The last decade has witnessed a growing interest in the use of Stirling engine cogeneration systems for residential applications, due to their prospect for high efficiency, good performance at partial load, fuel flexibility, including the possible use of renewables, low emissions, vibration and noise levels. Stirling engines have sealed operating chambers, low wear and, as a consequence, low operating costs. In the European building sector, micro-cogeneration power plants are being designed to fulfill the heating requirements of the building and, additionally, generate electricity for internal consumption or for feeding into the local grid.

Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. The mathematical formulation includes a set of equations able to describe and simulate the physical system, as well as a set of equations that define the cost of each plant component.

This paper presents a numerical study faithfully simulating the real conditions of a micro-CHP unit based on an alpha type Stirling Engine. The simulations were performed through a MatLab® code that assesses the thermodynamic efficiency, including heat transfer limitations and pumping losses throughout the system.

Results showed that heat-transfer limitations strongly affect cycle efficiency, particularly in the regenerator case. The pumping losses are less important when hydrogen or helium are used.

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