29 Jul 2021
India has planned to satiate the country’s growing energy demand by the year 2040. For sustainable growth, the country must optimize the use of available energy sources (conventional and renewable) in an environment-friendly manner. Since India is the third largest country in the world emitting greenhouse gases, it is very important to increase the share of renewable and green energy sources like geothermal energy, solar power, wind energy, etc. in the energy portfolio. While there has been a significant increase in solar and wind energy production, geothermal energy is yet to be exploited. India has several potential geothermal fields predominantly controlled by the high heat-producing granites are located in different parts of the country. Planned production of electricity from these fields is 850 GWh/year by the year 2020. A wet geothermal system, as well as enhanced geothermal system, can be utilized to generate electricity at low production cost. Moreover, some of these fields are also rich in helium content which can be extracted to be utilized for domestic purposes.
‘Geothermal’ literally means ‘Earth’s heat, which is estimated to be 5,500 degrees centigrade at the Earth’s core – about as hot as the surface of the sun. Geothermal energy is a clean, renewable resource that can be tapped by many countries around the world located in geologically favorable places. Geothermal energy can be harnessed from underground reservoirs, containing hot rocks saturated with water and/or steam. Boreholes of typically two kilometers depth or more are drilled into the reservoirs. The hot water and steam are then piped up to a geothermal power plant, where they are used to drive electric generators to create power for businesses and homes. Geothermal energy is considered a renewable resource because it exploits the Earth’s interior heat, which is considered abundant, and water, once used and cooled, is then piped back to the reservoir.
Utilization of geothermal resources
Geothermal energy can be utilized for electricity generation and for various other types of heat direct use applications, e.g. heating purposes, fish farming, bathing etc. Compared to other renewable energy technologies, geothermal is unique as it provides a base-load alternative to fossil fuels based electricity generation, but can also replace those used for heating purposes.
High temperature geothermal resources are most important for electricity generation (temperatures greater than 150 degrees Celsium), while medium-to-low temperature resources (below 150 degrees Celsium) are suited for many different types of applications utilizing heat. The classical Lindal diagram provides a good overview of the typical utilization forms of geothermal energy by temperature ranges.
Characteristics and Applications of heat energy
Geothermal energy is a colossal, underused heat and power resource that's clean (emits very little or no greenhouse gases), reliable (average system accessibility of 95%), and native (making US less addicted to foreign oil). energy resources vary from shallow ground to plight and rock many miles below the Earth's surface, and even farther right down to the very hot liquefied rock known as rock. Mile-or-more-deep wells are often trained into underground reservoirs to faucet steam and really plight that may be dropped at the surface to be used during a form of applications.
The general characteristics of heat that build it of great importance for each electricity production and direct use include:
Geothermal energy will be used terribly effectively in each on- and off-grid developments, and is very helpful in rural electrification schemes. Its use spans an oversized vary from power generation to direct heat uses, the latter potential mistreatment each vasoconstrictor resources and “cascade” strategies. Cascade strategies use the recent water remaining from higher temperature applications (e.g., electricity generation) in in turn lower temperature processes, which can embrace binary systems to get additional power and direct heat uses (bathing and swimming; house heating, as well as district heating; greenhouse and open ground heating; process heat; cultivation pool and raceway heating; agricultural drying; etc.)
Geothermal Energy Scenario: India and therefore the world
Geothermal power plants operated in a minimum of twenty four countries in 2010, and heat was used directly for warmth in a minimum of seventy eight countries. These countries presently have energy power plants with a complete capability of 10.7 GW, however half of 1 mile of its generated in barely seven countries: the us, the Philippines, Indonesia, Mexico, Italy, New island, and Iceland. The foremost vital capability will increase since 2004 were seen in Iceland and Turkey. Each country doubled their capability. Iceland has the biggest share of energy power conducive to electricity provide (25%), followed by the Philippines (18%).
The quantity of nations utilizing heat to get electricity has over doubled since 1975, increasing from ten in 1975 to twenty four in 2004. In 2003, total heat provide was twenty MToE (metric weight unit Oil Equivalent), accounting for zero.4% of total primary energy provide in IEA member countries. The share of energy in total renewable energy provides was seven.1%. Over the last twenty years, capital prices for energy power systems shrunken by a big five hundredth. Such giant price reductions area unit typically the results of resolution the “easier” issues related to science and technology improvement within the early years of development.
Although energy power development slowed in 2010, with world capability reaching simply over eleven GW, a big acceleration within the rate of readying is anticipated as advanced technologies leave development in new countries. Heat output from energy sources increased by a median rate of just about 9/11 annually over the past decade, due in the main to ascent within the use of ground-source heat pumps. Use of heat for combined heat and power is additionally on the increase.
India has moderately sensible potential for energy; the potential geothermal provinces will turn out 10,600 MW of power (but consultant’s area unit assured solely to the extent of a hundred MW). However energy power comes has not been exploited in the least, thanks to a spread of reasons, the chief being the provision of plentiful coal at low-cost prices. However, with increasing environmental issues with coal primarily based comes, Asian country can ought to begin betting on clean and eco-friendly energy sources in future; one amongst that may be energy.
Technology
Mile-or-more-deep wells will be trained into underground reservoirs to faucet steam and really plight that drive turbines that drive electricity generators. Four sorts of power plants area unit in operation today:
Flashed steam plant
The extraordinarily plight from drill holes once discharged from the deep reservoirs high steam (termed as flashed steam) is discharged. This force of steam is employed to rotate turbines. The steam gets condensed and is born-again into water once more that is come to the reservoir. Flashed steam plants area unit cosmopolitan throughout the planet.
Dry steam plant
Usually geysers area unit the most supply of dry steam. Those energy reservoirs that largely turn out steam and small water area unit utilized in electricity production systems. As steam from the reservoir shoots out, it's wont to rotate a rotary engine, when causing the steam through a rock-catcher. The rock-catcher protects the rotary engine from rocks that return alongside the steam.
Binary station
In this style of station, the energy water is gone through a device wherever its heat is transferred to a secondary liquid, specifically isobutene, iso-pentane or ammonia–water mixture gift in associate adjacent, separate pipe. Because of this double-liquid device system, it's known as a binary station. The secondary liquid that is additionally known as operating fluid ought to have lower boiling purpose than water. It turns into vapor on obtaining needed heat from the recent water. The vapor from the operating fluid is employed to rotate turbines. The positional notation is thus helpful in energy reservoirs that area unit comparatively low in gradient. Since the system could be a utterly closed one, there's minimum likelihood of warmth loss. Plight is straight away recycled into the reservoir. The operating fluid is additionally condensed back to the liquid and used over and yet again.
Hybrid station
Some energy fields turn out boiling water moreover as steam, that are utilized in power generation. During this system of power generation, the flashed and binary systems area unit combined to form use of each steam and plight. Potency of hybrid power plants is but that of the dry steam plants.
Enhanced energy system
The term increased energy systems (EGS), additionally called built energy systems (formerly hot dry rock geothermal), refers to a spread of engineering techniques wont to by artificial means produce hydrothermal resources (underground steam and hot water) which will be wont to generate electricity. Ancient energy plants exploit present hydrothermal reservoirs and area unit restricted by the scale and site of such natural reservoirs. EGS reduces these constraints by providing the creation of hydrothermal reservoirs in deep, hot however naturally dry earth science formations.EGS techniques can even extend the lifetime of present hydrothermal resources. Given the prices and restricted complete system analysis to this point, EGS remains in its infancy, with solely some analysis and pilot comes existing round the world and no commercial-scale EGS plants to this point. The technology is therefore promising, however, that variety of studies have found that EGS may quickly become widespread.
Potential
It has been calculable from earth science, geochemical, shallow geology and shallow drilling information it's calculable that Asian country has regarding ten,000 MWe of geothermic power potential which will be controlled for varied functions. Rocks coated on the surface of Asian country move in age from quite 4500 million years to this day and distributed in several geographical units. The rocks comprise of Archean, Proterozoic, the marine and continental Palaeozoic, Mesozoic, Teritary, Quaternary etc., quite three hundred thermal spring locations are known by earth science survey of Asian country (Thussu, 2000). The surface temperature of the new springs ranges from thirty five C to the maximum amount as ninety eight C. These hot springs are sorted along and termed as completely different geothermic provinces supported their incidence in specific geotectonic regions, earth science and strutural regions like incidence in orogenic belt regions, structural grabens, deep fault zones, active volcanic regions etc., completely different orogenic regions square measure – chain of mountains geothermic province, Naga-Lushai geothermic province, Andaman-Nicobar Islands geothermic province and non-orogenic regions square measure – Cambay graben, Son-Narmada-Tapi graben, west coast, Damodar vale, Mahanadi vale, Godavari vale etc.
Geothermal Energy Scenario: India and the world
Geothermal power plants operated in at least 24 countries in 2010, and geothermal energy was used directly for heat in at least 78 countries. These countries currently have geothermal power plants with a total capacity of 10.7 GW, but 88% of it is generated in just seven countries: the United States, the Philippines, Indonesia, Mexico, Italy, New Zealand, and Iceland. The most significant capacity increases since 2004 were seen in Iceland and Turkey. Both countries doubled their capacity. Iceland has the largest share of geothermal power contributing to electricity supply (25%), followed by the Philippines (18%).
The number of countries utilizing geothermal energy to generate electricity has more than doubled since 1975, increasing from 10 in 1975 to 24 in 2004. In 2003, total geothermal energy supply was 20 MToE (metric Tonne Oil Equivalent), accounting for 0.4% of total primary energy supply in IEA member countries. The share of geothermal in total renewable energy supply was 7.1%. Over the last 20 years, capital costs for geothermal power systems decreased by a significant 50%. Such large cost reductions are often the result of solving the “easier” problems associated with science and technology improvement in the early years of development.
Although geothermal power development slowed in 2010, with global capacity reaching just over 11 GW, a significant acceleration in the rate of deployment is expected as advanced technologies allow for development in new countries. Heat output from geothermal sources increased by an average rate of almost 9% annually over the past decade, due mainly to rapid growth in the use of ground-source heat pumps. Use of geothermal energy for combined heat and power is also on the rise.
India has reasonably good potential for geothermal; the potential geothermal provinces can produce 10,600 MW of power (but experts are confident only to the extent of 100 MW). But yet geothermal power projects has not been exploited at all, owing to a variety of reasons, the chief being the availability of plentiful coal at cheap costs. However, with increasing environmental problems with coal based projects, India will need to start depending on clean and eco-friendly energy sources in future; one of which could be geothermal.
Case Studies
Geothermal energy is obtained from heated water, steam, or soil which is derived from deep in certain land masses. There are two main uses for this energy: (1) hot water is used to create electricity or to provide hot water heating or warming; (2) the thermal mass of the soil or groundwater is used to drive heat pumps which provide either heating or cooling. The first use is more widely known and used and is obtained from geothermal geysers that find their way to the earth's crust.
The above uses are not really from renewable resources, however, with properly calculated use they can almost approach the “renewable” classification. The heated water, steam, or soil will gradually be depleted if overdrawn from the ground. This valuable ground resource will slowly regenerate itself over time so that if the withdrawal at the surface is timed to match that regeneration rate, the resource will be considered renewable. In any event, it will not deplete itself as fast as fossil or oil fuels are depleted by normal mining techniques. In addition, heat reservoirs are considered immense in magnitude compared to its current or even projected use, thus rendering it practically renewable.
In the United States the production of electricity from the geothermal energy of the earth's interior heat is centered in northern California. Here these geothermal sources provided just over 7% of California's electricity in the 15-year period ending the 20th century. However, the geyser production has decreased from supplying about 2,000 megawatts in 1989 to 1,100 megawatts near the turn of the century. Unfortunately, because of the specific location of these geothermal fields most individual households cannot make use of this energy. However, direct use of the heated water can save establishments as much as 80% in their fuel bills.
Geothermal Ground Source Heat Pumps for Residential Use
Heat pumps can reduce both air conditioning peak loads as well as winter heating loads, In addition, they are normally used to heat water (or as hot water) in households and buildings.
Economics of Geothermal Energy
Geothermal electricity can be produced practically and economically for about 5 cents per kilowatt-hour—slightly higher than wind or solar energy. This higher cost is largely due to the fact that it is necessary to drill deeper today to produce a given amount of power than in earlier years. It has been suggested (and even used) that the economics of geothermal power can be improved through co-production of other goods from high-temperature brine extracted from the depths of the ground. While geothermal power applications require more advances in exploration and drilling, heat pump, direct uses require that the engineer and the consumer understand the technology. It may be more expensive to install geothermal energy systems at the start, but over the long term the benefits may make it economically and environmentally worthwhile.
Effects on the Environment
Air pollution relative to conventional fossil fuel energy production will be minimized when selecting geothermal energy instead. It produces only about one-sixth of the CO2 and none of the NOxs or sulfur gases that fossil fuel plants emit. For these reasons alone this method of energy production can be a very environmentally friendly alternative to fossil fuel energy.
Amount of This Energy Already Being Produced
In 1998 geothermal energy provided 0.4% of the electricity generated in the United States. This amounted to 14.3 billion kilowatts of electricity to over 1,400,000 homes. At that time it was growing at a rate of slightly less than 3% over an 8-year period. Worldwide, geothermal energy was slightly more than 8 million kilowatts or about 3% of the 3,180 kilowatts used.
Some Examples of Geothermal Energy Uses
The Oregon Institute of Technology has been heated by the direct geothermal energy since 1964. In Iceland geothermal energy is used to provide the majority of households with residential heat. Tax neutrality, continued and increased federal funding, continued and expanded production tax credits, resource identification, renewable portfolio standards, contractor education, and the issuing of air emission standards have been and are being used to encourage the continued use of geothermal energy.
The reader of this section of the chapter is urged to consult the U.S. Department of Energy's Web site for more information of geothermal energy. In addition, the Renewable Energy Policy Project maintains a rather detailed bibliography of the uses of this form of energy.
Advantages & Disadvantages of Geothermal Energy
Geothermal energy does not cause any pollution. It is a clean source of energy and it has no harmful by- products. It is inexpensive, as no fuel is required to produce energy and hence, running cost of power plant is less. Further, it can be used to produce electricity 24 hours a day (comparatively other renewable sources of energy such as solar and wind energy have limitations). Geothermal power plants are generally small and have little effect on the natural landscape or the nearby environment. Though geothermal energy has several advantages, it also has some disadvantages and limitations. If harnessed incorrectly, it can sometimes produce pollutants. Improper drilling into the earth can release hazardous minerals and gases deep inside the earth.
Status of Geothermal Energy in India
Geological Survey of India has identified about 340 geothermal hot springs in the country. Most of them are in the low surface temperature range from 370C to 900C, which is suitable for direct heat applications. Only some are suited for power generation. The potential for power generation at these sites is about 10,000 MW. Though, India has been one of the earliest countries to begin geothermal projects way back in the 1970s, but at present there are no operational geothermal plants in India. The hot springs in the country are grouped into seven geothermal provinces, i.e., Himalayan, Sahara Valley, Cambay Basin, San-Narmada –Topi lineament belt, West Coast, Godavari Basin and Mahanadi Basin.
An experimental geothermal power plant of 5 kW capacity has been set up at Manikaran in HP. A cold storage plant has also been constructed there to utilise the geothermal energy at 900C for preserving vegetables and fruits grown in that area. Some of the prominent places where a power plant can be established based on geothermal energy are Puga Valley and Chhumathang in Jammu and Kashmir, Manikaran in HP, Jalgaon in Maharashtra, Tapovan in Uttarakhand, Bakreshwar in WB, Tuwa in Gujarat and Tattapani in Chhatisgarh. MNRE is giving thrust on exploration and harnessing of India’s geothermal energy resources.
International Status
The worldwide use of geothermal energy is increasing. Today 11,772 MW of power is being generated in at least 24 countries from geothermal energy and in 2010; it generated 67,246 GWh of electricity. This is a rise of about 20% since 2005. By 2015, figure is expected to grow even more to 18,500 MW. The largest producer of this energy is USA that generates about 3,086 MW of electricity. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California of USA. The Philippines is the second highest producer, with 1,904 MW of capacity online. Geothermal power makes up approximately 18% of the country’s electricity generation. Also in Indonesia 5% of overall electricity generation is from geothermal energy.
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