The Fraunhofer Institute for Silicate Research ISC is pursuing an innovative approach to regenerative electricity generation using hydroelectric power in the DEGREEN project.

The researchers are exploiting the extreme elasticity of ultra-thin elastomer membranes that can work like capacitors. The silicon films are coated on both sides with a conducive elastic layer, and with a protective insulating coating. When installed in shallow, slow-flowing bodies of water, the alternation between stretching and relaxation transforms the mechanical energy of motion into electricity. Flowing water expands the elastic film. In an expanded state the film is charged by applying a high voltage. Subsequently, the elastomer is mechanically relaxed into its original state. At 4000 volts, 100 milliwatts per film can be achieved, regardless of the degree of expansion. The elastomer generators are particularly well-suited to small rivers; and work with water speeds as low as 0.5m/s and depths of just 0.5m.