Seite - 137 - in Water, Energy, and Environment - A Primer

Twentyfourcountriescurrentlyhavegeothermalpowerplants, for a total generating capacity of just over 13 GW. Based on current data, total installations should reach 18 GW by 2021, and could reach 32 GW by the early 2030s. Based on country-by-country estimates, total hydrothermal geothermal potential could reachup to200GW(50). Future geothermal power plants will use so-called ‘enhanced geothermal systems’ (EGS), previously called ‘hot dry rock’ systems, in which deep wells are drilled into hot rock with no natural water; water is introduced into these wells from the surface to which it returns, heated and ready for power generation (seeFigure 8.16). Figure 8.16 Schematic of EGS power generation (Source: AltaRockEnergy). Renewableenergy 137