In pursuit of improved energy efficiency, German utility company Stadtwerke Gross-Gerau has added an organic rankine cycle (ORC) system from Dürr, Bietigheim-Bissingen, Germany. Using the ORC system, the local energy supplier is increasing the electricity generated by its biogas combined-heat-and-power (CHP) plant by more than 400,000 kWh. The additional electricity is obtained from waste heat generated when burning biogas in the CHP plant. The waste heat left over after electricity generation, which has a temperature of around 194°F (90°C), also is put to use for space heating and drying herbs on a neighboring farm.

According to Dürr, the higher energy yield means that the utility can supply some 360 more people with electricity.

 With Dürr’s ORC system, a steam turbine process uses the waste heat from combustion processes to generate electricity. The high temperature ORC system is installed as part of a combined-heat-and-power plant, demonstrating it possible to incorporate ORC technology in CHP plants with a low power output range from 50 kW.