A waste-heat-to-power technology at a German biogas site is the first of its kind to operate the ElectraTherm ORC (organic Rankine cycle) in tandem with a small steam engine, says the maker. The combination doubles the power output from waste heat, boosting the efficiency of the power plant by more than 10 percent.

The waste heat is provided by a 635 kW GE Jenbacher engine running on biogas, with exhaust heat used to generate steam for the small steam engine. The Green Machine —manufactured by Reno, Nev.-based ElectraTherm and distributed by SE-Tech — acts as the condenser on the steam engine, eliminating the need for a cooling loop and thereby increasing the steam engine’s efficiency. The waste-heat-to-power technology utilizes the low temperature 194°F (90°C) heat to generate up to 35 kWe, nearly doubling the output from the steam engine alone.

The power generated from the waste heat meets the German heat utilization requirements to earn renewable energy credits, resulting in a return on investment of approximately 3.5 years for the plant owner.

Hot water enters the Green Machine ORC, where it heats a working fluid into a pressurized vapor. The vapor expands through a twin-screw power block, spinning an electric generator to create electricity. The vapor returns to a liquid through direct air-cooled condensing to continuously cycle through the system. The waste heat-to-power technology converts sources of low-temperature heat (stationary engines, biogas, biomass, geothermal/co-produced fluids, etc.) into power.

 For additional information, visit www.electratherm.com