Overview
Wind, sun and biomass are usually named as the main sources of renewable energy, but there are other ways to produce clean energy. Below, geothermal energy and energy from water sources, such as hydroelectric power, wave energy and tidal energy are described.
Although they offer an alternative to fossil fuels, the use of these energy sources is not sensible or possible in Estonia. However, their research and development in the European Union is an important step in increasing the share of renewable energy in the EU's energy portfolio. Research and development and innovation can create new opportunities for the efficient and cost-effective use of these energy sources in the future.
Geothermal energy
Geothermal energy uses the heat hidden deep inside the earth's core. For this, deep holes are drilled into the ground to reach hot rock or water sources. Drilled holes allow heat to rise to the surface where it is used to generate electricity or heat. Two methods are usually used:
- Direct use, where hot water or steam is piped directly for heating or use in industrial processes.
- Electricity production, where hot water or steam is directed to turbines to generate electricity.
Geothermal energy can only be used in those areas of the world where heat flow is more easily reached. Such areas are mainly on the fault lines between the tectonic plates (i.e. giant pieces of the earth's crust). Estonia is not located in such an area and therefore the use of geothermal energy is limited, as geographically we do not have very hot sources near the surface (like, for example, in Iceland) that could be used for energy production. However, there are ways to use low-temperature geothermal energy, for example, in heating and cooling buildings.
The main advantage of geothermal energy is that, unlike solar and wind energy, it is constantly available. Carbon emissions are low in its production, and in suitable areas, geothermal plants can operate for decades without significant change. However, the initial costs are high for building such plants, as the necessary drilling and infrastructure are expensive.
Hydropower
Hydropower, or water energy, is generated by the natural flow of moving water due to the gravitational pull of the Earth. Such flow of water usually takes place in rivers and dams, which is why hydroelectric plants are built there. In the plants, water is directed through turbines, which then run generators and produce electricity.
In addition to the plant, larger hydroelectric plants have a dam, which directs water in a controlled flow through turbines, and a reservoir, which is also used for flood control.
Estonia has a low potential for hydropower due to our geographical conditions. We have limited use of hydropower because we have few large rivers suitable for large hydroelectric plants. However, there are several small hydroelectric plants, for example, in Keila-Joa, Kunda and Jägala-Joa.
Hydropower generation has several advantages: it does not cause air pollution or greenhouse gas emissions and hydroelectric plants can produce energy continuously and predictably – a dam helps to collect water and use it for energy production even in dry periods.
However, its main drawback is the negative environmental impact. The construction of dams and reservoirs can destroy natural habitats by changing the ecosystems of rivers and lakes. Dams can prevent the natural migration of fish in rivers, which is an important part of their life and reproduction cycle, and this has an impact on fish populations. Dams also stop the natural movement of sediment in rivers: it accumulates in reservoirs and does not flow downstream and this can cause coastline erosion.
Hydropower generation is also increasingly affected by climate change. Changing precipitation patterns can lead to extensive periods of drought and rain and that affect the productivity of hydropower plants.
Wave power
Wave power uses the kinetic energy of ocean and sea waves to generate electricity. For this, special devices are used, such as floating structures, wing converters and underwater turbines, which convert the movement of waves into electrical energy.
The length of the Estonian coastline and the relatively calm waves of the Baltic Sea do not provide good conditions for the use of wave energy. Since wave power has to be harnessed from a very extensive sea surface area, the amount of energy obtained from it is not very large. Therefore, wave power does not play a significant role in energy production. However, wave energy has potential in the open sea and future research and development may enable its use to become more widespread. The production volumes of wave power will never be comparable to the capacity of wind farms, but it may be able to generate energy for equipment or small ports at sea or on small islands.
Tidal energy
Tidal energy, or the energy of rising and falling tides, is generated by the change in the water level in the oceans and seas, which is caused by the gravitational pull of the moon and the sun. As an energy source, the rise and fall of tides are quite stable and predictable. Two main technologies are used to generate tidal energy:
- Using turbines: these turbines work in a similar way to wind turbines but are installed in bodies of water. The water from the rising tidal waves turns the turbines, which in turn generate electricity.
- Using dams: the dams are built on the coast or at the mouths of rivers. When the tide begins to come in, the sea level rises and the water is channelled into the reservoir behind the dam. When the tide recedes, water is channelled through turbines that generate electricity.
Since the Baltic Sea is an enclosed sea, it does not provide suitable conditions for using tidal energy in Estonia. The differences between high and low tides are small in the Baltic Sea, which rules out its widespread use in the countries bordering the Baltic Sea. The difference in tides is greatest in bays that open directly to the ocean and it is therefore a suitable and affordable way to produce energy in countries bordering oceans.
However, it must be taken into account that the construction of dams and turbines may affect marine life and coastal ecosystems, so extensive research is necessary before employing tidal energy.