Geothermal Energy

In the actual context of more and more talk around the green house gas emissions and the COP21 Agreement in Paris that will force countries to adopt new regulations to minimise their emissions, we need to look to all alternatives of renewables that we could use. One of them is geothermal energy, which is not so well known in Ireland 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 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.

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.

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).

How all this started…

Hot springs have been used for thermal spas for thousands of years.  The world’s oldest geothermal district heating system in France was developed in the 14th century. However, the use of Earth’s heat as a source of electrical energy began in the early 20th century when electricity was produced for the first time from a geothermal steam at Larderello, Italy in 1904.

The world's first Geothermal power station

The world’s first Geothermal power station

Advantages

  • Geothermal energy is not dependent on the weather
  • Available 24/7, it is a reliable provider of electricity and heat
  • It provides countries with a supply of sustainable energy
  • It is not subject to fuel price volatility
  • It has minimal visual impact, making it ideally suited to urban locations
  • It is cost effective, reliable, sustainable, and environmentally friendly

Disadvantages

  • Historically and geographically, it has been limited to areas near tectonic plate boundaries
  • Drilling and exploration for deep resources is very expensive
  • Thermal systems can run out of steam – over a period of time due to drop in temperature or if too much water is injected to cool the rocks

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

Geothermal energy in Ireland

Ireland’s geology is very complex.  There is a major fault in Ireland formed by the collision of two ancient land masses (tectonic plates) running diagonally from Clare to Antrim, dividing the country.  There also are two fault structures parallel with this fault (Iapetus Suture) and the presence of 42 warm springs across Ireland is largely associated with these faults.

Bedrock Geological Map of Ireland (GSI, 2006) & location of warm springs

Bedrock Geological Map of Ireland (GSI, 2006) & location of warm springs

Shallow geothermal energy

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 .

heatpumps

There are currently no district heating operations in Ireland, nor is any power (electricity) generated using geothermal energy.

Considering having a pump in your house? Read this HomeOwner manual from the Geological Survey of Ireland.

Deep Geothermal in Ireland

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.

Environmental concerns of deep geothermal:

  • The main concern is the release of hydrogen sulfide from the power plant, a gas that smells like rotten egg at low concentrations
  • The disposal of some geothermal fluids, which may contain low levels of toxic materials – nor currently a concern
  • Extracting geothermal fluids can reduce the pressure in underground reservoirs and cause the land to sink, there are recorded landslides around geothermal plants.

References:

Pasquali, R., et all, (2015), Geothermal Energy Utilisation – Ireland Country Update, standford.edu

Goodman, R. et all, (2004), Geothermal Energy Resource Map of Ireland, SEAI

Lund, J., Freeston, D., Boyd, T., (2005), Direct application of geothermal energy: 2005 Worldwide review, Science Direct

Gareth Ll. Jones, Róisín Goodman, Ricardo Pasquali, John G. Kelly, Nick O’Neill & Edward Slowey, (2007), The Status of Geothermal Resource Development in Ireland

Harsh K. Gupta, Sukanta Roy, (2006), Geothermal Energy: An Alternative Resource for the 21st Century, Science Direct

http://environment.nationalgeographic.com/

http://seai.com

http://www.dcenr.gov.ie/

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