In this study, performance tests of the co-generation system were carried out. The heat balance was calculated and evaluated based on the amount of generated electricity and waste heat recovered from the system. The results showed that the maximum system efficiency was 36.3%. The environmental conditions of the greenhouse were then defined and the required performance of the co-generation system in operation was studied, and the running costs were estimated. When comparing the running costs of common system and our co-generation system, it was found that our system is still more expensive with an electricity generation efficiency of 15%.

In the Stirling engine that utilizes waste heat, it is common to directly heat the working gas from high-temperature exhaust gas. However, this method results in a high temperature in the expansion space, leading to deterioration in reliability of engine components. To solve this problem, a low temperature Stirling engine was devised using a loop-type thermosyphon heat exchanger, which enables heat transfer by evaporating and condensing refrigerant between high-temperature exhaust gas and working gas. By using this method, the working gas can be indirectly heated through the low-temperature refrigerant, resulting in lower temperature in the expansion space and improved reliability. This study evaluated the condensation performance when applying a shell-and-tube heat exchanger to the heater. The results clarified the influence of the refrigerant amount on the heat transfer rate of the heater.

A thermoacoustic engine is an external combustion engine that can use low-temperature heat sources and has a simple structure that is easy to maintain, so it has received much attention for its potential use of industrial waste heat. There are two types of thermoacoustic engines: those driven by standing waves and those driven by travelling waves, the latter being theoretically more efficient. A loop-type thermoacoustic engine driven by travelling waves is thermally efficient but requires large space. This study focuses on a coaxial thermoacoustic engine. This is because it has smaller size than a conventional looped tube thermoacoustic engine. The coaxial thermoacoustic engine has a "Turn section" where the flow path bends 180 degrees. The turn section causes energy loss. The objective of this study is to investigate the energy loss at the Turn section. Experimental results indicated that the energy loss at the Turn section was dominated by minor loss, which is proportional to the cube of velocity amplitude, and the coefficient for energy loss was determined.

To understand the flow fields in the pulse tube with different strainers, a rectangular glass pulse tube refrigerator was fabricated for visualization, and the Schlieren method was used to visualize the flow in the pulse tube. The velocity distribution was estimated by applying the optical flow method from the Schlieren image. To obtain an accurate velocity distribution, the velocity distribution was averaged. The results showed that the flow turbulence was formed by attaching a strainer, and the flow was rectified by the strainer.

We present a design methodology for a thermoacoustic looped-tube engine connected to a piston-crank-flywheel assembly. The engine has a regenerator with heat exchangers at each end, which divides the main tube and the thermal buffer tube. These two tubes are connected by a feedback tube. The thermal buffer tube is also connected with branch tube, where acoustic power outputs to the piston. To determine the geometry of each duct element, they are expressed by equivalent electrical circuit elements based on the analogy between the governing equations in acoustic and electrical systems. By analyzing the circuit equations, we find that the real part of the acoustic impedance, which determines the output power, increases with the decrease in the volume of the main tube and in the volume ratio of the thermal buffer tube and the branch tube compared to the main tube. To experimentally validate this tendency, we measured the acoustic impedance of the looped tube engine. The result confirms the effectiveness of our design approach and implies the possibility of higher performance thermoacoustic engines with a a flywheel.

This study presents how to reduce vibration caused by excentric mass of an a-type Stirling engine with a Ross yoke. Firstly, we solve the kinematics of the mechanism to find the acceleration of its joints and the angular acceleration of T-shape yoke assuming constant angular velocity. Assuming also that mass of the piston is connected to each point of application of the yoke and the reaction forces of its acceleration force is exerted on the joint, the supporting forces to the yoke and the shaft are solved, which are expanded to Fourier series to find the counter balance including rotating mass, reciprocating mass and vibrating shaft torque. They are correlated as functions of the masses of the pistons, the T-shape yoke and the crank arm, and the moment of inertia and the position of the mass center of each of the latter two.

In this study, the performance of the chiller was first determined using a circular pulse tube made of acrylic, which is similar to the actual machine. After that, we attempted to take a Schlieren image of the circular pulse tube, but the curvature of the circular tube was too large to take a Schlieren image. Therefore, we attempted to improve the refrigeration capacity by switching back from a circular pulse tube to a rectangular pulse tube and changing the experimental conditions.

High-pressure helium is often used as the working fluid of Stirling refrigerators. Because, helium has a small molecular weight, which reduces pressure loss in piping sections. However, helium has been in short supply in recent years and its price is high. In this work, the performance of a two-piston alpha type Stirling engine operated as a motor-driven refrigerator was measured using nitrogen as an alternative working fluid. Also, the performance of conventional wire screen and a new type of matrix material called mesh sheet were compared as matrix materials for the regenerator.

Prototype of low temperature differential Stirling engine (LTDSE) has been made. The aim of the LTDSE was to be handcrafted within two days. Crankshaft of the LTDSE is supported by two bearings, and the bearing which is flywheel-side does not cover upper surface of the crankshaft. Both installation and removal of the crankshaft do not require both driver and pincers, due to the bearing which does not cover upper surface of the crankshaft. This bearing of flywheel-side is fixed by three bolts. The direction of these bolts is decided to make assembly easy. However, the direction caused that the nuts interrupted the rotation of crankshaft, because the bolts and nuts fixing crankshaft and flywheel contacted with the nuts fixing the bearing. Therefore, the parts fixing crankshaft and flywheel were redesigned. In addition, a tube connects bellows and displacer chamber, and the connecting position of the tube on displacer chamber has been moved from the position below a link mechanism.

The 27th Stirling Techno-rally was held on November 18, 2023. In this competition, participants compete on the performance and ideas of their self-made model Stirling engines. At this competition, an RC vehicle that ran using liquid heat stored by sunlight as its heat source won the idea prize.

Conventional methods for measuring the power output of small-power model Stirling engines can seem time-consuming and cumbersome to students who tune and improve their own engines. For small-output engines, analog direct-reading torque meters that utilize eddy currents are easier to use.