Direction Then The Other
Some types may combine or dispense with some of these. Heat sourcePoint focus parabolic mirror with Stirling engine at its center and its solar tracker at Plataforma Solar de Almera PSA in SpainThe heat source may be combustion of a fuel air diffuser, since the combustion products do not mix with the working fluid that is, external combustion and come into contact with the internal moving parts of the engine, a Stirling engine can run on fuels that would damage other that is, internal combustion engines' internals, such as landfill gas which contains siloxane.Some other suitable heat sources are concentrated solar energy, geothermal energy, nuclear energy, waste heat, or even biological. If the heat source is solar power, regular solar mirrors and solar dishes may be used. Also, fresnel lenses have been advocated to be used for example, for planetary surface fan coil unit. Solar powered Stirling engines are becoming increasingly popular, as they are a very environmentally sound option for producing power. Also, some designs are economically attractive in development projects. RecuperatorAn optional heat exchanger is the recuperator used when high efficiency is desired from combustion fuel input to mechanical power output. As the heater of a fuel-fired engine with high efficiency must operate at a nearly uniform high temperature, there is considerable heat loss from the combustion gases exiting the burner unless this can be cooled by preheating the air needed for combustion. Engines used within combined heat and power systems can instead cool the exhaust gases at the ”cold“ side of the fan coils. HeaterIn small, low power engines this may simply consist of the walls of the hot space s but where larger powers are required a greater surface area is needed in order to transfer sufficient heat.