Development of a Wood Powder Fuelled 35 kW Stirling CHP Unit

For biomass fuelled CHP in sizes below 100 kW, Stirling engines are the only feasible alternative today. Using wood powder as fuel, the Stirling engine can be heated directly by the flame like when using a gaseous or liquid fuel burner. However, the combustion chamber will have to be much larger due to the slow burning of the fuel. To avoid sintering of ash the flame temperature in a biomass burner has to be quite low. The flame temperature can be lowered by using a high excess air rate; however this will lower system efficiency and needs a large air preheater. By using combustion gas recirculation (CGR) a smaller air preheater can be used, while system efficiency will increase compared with using excess air for flame cooling. In a three-year project, a wood powder fuelled Stirling engine CHP unit will be developed and run in field test. The project will use the double-acting four-cylinder Stirling engine SM3D with an electric output of 35 kW. This engine is a further development of the engine SM3B that has been developed at the Technical University of Denmark. The engine heater is being adapted for use with wood powder as fuel. During a two-year period a combustion system for this engine, using wood powder as fuel will be developed at Lund University, Sweden, in cooperation with the Technical University of Denmark and with the wood powder boiler manufacturer VTS AB. The unit is to be run in CHP operation by Vattenfall - the largest electric power company in Sweden - in a one-year field test in Ĭvkarleby, Sweden, and the operation of the unit will be evaluated at the end of the field test period. The unit is intended for blocks of flats, schools, local heat production plants and the wood industry.