Geothermal energy

Nesjavellir Power PlantNesjavellir Power Plant
Gretar Ívarsson – Edited by Fir0002 [Public domain]

What is geothermal energy?

Most people would have heard about wind turbines and solar panels. Some of them might even have heard about ocean energy or biomass… But geothermal energy is a rather ignored source of energy.

It is however a renewable energy worth noting as its use keeps getting more and more popular; even in Ireland, its use doubled in four years, supplying 0.30% of total energy consumption of the country from 2009 to 2013.

Thermal energy means “heat energy”. Geothermal energy is the heat energy of the Earth’s crust. It comes from the original formation of the planet and from radioactive decomposition of materials.

Puhagan geothermal plant
Mike Gonzalez (TheCoffee) [CC BY-SA 3.0]

Types of geothermal energy

There are 2 types of geothermal energy.

The first is “Deep”. The centre of the earth is really hot, approximately 4,200 degrees but at the Earth’s surface the temperature is usually too low to be used directly. So researchers and companies dug deep to use this kind of heat back on Earth’s surface.

The second type of geothermal energy is “Shallow”, meaning it is nearer to the Earth’s surface. Water circulates in closed loop pipes underground, driven by pumps.  The water gains heat from its passage underground and brings the heat back to the surface into a house or into an industrial building. This kind of installation is the most common worldwide for energy purposes.

First use

The world’s first geothermal power station
Picture from “The Renewable Energy website

The idea to use this warmth started with hot springs being enjoyed as thermal spas for thousands of years.  The world’s oldest geothermal district heating system was developed in the 14th century in France. 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 geothermal steam in Italy in 1904.

Advantages / Disadvantages

One of the biggest advantages this energy source has upon many other renewable energy sources is that it does not rely on any type of weather. It is available all the time. It is a reliable provider for electricity and heat. It is also available in every country and it is not subject to price rises that fossil fuels impose on the market. Their installations are mostly underground so they have little impact on landscapes.

Salt Wells geothermal plant in Nevada
US Department of Energy

However, geothermal has some disadvantages as well. Historically and geographically, deep geothermal has been limited to areas near tectonic plates boundaries and drilling for acquiring this heat is actually really expensive. Thermal systems can also run out of steam because the temperature is suddenly too cold.

Some environmental concerns have been expressed about this industry’s development as well. The main concerns are about factories releasing a poisonous and flammable gas called hydrogen sulphide that smells like rotten eggs. Moreover, extracting geothermal fluids may cause changes underground that will make the soil sink, and those fluids are likely to contain a some toxic materials.

Studies need to be done in advance to prevent drilling in an area that may sink. There are various methods available to remove the hydrogen sulfide and other toxic materials from the fluids exploited in the geothermal energy’s industry. The right measures must be taken before this industry is allowed to be developed.

Irish case

The Irish underground is very complex because two different tectonic plates crashed in each other a long time ago, creating a crack in the earth running diagonally from Clare to Antrim, and dividing the country. Two other cracks, parallel to this one, divide the country again; making it difficult to organize any drilling for deep geothermal energy. Such drilling is still under study and some Irish areas show a lot of potential for it.

However, the use of shallow geothermal energy is quite common in Ireland. This sector quickly developed until 2009 and then slowed down. Still, no district heating operations has been organised in our country, neither is there any plan to generate electricity from this renewable energy source.