Inside the ground to accumulate large amounts of energy. Slowly penetrating the surface to form a thermal flow, which make an average of 0.063 W/m2. The thermal gradient measured temperature increase per unit of length near the ground surface, the thermal gradient that drives the geothermal heat flux, equal to about 30 ° C / km. This means that about 3 km length achieve an average of 100 ° C. These data lead to the conclusion that the resulting performance is very high, but is spread over a large area such that its density is very low. It is much lower than the density of heat flow coming from the sun under a clear sky. This makes the use of this energy is difficult, but in regions with an unusually large geothermal springs geothermal gradient is greater than the average. At such places can be found at a depth of 1500 and 2500 m the temperature to 200 ° C. Geothermal energy has multiple uses.
In Slovakia is located 25 prospective areas of geothermal water temperature to 150 ° C at depths to 5000 m. These springs are used mainly in agriculture. Today it is used for heating swimming pools with geothermal water, heating hospitals and residential development. Today's use of the SR is limited because of the high financial cost. Advantages of geothermal energy are high performance and no production of pollutants and the ability to position anywhere on the mainland. The disadvantage is that the use of this energy increases the number of earthquakes, loosing the earth's crust and the risk of leakage of toxic compounds from the well.
In practice, however, can also use geothermal energy from the lower calorific value than that of the superheated water, respectively. para. Only a few degree differences from the outside temperature can be utilized in heat pumps, which operate on the principle of thermodynamic cooling circulation.
Heat pump or cooling equipment can be used for heating and cooling processes in turn (especially in winter, hot air heating and air conditioning in summer) or even simultaneously, which is energy efficient. Using a heat pump of 1 kWh can be obtained on average approx. 2.5 to 4 kWh of thermal energy.