ZEH (Zero Energy House) is the prospective model of housings which enables the reduction of energy consumption in domestic uses. The authors are developing a Stirling engine solar power generation system using a hybrid heat source, which produces electricity and warm water from solar and woody biomass. This paper presents a 500W Stirling engine generator installed in that system. It is a two-piston type Stirling engine driven by a crank mechanism and has a generator built-in. In addition, dependency on He gas mean temperature in a hot space of the Stirling engine generator is made clear.

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Aiming at reduction of the energy consumed in domestic use, research and development of an energy system corresponding to ZEH (Zero Energy House) is advanced. The authors are developing a hybrid heat source Stirling engine combined heat and power system, which uses solar and woody biomass for a heat source. In this paper, summary of the 1kW solar Stirling power generation system and a solar tracking type collector using the Fresnel lens are described. And heating method of heater and design of solar power generation system are considered.

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We are now planning and design a new α⁺ -type engine that is considered about higher buffer pressure and higher engine speed. Note that the α⁺ -type mechanism is suitable for low-temperature-difference Stirling engines and the α⁺ -type engine has a displacer consisting of two pistons that are connected via rods. Therefore, it is possible to use a regenerator with a sufficiently large area within a small range of temperature difference and to suppress the load applied to the crankshaft. The α⁺ -type engine is most effectively applied to power generation using solar heat or combustion heat from a wood biomass because the engine can be driven by indirect heating using 300 degC thermal oil. We report the plan and design of new 10 kW class engine that reduces volume of 1/3, increases thermal efficiency from 16% to 20%.

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The utilization of the energy for local power application will benefit the society of Indonesia, especially those who live in remote area far from the national energy supply chain. Stirling engine, capable of utilizing multiple renewable energy fuels, is a promising prime mover for mechanical and electrical power generation. Since August 2016, performance tests of small-size Stirling Engine Cogeneration Technology (SECOTEC) demonstrator with a wood-fueled rocket stove have been in progress, as a joint research project of Teikyo University (TU) and Institute Technology of Bandung (ITB). Described herein are some of research achievements available from experiment and simulation analysis, on characteristics of thermal input to Stirling engine heater head integrated with a bamboo-fired rocket stove, yielding high heat release rates and large stack-draft force.

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The purpose of this study is to construct and evaluate a Stirling engine cogeneration system using a wood pellet gasified combustor which was developed in previous study. First, in order to confirm the basic performance of the Stirling engine, an electric heating furnace was developed and a performance test was carried out. As a result, the thermal efficiency reached 16.7% at maximum when heat input 5 [kW]. Also, the recoverable heat passing through the engine from previous research was predicted, and it was found that it is possible to recover the heat of 1036 [W] at maximum.

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The purpose of this study was to improve the combustion state by excess enthalpy combustion because the combustion state was unstable under low fuel flow conditions. In this experiment, the excess enthalpy combustion performed stacked grates in longitudinal and transverse. Temperatures in the combustor and concentrations of exhaust gas were measured at same positions last year. As the result, temperatures in the combustor were increased as a whole with longitudinal stacked grate. In addition, temperatures in the primary combustion chamber and enthalpy at the exit were increased which condition with low fuel flow rate using longitudinal stacked grate. Thus, it was found that gasification-reaction was promoted further and the enthalpy increased using the longitudinal stacked grate.

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For on-site power generation by biomass fuel combustion of livestock waste and Stirling engine, we made two-kinds of combustor, oscillating kiln type and high-speed burner type, for effective thermal energy transfer to the Stirling engine. Then we estimated the burner from some point of view, as frame temperature, contamination, emission, heat transfer, ash treatment, easy operation, and etc.

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Stirling engine attracts the attention recently, because it can use various energy including renewable energy as heat source. The condition of the high-temperature part of the engine is different from the convention, when the renewable energy is utilized. Therefore, conventional heat exchangers may not be suitable. In this study, it was examined about suitable matrix material and dimension for regenerator, using a calculation model, SETMA for various operating conditions.

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On a point that heat transfer on cylinder walls is important to improve thermal efficiency of Stirling engines, flow and heat transfer simulation was performed using a commercial CFD software. It is done for the expansion space of a beta-type engine for a working gas of air at nearly atmospheric pressure with combination with one-dimensional multicomponent analysis. Heat flux on the walls are picked up and total heat flow was obtained. Change in heat flow from CFD has the same tendency as that from 1-D analysis except that low heat addition in the cooling process and heat removal in the compression process. The results are not deterministic because some strange tendencies exist.

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Regenerator is the indispensable regenerative heat exchanger in Stirling cycle machines. The existence is the key factor so that Stirling cycle may have the highest thermal efficiency. Regenerator matrices are often made of the stacks of high mesh size wire gauzes, because of the optimum balance between flow loss and heat transfer characteristics. However, the matrix made of stacked wire gauzes is high cost. So, SMF (sintered metal fiber) is suggested as a new matrix. In this report, the basic characteristics of pressure drop and heat transfer are measured using steady flow experimental apparatus. The experiment results are reduced in the empirical equations between the friction factor and Reynolds number, and between f the Nusselt and Reynolds number.

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An effective way to improve the efficiency of a cryocooler is to improve the efficiency of the regenerator. In general, the heat capacity of materials decreases as temperature decreases. Thus, when temperature is below 40 K, lead or bismuth spheres are often used as regenerator materials. However, the pressure drop in a sphere regenerator is much larger than that in a screen regenerator. To overcome this dilemma, new low pressure loss metal-plated screens are proposed. A comparison test was performed with a two-stage GM cryocooler by replacing part of the first stage regenerator material, phosphorus bronze screens, with metal-plated screens. Compared to a regenerator filled with bronze screens, the cooling capacity of the first stage increased significantly at 30~40 K with these metal-plated screens. The detailed experimental results are reported in this paper.

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Since 2012, a new, compact Gifford-McMahon (GM) cryocooler for cooling superconducting single photon detectors (SSPD) has been developed and reported by Sumitomo Heavy Industries, Ltd. (SHI). Also, it was reported that National Institute of Information and Communications Technology (NICT) developed a multi-channel, conduction-cooled SSPD system. However, the size and power consumption reduction becomes indispensable to apply such a system to the optical communication of AdHoc for a mobile system installed in a vehicle. The objective is to reduce the total height of the expander by 33% relative to the existing RDK-101 GM expander and to reduce the total volume of the compressor unit by 50% relative to the existing CNA-11 compressor. In addition, considering the targeted cooling application, we set the design cooling capacity targets of the first and the second stages under 1 W at 60K and 20 mW at 2.3 K respectively. In 2016, Hiratsuka et al. reported that an oil-free compressor was developed for a 2K GM cryocooler. no-load temperature of less than 2.1 K and the targeted cooling capacity were successfully achieved with an electric input power of only 1.1 kW. After that, the total volume of the compressor unit and electrical box was significantly reduced to about 38 L, which was close to the target of 35 L. Also, the sound noise, vibration characteristics, the effect of the compressor unit inclination and the environmental temperature on the cooling performance, were evaluated. The detailed experimental results are discussed in this paper.

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Sumitomo Heavy Industries has developed cryocoolers for space application. In recent years, development of a compact and lightweight cryocooler with high cooling power is demanded. Therefore, we are working on the development of new model with greater cooling power than the current model. It is possible to shorten the development span by using a convenient numerical calculation method. In this paper, the comparison between calculation results using SAGE program and actual performance test results are introduced.

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Pulse tube cryocooler does not have moving parts in the expander. Therefore, this cryocoolers are low vibration, high reliability and long life. However, the cooling capacity of pulse tube cryocooler is lower than that of Stirling cryocooler. Therefore, an improvement of the cooling capacity is necessary. In this research, the effect of expander shape on cooling capacity has examined experimentally and numerically, using a model pulse tube refrigerator.

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In this study, the acoustic power gain of a traveling-wave thermoacoustic engine with liquid piston and phase change was measured. The traveling wave thermoacoustic engine amplifies acoustic power when a traveling wave passes through the regenerator. When the working gas is assumed as an ideal gas, the maximum gain of the acoustic power is determined by the absolute temperature ratio at the both ends of the regenerator. However, by using the liquid vapor phase change, the maximum gain is not necessarily to be the absolute temperature ratio. In this experiment, a liquid piston and the liquid vapor phase change was used in the energy conversion. Furthermore, the acoustic power was amplified from 3.48×10^-4W to 7.32×10^-4W and the gain was 2.11, when the absolute temperature ratio was 1.17.

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A regenerator is one of the most important components of a thermoacoustic device. There are two types of regenerators, one has uniform flow channels and the other has complex flow ones. Compared to a uniform-flow-channel regenerator, a complex-flow-channel one is difficult to be analyzed theoretically. We constructed a complex-flow-channel regenerator by stacking stainless mesh screens and measured acoustic power loss in it. Based on the measured results, the model of the stacked screen regenerator will be proposed.

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Numerical simulation of heat and fluid flow has been performed to clarify the time-averaged gas temperature distribution in a heat exchanger in oscillatory flows. Transient two-dimensional equations of continuity, momentum and energy were solved utilizing a TVD scheme. A physical model of a simple circular tube in which a stack is installed was used for the numerical simulation. In the previous study using the model without a stack, it was shown that the time-averaged gas temperature distribution in the radial direction at operating frequency of 100 Hz is not shaped like a parabolic curve. In this study, the temperature distribution in the model with a stack is investigated to clarify the temperature distribution in a more realistic condition. As a result, it was confirmed that the temperature distribution at operating frequency of 100 Hz approaches a parabolic curve.

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This paper experimentally analyzes a looped thermoacoustic engine with liquid pistons. The engine consists of three identical unit sections, each of which contains a liquid column and a gas column. The gas column region includes a regenerator, hot and cold heat exchangers and a thermal buffer tube. The critical temperature ratio at both ends of the regenerator is found to be 1.34 and the engine starts to operate with a frequency of 4.5 Hz. From simultaneous measurements of pressure and axial velocity of the gas column, we determine the complex acoustic impedance to show that the thermodynamic cycle equivalent to the Stirling thermodynamic cycle is executed. The magnitude of the acoustic impedance is found to be as high as more than 20 times the characteristic impedance of the working fluid. The pressure amplitude in the gas column increases with the temperature ratio, but its growth stops at a certain level of the pressure amplitude. This phenomenon is discussed on the basis of the acceleration of the liquid column motion and gravitational acceleration.

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In this study, we provide the experimental equation for metal porous media in order to simulate the flow including porous region by CFD. We measured pressure drop on various metal porous media and found the correlation between porosity and shape factor in the Kozeny-Carman equation and Ergun equation.

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