The main sources of energy are the sun, wind, terrestrial heat, ocean tides and waves, water, fuels and radioactive substances. The last three sources i.e. water, fuels and radioactive substances are most dependable and are commonly used for generation of electrical energy.
Source # 1. The Sun:
The sun is the primary source of energy. The energy radiated by the sun is in the form of electromagnetic waves, which include the heat, light and a lot of ultraviolet radiations. The radiated heat energy by the sun can be utilised for the generation of electric power. The steam can be produced by focusing the heat over a boiler by use of some reflectors.
This method is inconvenient as it requires a large area for generation of even small amount of electric power. This method cannot be adopted in cloudy sky or at night. This method is quite obsolete for generation of electric power because of uncertainty of weather. This method is used in U.A.R. for supplying irrigation and other pumping loads.
In our country, conditions for utilisation of solar energy are favourable since for nearly six months of the year. Sunshine is uninterrupted during the day and useful energy estimated at noon is 12,000 kW/km2, while in the other six months, cloudy weather and rain provide conditions suitable for water power. Thus a co-ordination of solar energy and water power can be a useful and workable plan for most of the places in our country.
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During the last few years more than 50 small power plants have been installed in U.P. and other states. The size of such plants is in the range of 2 to 10 kW. These plants are supplying power to the remote villages where power from grid is not available. Efforts are also being made to install large size power plants in some states.
Source # 2. The Wind:
The winds produced by the sun got sufficient energy which can be utilised in wind mills to drive small generators. Such generators are used for charging batteries for continuous use. The great advantage of this source of energy is that it is plentiful, inexhaustible, and non-polluting and it does not require any operator. It also does not require any maintenance and repairs for long intervals.
The Indian Wind Energy already has the 5th largest installed capacity in the world and is set to grow at a rapid pace driven by investments from the private sector attracted by the generous wind subsidies from the state and central government in India. Most of the Installed Wind Capacity in India is located in the southern and industrial states of the country.
The other states like UP, Bihar lacks sufficient Wind Energy Capacity despite having high power tariffs and substantial electricity deficits. It can be said that Wind Power in India is being developed only in the progressive states like Gujarat, Maharashtra and others. To continue to grow at the same rate, the industry needs to diversify geographically but that would need the backward state governments to pull up their socks.
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Wind generators of capacity ranging between 225 kW and 2.1 MW are best suited for wind conditions prevailing in our country. There are two types of windmills namely gear type windmills suited for installation in regions of high speed winds and direct acting windmills suited for regions of low and moderate speed winds.
This method is unreliable since the production of electrical energy depends largely upon the pressure of the wind.
During past 30 years a few hundred small windmills have been installed in South India for pumping water. The total number of wind turbine generators in operation in India is more than 6,000 with a total installed capacity of about 14,157 as on March 2011. More wind turbine generator installations are in hand. The average capital cost per MW is Rs 5 to 7 crores and generation cost per unit is about Rs 4.50.
Source # 3. Terrestrial Heat or Geothermal Energy:
The earth has a molten core. During volcanic action the material that comes out from the bowls of earth to form volcanic explosions also produces steam vents and hot springs. This steam has been used for many years in Italy, Iceland and France for the generation of electric power and space heating. There is a number of hot springs in India, but the total exploitable energy potential seems to be very little. There is no operational plant, based on geothermal energy, in India.
Source # 4. Ocean Tides and Waves:
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There is a tremendous energy in ocean tides and waves but it is very difficult to harness this power for generation of electrical energy. Only at a few favourable points where the geography of an inlet or bay favours the construction of a large scale hydro-electrical plant, their use can be made for generation of electrical energy. A small dam with larger gates can be made across the mouth of the bay and low head hydraulic turbines are installed in it.
At the time of high tide the gates are opened water is stored in the tidal basin and then the gates are closed. After the tide has receded, there is a working hydraulic head between the basin water and open ocean and the stored water is now allowed to flow back to the ocean through hydraulic turbines installed in the dam. In case use of reversible hydraulic turbines is made power generation is possible continuously, both during high tide and low tide.
The above source for generation of electrical energy has been vigorously investigated in some countries like France, Germany, UK, Canada and USA. Probably the best known and the most recent tidal scheme which utilises the tidal energy for generation of electrical energy have been constructed in France at the Ranee Estuary where a power station of 240 MW capacities has been in operation since 1967.
In India potential for tidal energy exists 1,200 MW in Gulf of Kutch and 100 MW in Sunderban of West Bengal. Hydrological studies have indicated that power plants can be established on rivers Malta and Curzon Creek in this region. Potential of tidal power (7,000 MW) also exists in the Gulf of Cambay, near Bhavnagar, where tidal range is of the order of 11 to 12 metres.
Source # 5. Water:
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Water at a high pressure or flowing with a high velocity can be used to run turbines or waterwheels coupled to generators and, therefore for generation of electric power. This method of generation of electric power is becoming more and more popular as it is reliable and requires least maintenance and care. Though this method is costlier in initial cost, but it is cheapest in maintenance and production cost.
Source # 6. Fuels:
The main source of energy is fuels. The fuels may be solid, liquid or gas such as coal, oil and coal gas.
The coal is available in huge quantities in almost all industrialised countries. The coal is fired in the boiler, which produces steam. The steam so produced is utilised in steam engines or turbines coupled to generators and therefore, for generation of electric power. The average calorific value of coal is 6,700 cal/kg.
Though this method is most inefficient because of overall efficiency as low as 20 to 25% but due to availability of coal in huge quantity the cost per unit generated is not so high. The disadvantage of this source of energy for generation of electric power is that it requires a large space for storing the coal and involves heavy cost of transportation where the coal mines are away from the generating station.
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Liquid fuel has a high calorific value say 8,300 k. calories/kg for light oil and 11,000 k. calories/kg for heavy oil but being costly, it is used for power production only where small power is required. The power stations employing liquid fuels are adopted either as standby power stations or as peak load power stations in interconnected grid systems.
Natural gas available in large quantity can be used to run gas engines (or gas turbines) or can be burnt to produce steam and steam turbines can there after run. Average calorific value of coal gas is 4.6 k. calories/litre and of producer gas varies from 0.11 k. calories/litre to 0.15 k. calories/litre.
Gas engines are employed either near oilfields or near gas works i.e., where gas is the cheapest available fuel or where the process concerned does not require steam and a boiler plant would be uneconomical. The gas turbines have found great use in aircraft engines. In conjunction with hydroelectric stations gas turbo-sets are used to meet the power demand during peak load hours or as standby units.
Source # 7. The Atomic Energy:
The tremendous amount of heat energy is liberated by fission of nuclear disintegration of uranium and other similar fissionable materials. It is estimated that 1 kg of nuclear fuel is equivalent to about 2,500 tonnes of coal. The heat energy so liberated in atomic reactors is extracted by pumping fluid or molten metal like liquid sodium or gas through the pile.
The heated metal or gas is then allowed to exchange its heat to the heat exchanger by circulation. In the heat exchanger the gas is heated or steam is generated which is utilised to drive gas or steam turbines coupled to alternators thereby generating electrical energy.
The high capital cost (Rs. 15,000-60,000 per kW of installed capacity) of such generating stations, dearth of well trained personnel to man them and the difficulties associated with availability of suitable nuclear fuel and disposal of radioactive waste are the main hindrances in the development of nuclear power stations.
These power stations are best suited in areas far away from collieries (more than 800 km away from coal mines) and where alternative hydropower is not available as in Western UP, Northern and Western Rajasthan, Punjab and Haryana.