Geothermal ORC Plant as a Replacement of Diesel Generators on Isolated Grids

Abstract

Isolated electric networks with no connection to a large grid have often used Diesel generators as a source of power. In some cases a geothermal resource is found within a reasonable distance to such a grid, inviting to replace the expensive Diesel generated Electricity with clean geothermal energy. An ORC plant generating electricity for such an isolated grid has to fulfill certain demands. The plant must be capable of running even if all external load to the plant is lost. The plant has thus to be able to regulate itself from maximum generation load down to the load of the plants own consumption. This paper treats how such a plant has to be designed. Variable geometry turbine IGV’s are a key item in such a design, and they enable a fast and efficient reaction to this abrupt change of power generation. The geothermal fluid supply system has to be designed accordingly, so that a minimum of geothermal fluid is released to the environment. Finally a design made by Atlas Copco of such a plant is presented.