Case study - ElectraTherm partners with GB Consulting and EnviTec Biogas on first of its kind biogas application


Courtesy of ElectraTherm

Biogas/ORC Application on GE Jenbacher 412 Engine
Site: Straznice, Czech Rep.
Engine Power: 844kWe
Green Machine Gross Power Output Avg: 30-40 kWe
Thermal Input to the Green Machine: ~500kW
Hot Water Input Range: 94°C
Hot Water Flow: 12 l/s
Liquid Loop Radiator Water Temperature: -7 to 40°C

In the Czech Republic, ElectraTherm, distributor GB Consulting and biogas plant constructor EnviTec Biogas commissioned an ElectraTherm Green Machine at a biogas plant to generate additional power and increase energy efficiency on site. The Green Machine uses Organic Rankine Cycle (ORC) technology to generate fuel-free, emission-free power. To date, the machine has maintained over 97% uptime.

The Green Machine was added at an existing biogas power facility with a Jenbacher 412 internal combustion (IC) engine producing 844kWe. The engine is equipped with an exhaust gas heat exchanger, and is configured to have a higher jacket water temperature, which provides a combined jacket water and exhaust heat stream of 95°C. The Green Machine is the first heat load on this hot water circuit, and generates up to 40kWe. After the Green Machine has removed heat from the hot water circuit, the anaerobic digester removes heat, followed by several buildings for district heating. Any excess heat not consumed by the Green Machine, anaerobic digesters, or building heat is removed by the engine cooling radiator.

ElectraTherm’s patented ORC technology begins with hot water entering the Green Machine at 94°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 the use of a liquid loop radiator with some heat also being used for nearby district heating.

This biogas plant is the first of its kind to connect the Green Machine to the first heat loop, providing it with higher waste heat temperatures to increase power output, while maintaining proper heat input to the anaerobic digesters. The addition of the machine reduces the onsite electricity needed to reject excess heat through radiator fans, increasing plant efficiency by up to 8%. As a result, the Green Machine improves site economics by producing electricity and lowering onsite power demands.

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