Ground heat exchangers use underground soil as a heat sink or source. When water flows through pipes, heat is transferred from the water to the earth or from earth-to-water depending upon the temperature of water relative to temperature of earth that remains nearly constant at the annual mean temperature of that place. In some cases, the thermal condition of water coming out from the pipes is such that it can be directly supplied to the space where it is to used, whereas in extreme weather conditions, it needs another stage of processing before becoming acceptable for supplying to the connected space.

Ground temperature below a certain depth remains relatively constant throughout the year because temperature fluctuations at the surface of the ground are diminished as the depth of the ground increases because of the high thermal inertia of the soil. Therefore ground temperature is always higher than that of the outside environment in winter and is lower in summer at a sufficient depth. The difference in temperature between the outside environment and the ground can be utilized as a preheating means in winter and pre-cooling in summer by operating a ground heat exchanger. Efficiency of a heat pump is higher than conventional natural gas or oil heating systems, a heat pump may be used in winter to extract heat from the ground and pump it into the conditioned space. In summer, the process may be reversed and the heat pump may extract heat from the conditioned space and send it out to a ground heat exchanger that warms the relatively cool ground. A ground source heat pump extracts heat from the ground – whose temperature will be warmer than the air in winter (and cooler than the air in summer). Therefore ground heat exchangers are more efficient than air source heat pumps, especially in the coldest weather when they are most needed. Ground heat exchangers generate very little noise and should last for many years with minimal servicing.

Ground heat exchanger are the system that is simple to use and easy to maintain. In addition, since the system takes care of both heating and cooling. Geothermal energy is a form of clean energy because using it doesn’t emit any type of pollutions.3 Ground heat exchangers use underground soil as a heat sink or source. Ground temperature below a certain depth remains relatively constant throughout the year because temperature fluctuations at the surface of the ground are diminished as the depth of the ground increases because of the high thermal inertia of the soil. When water flows through pipes, heat is transferred from the earth to the water or from the water to the earth depending upon the temperature of water relative to temperature of earth that remains nearly constant at the annual mean temperature of that place7.

Heat is transferred in the ground by two ways, convection and conduction.3