About 71% of the total installed capacity of the country is based on thermal power generation by burning fossil fuels-coal, oil & natural gas. However, these fossil fuels have got limited stock and are going to last up to a certain time. Moreover, these are not environmental friendly and dependence on them specially oil makes country economy susceptible to foreign countries polices and pressure.
The source of geothermal energy is very vast and almost infinite as the heat stored below the surface of the earth. A geothermal source may contain steam, water, a steam/water mixture or just hot dry rock.
The economic viability of hydrothermal (hot water or steam) system for electrical power generation is guided by temperature of the reservoir. When hot water resources are used through a ‘binary’ process to generate electric power, the heat from hot water is allowed to vaporize a heating fluid. This heat transfer fluid in a closed system is used to turn a turbine which runs a generator.
Geothermal energy can solve the power shortage problem of the country as India contains part of one of the largest geothermal areas in the world.
Power Scenario Of India
The latest power generation scenario of the country is :
As per Central Electricity Authority (CEA), the peak demand estimated for the September 2015 was 3.20 % less to generation. This indicates the acute power generation scenario of the country.
Different Source Of Power Generation
As seen from above, burning fossil fuels-coal, oil & natural gas generates 60.69% of electrical power. Coal, oil & natural gas have got their limited stock and are going to last up to a certain period. To enhance their known reserves and to increase exploitation more complicated technology is needed to be applied. The import of fossil fuel, mainly oil & coal, makes India more prone to outside pressure and our economy becomes dependent on other countries policies. Moreover, these fossil fuels are not environmentally friendly, and their increasing use is concern for environmental pollution. Nowadays, stress is shifting on using renewable and relatively non-polluting energy resources such as solar, wind, tidal, geothermal for electrical power generation. Geothermal energy is a renewable form of energy and is most widely utilized non-conventional alternative to fossil fuels today. Today, USA generates about 3,386 MW through geothermal power plants. The total worldwide generation of electricity from geothermal energy is about 12,800 MW.
Figure 1: Binary cycle geothermal power plant…
Figure 2: Showing approximate location of geothermal springs…
Figure 3: Temperature range of geothermal springs in India…
Advantages Of Geothermal Energy
Geothermal energy has the following advantages:
- It is one of the cheapest methods to generate electrical power.
ii. It is environment friendly and there is no danger of any type to life.
iii. Area required to set up a power plant is less than that for a similar capacity of other power plant.
iv. It is not dependent upon weather and most of the market variables and policies as the source of energy is free from such constraints.
v. Besides power generation, additional minerals can be obtained from the produced hot water depending upon the reservoir source.
vi. There is no waste by product, which is very big problem for coal based and nuclear power plants.
Geothermal Process
The source of geothermal energy is very vast and almost infinite as the heat stored below the surface of the earth. The heat from the earth’s core continuously flows outward. Sometimes the hot magma (molten rocks and minerals) rises all the way to the surface. Most often, however, it remains just below the earth’s crust, heating nearby rock and water(rain water that has seeped into the earth) – sometimes to temperature exceeding 700oF. Some of the water travels back up through faults and cracks and reach the surface as hot springs but most stays below as a geothermal reservoir. The earth’s natural heat is cleaner and has less detrimental environmental impact than conventional source of energy. If only 1% of this energy were harnessed, this would amount to more than 500 times the known oil & gas resources in the world. With time and technology improvements more of this enormous reservoir of energy will be utilized.
Geothermal Technology For Power Generation:
A geothermal source may contain steam, water, a steam/ water mixture or just hot dry rock. In order for the geothermal resources to be of commercial value, it must contain water or steam.
Power generation from geothermal energy can be divided into three phases:
- Project planning, drilling and testing to establish production capacity of geothermal wells and proper management of the geothermal reservoir.
ii. Construction of the insulated pipeline to transport geothermal fluid to the power plant from the wells and transport back the spent water, after the heat is extracted to injection wells located on the periphery of the reservoir.
iii. Erection and management of the power plant and supplying the power to the grid.
The economical viability of hydrothermal (hot water or steam) system for electrical power generation is guided by temperature of the reservoir. When hot water resources are used through a ‘binary’ process to generate electric power, the heat from the hot water is allowed to vapourize a heating fluid (Freon, Isobutene, Isopentane etc.). This heat transfer fluid in a closed system is used to turn a turbine, which runs a generator as shown in the figure I.
After exploration is completed and the geological condition of a tract arc right, a number of wells are drilled into the production zones. The process of drilling, completion and stimulation of a geothermal well is basically similar to those of oil & natural gas wells by utilizing techniques such as hydraulic fracturing used in oil and gas industry and combining this with technological advances specific to geothermal energy, the production rates from geothermal wells could be increased far beyond their natural capacity.
In addition, a bi-phase turbine (currently in use) are capable of producing power from both the steam and brine flow, thereby potentially increasing power generation.
Temperature within the reservoir will have direct bearing on the viability of the power generation project. If the temperatures within the reservoir are high, the pressure within the reservoir will be greater – and the number of wells needed to sustain the power plant can be reduced. The high pressure will also allow for use of a less expensive high-pressure turbine for the plant.
Electricity from geothermal energy will be economical where the temperature gradient is greater than 5oF per 100 ft. The electrical power generated from a geothermal reservoir is directly proportional to the rate of fluid production. After the heat is extracted from the produced geothermal fluid (hot water or steam) the spent hot water and condensed steam is injected back into the periphery of the reservoir to keep it in recharged condition throughout the life of the period. Well productivity is indicated in table-1.
Geothermal Sites In India
India contains parts of one of the largest geothermal areas in the world, namely the Himalayan geothermal belt. It is 150 km wide and 3000 km in length covering parts of India, Nepal, Tibet, China, Myanmar and Thailand.
There are over 340-recorded geothermal sites in India. Table 2 shows the number of hot springs in India. The highest numbers of geothermal springs (60) are recorded in Bihar.
Table 3 indicates most five suitable geothermal sources in India. Fig 2 depicts the approximate location of geothermal springs in India. Fig 3 depicts the temperature range of geothermal regions.
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