What is geothermal energy?

Thermal energy is heat energy. Geothermal energy is the heat energy of the Earth’s crust, which originates from the original formation of the planet and from radioactive decay of materials. In Ireland is not well known but does have a high rate of growth. Since 2009, its use doubled in 4 years getting to 0.30% of total energy consumption in Ireland in 2013.

What types of Geothermal Energy exists?

There are 2 types of geothermal energy:

  • Deep:

The centre of the earth is approximately 4,200 degrees Celsius.  Some of this heat is produced from the geological process which helped to form the earth 4.5 billion years ago, but most of this heat comes from the decay of radioactive material deep underground.  At the surface of the earth, the temperature of the earth is usually too low to be used for heating or power generation activities.  Deep geothermal energy can be used if it ascends to the earth’s surface through fault lines on the earth’s crust and/or volcanoes; or by deep drilling to access it.

Exploitation of deep geothermal energy resources is still under study in Ireland.  Some of the areas identified with potential are the subject of more extensive research being undertaken by IRETHERM.

  • Shallow:

Shallow energy is where the existing thermal energy resource near the earth’s surface is augmented through the use of a heat pump to provide heating (and/or in some cases cooling). In a shallow geothermal system, water is usually pumped through closed loop pipes, gaining heat from the ground and returning it to an above-ground system, e.g. house or industrial building.  There are also open loop systems using ground or marine water, where the water is re-injected back to the ground or discharged to streams, rivers or the sea (sometimes used in fish farms).

Ireland had a very high growth rate in the use of shallow geothermal energy until 2009 but since then its use has slowed down. The installed capacity for ground source heat pumps in 2012 totaled 268 MW.

How is Geothermal used around the world?

Geothermal direct applications worldwide in 2005, distributed by percentage of total energy use










Geothermal shallow heat pumps have the largest energy use and installed capacity, accounting for 54.4% of worldwide use and 32.0% of worldwide capacity.

Important uses of geothermal energy include:
  • Aquaculture (2.2%)
  • Greenhouse heating (5%)
  • Space heating (20.2%)

Other uses include:

  • Agricultural crop drying
  • Industrial process heat
  • Snow melting and space cooling
  • Bathing and swimming


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