Biogas Waste Heat Recovery

The IC60 ORC-module is an Organic Rankine Cycle system that produces electricity from waste heat of biogas engines. Up to now this heat had to be discharged unused.

The basic principal of the IC60 ORC-module is the organic thermodynamic cycle (Organic Rankine Cycle) where instead of water an organic medium patented by GMK performs mechanical work. By using an organic medium it is also possible to use similar low-temperature-potentials as heat source.

IC60 functional principle

The waste heat of the engine is supplied as exhaust gas, cooling water and lubricating oil heat to evaporate the organic medium. The organic medium in the evaporator generates a maximal pressure below 20 bar. To expand the working medium GMK uses a special developed expander. After the relaxed steam left the expander it is cooled down to ambient air temperature by an air condenser. There the medium condenses and flows into the hotwell where it is drawn by the feed pump. Afterwards the Organic Rankine Cycle fluid is conducted to the evaporator again.

The mechanical energy at the expander is transformed without a gearbox by a synchronous generator to electric energy to be fed into the public grid.

Application range

The IC60 ORC-module has been developed for a wide application range from a thermal input of 400 kW up to 800 kW. For this reason the IC60 ORC-unit is predestined for the application in many biogas engines as well as on other similar heat sources. Due to the use of a synchronous generator the IC60 ORC-module can be used to supply electric power for internal consumption of the biogas plant or to produce electric energy to be fed in the public grid.

Due to the compact design the IC60 ORC-module fits into a 20 feet special container and therefore can be installed directly next to the biogas engine. The air condenser as well as the thermal oil tank is installed on the roof of the container.

Quality

As a producer of Organic Rankine Cycle-units GMK possesses over own power plants at the technical centre that already completed over 80.000 hours of operation. During the construction of the IC60 ORC-unit GMK assured that main parts are produced and certified in Germany to place reliable ORC-units on the market. For example GMK uses special high-efficiency expanders (η>75 %) that were developed together with a well-respected company to reach more than 100.000 operating hours. These average fast running expansion plants (3.000 U/min) have significant advantages compared to small turbines concerning efficiency and durability as the small turbines underlie higher abrasion since the rotor turns at rpm of over 20.000. Furthermore GMK uses as evaporator an exchangers made by Germania Apparatebau GmbH. As SPS-assembly there is the Siemens S7-300 control in a control box made by Elpro GmbH Berlin.

Reliability

Based on the space-saving and operationally reliable construction of the IC60 ORC-unit a high efficiency can be granted which works in accordance to the availability of the upstream gas engine generator. As a result of the robust construction of the IC60 ORC-module, for example by a small number of moving parts, there is little maintenance necessary. The few hours that has to be spend for the yearly oil changing can be adapted to the maintenance interval of the gas engine.

Installed safety chains assure that the IC60 ORC-module can be operated fully automatic. The biogas engine can also be operated when the IC60 ORC-module sustains a technical breakdown. The control as well as the operation runs remote controlled, therefore no additional staff is necessary. Possible disturbances will be sent to the operator via wireless-module.