Due to the complexity of the power generation

Many researchers and scientists strived to improve the performance of the low-temperature Stirling MLN9708 machines. Kolin [4] developed the first conventional LTD Stirling engine. The engine operated at temperature difference as low as 15 K. Senft [5] was one of the pioneers of LTD Stirling engines. Senft designed and developed an amazing small prototype of the LTD Stirling engine based on a temperature difference of 0.5 K. Indeed, it was the lowest temperature difference reported amongst the previous works. Iwomoto et al. [6] presented a comparison between the performance of the LTD and high-temperature Stirling engines. It was shown that the efficiency of the LTD Stirling engines could approximately achieve 50% of the ideal Carnot cycle. It could be attributed to the fact that at lower temperatures the frictional and mechanical losses were less significant than high-temperature conditions. Kongtragool and Wongwises [7] presented eminent works on the LTD Stirling converters. They designed a single-acting twin-power piston LTD Stirling engine with gamma configuration. Non-pressurized air was used as the working fluid. The heater temperature was about 589–779 K. The simulation and experimental results revealed the effectiveness of the proposed LTD Stirling engine. Mertaj et al. [8] carried out a thermodynamic analysis for an LTD Stirling engine at steady state operating conditions. In this analysis, energy, entropy and exergy balances were applied to each element of the engine. Tavakolpour et al. [3] presented a two-cylinder LTD Stirling engine powered by a 0.5 m2 flat plate solar collector and without the application of regenerator. They proposed the procedure of finite dimension thermodynamic together with the Schmidt theory for optimizing the parameters of the proposed Gamma-type engine based on the assumption of low temperature difference. However, the proposed analytical technique was not usable for high temperature Stirling converters. They thus proposed an optimal volume ratio of 12.5 according to the collector temperature of 373 K and sink temperature of 293 K through the proposed mathematical scheme. Noureddine et al. [9] developed an LTD solar Stirling engine coupled with a water pump for developing countries. Experimental investigation was implemented to improve the output power of the gamma-type Stirling engine for sinusoidal and discontinuous motions of the displacer piston considering flat-plate heat exchangers. Chen et al. [10] studied the heat transfer characteristics of a twin-power piston Gamma-type Stirling engine using CFD analysis. They presented temperature contours, velocity vectors, and distributions of local heat flux along solid boundaries at several important time steps. They then investigated the variation of the average temperatures, rate of heat transfer and engine power.