Small-scale CHP Plant based on a 35 kWel Hermetic Four Cylinder Stirling Engine for Biomass Fuels- Development, Technology and Operating Experiences

Within the scope of a comprehensive study and two development and demonstration projects, various technologies in the power range of up to 2 MWel for small-scale biomass-fired CHP plants have been investigated, evaluated and compared considering technical as well as economic aspects. Such plants should normally be operated on a heat-controlled basis in order to achieve a high overall efficiency and should run for more than 5,000 annual full load operating hours to ensure economical operation.

Two of the technologies examined are very promising and innovative: the Organic Rankine Cycle (ORC) process and the Stirling engine process. The ORC process represents an economically interesting technology for small-scale biomass-fired combined heat and power plants in a power range between 400 and 1,500 kWel.

A newly developed ORC technology with a nominal electric capacity of 1,000 kW was implemented in the biomass CHP plant Lienz (A) in the framework of an EU demonstration project. This plant was put in operation in February 2002. Stirling engines are a promising solution for installations with nominal electric capacities between 10 and 150 kW.

A biomass CHP pilot plant based on a 35 kWel-Stirling engine was developed and put into operation in the end of summer 2002. Up to the end of June 2003 the plant has run for more than 4,300 hours with very promising results.