Case study - ElectraTherm’s green machine operates in tandem with small steam engine to double power output and increase efficiency


Courtesy of ElectraTherm

Niedersachsen, Germany
IC Engine: 635kW GE Jenbacher
Hot Water Temp:  90°C
Hot Water Flow:  10-11 l/s
kWth Average (Thermal Input): 550-600kWth
Cooling:  Air Cooled Condenser
Ambient Temp: 5-30°C
Green Machine Average Gross Output: Up to 35kWe, and up to 67kWe combined with Steam Engine

ElectraTherm, a leader in small-scale, waste heat-to-power generation, and its distributor SE-TECH, have installed a Green Machine at a German biogas site; the first of its kind to operate the ElectraTherm ORC in tandem with a small steam engine. This combination of the Green Machine and steam engine doubles the power output from a GE Jenbacher 312’s waste heat up to 67kWe, boosting the efficiency of the power plant by more than 10%.

The waste heat is provided by a 635kW GE Jenbacher engine running on biogas, with exhaust heat used to generate steam for the small steam engine. The Green Machine acts as the condenser on the steam engine, eliminating the need for a cooling loop and thereby increasing the steam engine’s efficiency. The Green Machine utilizes the low temperature (90°C) heat to generate up to 35kWe, 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 very strong ROI for the Green Machine of approximately 3.5 years for the plant owner.

The GE Jenbacher engine runs off the biogas produced by a corn/manure mix. The exhaust heat is used to generate steam for the small steam engine.  The waste heat from the cooling of the steam engine is combined back into the engines jacket water circuit.  The Green Machine uses the heat from the jacket water and the additional heat from the steam engine to further increase power output and efficiency of the Jenbacher engine. The Green Machine ORC uses direct air condensing for the cooling, with the ambient temperature ranging between 5-30°C.

“SE-TECH pioneered the combined ElectraTherm ORC/steam engine integration and its success has been proven with more than 5,000 hours runtime,” said Stefan Farwick, President of SE-TECH. “This unique configuration of two technologies ensures every kilowatt of heat is utilized to make electricity.”

ElectraTherm’s patented ORC technology begins with hot water entering the Green Machine at 90°C, where it heats a working fluid into a pressurized vapor. The high pressure vapor expands through ElectraTherm’s patented twin screw power block, spinning an electric generator. After turning the expander, the vapor is condensed back into a liquid through direct air cooled condensing.

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