Geothermal energy: Extracting heat stored in the Earth

01-02-2018

If we are to achieve the objectives of the Paris climate agreement in terms of reducing CO2 emissions, we need to make smarter use of our energy and focus more on new technological developments. One of the technological developments already under way in the Netherlands is geothermal energy.

Geothermal energy is nothing more than heat from the Earth. That is why, the Dutch term for geothermal energy, ‘aardwarmte', can be translated as ‘earth heat’. Deep underground, hot water is stored in (porous) rock strata. The deeper down towards the Earth's core, the warmer it gets. With every kilometre of depth, the temperature rises by about 30˚C. At a depth of two to three kilometres, the water temperature is between 60 and 90˚C. The energy contained in this hot water is called geothermal heat or geothermal energy. The water can be pumped up and the heat can be used to heat homes, buildings, industry or greenhouses in greenhouse horticulture. It is a sustainable source of energy, because it generates hardly any CO2.

To extract geothermal heat, the hot water is pumped out of the deep subsoil and the heat is extracted using a heat exchanger. The cooled water is then pumped back and eventually heats up again because of the heat in the Earth. A geothermal installation therefore consists of at least two wells, one for the production of hot water, the production well, and one for the injection of cooled water, the injection well. The distance between these two wells in the deep subsoil is about 1 to 2 kilometres, and therefore they are partly drilled at an angle.

As a renewable energy source, geothermal energy may be able to meet up to 30% of the heat demand in the Netherlands, saving a lot of CO2. Safe and responsible development of geothermal energy is a top priority. As with the extraction of oil and gas, great care is required to prevent leaks, earthquakes and other problems in drilling and extracting this type of energy from the Earth.

Greenhouse with peppers
Greenhouse with peppers

Applications in the Netherlands

In the Netherlands, there are currently about 20 projects that utilise geothermal heat, most of which can be found in greenhouse horticulture. These projects combined save up to 77 million m3 of natural gas and therefore approximately 138,000 tonnes of CO2 per year. A very sustainable energy source. In addition to the heating of greenhouses, geothermal energy is also suitable for the heating of homes, swimming pools and businesses.

What is the role of the gas sector in geothermal energy?

The gas sector can play an important role in geothermal energy, because people in this sector have a lot of knowledge and experience of working with the deep subsoil. The geothermal and gas sectors are working together to create more and deeper geothermal projects in a smart, safe and responsible manner. Meanwhile, opportunities have also been identified to drill deeper, for higher-temperature geothermal heat. In addition, research is being carried out into whether the wells in depleted gas fields can be reused for geothermal energy. When the gas in a well is nearly or completely exhausted, hot water will almost always come up with the gas. If this happens, the well is usually closed and the location is cleared, but the gas sector is now looking into whether these wells can be used as geothermal wells. It is expected that a number of wells may possibly be given a second sustainable life.

 Do you want more information about geothermal energy? Go to: www.hoewerktaardwarmte.nl (in Dutch only)