Comparative energy performance analysis of micro gas turbine and internal combustion engine in a cogeneration plant based on biomass gasification

With a view to replacing fossil fuels, biomass electricity generation worldwide has grown from 509 TWh in 2015 to 685 TWh in 2021 and an upward trend is expected for the next years. It is about dispatchable, low-emission power to complement generation from variable renewables. Although modern bioenergy is considered a stable and carbon-neutral source, there is a need to boost the efficiency of the Biomass-to-Energy (BtE) conversion technologies. Accordingly, in this modeling study, attention was drawn to biomass gasification for heat and power, with a special focus on the prime mover characterization for distributed generation. An internal combustion engine (ICE) and a micro gas turbine (mGT), having the same nominal capacity of about 240 kWel when fueled by natural gas (NG), were inserted into a two-way biomass gasification chain and hence fed by clean syngas deriving from a downdraft gasifier. Simulations of the main components of the thermal power plant (gasifier, syngas cleanup, power island) were validated against data available in the published literature and in technical sheets, for specific operating conditions. The next step was to evaluate the overall performance of the entire BtE chain in terms of electrical, thermal, and total efficiency, both at full and part load, in order to highlight the pros and cons of each generator, in a twofold perspective. The last goal was to simulate a load following strategy, for two typical cold and hot days. The results of the thermodynamic analysis indicate that ICE is better performing than mGT, in the simulated context where the power demand from the grid ranges from 80 kWel to 190 kWel, with an ambient temperature between 2 and 35 ◦C. ICE provides the best performance in CHP mode, with a total efficiency of 62–69%.