Innovative combined heat and power system based on a double shaft intercooled externally fired gas cycle

This paper presents a new CHP solution based on a double shaft intercooled gas cycle with external combustion (EFGT cycle). This configuration exploits the turbocharger technology widely diffused in the automotive industry, taking advantage of the capital cost reduction due to the economy of scale typical of the automotive market. Thermodynamic calculations based on actual turbochargers maps available from manufacturers data are carried out in order to evaluate the performances of the system. It is shown that the system results competitive both with natural gas fuelled solutions such as internal combustion engines and microturbines achieving conversion efficiency of 25–30%, as well as with low grade fuels like biomass. For a 50 kW biomass system with a grate combustor boiler and turbine inlet temperature of 750 °C, an electric efficiency of 21% is obtained, which is higher than the available state of the art solutions based on ORC technology for this size. A preliminary design of the system is performed, including the sizing of the boiler, showing its technical feasibility, while complete economic evaluations will be considered in future works.

► A new CHP solution: a double shaft intercooled gas cycle with external combustion.
► Turbocharger technology from automotive industry has been exploited.
► Thermodynamic calculations are based on real turbochargers maps.
► Technical feasibility of a 50 kW biomass system with TIT of 750 °C is discussed.
► Electric efficiency of 21% is achieved, higher than ORC plants of this size.