Ormat ORC: Ormat geothermal power stations work all over the world with more than 950 MWe capacities, that means many million hours of operation experience. An Organic Rankine Cycle is a thermodynamic process where heat is added to a special kind of organic fluid at a constant pressure, the fluid is vaporized and then expanded in a vapour turbine, which drives a generator, producing electricity. The spent vapour flows to a condenser where it is condensed to liquid and recycled back.
At higher temperatures the cycle could be further improved in order to achieve higher efficiency.
With good steam based reservoirs the best avaialble option is the Combined Cycle Power plant.