We can produce electrical energy by converting different energies available in nature. So we should look into various natural sources of energy which we use to produce electricity. Some common sources of energy are
- The Sun
- The Wind
- The Water Head
- The Fuel
- The Nuclear Energy
Out of five above listed sources of energy we do not use first two in very large scale. This is because there are some limitations. But in present days water head, fuel and nuclear energy are three most primarily used natural energy sources for producing electricity. We call these three sources collectively as conventional sources of energy.
Energy of Sun
The Sun is the basic source of energy. The sun is the source of both heat and light. We can use both heat and light for producing electricity.
Energy of Sun Heat
We focus sun rays at a small area with the help of concave mirror. The heat of the concentrated sun rays to heat up the water in boiler. The steam produced in boiler rotates a turbine. The turbine rotates an alternator to generate electricity. Although production cost of electricity is quite low here because no fuel like coal or diesel is required. However, production of electricity is not very popular. Because the area required for establishing this power plant is quite large even for smaller electrical energy generation. This is also because of unavailability of sun light in night and in cloudy weather. Also sun light varies time to time during a day. Over all the technique of producing electricity is not at all economical.
Energy of Sun Light
We can use sun light directly to produce electricity. This is done by photovoltaic cell. Here, sunlight directly strikes on the surface of voltaic cell. The photovoltaic cells are basically semiconductor p n junction cells. The potential difference or voltage appears across the junction of cell due to the incident sunlight. This potential difference or voltage creates electricity in the circuit connected to the solar panel system. Solar panels for producing electricity are becoming popular now days because of limitations of other conventional resources.
Energy of Wind
We can use wind power to generate electricity. Where sufficient wind is available for long periods of time, we can construct efficient wind power mill to produce electricity. Here the wind mill rotates an electrical generator. As the speed of wind is not fixed we should not use the electrical energy produced by wind mill directly to the load. Instead we charge a battery connected to the system. We feed the output of the battery to load through an inverter. The main advantage of the system is that it has very low running cost, because of zero fuel cost and negligible maintenance cost. The main disadvantages of the system are variable output, unreliable because of variable wind pressure throughout a day as well as throughout a year and production rate of electricity is also quite low compared to conventional sources of energy.
Energy of Water Head
When we obstruct the natural flow of water from upstream to downstream in a river by constructing a dam across the river, a head is created in this water. When we allow to flow this stored water in a controlled way through the dam the potential energy stored in this high headed water gets released in the form of kinetic energy. This kinetic energy rotates a water turbine. An alternator coupled with the shaft of the turbine generates electrical energy. The power plants which use water head to produce electricity are referred as hydroelectric power plant. Water head is the most acceptable source of electricity because it is clean, it does not cause pollution in atmosphere, it is simple in construction, it is robust and demands very less maintenance. In addition to these reasons, the dam helps irrigation in the localities and controls flood. But the construction of dam needs huge monetary investment and complex engineering. Another drawback of the system is that we can not construct a hydroelectric plant at load centre, we only can construct it in downstream river which may be far away from the load centre.
Energy of Fuel
Till date the fuels are the main source of electricity. We can use three types of fuel for the purpose. Solid fuel such as coal, liquid fuel such as diesel and gaseous fuel such as natural gas. Whatever may be the form of fuel that is either solid, or liquid or gaseous the basic principles is same in this system. Here heat generated due to combustion of fuel in the furnace creates steam by boiling water in a vessel called boiler. This steam is then allowed to expand through nozzles in a turbine. This creates kinetic energy on the turbine blades which turns the turbine shaft. The alternator coupled with the shaft of the turbine generates electrical energy. We refer this system of producing electricity as thermal power generating plant. Although till date fuel is the main source of electricity generation but it has a limitation of availability in nature and it is true that the availability is diminishing day by day.
Energy of Nuclear
Nuclear fission releases a huge quantity of energy. This energy is used to produce steam which rotates a turbine coupled with an alternator. The alternator produces electrical power. In nuclear reaction the requirement of radio active material quite small for producing a large quantity of energy. Although the cost of nuclear fuel is quite high but till it is cost effective process of generating electrical energy since the quantity of nuclear fuel used in the process is very small. It is found that one kg of uranium (radioactive material that is nuclear fuel) is equivalent to 4500 kg of coal fuel. The plants where nuclear reaction is the source of energy for boiling water to produce steam is called nuclear power plants. The nuclear power plants do have two major drawbacks.
- The establishment costs, maintenance costs and running costs of the plants are higher than that of other conventional thermal power generating plants.
- The disposal of nuclear wastes is another big issue for nuclear power plant.