CONVENTIONAL SOURCES OF ENERGY
Conventional energy directly mean the energy source which is fixed in nature like oil, gas and coal. In other words conventional energy is also termed as non-renewable energy sources.
- Increasing industrialisation has led to a better quality of life all over the world. It has also caused the global demand for energy to grow at a tremendous rate.
- The growing demand for energy was largely met by the fossil fuels – coal and petroleum.
- Our technologies were also developed for using these energy sources.
- But these fuels were formed over millions of years ago and there are only limited reserves.
- The fossil fuels are non-renewable sources of energy, so we need to conserve them.
- But we continue to be largely dependent on fossil fuels for most of our energy requirements.
Disadvantages of using Fossil Fuels
Burning fossil fuels has other disadvantages too.
- The oxides of carbon, nitrogen and sulphur that are released on burning fossil fuels are acidic oxides.
- These lead to acid rain which affects our water and soil resources.
- In addition to the problem of air pollution, recall the green-house effect of gases like carbon dioxide.
- which leads to global warming.
do you know fossil fuels are the major fuels used for generating electricity?
Thermal Power Plant
- Large amount of fossil fuels are burnt every day in power stations to heat up water to produce steam which further runs the turbine to generate electricity.
- Thermal power plant is a power generation plant which converts thermal energy into electrical energy.
- The term thermal power plant is used since fuel is burnt to produce heat energy which is converted into electrical energy.
- Mostly thermal power plants are situated near the coal field and oil fields. Because transporting coal and oil is costlier than transporting electricity.
Hydro Power Plant
- It is a renewable source of energy which converts potential energy into electrical energy.
- Since there are very few water-falls which could be used as a source of potential energy, hydro power plants are associated with dams.
- In order to produce hydro electricity, high-rise dams are constructed on the river to obstruct the flow of water and thereby collect water in larger reservoirs.
- The water level rises and in this process the kinetic energy of flowing water gets transformed into potential energy.
- The water from the high level in the dam is carried through pipes, to the turbine, at the bottom of the dam.
Since the water in the reservoir would be refilled each time it rains (hydro power is a renewable source of energy) we would not have to worry about hydro electricity sources getting used up the way fossil fuels would get finished one day.
- Constructions of big dams have certain problems associated with it.
- The dams can be constructed only in a limited number of places, preferably in hilly terrains.
- Large areas of agricultural land and human habitation are to be sacrificed as they get submerged.
- Large eco-systems are destroyed when submerged under the water in dams.
- The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane which is also a green-house gas.
- It creates the problem of satisfactory rehabilitation of displaced people. Opposition to the construction of Tehri Dam on the river Ganga and Sardar Sarovar project on the river Narmada are due to such problems.
Technology improvements in conventional source of energy
- We mentioned earlier that wood has been used as a fuel for a long time.
- If we can ensure that enough trees are planted, a continuous supply of fire-wood can be assured.
- You must also be familiar with the use of cow-dung cakes as a fuel. Given the large live-stock population in India, this can also assure us a steady source of fuel.
- Since these fuels are plant and animal products, the source of these fuels is said to be bio-mass.
- These fuels, however, do not produce much heat on burning and a lot of smoke is given out when they are burnt. Therefore, technological inputs to improve the efficiency of these fuels are necessary.
- When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue. Charcoal burns without flames, is comparatively smokeless and has a higher heat generation efficiency.
- cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give bio-gas.
Since the starting material is mainly cow-dung, it is popularly known as ‘gobar-gas’.
Gobar gas plant
- The plant has a dome-like structure built with bricks.
- A slurry of cow-dung and water is made in the mixing tank from where it is fed into the digester.
- The digester is a sealed chamber in which there is no oxygen.
- Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow-dung slurry.
- It takes a few days for the decomposition process to be complete and generate gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.
- The bio-gas is stored in the gas tank above the digester from which they are drawn through pipes for use.
Bio-gas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning.
- Its heating capacity is high. Bio-gas is also used for lighting. The slurry left behind is removed periodically and used as excellent manure, rich in nitrogen and phosphorous.
- The large-scale utilisation of bio-waste and sewage material provides a safe and efficient method of waste-disposal besides supplying energy and manure.
- Heating of the landmass and water bodies by solar radiation generates air movement and causes winds to blow.
- Wind energy is used to produce electricity by rotating the turbine generator.
- This kinetic energy of the wind can be used to do work.
- This energy was harnessed by windmills in the past to do mechanical work. For example, in a water-lifting pump, the rotatory motion of windmill is utilised to lift water from a well.
- A windmill essentially consists of a structure similar to a large electric fan that is erected at some height on a rigid support.
- To generate electricity, the rotatory motion of the windmill is used to turn the turbine of the electric generator.
- The output of a single windmill is quite small and cannot be used for commercial purposes.
- Therefore, a number of windmills are erected over a large area, which is known as wind energy farm. The energy output of each windmill in a farm is coupled together to get electricity on a commercial scale.
- Wind energy is an environment-friendly and efficient source of renewable energy.
- Wind energy farms can be established only at those places where wind blows for the greater part of a year.
- The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine.
- There should be some back-up facilities (like storage cells) to take care of the energy needs during a period when there is no wind.
- Establishment of wind energy farms requires large area of land. For a 1 MW generator, the farm needs about 2 hectares of land.
- The initial cost of establishment of the farm is quite high. Moreover, since the tower and blades are exposed to the vagaries of nature like rain, Sun, storm and cyclone, they need a high level of maintenance.