In wake of global warming and energy source depletion issues, when the whole world is trying to find out new sources of renewable and clean fuels, geothermal energy is being touted as a good option which comes from natural sources and does not cause pollution unlike the fossil fuels.
What is Geothermal Energy?
The heat which is generated and is present inside the Earth can also be a useful source of energy and is known as geothermal energy. This energy can be gathered from multiple sources like the hot springs, the heated rocks which are there within the surface of the earth or also the extremely hot magma which comes out from the core of the Earth. The usual temperature which is found in the shallow parts of the Earth’s crust varies between 50 degree and 60 degree Fahrenheit. As per the data of 2012, 11,400 megawatts of power generated from geothermal energy was being used by 24 countries worldwide.
What are the benefits of geothermal energy?
The best benefits of geothermal energy are that it is clean and friendly to the environment. Geothermal energy proves to be a cost effective source which is reliable in nature. The heat can be used directly and also by means of steam which in turn helps in producing electricity. Previously, the best sources of geothermal energy were parts of the globe which fell on the tectonic boundaries however, with the technology getting advanced; the range of availability has also got increased.
How is geothermal energy harvested?
Geothermal energy is harvested in a number of means for producing both heat and electricity. Below is a description of the processes in which it is used to generate both heat and electricity.
- Low Temperature Geothermal Energy: It is the heat which is obtained from certain pockets below the ground level and usually has a temperature of 150 degree Celsius. The easiest source of low temperature geothermal energy is the hot springs which have been there in many parts of the world for long. The normal use of this kind of energy is in homes, greenhouses, and some particular industries and fisheries. Although used mainly for heating purposes, low temperature geothermal energy is also sometimes used for generating electricity.
- Co-Produced Geothermal Energy: In this procedure, there is also an involvement of other energy sources like water. Hot water which gets generated in the oil and gas wells got wasted in the earlier times but now are used for generating electricity. An example of co-produced geothermal energy is the Ricky Mountain Oilfield Testing Centre which is based in Wyoming in United States.
- Geothermal heat pumps: In this method, heat is circulated by means of a pipeline and can be used to warm buildings, landscape areas and so on. The earth’s heat is tapped by making a drill which is about 3 to 90 metres in depth and usually does not require breaking through the rocky layer of the earth. The pipeline, which moves both over ground and underground, then carries some kind of liquid which during the winters is able to absorb the geothermal heat and provide a warmth and during the summers absorbs the outside heat to send it underground and get it cooled. In United States geothermal heat pumps are known to be an energy efficient heating and cooling system.
For providing electricity, geothermal energy has to depend on the heat which exists in the deeper parts of the earth’s crust. While sometimes, this heat is present as hot water and other times water gets injected in suitable areas to generate steam and use the heat.
- Dry-steam power plants: In some of the pockets where geothermal energy is present in the form of steam, pipes are inserted to carry the steam to the power plants so that they get used to move turbines and thus generate electricity.
- Flash-steam power plants: This process also depends on areas which have natural presence of hot water and steam. Water with a temperature o about 182 degree Celsius is pumped into a low pressure zone where it “flashes” in to steam which is collected and used to power turbines. The residual water meanwhile gets collected in another tank and is put to use for generating energy in other means.
Amongst the different types of geothermal power plants, the flash steam power plant is the most popular type and countries like Iceland get most of its power by this means.
- Binary Cycle Power Plants: This is a good source of generating power through a renewable fuel that is water. Water is conserved underground where it gets heated to a temperature of about 182 degree Celsius. It is then brought over ground through a series of pipeline which is used to heat another liquid that has a lower boiling point than water. Once this liquid starts producing steam, the steam gets used to turn the turbines and meanwhile the water goes back underground to be re-heated once again. The US State called Nevada has a binary cycle power plant which is known as Beowawe Geothermal Facility.
How much sustainable is geothermal energy?
The concentration of radioactive elements in the core of the Earth is quite high. As geothermal energy is produced due to the decay of these radioactive elements, it is expected that emission of heat will continue for some billion years in the future as well. Whatever is taken by the human beings accounts for a small fraction of the total outflow of heat and so, the future generations do not face any risk. However, having said that we should also remember that with the current and increasing rate of energy tapping a number of heat wells will also start cooling off. The sustainability factor of geothermal energy is still counted to be on a higher scale as it does not negatively affect the ecosystems of the Earth. It also helps in mitigating global warming issues.
What are the environmental implications of geothermal energy?
It has been observed that the gases which come out of the centre of the earth usually have high levels of polluting gases like methane, carbon dioxide, hydrogen sulphide, and also ammonia. If these gases get released in the atmosphere in large amounts it can lead to environmental hazards like global warming, acid rain and so on. The amounts of these gases which generally get released by the plants remain in the range of 122 kilograms per megawatt of electricity which is much lesser than that produced by the fossil fuel plants. Still the plants which deal with the production of geothermal energy and have to handle the generation of acids and other harmful chemicals usually also build good quality emission control apparatus so that the exhaust release amount can be further reduced.
Apart from the gases, geothermal energy tapping also brings with it some harmful elements like arsenic, boron, mercury and so on. These usually come out with hot water and they tend to get precipitated once the water gets cooled. In the modern practises these geothermal components usually get injected back in to the Earth so that the production of heat continues in the certain area. The best part of this practise is that it brings down the element of environmental risk associated with the release of these toxic elements.
The other environmental hazards which occur in wake of harvesting geothermal energy can be in the form of adverse land stability which happens when the plants are constructed. It has happened in Germany, New Zealand and Switzerland that problems like tectonic uplift, earthquakes because of hydraulic fracturing and other such problems have taken place due to the construction of geothermal plants.
However, despite of all problems the emission of pollutants in geothermal energy still remains less than that produced by burning of fossil fuels.
What are the advantages and disadvantages of using geothermal energy?
Here are the advantages of direct or indirect use of geothermal energy
- Coming from the core of Earth which will go on for another billion years, geothermal energy is a renewable source which unlike the fossil fuels which tend to get depleted and exhausted
- Some kinds of geothermal energy can be accessed from any part of the globe
- Geothermal energy most of the times comes in the form of water vapours with considerably less amount of toxic gases and thus it is considered a clean option.
- With a proper utilisation geothermal energy sources can go on for long times.
- In a deviation from other renewable sources of energy, geothermal energy is not dependent on sunshine or wind and is available in both summers and winter.
- The nature of geothermal plants is more compact as compared to the other energy plants. For example, the production of one million kilowatt for the duration of an hour requires an area of 3,458 square kilometres.
The following are the disadvantages of the geothermal energy.
- During harvesting of geothermal energy sometimes water is sprayed inside the Earth which may cause some seismic movements.
- Sometimes it’s said that the plants cause gradual sinking of the land because of the fractures which happen in the layers of the Earth. This has happened in New Zealand and can cause damage to buildings, roads and also the drainage systems.
- While harvesting geothermal energy some amounts of toxic gases are expelled in the atmosphere which may contribute in the greenhouse effect.
- The water produced while harvesting process sometimes carries toxic chemicals like arsenic which may get mixed with the normal water sources in case of improper insulation.
- The biggest challenge of harvesting geothermal energy is the cost that is involved in the initial setting up of the plant. Developing countries often find it challenging in setting up the proper infrastructure to culture this form of energy.
How popular is geothermal energy in the world?
Be it through geothermal pumps, natural hot springs or volcanoes, geothermal energy has found its use in almost all parts of the world. Countries like New Zealand and Iceland have used this medium in a variety of their set ups like prawn farms, greenhouses, swimming pools and also to keep the homes warm. The United States is another major country which has made great use of geothermal energy in a number of its states. It produces about 15 kilowatts-hours of electricity which would have otherwise needed 25 million barrels of oil. In the state of Nevada alone there were 59 geothermal stations in the year 2012. All this has positively contributed in bringing down the cost of technology and has made geothermal energy much more affordable.