The Stirling engine is an alternative solution to produce cleaner energy in order to achieve the reduction of the fossil fuel consumption and the CO₂ emissions. It comprises an external combustion engine that can convert any external heat source into mechanical power, through cyclic expansion and compression of a working gas in a closed-regenerative cycle, with or without driving mechanisms. The free-piston Stirling Engine is significantly preferred because of the absence of any mechanical linkage resulting in longer operating life, lower noise pollution, maintenance and vibration free, self-starting and high thermal efficiency. The aim of this paper is to summarize the research works on the free-piston Stirling engine technologies and models. First, the working principles of the free-piston Stirling engine are described, identifying different configurations. Then, several applications are presented. Finally, a detailed review of the models available in literature is given, pointing out the main assumptions and equations.

In this paper, exergy analysis is used to evaluate the performance of a combined cycle: organic Rankine cycle (ORC) and absorption cooling system (ACS) using LiBr–H₂O, powered by a solar field with linear concentrators. The goal of this work is to design the cogeneration system able to supply electricity and ambient cooling of an academic building and to find solutions to improve the performance of the global system. Solar ACS is combined with the ORC system—its coefficient of performance depends on the inlet temperature of the generator which is imposed by the outlet of the ORC. Exergetic efficiency and exergy destruction ratio are calculated for the whole system according to the second law of thermodynamics. Exergy analysis of each sub-system leads to the choice of the optimum physical parameters for minimum local exergy destruction ratios. In this way, a different connection of the heat exchangers is proposed in order to assure a maximum heat recovery.