HRP develops enhanced geothermal power plant at an appropriately identified hot rock zone within South Africa. Depending on the amount of geothermal energy available within the geothermal hot rock zone, it could be possible to generate in excess of 50MW per site using multiple modular 10MW power units. This generation capacity can only be determined once a complete geothermal survey of the specific hot rock zone has been completed.
Due to the rock temperatures found in Southern African, an Organic Rankine Cycle (ORC) power plant is the preferred technology. HRP’s application of this ORC technology is to allow for lower temperature heat sources, in the 100 - 150C temperature range.
In the proposed power plant, the heat source used to heat the working fluid is the actual rock in the hot rock zone. The heat is extracted from the rock strata via hot rock injection, whereby water will be artificially injected under high pressure into the rock strata through large bore injection wells. This occurs around and in the centre of the hot rock zone. The water will then be heated by the rock, while seeping through microscopic cracks and pores. The water proceeds to the head of the production wells, which are drilled round the outside of the hot rock zone where the now hot water (between 120-150C) is pumped out and through a high efficiency heat exchanger to heat the working fluid of the power plant. The cooled water will then be pumped back into the rock strata again via the injection wells. The water cycle of the power plant is a closed cycle and can utilize wastewater from the surrounding area and mines. Total water loss into the geothermal rock field will vary between 2-5% depending of the geology of the hot rock field.