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Combining thermoacoustic concepts with free piston Stirling systems, this paper puts forward a resonance tube-coupled duplex Stirling cooler which is thermally driven. The novel configuration consists of a free piston Stirling engine, a free piston Stirling cooler and a resonance tube to couple them. Possessing advantages of high exergy efficiency, high reliability and simple structure, it serves as a promising candidate for small scale natural gas liquefaction by burning a small part of natural gas to liquefy the rest and long lifetime space coolers. Using the off-the-shelf components in our laboratory, an experimental setup has been built and a no-load temperature of 110 K has been achieved. As the feasibility of the concept has been verified experimentally, further calculation was done to explore the potential of the configuration. Based on Sage software, the engine and the cooler subsystem were optimized respectively, then a system level numeric model was established and the performance of the system was studied. Among the numeric results, a heat-to-cooling-power exergy efficiency of 26.8% and a cooling power of 2.4 kW were obtained at 110 K with an inner diameter 60 mm resonance tube, charging pressure of 6 MPa, hot temperature of 923 K, ambient temperature of 303 K, working frequency of 75 Hz.

The development of green power generation such as solar systems that have become a great interest for several countries especially for Tunisia as it presents a significant solar potential. For this purpose, this research has investigated the feasibility and the performance of standalone solar dish/Stirling micro generation plant for rural electrification. The considered hybrid system includes solar dish/Stirling engine, permanent magnet synchronous generator and a storage battery. To start with, thermal modeling and simulation have been carried out using Matlab® for the solar-driven Stirling heat engine system composed of an Alpha Stirling engine, a solar collector and a receiver, in which the radiation, convection, conduction and radiation heat loss have been taken into consideration for the selected design. For numerical validation of the receiver’s thermal model, simulation results were compared with experimental measurements reported for the EURODISH system with a reasonable degree of agreement. Second, the generated torque driving the generator has been estimated by the Adiabatic model of URIELI based on the classical fourth-order Runge-Kutta. In order for an autonomous control, the dish generator is connected to the load via power electronic converters where the bidirectional power flow is possible by the use of two voltage source converters in a back-to-back configuration. They are referred to as Stirling/generator side converter and load side inverter, both are oriented control by space vector pulse width modulation. In this context, the Stirling side converter is used to adjust the synchronous generator while the inverter controls the power flow between the direct current bus and the alternative side. Detailed tests of the proposed hybrid configuration was implemented in Matlab/Simulink software, by taking as a case study a measured load profile for a rural house and solar radiation data at the target area. The analysis of simulation results has shown that solar dish Stirling/synchronous generator system achieves the objectives of system autonomy and power supply stability. The effectiveness of the management strategy was also proved. It has been obtained that the variable speed Stirling/generator system is capable to feed an uncontrollable load under variations of climatic conditions during hot, moderate and cold seasons, in remote areas in Tunisia.

Using the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is negative even when the duration of heat addition is optimized to give the maximum amount of heat addition, which is the same situation for the Brayton cycle described in our previous paper. For the Stirling cycle, the net work done is positive, and the thermal efficiency is greater than that of the Otto cycle described in our previous paper by a factor of about 2.7–1.4 for compression ratios of 5–30. The Stirling cycle is much better than the Otto, Brayton, and Carnot cycles. We have found that the optimized piston trajectories of the isothermal, isobaric, and adiabatic processes are the same when the compression ratio and the maximum volume of the same working fluid of the three processes are the same, which has facilitated the present analysis because the optimized piston trajectories of the Carnot and Stirling cycles are the same as those of the Brayton and Otto cycles, respectively.

The free-piston Stirling machine has been used as either thermal engine, cryocooler, or heat pump, due to its compact structure, high efficiency, and reliability. A compact engine-refrigerator dual-functional coaxial free-piston Stirling engine was designed and fabricated. It could output 1000 W electricity power with a conversation rate of 20%, when the hot end was heated up to 530°C and the cold end cooled by water which was heated from room temperature to 65°C. The engine was reversely operated as a refrigerator without any modification, and its cooling performance was measured at different input power. The results indicate that, a none-load cooling temperature 142.4 K was obtained at a maximum power supply voltage of 300 VAC (50 Hz), and 193.1 K was reached at a minimum input power of 60 VAC (50 Hz). For a nominal power supply 220 VAC@50 Hz (i.e., 716.8 W), the cooling power increases from 2.4 to 276 W when the temperature at the cold head changes from 156.6 to 203 K. The relative Carnot coefficient o...

Stirling engine is a device that produces mechanical energy using heat from any source of energy, without the need of combustion of any fuel inside the device. Renewable energy sources, which are mostly low-temperature energy sources, can be used to produce mechanical and electrical energy in Stirling engines. The paper presents an overview of the existing prototype Stirling engines designed for using of low-temperature energy sources, including renewable energy sources. Commercial devices for electric power generation offered for use in home, usually do not exceed 1 kW. Using the Schmidt model, the analyze of influence of temperature working fluid in the expansion space (heater) on the efficiency and the electric power generated in the Stirling engine of alpha type has been presented in the paper.

>> This paper describes the continuing effort to analysis and design on dynamic and electrical behaviorof gamma-type free piston Stirling engine/generator with dual–opposed linear generator for domestic micro-CHP (Combined Heat and Power) system. The double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric sinusoidal displacementand are connected with moving magnet type linear generators for power generation. To operate Stirling engine/ generator, combustion heat of natural gas is supplied to hot-end and heat is rejected from cold-end by coolingwater. The temperature difference across the displacer induces the oscillating motion, and it can be explained withmass-spring vibration system. The purpose of this paper is to describe the design process of linear generator for the double acting free-piston Stirling engine. Key words : Double acting free piston Stirling engine/alternator(양방향 자유 피스톤 스털링엔진 /발전기), Lineargenerator(선형발전기), Piston(피스톤), Displacer(변위기), Operating frequency(작동주파수)

In this work, a power generation system dish/Stirling with cavity receiver and an electrical induction generator was simulated. We propose a control system using a variable-dead-volume and analyze its influence on the mechanical performance. A system with a dead volume of 160 cm3 was designed to control the power and speed of the engine considering annual insolation, mechanical properties of the heater and the limits of frequency and voltage for the systems interconnected to the electricity network. The designed system achieves net efficient solar conversion to electric of 23.38% at an irradiance of 975 W/m2 and allows an annual increase of 18% of the useful electrical energy compared to a system without control.

A multimission radioisotope thermoelectric generator (MMRTG), developed by the US Department of Energy for the National Aeronautics and Space Administration, powers the Mars Science Laboratory Curiosity rover on Mars. New thermoelectric couples (TECs) have been developed in recent years that offer significant improvements over the TECs used in the MMRTG. The maturity of the new TECs and the design flexibility of the MMRTG enable a low-risk system upgrade that is predicted to substantially enhance the MMRTG’s performance. System design trades are looking at changing the TECs and increasing the hot-side temperature to find the best combination of performance and program cost in this enhanced MMRTG (eMMRTG). Initial studies indicated that a low-risk enhancement would be to use skutterudite (SKD) materials developed at JPL to form TECs for the eMMRTG. Simply replacing the PbTe/TAGS TECs with SKD TECs and making a few low-risk modifications to the MMRTG design could potentially provide a 25% increase in power output at beginning of life (BOL). More important than the BOL power output increase is the end of design life (EODL) power output increase. With the anticipated lower degradation rate of the SKD materials, it is anticipated that the EODL power output will be more than 50% higher than for the MMRTG (with EODL defined as 17 years from fueling). This paper presents an overview of the results of the initial trades leading to the pursuit of the eMMRTG and the progress made since those were concluded.

Solar energy is one of the more attractive renewable energy sources that can be used as an input energy source for heat engines. In fact, any heat energy sources can be used with the Stirling engine. Stirling engines are mechanical devices working theoretically on the Stirling cycle, or its modifications, in which compressible fluids, such as air, hydrogen, helium, nitrogen or even vapors, are used as working fluids. When comparing with the internal combustion engine, the Stirling engine offers possibility for having high efficiency engine with less exhaust emissions. However, this paper analyzes the basic background of Stirling engine and reviews its existing literature pertaining to dynamic model and control system for parabolic dish-stirling (PD) system.

At present, ecology is of primary concern. Looking for savings is an equally important factor forcing to implement innovative technologies. Many of industrial plants, devices and installations, heat energy is lost. An innovative solution is the use of Stirling engines for the use of waste heat energy. They can operate with relatively small temperature differences. Among the three configurations such as the alpha, beta and gamma types, the gamma type is very economical and simple in fabrication. So that we have decided to fabricate a gamma-type Stirling engine. We designed and fabricated a Gamma-type Stirling engine with rotary displacer for utilizing the waste heat in a cost for a better economy. Prior to the fabrication, the engine was modeled by using Autodesk Inventor. We used the parts of dumped machines for fabricating the Engine. The power piston which is used to extract the power from displacer cylinder is the compressor of a refrigerator. We have designed the engine to utilize the waste heat from the steam-boiler in our college. Similarly all the other components along with frame are dispatched from many other waste machines. This simple Engine can be easily fabricated and can be used for house-hold applications.

Stirling Radioisotope Power Systems (RPS) are being developed by NASA's RPS Program in collaboration with the U.S. Department of Energy (DOE). Efforts ranging from 2001 to 2015 enabled development of the Technology Demonstration Convertor (TDC) for use in the 110-watt Stirling Radioisotope Generator (SRG-110) and the Advanced Stirling Convertor (ASC) for use in the Advanced Stirling Radioisotope Generator (ASRG). The DOE selected Lockheed Martin Space Systems Company (LMSSC) as the system integration contractor for both flight development efforts. The SRG-110 housed two TDCs fabricated by Infinia and resulted in the production of 16x demonstration units and 2x engineering units. The project was redirected in 2006 to make use of a more efficient and lower mass ASCs under development by Sunpower Inc. The DOE managed the flight contract with LMSSC and subcontractor Sunpower Inc. from 2007 to 2013 to build the ASRG, with support from NASA Glenn Research Center (GRC). Sunpower Inc. held two parallel contracts to produce ASCs, one with Lockheed Martin to produce ASC-F flight units and one with GRC for the production of ASC-E3 engineering unit pathfinders that were used to refine the flight design and production processes. The DOE initiated termination of the ASRG contract in late 2013. After ASRG had ended, GRC completed characterization testing of the ASRG Engineering Unit #2 (EU2) and the GRC contract with Sunpower was also completed. The NASA RPS Program Office has recently initiated a new Dynamic Power Conversion development effort which includes the potential maturation of Stirling, Brayton, and Rankine power convertors for the next generation of RPS. The effort started with the request for proposal and review of submits. Contracts are anticipated for release in 2017 and will initially focus on a design phase prior to fabrication and testing. This new effort will focus on robustness in addition to high efficiency, specific power, and reliability. Also, some requirements introduced during the ASRG contract have also been included in the new effort, such as constant lateral loading. Due to the focus on robustness and new requirements relative to the older TDC design, the Stirling Cycle Development Project has initiated an assessment of government owned hardware to help inform requirements evolution and evaluation of future designs. While lessons learned from the ASRG flight development project have been taken into consideration, the evaluation of the TDC design had not been completed for some existing environments or relatively new requirements. To further assess the TDC design, a series of tasks were initiated to evaluate degradation for units that have operated unattended for over 105,000 hours, demonstrate robustness to a random vibration environment, characterize and evaluate performance for varying lateral load profiles. The status for each task are described.

Stirling Radioisotope Power Systems (RPS) are being developed as an option to provide power on future space science missions where robotic spacecraft will orbit, flyby, land or rove. A variety of mission concepts have been studied by NASA and the U. S. Department of Energy that would utilize RPS for landers, probes, and rovers and only require milliwatts to tens of watts of power. These missions would contain science measuring instruments that could be distributed across planetary surfaces or near objects of interest in space solar flux insufficient for using solar cells. A low power Stirling convertor is being developed to provide an RPS option for future low power applications. Initial concepts convert heat available from several Radioisotope Heater Units to electrical power for spacecraft instruments and communication. Initial development activity includes defining and evaluating a variety of Stirling configurations and selecting one for detailed design, research of advanced manufacturing methods that could simplify fabrication, evaluating thermal interfaces, characterizing components and subassemblies to validate design codes, and preparing for an upcoming demonstration of proof of concept in a laboratory environment.

Low-temperature heat sources are ubiquitous. Harvesting this heat in an efficient and cost-effective way improve overall systems efficiency and reduce energy costs. Numerous studies shed light on these sources and technologies to utilize low-temperature heat. This paper evaluates the technical and economic feasibility of low-temperature Stirling Engine (SE) powered by hot water energy from evacuated tube solar water heater for distributed power generation when excess hot water energy is available. Evacuated tube solar collector provides hot water on-demand. When hot water is not consumed domestically, a SE is used to utilize the untapped heat from the solar water heater. The objective of this study is to evaluate the energy savings by using a SE to recover untapped heat from solar collectors. Thermal performance of the selected evacuated tube was measured experimentally under local weather conditions for different periods in summer and winter in the Mediterranean region and then simulated on hourly basis for a whole year to estimate the energy and hot water temperature output. Three different cases were taken to assess the potential of energy savings using SE to generate power namely, typical homes, office buildings and schools. SE is modeled using the most advanced third-order design analysis method. Air, helium, and hydrogen are used as working fluids in the SE at different charging pressures. Results obtained from solar collector’s thermal performance for the three cases are integrated with the results achieved from Stirling engine simulation of the various working fluids and pressures to evaluate the engine performance based on a dynamic approach. The study also investigates the economic feasibility of using Stirling engines for power generation from such low-temperature, intermittent heat sources. Results show that using hydrogen as working fluid is the most feasible. Typical schools show the most economical case to recover heat.

In this paper, a double-acting thermoacoustic Stirling electric generator is proposed as a new device capable of converting external heat into electric power. In the system, at least three thermoacoustic Stirling heat engines and three linear alternators are used to build a multiple-cylinder electricity generator. In comparison with the conventional thermoacoustic electricity generation system, the double-acting thermoacoustic Stirling electric generator has advantages on efficiency, power density and power capacity. In order to verify the idea, a prototype of 3 kW three-cylinder double-acting thermoacoustic Stirling electric generator is designed, built and tested. Based on the classic thermoacoustic theory, numerical simulation is performed to obtain the thermodynamic parameters of the engine. And distributions of key parameters are presented for a better understanding of the energy conversion process in the engine. In the experiments, a maximum electric power of about 1.57 kW and a maximum thermal-to-electric conversion efficiency of 16.8% were achieved with 5 MPa pressurized helium and 86 Hz working frequency. However, we find that the mechanical damping coefficient of the piston is dramatically increased due to the deformation of the cylinder wall caused by high thermal stress during the experiments. Thereby, the system performance was greatly reduced. Additionally, the performance differences between three engines and three alternators are significant, such as the heating temperature difference between three heater blocks of the engines, the piston displacement and the output electric power differences between three alternators. These problems need further investigation. This work presents a new thermal-to-electric conversion technology, which can be utilized in many energy area, such as solar energy, industrial waste heat and so on.

This paper describes a solar-thermal run Stirling engine based uninterrupted power generating system employing magnesium sulphate impregnated Zeolite pellets for thermal energy storage. In the proposed system, Stirling engine design is based on the average temperature difference of 480 °C, assuming the heat sink temperature equal to the ambient temperature of that place. In presence of sun, Fresnel lenses of a specially designed hybrid capsule capture solar energy and concentrate them to provide necessary heat for the operation of the engine. In absence of the sun, required heat is provided by the thermo-chemical energy stored in Zeolite pellets. Working methodologies, modelling and simulation of the proposed system along with analyses of the obtained simulated results are presented in this paper. Possible performance of the scheme at different global positions for different period of a year has also been investigated.

A novel dish Stirling solar power generation (DSSPG) system has been designed incorporated with a high temperature superconducting (HTS) linear synchronous generator (LSG). The high efficient HTSLSG is a compact energy converter for a Stirling engine in the DSSPG system, where a duplex of Stirling cycles is applied, in which a Stirling engine replaces the conventional linear compressor forming a Stirling pulse tube refrigerator (SPTR). This paper presents the DSSPG system designed with the HTSLSG cooled by the duplex Stirling system, and analyzes the thermal load and power distribution in the system to provide bases for consideration of practical application. Analysis results show that the DSSPG system with the HTSLSG refrigerated by the SPTR powered by the DSSPG system itself can be realized, and has higher efficiency than that with the conventional LSG and has larger system capacity.

This paper presents the modeling and simulation for a prototype of the solar-powered Stirling engine working at the low temperature range. A mathematical model for the thermal analysis of the solar-powered low temperature Stirling engine with heat transfer is developed using Matlab program. The model takes into consideration the effect of the absorber temperature on the thermal analysis like as radiation and convection heat transfer between the absorber and the working fluid as well as radiation and convection heat transfer between the lower temperature plate and the working fluid. Hence, the present analysis provides a theoretical guidance for designing and operating of the solar-powered low temperature Stirling engine system, as well as estimating output power from the solar Stirling engine using Matlab program. This study attempts to demonstrate the potential of the low temperature Stirling engine as an option for the prime movers for Photovoltaic tracking systems. The heat source temperature is 40–60 °C as the temperature available from the sun directly.

This research studies the possibilities of generating electricity by using small scale solar dish Stirling engine system in Thailand. A solar dish Stirling engine system was evaluated and designed as prototypes for Thailand . The performance of system for electricity generation was also simulated under Thai climate condition. The results of the study can be structured in two parts. First is testing the existing Stirling engine and second is simulation the electricity generation by solar dish Stirling engine system prototype in Thailand. The existing Stirling engine at the Komplexlabor of the FH – Stralsund University, Germany was tested to understand the characteristics of the operating system. Stirling engine was operated at temperature of about 800 o C in the combustion chamber, being its nominal rotational speed 1,517 rpm. Finally, the average Stirling engine efficiency was established in 22%. The results of simulation on solar dish Stirling engine were that the main components for a prototype of a solar dish Stirling engine system in Thailand shall consist of a Stirling engine with a nominal power of 25 kW, and a 131 m 2 dish concentrator. It can generate electricity about 27,946 kWh/year of electricity under Thai climate condition. During the working process, the heat lost on dish concentrator was 22% and heat lost within the Stirling engine was 60.84%. The system efficiency of this solar dish Stirling engine system was 17%.

Most of days, the summer temperature in Taiwan is higher than 30 degree Celsius. Where, heat dissipation for devices becomes more difficult and needs more electric power. In addition, devices discharging waste heat via traditional ways that accelerates global warming. In order to serve above problems, a self-balanced cooling system is developed. Based on Stirling engine, waste heat is recycled and transformed into a kinetic power. In this paper, this power is used to relieve heat via a fan by devices themselves. Besides, for higher heat input yields larger power to drive a fan and vice versa to Stirling engine, a self-cooling cycle naturally forms under above autonomous control. The feasibility assessment will be confirmed via simulation studies.

To supply electric power in certain extreme environments such as a spacecraft or in military applications, a radioisotope thermoelectric generator has been highlighted as a useful energy source owing to its high energy density, long lifetime, and high reliability. A radioisotope thermoelectric generator generates electric power by using the heat energy converted from the radioactive energy of a radioisotope. In this study, FE analyses such as radiation shield analysis, heat transfer analysis, and power recovery rate analysis have been carried out to achieve an optimal design for a radioisotope thermoelectric generator using .

The National Aeronautics and Space Administration Glenn Research Center (GRC) has an extensive history in dynamic energy conversion dating back to the early 1960s. This legacy puts the GRC at the forefront of nuclear power systems using thermodynamic power cycles such as Stirling and Brayton. The advantages of dynamic energy conversion include high efficiency, long life, and scalability to high power. These attributes make Brayton and Stirling power cycles an ideal solution for nuclear energy conversion.

Low temperature differential (LTD) Stirling engines (SE) are useful devices when attempting to obtain useful work from low temperature heat sources. In an attempt to implement a renewable small scale LTD SE on a fishing boat, the required energy sources must operate on green energy. This research focuses on the feasibility of a LTD Stirling engine as one of the primary energy sources for a sustainable marine transport. The main focus is on the design and construction of a low temperature differential Stirling engine whose primary source of heating is directed from the sun and cooled through natural convection. This paper reports findings from the LTD SE design analysis.

Stirling Radioisotope Power Systems (RPS) are being developed as an option to provide power on future space science missions where robotic spacecraft will orbit, flyby, land or rove. A Stirling Radioisotope Generator (SRG) could offer space missions a more efficient power system that uses one fourth of the nuclear fuel and decreases the thermal footprint compared to the current state of the art. The Stirling Cycle Technology Development (SCTD) Project is funded by the RPS Program to developing Stirling-based subsystems, including convertors and controller maturation efforts that have resulted in high fidelity hardware like the Advanced Stirling Radioisotope Generator (ASRG), Advanced Stirling Convertor (ASC), and ASC Controller Unit (ACU). The SCTD Project also performs research to develop less mature technologies with a wide variety of objectives, including increasing temperature capability to enable new environments, improving system reliability or fault tolerance, reducing mass or size, and developing advanced concepts that are mission enabling. Active vibration reduction systems (AVRS), or "balancers", have historically been developed and characterized to provide fault tolerance for generator designs that incorporate dual-opposed Stirling convertors or enable single convertor, or small RPS, missions. Balancers reduce the dynamic disturbance forces created by the power piston and displacer internal moving components of a single operating convertor to meet spacecraft requirements for induced disturbance force. To improve fault tolerance for dual-opposed configurations and enable single convertor configurations, a breadboard AVRS was implemented on the Advanced Stirling Convertor (ASC). The AVRS included a linear motor, a motor mount, and a closed-loop controller able to balance out the transmitted peak dynamic disturbance using acceleration feedback. Test objectives included quantifying power and mass penalty and reduction in transmitted force over a range of ASC operating parameters and mounting conditions. All tests were performed at three different piston amplitudes, 3.0, 3.75, and 4.5 mm. Overall, the transmitted force was reduced to 2 percent of the total unbalanced force by actively balancing out only the first fundamental frequency, with balancer motor power remaining under 1 watt. The test results will be used to guide future balancer designs.

The NASA Glenn Research Center has conducted performance testing of a high temperature linear alternator (HTLA) in support of Stirling power convertor development for potential future Radioisotope Power Systems (RPS). The high temperature linear alternator is a modified version of that used in Sunpower's Advanced Stirling Convertor (ASC), and is capable of operation at temperatures up to 200 deg. Increasing the temperature capability of the linear alternator could expand the mission set of future Stirling RPS designs. High temperature Neodymium-Iron-Boron (Nd-Fe-B) magnets were selected for the HTLA application, and were fully characterized and tested prior to use. Higher temperature epoxy for alternator assembly was also selected and tested for thermal stability and strength. A characterization test was performed on the HTLA to measure its performance at various amplitudes, loads, and temperatures. HTLA endurance testing at 200 deg is currently underway.

Stirling Radioisotope Power Systems (RPS) are being developed as an option to provide power on future space science missions where robotic spacecraft will orbit, flyby, land or rove. A Stirling Radioisotope Generator (SRG) could offer space missions a more efficient power system that uses one fourth of the nuclear fuel and decreases the thermal footprint of the current state of the art. The RPS Program Office, working in collaboration with the U.S. Department of Energy (DOE), manages projects to develop thermoelectric and dynamic power systems, including Stirling Radioisotope Generators (SRGs). The Stirling Cycle Technology Development (SCTD) Project, located at Glenn Research Center (GRC), is developing Stirling-based subsystems, including convertors and controllers. The SCTD Project also performs research that focuses on a wide variety of objectives, including increasing convertor temperature capability to enable new environments, improving system reliability or fault tolerance, reducing mass or size, and developing advanced concepts that are mission enabling. Research activity includes maturing subsystems, assemblies, and components to prepare them for infusion into future convertor and generator designs. The status of several technology development efforts are described here. As part of the maturation process, technologies are assessed for readiness in higher-level subsystems. To assess the readiness level of the Dual Convertor Controller (DCC), a Technology Readiness Assessment (TRA) was performed and the process and results are shown. Stirling technology research is being performed by the SCTD Project for NASA's RPS Program Office, where tasks focus on maturation of Stirling-based systems and subsystems for future space science missions.

This document describes the radioactive heat source and generator used in the building of NASA space craft.

The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or insufficient to meet the needs of the missions. To meet this goal, the RPS Program, working closely with the Department of Energy, performs mission and system studies (such as the recently released Nuclear Power Assessment Study), assesses the readiness of promising technologies to infuse in future generators, assesses the sustainment of key RPS capabilities and knowledge, forecasts and tracks the Program's budgetary needs, and disseminates current information about RPS to the community of potential users. This process has been refined and used to determine the current content of the RPS Program's portfolio. This portfolio currently includes an effort to mature advanced thermoelectric technology for possible integration into an enhanced MultiMission Radioisotope Generator (eMMRTG), sustainment and production of the currently deployed MMRTG, and technology investments that could lead to a future Stirling Radioisotope Generator (SRG). This paper describes the program planning processes that have been used, the currently available MMRTG, and one of the potential future systems, the eMMRTG.

The Institute for Energy Economy and Application Technology (IfE), together with the Energie Südbayern (ESB), the local gas supplier in southern Bavaria, are responsible for a field measurement campaign of four gas fired Stirling engine micro-combined heat and power units. These units and the measurement equipment were installed in four different single family houses at the end of 2009. After monitoring over 1 year, it can be said that the Stirling engine micro-combined heat and power units are capable in supplying small residential buildings with thermal and electric power. The data evaluation shows the micro-combined heat and power-units work with a steady-state efficiency above 90%. The main goals of this field test, besides the verification of the Stirling engine’s efficiency, are an analysis of the complete system’s overall energy performance. Therefore, a detailed examination of not only the heat-consuming devices, space heating and the domestic hot water system, but also the examination of heat-generating devices, the Stirling engine and the auxiliary burner were made. The implementation of heat demand curves helps to assess not only the steady state, but also the yearly performances of each micro-combined heat and power units. For a future integration of micro-combined heat and power units into a smart grid, they have to be predictable. Hence, a detailed analysis was taken onto the electricity generation curves at different ambient temperatures and its hourly behaviour. Lastly, for the economic evaluation, the onsite consumption characteristics were considered in depth.

태양 에너지 변환 효율이 높은 접시형 집광기와 스털링 엔진을 이용한 발전 방식을 조사하기 위하여 본 연 구에서는 소형 스털링 엔진을 이용하여 좁은 공간에서 발전용으로 사용할 수 있는 시스템을 개발하였고, 기초 실험을 수행하였다. 본 연구에서 제작한 발전 시스템을 위하여 50만원의 제작비가 소요되었고, 제작한 시스템으로 최대 0.56 kWh의 전기를 발전하였으며, 에너지 변환 효율은 약 10%로 측정되었다. 시스템의 최적 설계를 통하여 더 높은 출력 을 얻을 수 있으며, 본 연구의 기초 실험 데이터는 많은 태양열 발전 관련 분야에서 유용하게 사용될 것으로 사료된다.

The ultimate aim of a Moroccan–German study is to develop a simple solar pumping system, using the concept of low delta-T Stirling engines. This paper describes the main parts of the engine and presents several experimental measurements made under laboratory and field-test conditions in Morocco. Measurements with flat plate cooler and discontinuous motion of the displacer were conducted to verify two essential recommendations of Kolin in expectation of power-output improvements of the gamma-type engine.

In recent years, micro-CHP systems are attracting world attention. As one kind of external heating engines, Stirling engines could be applied to the micro-CHP systems driven by solar, biogas, mid-high temperature waste gases and many other heat sources. The development of a Stirling engine driven by mid-high temperature waste gases is presented first. The thermodynamic design method, the key parameters of the designed Stirling engine and its combustion chamber adapted for waste gases are described in detail. Then the performance test of the Stirling engine is carried out. During the test, the temperature of the heater head is monitored by thermocouples, and the pressure of the working fluid helium in the Stirling engine is monitored by pressure sensors. The relationships among the output shaft power, torque and speed are studied, and the pressure losses of the working fluid in the heat exchanger system are also analyzed. The test results demonstrate that the output shaft power could reach 3476 W at 1248 RPM, which is in good agreement with the predicted value of 3901 W at 1500 RPM. The test results confirm the fact that Stirling engines driven by mid-high temperature waste gases are able to achieve a valuable output power for engineering application.

This paper investigates the optimization of the performance of a solar powered Stirling engine based on finite-time thermodynamics. Heat transference in the heat exchangers between a concentrating solar collector and the Stirling engine is studied. The irreversibility of a Stirling engine is considered with the heat transfer following Newton's law. The power generated by a Stirling engine is used as an objective function for maximum power output design with the concentrating solar collector temperature and the engine thermal efficiency as the optimization parameters. The maximum output power of engine and its corresponding system parameters are determined using a genetic algorithm.

This study proposes a biomass power and heat cogeneration system that comprised of a gasifier, Stirling engine/alternator, and absorption cooler. Gasification is the most versatile approach to utilize biomass for the flexibility and affectivity of this technology. The flue gas from the combustion of the gasified gas propels a free-piston Stirling engine/alternator, which produces 50 or 60 Hz alternating current as output. The absorption cooler absorbs the residual heat from the flue gas after Stirling engine’s hot end and produces low temperature energy. This cold energy could be used to satisfy air conditioning requirement or be directed to the cold end of Stirling engine to further increase the power efficiency of the Stirling engine. The solid biomass rice husks were tested in this study, in addition, the current power and heat cogeneration system’s gross output exceeded the rated 500w engine gross output for this tested feeds. The total efficiency of this system was approaching to 46%.

Results of design and experimental studies aimed at developing a milliwatt-power radioisotope thermoelectric generator (RTG) based on plutonium-238 for space power are considered and analyzed. Milliwatt-power RTGs based on plutonium-238 are completely self-contained electric power sources offering a long proven service lifetime (>15 years) and high reliability. Such electric power sources find application both for space exploration and in terrestrial equipment, especially with the advance of microsystem technologies.

Conventional mobile hydraulic power supplies involve numerous kinematic connections and are limited by the efficiency, noise, and emissions of internal combustion engines. The Stirling cycle possesses numerous benefits such as the ability to operate from any heat source, quiet operation, and high theoretical efficiency. The Stirling engine has seen limited success due to poor heat transfer in the working chambers, difficulty sealing low-molecular weight gases at high pressure, and non-ideal piston displacement profiles. As a solution to these limitations, a liquid piston Stirling engine pump is proposed. The liquid pistons conform to irregular volumes, allowing increased heat transfer through geometry features on the interior of the working chambers. Creating near-isothermal operation eliminates the costly external heat exchangers and increases the engine efficiency through decreasing the engine dead space. The liquid pistons provide a positive gas seal and thermal transport to the working chambers. Controlling the flow of the liquid pistons with valves enables matching the ideal Stirling cycle and creates a direct hydraulic power supply. Using liquid hydrogen as a fuel source allows cooling the compression side of the engine before expanded the fuel into a gas and combusting it to heat the expansion side of the engine. Cooling the compression side not only increases the engine power, but also significantly increases the potential thermal efficiency of the engine. A high efficiency Stirling engine makes energy regeneration through reversing the Stirling cycle practical. When used for regeneration, the captured energy can be stored in thermal batteries, such as a molten salt. The liquid piston Stirling engine pump requires further research in numerous areas such as understanding the behavior of the liquid pistons, modeling and optimization of a full engine pump, and careful selection of materials for the extreme operating temperatures. Addressing these obtainable research quandaries will enable a transformative Stirling engine pump with the potential to excel in numerous applications.

In this paper, the principle of heat energy conversion via Stirling pump into electricity is considered. New scheme of Stirling pump is proposed, that differs from known ones in application of offset heater and cooler and valves controlling the motion of liquid. The mathematical model is implemented to examine the liquid flow and gas heat exchange in cylinders and regenerator. The numerical simulation of engine’s working cycle is conducted for the purpose of determining the characteristic parameters of its design. A possibility of achieving high thermal efficiency at acceptable power level is shown.