Scaling up a woodchip-fired containerized CHP ORC unit toward commercialization

Abstract

Microcogeneration utilizing organic Rankine cycle technology has seen challenges in commercialization, despite its vast application potential. The market is large, but so is the competition from standard boilers. This was also the case for a previously developed biomass-fired 50 kWth 2 kWe unit intended for large buildings and small industries. Therefore, a scaled-up 120 kWth and 6.2 kWe unit has been proposed with better commercialization prospects.

This paper discusses the process of scaling up, designing, assembling and operation of this system. It includes innovative modifications of previously applied technologies regarding the boiler, expander and the overall system configuration. Both units utilize a rotary vane expander as a specific feature of the design. A comparison with the previous smaller unit is performed on several thousand hours of experimental data. The larger unit reaches higher net combined heat and power production efficiency, reaching 89.3%, even though the expander nominal isentropic efficiency slightly drops to 56%. Economic considerations and market feasibility are discussed with respect to the scaling-up from the laboratory scale unit towards commercialization. Thanks to the simplification of the unit, regardless of the scale-up, the absolute cost remains nearly the same for both units.