The present patents relate to power generating apparatus suitable for use in extracting geothermal energy. The
geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a
continuous conduction of thermal energy in the form of heat from the core to the surface. As our reliance on fossil fuels
have started to decrease, geothermal energy is seen as one of the new sources of power generation by digging out the heat
stored inside the earth. Geothermal direct use dates back thousands of years, when people began using directly hot springs
for bathing or cooking food although in modern direct-use systems, a well is drilled into a geothermal reservoir to provide
a steady stream of hot water. Many technologies have been developed to take advantage of this clean energy in one way
for electricity production in power plants or in other way to produce heat or cold as support of heating and air conditioning
installations. This latter option uses the air-to-air or air-to-water systems. The paper introduces this type of energy, its
resources, summarizes the most relevant technologies implemented and highlights environmental issues compared to
other technologies. It is finally focused on the review of the most recent and relevant patents related to the devices devoted
to extract this energy from the earth, highlighting their significance and limitations. The paper concludes by addressing
current and future developments in the field.
Keywords: Geothermal energy, subterranean heat sources, heat pumps, earth-based cooling/heating systems, combined geothermal
and fossil power plants, patents.
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