Geothermal system, heat in place, enthalpy classes, EGS কী?

A geothermal system is a volume of the crust where heat, permeability and water come together so that hot water or steam can be produced from wells. The heat in place of a reservoir is the heat it would give up in cooling from its temperature to a reference temperature. A high-enthalpy resource is a geothermal system above about $150\,{}^{\circ}\mathrm{C}$; a low-enthalpy resource one below about $90\,{}^{\circ}\mathrm{C}$; between the two the resource is called moderate. All three suit direct use of the heat, but generally only the moderate and high classes can generate electricity. An enhanced geothermal system (EGS) is a body of hot rock of low natural permeability in which permeability is created by engineering, so that water can be circulated through it and its heat recovered.