The goals of the project were the design, construction and operation of a Stirling engine, which is heated by the flue gas of a biomass furnace. The a-type Stirling engine was selected for cost reasons, because many parts from industrial mass production can be used. The necessary maintance and repair work of the Stirling engine can be done by a standard car work shop. The major problem of this development is given by the dust content of the flue gas. To avoid obstacles and fouling at the outside of the heat exchanger smooth heat resistant tubes have to be used. All kinds of biomass, e.g. agricultural waste, log or chiped wood, shells of fruits like coffee, may be used as fuel. A biomass Stirling engine with air (nitrogen) as working gas and a shaft power of 3 kW was designed and constructed for lab tests. With a working gas pressure of 33 bar, 600 rpm, a shaft power of 3,2 kW at a coefficient of performance of 25% (shaft power/heat) was verified. Engine durability tests, performance measurements and improvements were finished in 1997. In the next step of the development the shaft power will be enlarged to 30 kW. (C) 1998 Elsevier Science Ltd. All rights reserved.
