Geothermal energy is heat derived within the sub-surface of the earth. Water and/or steam carry the geothermal energy to the Earth’s surface. Depending on its characteristics, geothermal energy can be used for heating and cooling purposes or be harnessed to generate clean electricity.
Geological Survey of India has found around 340 hot springs across India. India has 5 geothermal provinces and a number of geothermal springs. Geothermal resources in India have been mapped by GSI and broad estimate suggests that there could be 10 gigawatt (GW) geothermal power potential, as per the Ministry of New and Renewable Energy (MNRE).
Examples of Geothermal Fields in India
- Puga geothermal field
- Chhumathang geothermal field
- Manikaran geothermal field
- Beas valley
- Satluj and spiti valley
- Tapoban geothermal field, Chamoli, Uttarakhand and Alaknanda Valley
- Tatapani geothermal field
- Salbardi region
- Anhoni- Samoni area
- Unkeshwar
- Godavari Graben
- Andaman-Nicobar region
- Damodar Valley basins
- Western thermal province
- Cambay geothermal region
- Konkan geothermal provinces
- Sohna thermal region
- Tuwa and Chhabsar geothermal fields, Gujarat
- Lasundra geothermal province
Two basic types of geothermal heat resources that can be harnessed.
- Hydrothermal Heat Source : –
In this the heat is transferred by water to the surface, water is recharged into the ground by rain or surface bodies (like river, lakes or glaciers) and is then heated by underlying hot rock which is hot due to seismic or volcanic activity.
The presence of hot springs in Iceland, The Himalayas, and The Alps is an example of this. The lithology of the area needs to permeable so that it can allow water to flow freely, it is necessary to recharge the system and also for the hot water to come up
- The second type of resource extraction can be done by Deep/Enhanced Geothermal systems in which a deep borehole is dug to reach the hot basal rock and then water is pumped into the holes to obtain steam, which is aimed to run a turbine.
Accessing the deep basal rock bed is an expensive process and hence this method isn’t as popular.
Challenges
- The Resource and Location
There is geothermal energy beneath the entirety of the earth’s surface, but not all of that energy can be harnessed. There is only a small percentage of land that lies above suitable pockets of water and steam that can heat homes or power electrical plants, limiting the possibility of installation of geothermal power plants. Many of the places that are ideal for providing substantial amounts of geothermal energy that can be converted into electricity are also located in areas that are extremely tectonically active. When there is a constant risk of earthquakes or volcanic activity, corporations are hesitant to install large-scale electricity generating facilities.
- Infrastructure
Aside from the lack of adequate resources, one of the reasons that geothermal electricity is not widely used in the United States is due to a lack of infrastructure for it. By nature, a geothermal energy source could only be used to produce the baseline power for an electrical grid which causes problems in and of itself. Equipment for drilling wells and setting up power plants is extraordinarily expensive and training people to staff a geothermal power plant is time consuming and costly. There is also the restriction of where the geothermal energy can be used. Once the energy is extracted form the underground wells, it cannot be transported to a different facility whose grid is more in need, it has to be used as it is extracted.
- High Cost
Geothermal energy is an expensive resource to tap into, with price tags ranging from around $2-$7 million for a plant with a 1 megawatt capacity. However, where the upfront costs are high, the outlay can be recouped as part of a long-term investment.
- Renewable Does Not Mean Unlimited
Contrary to popular belief, the water and steam that is extracted from the earth is not boundless. Every well only has so much water that can be extracted and without proper reinjection of used water back into the wells, there is not enough pressure to propel the steam and water upwards. If the pressure gradient is not adequately reestablished, not only is there the potential for the energy source to dwindle, but there is also the possibility of greater geological impacts like the creation of sink holes.
- Location Restricted
The largest single disadvantage of geothermal energy is that it is location specific. Geothermal plants need to be built in places where the energy is accessible, 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 readily accessible, such as Iceland.
- Environmental Side Effects
Although geothermal energy does not typically release greenhouse gases, there are many of these gases stored under the Earth’s surface which are released into the atmosphere during digging. While these gases are also released into the atmosphere naturally, the rate increases near geothermal plants. However, these gas emissions are still far lower than those associated with fossil fuels.
- Earthquakes
Geothermal energy also runs the risk of triggering earthquakes. This is due to alterations in the Earth’s structure as a result of digging. This problem is more prevalent with enhanced geothermal power plants, which force water into the Earth’s crust to open up fissures to greater exploitation of the resource. However, since most geothermal plants are away from population centres, the implications of these earthquakes are relatively minor.
- Sustainability
In order to maintain the sustainability of geothermal energy fluid needs to be pumped back into the underground reservoirs faster than it is depleted. This means that geothermal energy needs to be properly managed to maintain its sustainability.
It is important for industry to assess the geothermal energy pros and cons in order to take account of the advantages while mitigating against any potential problems.
