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Geothermal Energy: Geothermal Pumps

One of the best ways to utilize the potential of geothermal energy is through geothermal heating. Whilst the earth's hot underground temperatures can be relied upon to create steam for generating electricity, they are also great sources of heat for warming internal spaces and even for providing hot water. This technology is known as ground source heat pumping, geo-exchanging or geothermal heat pumping, and has been in practice in regions all over Europe, the United States and the UK for several decades.

Because temperatures several feet below the surface remain at a stable temperature year round, heat exchange systems can draw out heat in the winter months and inject heat in the summer months, all with minimal use of electricity (to power the pumps). In some cases systems have been set up to be powered by electricity garnered from solar or wind power, making them entirely carbon neutral and completely self sufficient. This is a particularly attractive option for people tired of rising gas and electricity bills in the cold winter months.

Closed Loop Systems

The most common type of geothermal heat pump is what is known as a 'closed loop' system. Closed loop systems use piping laid under the ground that are filled with water and antifreeze to draw out heat and transfer it to a pump, radiator or under-floor heating system.

There are several types of closed loop systems, usually determined by the direction they are laid in (either horizontally or vertically). A vertical closed loop field can be quite expensive to install as it involves the drilling of a bore hole (or several holes) that can be as deep as 150 metres. This intensive style of heat exchange is usually used in areas where horizontal ground space is at a minimum or for the building (or buildings) to be heated are larger than a single-family home.

In a domestic setting it is generally preferable to install one of two horizontal closed loop systems - either a horizontal closed loop field or a slinky closed loop field. Both are laid in shallow trenches (below the frost line) and both are ideal for home heating. Slinky closed loop systems use coils of piping that cross over one another when laid horizontally, maximizing the absorption of heat. Normal horizontal closed loop systems do not cross over one another in coils.

Standing Column Wells

Another suitable choice for many domestic and industrial heating requirements is a standing column well. These types of wells circulate water between the surface and the bottom of the well, allowing the hotter temperatures under the ground to warm the water. It is important to note that standing column wells will require more intensive planning than the closed loop systems discussed above, particularly because they need strong, stable ground soil to prevent collapse or failure.

Types Of Pump

The final consideration that will need to be made prior to installing a geothermal heat pumping system is the type of pump the system will require. There are a few different types, such as water-to-water, water-to-air and hybrid pumps, all of which use specific techniques to transfer the heat drawn from under the ground into usable heat above. For a domestic situation hybrid pumps are recommended, simply because they can be used to for under-floor heating, air heating and even providing hot water.