India became the world’s third largest producer of electricity in the year 2013 and accounts for 4.8% of global share in electricity generation. But its per capita electricity consumption is only 746 kWh, which is lower compared to many countries, though electricity tariff is cheaper in India. Energy is the basic input in all sectors of the nation’s economy, and the standard of living is directly related to per capita energy consumption. As the country is heavily populated, provision of adequate quantities and kinds of energy is a challenge to the government, and the institutions in the country engaged in tasks relating to energy supply and transport. The commercial energy inputs to the Indian economy are from conventional sources like coal, hydroelectricity and nuclear energy. The country currently has total installed capacity of thermal 70%, hydroelectric 16%, nuclear 2% and renewable 12%. For long-term sustainability, minimum utilisation of fossil fuel for energy and maximum utilisation of renewable energy are to be considered. At the same time, minimum losses during generation, transport and utilisation sector is also important.
Renewable sources and their potential for supplying electricity
Renewable energy is generally defined as energy that comes from resources, which are naturally replenished on their own. Renewable energy sources are all essentially based on the direct or indirect use of solar energy. The only exception is tidal energy, which essentially derives its power from the interaction between the earth and the moon.
Renewable energy can replace conventional fuels in the distinct areas like electricity generation, water heating, space heating, motor fuels, and rural energy services. The important renewable energy sources, which can be utilised for generating electricity in our country are as follows: (i) solar energy (direct): Solar thermal power and solar photovoltaic (PV) power, Solar energy (indirect), (ii) Hydroelectric power (large and small units); (iii) Wind energy (on land and offshore), (iv) Biomass power, (v) Wave energy, marine currents, and ocean thermal energy conversion (vi) Tidal energy.
Solar thermal power and PV power
Solar energy is utilised for direct thermal applications and for solar-electric applications. Solar thermal applications include water heating, space heating, drying, cooking etc. Generation of electricity is possible in solar thermal-electric power plants.
These plants use concentrating collectors to collect the sun’s energy at high temperatures and use this energy to generate high-pressure steam. The steam in turn is used in a conventional Rankine cycle to generate electricity. India is ranked number one in terms of solar electricity production per watt installed. As on 30 March 2015, the installed grid connected solar power capacity is 3,383 MW, and India expects to install an additional 10,000 MW by 2017 and a total of 100,000 MW by 2022.
Photovoltaic conversions are also a direct method of utilising solar energy, which makes use of solar cells to convert solar energy directly into electrical energy. The electrical energy requirement for localised use in the remote locations all over India is estimated at about 11,000 MW – a substantial part of which is expected to come from PV systems that are not connected to the grid. These systems may be located as far as possible on rooftops, so that no land space is used. India has total installed capacity of almost 4101.68 MW grid-connected PV power systems having small capacities.
Indirect solar energy is the solar power that goes through more than one change to become in the useful form of energy. Examples of indirect solar energy are hydropower, biomass and wind energy.
India is ranked as the 6th largest producer of hydroelectric power in the world and has great potential for hydro-electric power. Hydroelectric power projects are the largest contributors amongst renewable energy sources in our country. Apart from generating electricity, they provide water for irrigation, help in flood control and drinking water purposes.
Hydroelectric power is the generation of electric power which utilises the potential energy of water at a high level. A hydroelectric facility requires a dependable flow of water – and the water head is created by constructing a dam across the river. In a typical installation, water is fed from a reservoir through a channel or pipe into a turbine and the pressure of the flowing water on the turbine blades causes the shaft to rotate, which, in turn, is connected to an electrical generator, which converts the motion of the shaft into electrical energy.
The present installed capacity is approximately 40,661.41 MW, which is 16.36% of total electricity generation in India and small hydro power capacity is 4101MW.
India has huge hydro potential of about 84,000 MW at 60% load factor, which can be economically exploited. Almost 49 large hydropower projects are under construction in India, which will be completed by the year 2022 with a cumulative capacity of 15,006 MW.
In addition, a potential of 6,740 MW of installed capacity from small, mini and micro hydel schemes have been assessed – and pumped storage schemes with an aggregate installed capacity of 94,000 MW have been identified. Pumped storage schemes would be helpful for meeting peak load demand and storing the surplus electricity, which can also produce power at no additional cost when rivers are flooding. India has already established nearly 6,800 MW pumped storage capacity. For small units, 5,718 sites with a total capacity of 15,384 MW have been identified all over the country.
India has great potential of wind energy to project as an alternate source of energy. Electricity can be generated from wind power by converting the kinetic energy in the wind into mechanical energy utilising wind turbines. The energy in the wind is utilised to turn propeller shaped blades around a rotor, which when connected to the main shaft can spin a generator to produce electricity.
The power that can be extracted theoretically from wind is proportional to the cube of its velocity and the energy generated depends on wind speed and rotor size of the turbine. Wind energy is regarded as a means of saving fuel by injecting power into an electrical grid and to run wind power plant in conjunction with a pumped storage plant. Wind power has application to rotate machinery to do physical work, such as crushing grain or pumping water and has application to desalinate water.
The estimation of the potential wind resources in India is 102,788 MW assessed at 80m Hub height. The installed capacity of wind power in India was 22,645 MW as of 30 March 2015. The target set for wind power generation capacity is 60,000 MW by the year 2022. The preliminary assessments along the 7,600 km long Indian coastline have indicated prospects of development of offshore wind power as the wind speeds offshore are usually higher and steadier.
Energy from biomass
Biomass energy has been an important alternate energy source for the countryand more than 70% of the country’s population depends on biomass for energy needs. It is renewable, widely available, and free from greenhouse gases. Biomass is biological material derived from agricultural and forest resources including plant and animal manure. As an energy source, biomass can be used directly via combustion to produce heat. Indirectly, biomass can be converted into forms of bio fuel, like ethanol and methanol, to be used in engines; gaseous fuel called biogas can be obtained from biomass by anaerobic fermentation.
Biomass fuels can be most efficiently used when generating both power and heat through a combined heat and power (or cogeneration) system. A total of 288 biomass power and cogeneration projects with 2,665 MW capacity have been installed in the country for feeding power to the grid. Bagasse cogeneration projects in sugar mills have capacity aggregating to 1,666 MW. A target of 10,000 MW has set for biomass energy till 2022.
Wave energy is indirectly derived from solar energy and is available at the ocean surface – because of the interaction of the wind with water surface. Wave energy can be generated directly from surface waves or from pressure variations below the surface. Wave energy converters are devices, which can capture wave power for generating electricity and extract useful work like water desalination or pumping of water. India has a coastline of 7,500 km with an estimated wave energy potential of about 40,000 MW.
Tides are the largest source of short-term sea-level fluctuations and caused by the combined effects of gravitational forces of sun and moon and the rotation of the earth. When the gravitational forces due to the Sun and the Moon add together, tides of maximum range called spring tides form, and when the two forces oppose each other, tides of minimum range, called neap tides, are obtained. Electrical energy can be extracted from tides in several ways by constructing a reservoir behind a barrage, and then tidal water is allowed to pass through turbines in the barrage to generate electricity.
India has a potential of 8,000 MW of tidal energy as per the estimates. Despite the huge potential, there is no progress in extracting tidal energy. Agreement is signed to implement India’s first 3.75 MW mini-tidal power project in West Bengal.
Ocean Thermal Energy Conversion (OTEC)
Ocean thermal energy conversion, uses difference in ocean temperature from the surface to depths lower than 1,000 metres, to extract energy. A temperature difference of only 20°C can yield usable energy. The closed cycle and open cycle OTEC technologies are commonly used to extract thermal energy and convert it to electric power. The total OTEC potential around India is estimated as 180,000 MW considering 40% of gross power for parasitic losses. The Government of India proposed to establish a 1 MW gross OTEC plant in India, which will be the first ever MW range plant established anywhere in the world.
Geothermal energy is the thermal energy stored in the earth’s interior. The steam and hot water at high temperature and pressure come naturally to the surface of the earth at some places that can be utilised for electricity generation, residential and industrial heating, greenhouses and other local uses.
According to the estimates, India has 10,600 MW potential in the geothermal energy sector but it still needs to be exploited. Union Ministry of New and Renewable Energy (MNRE) recently drafted a national policy, which intends to exploit the sector by generating 1,000 MW in phase-one by 2022.
Total installed power generation capacity (30.06.15)
The total installed power generation capacity is the sum of utility capacity, captive power capacity and other non-utilities.
Utility power: The utility electricity sector (Table-1) in India had an installed capacity of 274,817.94 MW as of end June 2015. Renewable Power plants constituted 28% of the total installed capacity and Non-Renewable Power Plants constituted the remaining 72%.
Captive power: Presently India has a total installed captive power generation capacity (above 1 MW capacity) of 47,082 MW in the industries and almost 75,000 MW capacities with diesel power generation sets. In addition, there are a large number of DG sets of capacity less than 100 kVA cater to emergency power needs in all sectors such as industrial, commercial, domestic and agriculture.
The total demand for electricity in India is expected to cross 950,000 MW by 2030. Renewable forms of energy, especially solar, wind and hydro power, could contribute to India’s energy needs. In case India has to switch from coal, oil and natural gas, it is possible that 70% of the electricity could be derived from renewable resources by 2030.
Realising the need to generate more electricity from clean energy sources, a renewable power production target of 1,75,000 MW is projected for the year 2022 by the Government of India, out of which solar power will have a share of 1,00,000 MW followed by 60,000 MW from wind energy, 10,000 MW biomass energy and 5,000 MW of small hydro projects.
Comparisons of costs per kilowatt hour of electricity produced show that newly built solar and wind plants are already considerably cheaper than new nuclear plants. In coming years solar and wind energy will compete more favourably with conventional energy generation.
India’s ocean resources for energy development remain untapped as of now, though a coastline of 7,500 km can be utilised and geothermal energy sector can also supply the future energy needs.
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