Geothermal energy derives from the decline of the earth’s uranium and thorium. The Earth’s total power emitted is 22 TW. The surface evacuates all this power, a flow of about 0.06 W / m2. Such 22 TW are of the same size as the current consumption. These 22 TW are of the same magnitude as the current consumption.
Nevertheless, due to its low density, there is a quantity of energy stored in the rocks in the form of heat, although difficult to use. Of moreover, this energy is not renewable; in most of the current installations, the deposit is running out in about thirty years.
It is quite rare to have high-temperature steam that can directly produce electricity. In most cases, the rocks hot shallow depths are difficult to access; the rock must be fractured so that water can circulate and extract the heat. For these reasons, it is difficult to envisage massive production globally from geothermal energy. However, there are special cases, such as Iceland, where geothermal energy is available in large quantities. Geothermal energy currently accounts for 0.3% of global electricity generation and about as much for heating.