Small-scale biomass power generation

In recent years considerable attention has been paid to power generation from biomass, especially in small scale plants. Several plant configurations have been proposed and investigated, but so far, definitely preferable technological solutions have not been found yet. Moreover, a comparison of their performances is often difficult, due to the fact that working assumptions are not always consistent. The aim of the present work is to provide a full overview on small scale technologies regarding biomass exploitation (particularly woody one) for power generation, in order to define the most interesting solutions from a thermodynamic and economic point of view. Existing configurations or those which are expected to be potentially available on the market in the near future have been considered. Three plant sizes have been focused: 100 kWel, 1 MWel and 5 MWel. Internal combustion engines (ICE), (micro) gas turbines (mGT/GT), both internally and externally fired, and organic Rankine cycles (ORC) have been taken into account as power plants, while direct combustion and gasification have been considered for biomass. Simulations show that the externally fired gas turbine is the most promising technology at small scale (100 kWel), if a high temperature heat exchanger is available. A gasifier coupled with an internal combustion engine is instead preferable at larger scales (1 MWel and 5 MWel). An also proposed sensitivity analysis concerning moisture effects shows that biomass drying with flue gas is generally disadvantageous, even if sometimes (e.g. in gasifiers) necessary, because of the dryer cost.