Distributed power generation in industrial, urban and commercial applications is a key topic for the strategic development and implementation of modern energy policies. Solid biomass fired small scale cogeneration plants can play an important role in Europe to improve environmental and economic impact of such policies. As a result of advances in the design and development of twin-screw wet steam expanders, they now appear as an efficient enabling technology for this small scale de-centralized cogeneration plants. Same as backpressure turbines, twinscrew steam expander can generate power by reducing the pressure between the steam source and the downstream steam/heat user, but with the advantage of adopting wet steam as working fluid. The paper will describe the principles of steam screw expander operation and performance characterization and discuss installations of the expander genset in various industrial and urban (district heating) applications where steam is generated with solid biomass fired saturated steam boilers
