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Geothermal energy
Geothermal is the Earth’s natural heat created by the decay of radioactive elements in the Earth’s crust and is transferred to higher layers of the Earth’s crust.
When energy from the interior of the Earth accumulates in water and gases, then we are talking about hydrogeothermal energy, while petrothermal energy means its retention in solid rocks. Although hydrogeothermal energy has been used for decades, either directly or to produce heat and electricity, petrothermal energy has only recently been used for heating and cooling buildings.
When it comes to electricity production from hydrogeothermal energy, the term geothermal energy is most often used.
It is estimated that the Earth’s geothermal resources are more than enough to supply humanity’s energy needs, although only a very small part is currently profitably exploited.
As of 2019, the world’s geothermal energy capacity is 15.4 gigawatts, of which 23.86 per cent or 3.68 GW is installed in the United States. The Geothermal Energy Association (GEA) estimates that only 6.9 per cent of the total global potential has been used so far. At the same time, the IPCC reported that the potential for geothermal energy ranges from 35 GW to 2 TW.
Geothermal energy is a key renewable source that covers a significant share of electricity demand in countries such as Iceland, El Salvador, Kenya, the Philippines, and New Zealand and more than 90 per cent of Iceland’s heating demand.
Geothermal energy will certainly play an important role in the energy transition because the costs of producing geothermal energy are lower. During the 80s and 90s of the last century, they decreased by 25 per cent.
Advantages and disadvantages of geothermal energy
Unlike traditional energy sources, geothermal energy has the following advantages:
- It is clean and safe for the environment – Geothermal energy is more environmentally friendly than conventional fuel sources such as coal and other fossil fuels. In addition, the carbon footprint of the geothermal power plant is low. Although there is some pollution associated with geothermal energy, this is relatively minimal compared to fossil fuels.
- It is practically inexhaustible – World energy consumption currently amounts to about 15 terawatts, far from the total potential energy available from geothermal sources. Although we cannot now use most of the reservoirs, there is hope that the number of exploitative geothermal resources will increase with ongoing research and development in the industry. It is currently estimated that geothermal power plants could provide between 0.0035 and 2 TW of energy.
- It is reliable – its exploitation is not limited by meteorological conditions, period of year or day (unlike hydro, solar or wind power plants).
- It is economical – when a geothermal power plant is built, energy is almost free, with low self-consumption.
- Heating and cooling – provides the possibility of multipurpose use, which affects the economic justification of exploitation.
However, this type of renewable energy has several disadvantages, namely:
- Release of underground greenhouse gases during works.
- Location dependency – the biggest individual disadvantage of geothermal energy is that it is location-specific. Geothermal plants should be built in places where energy is available, which means that some areas are not able to exploit this resource. Of course, this is not a problem if you live in a place where geothermal energy is easily available, such as Iceland.
- Increased risk of earthquakes – geothermal energy also risks causing earthquakes. It is due to changes in the structure of the Earth due to digging. This problem is more common with improved geothermal power plants, which push water into the Earth’s crust to open cracks for greater resource exploitation. However, since most geothermal plants are far from populated centers, the implications of these earthquakes are relatively small.
How can this renewable energy source be used?
Geothermal energy can be widely used – from the production of electricity in power plants through district heating to heating greenhouses and hothouses, paper production, milk pasteurization, swimming pools, wood drying, livestock and more.
Contrary to popular belief, natural and artificial hot water sources are not the only ones suitable for exploitation. Low-temperature geothermal resources can also be used with heat pumps.
Geothermal energy is the easiest to use for heating and cooling houses and business premises using the so-called open system, either by direct use of geothermal water or indirectly by heat pumps. It is predicted that the use of heat pumps in the next period will be significantly higher because we will take on this obligation by adopting the legislation of the European Union.
When it comes to using geothermal energy for electricity production, most modern geothermal power plants work on the principle of steam separation, which means that water is pumped from geothermal tanks to the power plant, which causes pressure reduction and hot water turns into steam and drives generator turbines. Binary power plants use colder water than plants with a different way of electricity production from geothermal sources, so the availability of geothermal supplies is higher than with other processes.
The choice of the principle of operation of the power plant depends on the type of geothermal source, temperature, depth and quality of water and steam.
The Earth’s internal heat energy flows to the surface by conduction at a rate of 44.2 terawatts (TW) and is replenished by radioactive decay of minerals at a rate of 30 TW. In addition to internal heat fluxes, the top layer of the surface at a depth of 10 m is heated by solar energy during the summer and releases that energy and cools down in the winter.
How much geothermal energy is available?
Today, there are technological possibilities for exploiting of rock energy to a depth of 10 km. Still, at but at greater depths, this energy is many times higher and currently unavailable to us. Hydrogeothermal resources are technically much more usable and cost-effective, although there are fewer. If we consider the possibility of using this energy to a depth of 3 km, its global reserves are 2,000 times greater than coal reserves.
To assess whether an area meets the conditions for exploiting geothermal energy, it is necessary to determine the proximity and temperature of the hot mass concerning the Earth’s surface. Hot water and steam can be delivered to the surface and used regardless of whether their tanks are in shallow surface layers or at a depth of several kilometers. The choice of technology for exploitation and application of energy depends primarily on the reservoir temperature. However, it is most practical to use this energy in areas where the hot mass is close to the Earth’s surface.
What is the geothermal potential of Serbia?
According to some data, Serbia has as many as 360 sources of thermal and thermo-mineral waters (with temperatures ranging from 14 to 98 degrees). Our country stands out with significant hydrogeological and geothermal resources in relation to the average values in Europe since the amount of geothermal heat in Serbia – heat erupting on the Earth’s surface, calculated per m2 per second (radiation intensity) is more than 100 mW/m2, versus the European potential of 60 mW/m2.
However, although experts state that the total amount of heat from geothermal resources in Serbia is about twice as much as the heat that would be generated from domestic coal reserves, this potential is almost not used at all. We mostly use water from geothermal springs or wells for therapeutic purposes in numerous thermal spas and sports and recreation centers, although irrationally and inefficiently.
Which is the first step in preparing the project for the construction of a geothermal power plant?
Preliminary verification of the profitability of investments in a geothermal power plant implies preparing a feasibility study and a preliminary design. This work should be entrusted to experts with experience in preparing the necessary technical documentation. If you have any questions regarding investing in a geothermal power plant, please write to us at info@energetskiportal.rs, and we will do our best to get an answer from our experts as soon as possible.
Useful links:
Energy Agency of the Republic of Serbia
Ministry of Construction, Transport and Infrastructure
Provincial Secretariat for Energy, Construction and Transport
