Geothermal Energy
The word 'geothermal' is a combination of the words 'geo' which means 'Earth' and 'thermal' which means heat. The name gives us a hint as to how it is produced. The inside of the planet is scorching. This heat sometimes breaks through the Earth in the form of geysers and volcanoes. The heat from these is known as geothermal energy.
History: Geothermal energy has been utilised for many centuries. The ancient Romans took it further and used hot springs to heat flooring and baths. The first use of Geothermal energy for electricity was in 1904 when the geothermal electric generator was invented. The first-ever geothermal plant was set in Larderello, Italy, in 1904. Steam from that geothermal source was used to turn a small turbine that powered five light bulbs. A few years later, in 1911, the first geothermal electric plant was built. In the 1940s, a heat pump was developed, which was used to heat buildings.
The Geological Survey of India has found around 340 hot springs across India. Most of India’s hot springs are located along the following five major regions - the NW-SE Himalayan arc system extended to Andaman Nicobar Island, Son-Narmada-Tapti lineament, West Coast continental margin with its adjacent and surrounding areas, Gondwana graben and Delhi fold regions.
The Process: Geothermal energy can be used through geothermal heat pumps. At 10ft below sea level, the ground has a consistent temperature between 10 and 15 degree Celsius. This temperature remains constant, allowing geothermal heat pumps to maintain water at a constant temperature. By moving the water through through the ground, it can be heated during the winter or cooled during the summer. A heat exchanger can then use this water to heat or cool the air in homes.
Geothermal energy can also be used to generate electricity. Power plants take advantage of water 3.2kms deep in the ground.
Water is utilised in several ways.
* Dry steam engine: It takes steam from cracks in the ground to drive a turbine. The heated water vapour (steam) is directed towards a turbine that drives an electrical generator.
* Flash points: These pull hot water with high pressure and mix it with cool water. This process creates steam, which drives a turbine.
* Binary cycle: In this process, heated water is drawn through a set of pipes and much of the energy stored in the heated water is transferred to a working fluid, such as ammonia, through a heat exchanger. The active liquid is vaporised to spin turbines and generate electricity.
Applications: Geothermal energy is also used to heat individual buildings with directly and to heat multiple buildings with district heating systems. Hot water near the Earth’s surface is piped into buildings for heat. A district heating system provides warmth for most of the buildings in Reykjavik, Iceland. In fact, 87% of the country’s homes are heated using geothermal energy.
Industrial applications of geothermal energy include food dehydration (drying), gold mining and milk pasteurising. Moreover, geothermal energy can be used in the desalination of water, heavy water production, extraction of minerals from geothermal fluids and seasoning of timber. However, geothermal energy is presently utilised mainly for power generation and space heating purposes only.
Advantages:
* Since fossil fuel reserves are limited, geothermal energy is an alternative that emits fewer harmful gases than when fossil fuels are burned. It produces 0.03% of the emissions that coal produces and 0.05% of the emissions that natural gas produces.
* Geothermal energy does not require as much energy to be utilised. Moreover, technology has been developing exponentially, making discoveries every day. Each new step might hold the key to a sustainable world.
Disadvantages:
* Geothermal energy can only be found in some areas, such as Iceland.
* Sometimes, harmful gases can be released from the ground while digging, which negatively impacts the ozone layer.
* The cost of building geothermal plants is exceptionally high. However, as technology develops, the prices should fall.
