displays that the bore energy cannot be calculated only from the wave height as it is done for non-breaking waves. It is certain that most the energy is dissipated through the roller formation in the outer surfzone, but a certain amount of energy is transferred to the roller at the same time and it accelerates the bore speed. Slow decay of the roller propagation speed indicates that the excess energy left in the roller dissipates in the inner surfzone at much slower rate than in the outer surfzone. Therefore, these two zones have to be clearly separated, but the amount of energy transferred into the roller is unknown. In this paper, we focus on the examination of the peak roller propagation speed that appears at the border of the outer and the inner surfzone by using the experimental data collected at the wave tank. In that way, the initial condition of roller propagation speed can be determined for the inner surfzone. The energy conservation between the wave motion and the roller kinetic energy derives an equation to calculate the roller propagation speed. The energy transfer rate is estimated by adjusting the value given by the full energy conversion with the observed roller propagation speed. It is found that about half of the energy is transferred into the roller. The model successfully illustrates the peak bore propagation speed which existing formulae cannot explain.Copyright © 2011 by ASME

Nanocomposites consisting of a piezoceramic inclusion and polymer matrix offer a combination of electromechanical coupling with high toughness and ductility inherent to polymers. There is a wide range of applications for these types of materials due to their intrinsic piezoelectric and dielectric properties, such as vibration sensing, actuation, energy harvesting and capacitive energy storage. However, the relatively low piezoelectric strain coefficient and dielectric permittivity of these nanocomposites significantly limit their application in energy conversion and energy storage applications. There are mainly two coupled to improve the dielectric permittivity and electromechanical properties of piezoceramic nanocomposites, namely higher aspect ratio active inclusions and alignment of inclusions in the direction of the applied electric field. Previously, we have demonstrated that using higher aspect ratio lead zirconate titanate (PZT) nanowires (NWs) could significantly enhance the energy density and d33 coupling as compared to the samples with lower aspect ratio PZT nanorods [11]. In this paper, we will show that orientation of PZT NWs also influences energy storage capability of nanocomposite. Nanocomposites with aligned PZT NWs in the direction of the applied electric field show increased dielectric permittivity and energy density as compared to those with randomly dispersed inclusions. PZT NWs are hydrothermally synthesized, dispersed into a polyvinylidene fluoride (PVDF), cast into a film and then aligned through uniaxial stretching. Scanning electric microscopy (SEM) shows the PZT NWs are successfully aligned in direction of stretching. This work demonstrates that the energy storage and conversion capability of the nanocomposite can be significantly enhanced through the alignment of PZT NWs in the direction of the applied electric field. The findings of this research could lead to broad interest due to demonstration of developing piezoceramic nanocomposites with enhanced dielectric and electromechanical properties for next generation energy storage and conversion devices.Copyright © 2011 by ASME

In order to maximize tidal energy capture from a specific site free stream devices are situated in arrays. In an array the downstream evolution of the wake generated by a rotating tidal energy conversion device influences the performance of the device itself, the bypass flow to either side as well as the performance of any downstream device. As such it is important to design a turbine that can perform efficiently and effectively in these circumstances. Use of passively adaptive composite blades for horizontal axis tidal turbines has been shown to improve performance in fluctuating inflows. Active adaptation and/or bi-directional hydrofoil sections could be implemented in order to optimize performance throughout the tidal cycle. This paper considers the performance in an array of four free stream turbines implementing standard rigid blades, wholly bidirectional blades, passively adaptive blades and actively adaptive blades. The method used to evaluate the performance of tidal current turbines in arrays couples an inner domain solution of the blade element momentum theory with an outer domain solution of the Reynolds averaged Navier Stokes equations. The annual energy capture of four devices with each blade type in a staggered array is then calculated for a single tidal cycle and compared.

Although conventional exergy-based analyses uncover a path towards plant improvement, they suffer from some limitations, which are addressed by advanced exergy-based analyses. Advanced exergy-based methods identify interdependencies among plant components, and reveal the potential of improvement both at the component and plant level. Thus, data obtained from these methods pinpoint strengths and weaknesses of energy conversion systems and are of great importance when complex plants with a large number of interconnected components are considered. In this paper an advanced exergoeconomic analysis is applied to an advanced zero emission plant (AZEP). The most important components, in terms of the total avoidable costs, are the components constituting the main gas turbine system, while of particular importance are also the components of the mixed conducting membrane reactor incorporated in the plant. It has been found that for the most influential components of the plant, the largest part of investment cost rates and costs of exergy destruction are unavoidable. Additionally, for both the investment cost and the cost of exergy destruction, the interactions among the components are in most cases of lower importance, since for the majority of the components, the endogenous parts of the costs (related to the operation of the components themselves) are significantly larger than the corresponding exogenous parts (related to the operation of the remaining components). Nevertheless, strong interactions have been found among the components of the mixed conducting membrane reactor.Copyright © 2011 by ASME

This paper is concerned with the direct energy conversion of waste heat into electricity using pyroelectric materials. It reports detailed numerical simulations of a prototypical pyroelectric energy converter assembled experimentally and previously reported. The device consisted of a hot and cold source separated by a series of microchannels supporting pyroelectric thin films. A piston was used to vertically oscillate a working fluid back and forth between the thermal sources. The experimental device was fully instrumented with thermocouples and pressure sensor. The transient two-dimensional mass, momentum, and energy equations were solved numerically to determine the local and time-dependent temperature at various locations inside the device for operating frequency varying from 0.025 to 0.061 Hz. Excellent agreement was found between the simulated and experimentally measured local temperatures at all operating frequencies considered. These results confirm our previous numerical results and the simulation tool can now be used to design the next generation of pyroelectric energy converters.Copyright © 2011 by ASME

Back in 2008 IBM reintroduced water cooling technology into its high performance computing platform, the Power 575 Supercomputing node/system. Water cooled cold plates were used to cool the processor modules which represented about half of the total system (rack) heat load. An air-to-liquid heat exchanger was also mounted in the rear door of the rack to remove a significant fraction of the other half of the rack heat load; the heat load to air. The next generation of this platform, the Power 775 Supercomputing node/system, is a monumental leap forward in computing performance and energy efficiency. The compute node and system were designed from the start with water cooling in mind. The result, a system with greater than 96% of it’s heat load conducted directly to water; a system that, together with a rear door heat exchanger, removes 100% of it’s heat load to water with no requirement for room air conditioning. In addition to the processor, memory, power conversion, and I/O electronics conduct their heat to water. Included within the framework of the system is a disk storage unit (disc enclosure) containing an interboard air-to-water heat exchanger. This paper will overview the water cooling system featuring the water conditioning unit and rack manifolds. Advances in technology over this system’s predecessor will be highlighted. An overview of the cooling assemblies within the server drawer (i.e. central electronics complex,) the disc enclosure, and the centralized (Bulk) power conversion system will also be given. Further, techniques to enhance performance and energy efficiency will also be described.Copyright © 2011 by ASME

Wave energy conversion as a means for small scale energy production is approaching commercial viability. This paper presents the undergoing development of a wave energy conversion device at the University of Hawaii at Manoa. The device is a three part point absorber with two buoys, one floating and absorbing incoming waves; the other maintaining tension on the third mechanism, the submerged power-take-off unit. This design is discussed as three concept configurations for WEC construction. The analytical solution is developed, and the buoys response is computed due to a selected and analyzed sea-state.Copyright © 2011 by ASME

This paper presents an investigation of the tribological films formed in hydraulic motors. Hydraulic motors convert the fluid power energy produced by positive displacement pumps into rotary motion. Earlier research found that the efficiency of this energy transformation can be enhanced by reducing boundary friction. In order to study the nature of the boundary films formed in an orbital motor, a prototype ashless hydraulic fluid was evaluated in a low-speed high-torque dynamometer. The resulting tribofilm was probed via Energy Dispersive X-Ray Spectroscopy. The results reveal that increasing the hydraulic system temperature raised the relative phosphorus level of the tribofilm.Copyright © 2011 by ASME

The connection between combined power and heat generation, and the concept of distributed generation is a relevant issue viz. improvement of the overall efficiency of energy conversion and distribution. In this context, the use of biomass may be of particular interest due to its potentially very low CO2 emissions as well as low kWh production cost with respect to other renewable energy sources. Traditional methods to convert biomass involve micro-turbines or steam power plants. However, both electrical and overall efficiencies may not be particularly high for both technological and thermodynamic reasons; the latter being hard to supersede. High temperature Solid Oxide Fuel Cells (SOFCs) offer an attractive solution because they are characterized by electrical efficiencies in the range of 35% to 48% [1], and present a significant potential for integrating with the biomass gasification process; thus, exploiting advantages of high operating temperatures. Moreover, thermal integration is of prime importance. In fact, optimal management of thermal integration may allow operation with high moisture content feedstocks and with high water concentration in the SOFC; thus, promoting further hydrogen production via the water gas shift reaction [2]. In this paper, an integrated solid oxide fuel cell-gasifier system is modeled to identify the main effects on fuel cell performance under several operating conditions in terms of biomass flow rates and moisture contents. The SOFC and the gasifier are modeled by a zero dimensional approach to perform a sensitivity analysis with a numerical tool which requires less computational effort compared to those previously presented. The thermochemical phenomena are taken into account with a high degree of detail, and model validation is also showed via comparison with literature available data. Results highlight the impact of biomass feedstock and its moisture content on the electrical current density value. Final performance depends on the interaction among gasifier thermal sustainability, SOFC operating temperature and chemical equilibrium concentrations, via water gas shift reactions. In particular, it has been shown that thermal integration allows operation with higher moisture content biomass, thereby further exploiting H2 O conversion into H2 via water gas shift reactions and high fuel utilization operating conditions. The importance of thermal integration and advanced control of SOFC based biomass fueled systems is demonstrated by this study, as well as the use of a fast and reliable zero-dimensional modeling for system design and control purpose.Copyright © 2011 by ASME

Synthetic jets are driven by a periodic electrical signal to generate pulsated airflow that can provide cooling to a hot surface. The working principle of synthetic jets involves conversion of electrical energy into mechanical and fluid energy. Piezoelectric actuators, comprising of a thin metal substrate bonded to a piezoelectric disk are induced to undergo vibration motion in bending mode by an AC sine-wave voltage with zero bias. Synthetic jets, which consist of two piezoelectric actuators separated by a compliant ring at the outer periphery of the actuators, undergo a bellow-like action due to the periodic motion of the actuators, thereby ingesting air and pushing air at high velocities through the orifice. In this paper, we seek to understand and quantify the efficiency of synthetic jets with a view towards optimizing their design. In this study, energy efficiency of synthetic jet is defined based on thermodynamics principles. Analytical equations for calculating consumed electric power and airflow power are derived. Using the derived equations, energy efficiency of synthetic jets is experimentally investigated. Air velocity at the jet orifice is measured using constant temperature hotwire anemometry. Voltage signal and resultant current waveform are recorded to calculate electric power. In order to understand the structural behavior, laser vibrometer is used to measure the center out-of-plane deflection of the piezoelectric synthetic jet. Electrical power input is varied by changing signal frequency and voltage amplitude. Synthetic jets with two different orifice sizes are tested, and the efficiency of energy conversion is determined. The effects of jet design and operation conditions on energy efficiency are discussed.

MEMS and NEMs devices benefit many applications due to their unique performance and tiny size. We have researched replacing components of a Wireless Sensor Network (WSN) mote with several such devices. In this paper, we present an energy conversion and storage circuit that can be used with piezoelectric nanogenerators for self powered motes. Energy from external vibration or environmental acoustics is capacitively stored and released at certain time intervals according to the application. Stored and lost power is compared against a detailed WSN mote power budget to size the generator and capacitor.Copyright © 2011 by ASME

This paper presents the pilot model tests on the ‘Green Water Concept’ for wave energy conversion. These tests also included the initial modelling of an electric and hydraulic Power Take Off (PTO). The accurate modelling of a PTO is an important aspect in testing of wave energy conversion concepts numerically and in a wave tank: at the moment that energy is converted into electricity in the PTO, the hydrodynamic behaviour of the structure is changing. The present tests confirmed the high motions and large amount of green water of the Green Water Concept as predicted in previous simulations. The application of a real PTO gave important insight in the possibilities and challenges of PTO modelling at model scale. For the present concept a mean Power (at full scale) close to 1MW was generated in a regular wave of H = 3.0m for the maximum possible setting in the chosen test set-up. This setting was limited by the chosen mechanical and electronic motor set-up in this pilot test series, not the actual maximum of the Green Water Concept itself. Considering the test results, it is clear that the potential of the system is significantly larger.Copyright © 2010 by ASME

Since many renewable energy technologies use low cost or free primary energy sources such as solar insolation or wind, the capital cost of conversion equipment can become the dominant factor in determining economic feasibility. A natural approach to lowering the capital cost per unit of electricity is to strive for high efficiency equipment, i.e., increase the amount of electricity produced. Another approach is to seek out low cost conversion technologies, i.e., lower the capital cost. Capital equipment costs must be significantly lower than currently available off-the-shelf technologies to make solar power generally attractive economically for small-scale electricity generation. One potential low capital cost energy conversion technology is the liquid piston Stirling engine. A necessary design component for liquid piston Stirling engines is estimation of the frictional losses in the oscillating liquid columns. While frictional losses for fully developed laminar and turbulent pipe flow are characterized quite completely, average frictional loss factors for the continually starting and stopping liquid flow in oscillating columns are less complete. Direct measurements of frictional loss using a log-decrement method are reported in the paper. Measurements were completed for a variety of piping and tubing sizes and configurations. It was found that liquid volume correlated damping coefficient data well. A comparison with an equivalent fully developed laminar flow damping coefficient is presented.Copyright © 2010 by ASME

We investigate a lift based wave energy converter (WEC), namely, a cycloidal turbine, as a wave termination device. A cycloidal turbine employs the same geometry as the well established Cycloidal or Voith-Schneider Propeller. The interaction of intermediate water waves with the Cycloidal WEC is presented in this paper. The cycloidal WEC consists of a shaft and one or more hydrofoils that are attached eccentrically to the main shaft and can be adjusted in pitch angle as the Cycloidal WEC rotates. The main shaft is aligned parallel to the wave crests and fully submerged at a fixed depth. We show that the geometry of the Cycloidal WEC is suitable for wave termination of straight crested waves. Two-dimensional potential flow simulations are presented where the hydrofoils are modeled as point vortices. The operation of the Cycloidal WEC both as a wave generator as well as a wave energy converter interacting with a linear Airy wave is demonstrated. The influence that the design parameters radius and submergence depth on the performance of the WEC have is shown. For optimal parameter choices, we demonstrate inviscid energy conversion efficiencies of up to 95% of the incoming wave energy to shaft energy. This is achieved by using feedback control to synchronize the rotational rate and phase of the Cycloidal WEC to the incoming wave. While we show complete termination of the incoming wave, the remainder of the energy is lost to harmonic waves travelling in the upwave and downwave direction.Copyright © 2010 by ASME

This paper investigates thermal transport in single wall carbon nanotubes (SWCNTs) and the interfacial thermal interaction in double-wall carbon nanotubes (DWCNTs) using molecular dynamics (MD) simulation and wavelet methods. The simulations are performed on three groups of carbon nanotubes (CNTs), as shown in Figure 1: 200 nm SWCNTs, 200 nm DWCNTs with 50 nm cut in the middle, and 100 nm complete DWCNTs. A heat pulse is applied in the middle of the CNTs, and wavelike responses of temperature as well as its three components (radial, tangential, and longitudinal) along the CNTs are analyzed to explore the underlying thermal transport mechanism. Wavelet analysis is carried out on the three components of velocity to investigate the evolution of frequency spectrum along CNTs in time. The heat pulse analysis in SWCNTs shows that the longitudinal components propagate as the leading wave packet of heat at the largest speed but only carry a small fraction of the total energy. The high frequency radial components carry most of the energy and dominate in the middle diffusion regions. In DWCNTs, the radial components and tangential components carry most of the total energy while the longitudinal components carry only a small fraction of the total energy. We observe dramatic energy transfer from outer tube to inner tube of a DWCNT without any cut during the heating period. This energy transferred to inner tube is primarily contained in the slowly moving radial modes indicating that energy can be transferred effectively by the radial modes. However, the energy transfer between tubes of DWCNTs through tangential and longitudinal components is quite ineffective.Copyright © 2010 by ASME

Aqueous calcium chloride has a number of potential advantages as a compact and long-term solar storage medium compared to sensibly heated water. The combination of sensible and chemical binding energy of the liquid desiccant provides higher energy densities and lower thermal losses, as well as a temperature lift during discharge via an absorption heat pump. Calcium chloride is an excellent choice among desiccant materials because it is relatively inexpensive, non-toxic, and environmentally safe. This paper provides an overview of its application for solar storage and presents a novel concept for storing the liquid desiccant in a single storage vessel. The storage system uses an internal heat exchanger to add and discharge thermal energy and to help manage the mass, momentum, and energy transfer in the tank. The feasibility of the proposed concept is demonstrated via a computational fluid dynamic study of heat and mass transfer in the system over a range of Rayleigh, Lewis, Prandtl, and buoyancy ratio numbers expected in practice.Copyright © 2010 by ASME

In a thermoacoustic refrigerator, energy conversion between thermal and acoustic power is achieved by means of an oscillatory motion of a compressible fluid along a solid body referred to as “stack”. Traditionally, stacks have been most often made by arranging large number of thin plates at equal spacing to fill out the cross section of a thermoacoustic resonator. Other geometries such as circular pores, square or hexagonal pores (honeycombs) or pin-arrays can also be considered. Most common irregular geometry includes layers of woven wire mesh stacked along the resonator length. The advantages of thermoacoustic engines over other conventional energy conversion devices lie in their relatively simple hardware assembly, without the need for any dynamic sealing and lubrication. However, the fabrication of stacks, for example made out of very thin parallel plates, is usually costly and impractical, while using pre-fabricated stacks (e.g. ceramic catalytic converter substrates or honeycomb used in aerospace industry) has high materials costs, which limits the cost advantages of thermoacoustic engines. However, many of these problems could be avoided if irregular stack geometries made out of random (very often waste) materials could be used. There is a wide range of such candidate materials, including glass or steel wool, ceramic chippings, waste material from metal machining (swarf, Scourers), beds of glass or metal balls etc. However the main difficulty is the lack of experimental data characterising the performance of such stacks at the design stage. In this paper, the performance of a standing wave thermoacoustic refrigerator with a stack made of a few chosen random materials, is measured and compared to the one with a parallel plate stack. It is hoped that this work will be beneficial for developing low-cost thermoacoustic prime movers and heat pumps.Copyright © 2010 by ASME

The NPP design that integrates a high temperature helium cooled nuclear reactor with a gas-turbine power conversion unit requires investigations and development of high-efficiency heat-exchange equipment operating in the closed primary circuit. The equipment must be very compact, which implies highly efficient heat transfer at minimum pressure loss. This paper presents an analysis of optimal heat-exchange surface selection, as well as design and layout features of recuperators, precoolers and intercoolers. Considered are tube (made of straight, helical, including those with the small bending radius, finned tubes etc.), plate-and-fin and matrix heat-exchange surfaces combined as separate modules or as a single bundle. Suggested are methods and criteria to select rational heat-exchange surfaces with account of critical factors and limitations. Given are results of the comparative analysis and computational and experimental investigations of surfaces; design and layout solutions for heat-exchange apparatuses arranged in the vertical high-pressure vessel with limited dimensions.Copyright © 2010 by ASME

Thermoacoustic energy conversion was introduced into engineering systems during the past three decades as a new, alternative, environmentally safe energy conversion technology. It uses noble gases and mixtures of noble gases as working fluids rather than hazardous refrigerants required for the vapor compression cycle. A thermoacoustic system can operate both as a prime mover/engine (a temperature gradient and heat flow imposed across the stack lead to the generation of acoustic work/sound in the resonator) and, when reversing the thermodynamic cycle, as a refrigerator (acoustic work is used to pump heat from the low temperature reservoir and release it into a higher temperature ambient). Energy transport in thermoacoustic systems is based on the thermoacoustic effect. Using an acoustic driver, the working fluid in the resonance tube is excited to generate an acoustic standing wave. When introducing a stack of parallel plates of length Δx into the acoustic field at a suitable location, a temperature difference ΔT develops along the stack plates. This temperature difference is caused by the thermoacoustic effect. In this paper the thermoacoustic effect is visualized using real-time holographic interferometry combined with high-speed cinematography. In holographic interferometry both temperature and pressure variations impact the refractive index and both of these variations are present in our thermoacoustic system. In our analysis temperature variations are uncoupled from pressure variations to quantitatively visualize the oscillating temperature fields around the stack plate.Copyright © 2010 by ASME

Greater utilization of hydrocarbon fuel in the transport sector is causing serious challenges to maintaining depletion of oil resources and also causing environmental and ecological imbalances. This makes it imperative to lay major thrust upon the search of alternative energy sources. Atmospheric air also offers one of the cost effective energy conversion system. The compressed air can be utilized as potential zero pollution working fluid for producing shaft work in the air turbine prime-mover for light vehicle. This paper details the mathematical modeling and performance evaluation of a small capacity compressed air driven vaned type novel air turbine. Effect of impingement and expansion action of high pressure air for different dimensional situations of casing and rotor diameters of the turbine have been considered and analyzed here. Study shows that the impingement work has significant contribution in total work output and varies from 2.4% to 16.8%, when other parameters like injection angle and vane angle are kept constant at 22.5° and 36° respectively and injection pressure varies from 2 to 6 bars. It is also concluded that the expansion work as well as total work is optimum when casing diameter (D) and rotor diameter (d) are 90 mm and 85 mm respectively.Copyright © 2009 by ASME

Progress in synthesis technologies of micro and nanocomposite materials has opened the way to the control of electromagnetic field these media spontaneously emit in their surrounding. If numerous nanostructured materials [1–3] have been designed during the last decade to control both spectrally and directionally the far (propagative) field that they radiate in their surrounding, very few attention has been paid so far to the control of non-radiative field which exponentially decreases from their surface. However, such control is very important to improve the performance of numerous near-field technologies such as the plasmon assisted nanophotolitography [4], the near-field spectroscopy [5] and to develop new energy conversion technologies such as the near-field thermophotovoltaic energy conversion [6]. The near field properties of micro and nanostructured materials are closely conditioned by the presence, hybridization and coupling of localized modes within the structure. These modes come from the presence of collective oscillations of free electrons in metallic compounds or from the vibrations of partial charges carried out by atoms in polar materials. In this paper we present an approach we have recently developed [7] to design micro and nanolayered thermal sources with a tailored near-field emission spectrum and we briefly discuss the basic physical mechanisms involved in these modifications of field.Copyright © 2009 by ASME

For the past several years an inter-disciplinary research group at Oregon State University (OSU), working in conjunction with Columbia Power Technologies (CPT) has been researching innovative direct-drive wave energy systems. These systems simplify the conversion of wave energy into electricity by eliminating intermediate energy conversion processes. In support of this research OSU and CPT have developed a hybrid numerical/physical modeling approach utilizing a large scale linear test bed (LTB), and a commercial coupled analysis tool. This paper will present an overview of this modeling approach and its application to the design of a 10kW prototype wave energy conversion system that was tested in the open ocean in the fall of 2008. The data gathered during ocean testing was used to calibrate the numerical model of the device and predict the energy capture potential of the system.Copyright © 2009 by ASME

Wave energy converters of the wave activated body class are designed to have large amplitudes of motion, even in moderate sea states, because their efficiency is directly related with the amplitude of their motion. Hence, classical seakeeping numerical tools based on linear potential theory, which are widely used in the design process of offshore structures, are not accurate enough in the case of wave energy conversion. So, large differences between numerical predictions and wave tank experiments are often observed. On the other hand, the use of CFD models theoretically able to provide more accurate results is still difficult for wave energy applications, mainly because this requires a huge computation time. Moreover, it is well known that viscous solver have difficulties in propagatating gravity waves accurately. In this paper, we assess the potential of two advanced hydro-dynamic numerical models in the numerical modelling of wave energy converters. These numerical models are expected to provide more accurate results than classical linear theory based numerical models and faster results than CFD models. Particularly, these tools are expected to be able to deal efficiently with large motions of wave energy converters. In the first one, the hydrostatic forces and the Froude-Krylov forces are computed on the exact wetted surface of the wave energy converter, whereas radiation and diffraction forces are computed using the standard linear potential theory. Using this model, it is shown that we were able to predict the parametric roll phenomenon in the case of the SEAREV wave energy converter. In the second one, a Navier Stokes solver, based on RANS equations, is used. Comparisons are made with experiments and it is showed that this tool is able to model quite accurately viscous effects such as slamming. However, computation time is found to be long with this last tool.Copyright © 2009 by ASME

The emergence of electro-active materials such as piezoelectric ones allows recently to think back actuating and sensing functions thanks to new principles of electromechanically conversion of energy. The interesting properties of these materials lead up to considering the generalization of their use in various applications such as automobile, aeronautics or machining. However this enthusiasm quickly goes away when a common engineer has to be confronted to the quasi absence of ready-to-be-used models of devices made of these materials [14]. This comes from the fact that piezoelectricity still remains the mind of the experts of materials. This is why in this paper we aim to formalize and wittingly simplify existing approaches of modeling piezo-actuators. Our goal is to make available to all a method of constituting at least a basic library of piezo-actuators models. This set of models is intended and designed to be completed by more deepen models integrating several aspects neglected in basic models.

In the Gas Fast Reactor development plan, ALLEGRO is the first necessary step towards the electricity generating prototype GFR. The ALLEGRO start of operation is planned by 2020. This needs to define all design options in 2010 and to start detailed design studies in 2013. ALLEGRO is a low power Gas Cooled Fast Reactor studied in the European framework. It is a loop type, non electricity generating reactor. Its power is about 80 MW. Several objectives are assigned to ALLEGRO. At first, it will demonstrate the viability of the GFR reactor system, no reactor of this type having been built in the past. Most of the GFR architecture, materials and components features are considered at reduced scale in ALLEGRO, excluding the energy conversion system. ALLEGRO will rely on the same safety options as the reactor system. In addition, the ALLEGRO core will allow the progressive qualification of the GFR ceramic fuel, with the possibility to load some ceramic carbide or nitride sub-assemblies in a first MOX core, with SiC/SiCf cladding and wrappers. When such unit test will be considered convincing enough, the diagrid and circuits are designed to accept full high temperature ceramic cores. The core neutrons can also be used to irradiate structural materials with fast neutron spectrum and in a large temperature range. The core can also include innovative irradiation fuel devices (samples or full bundles) for other reactor systems. Finally, branches on the main intermediate heat exchanger will allow the testing and validation of high temperature components and processes. The pre-conceptual design of ALLEGRO is shared between European partners through the GCFR 6th R&D Framework Program. After recalling the role of the European partners in the different design and safety tasks, the paper will give an overview of the current design with recent progresses in various areas like: • Core design and neutron performances, • The design of experimental advanced ceramic GFR fuel sub-assemblies included in several locations of the MOX core, • Fuel handling principles and solutions, • System design and global reactor architecture which is largely influenced by the Decay Heat Removal strategy (DHR) for depressurized accidents.Copyright © 2009 by ASME