Management of Electricity

Electricity is a secondary energy source.We call it so because it is produced from the primary sources like coal,natiral gases,nuclear power etc.Electricity itself is neither renewable nor non renewable. It has now become a basic part of human existence and hence it is the most widely used form of energy.Most of the energy sources which we depend are non renewable,that is,
once we use them up, they are gone for ever.The excessive use of electricity leads to an increase in the production of electricity, which results in excessive pollution of environment.

Selection of a particular type of power plant for an area depends on a number of factors like energy demand,availability of fuel,pollution standards and financial considerations.Based on the requirement of fuel,energy sources are broadly classified as renewable energy sources and non renewable energy sources.Renewable energy sources are considered to be available forever.Examples are hydel energy ,solar energy,wind energy,wave energy etc.Non renewable sources use some fuel like,which will be available for a limited period of time only.Energy sources like solar energy,wind energy,wave energy,tidal energy etc are relatively new in bulk electricity generation and therefore are called non conventional energy sources

HYDRO ELECTRIC POWER PLANTS

• Hydro electric power plants convert energy available from flowing water into electricity. These power stations are suitable where water resources with sufficient head are available.There are a lot of advantages by using free flowing water to produce electricity. Some of them are:
• The generating cost is very low.
• No fuel is required for operating a hydro electric power plant.
• Uses simple technology.
• It is a clean source of enery and no pollutants are generated.
• The dams and reservoirs serve the purpose of irrigation and flood control .
• Hydelpower plants have longer life compared to other types.
  Even though the hydro electric power plants are advantageous in many respects,still they have many draw back:
• Area of installation is very high.
• The ecological balance of the area is severely affecte.
• The cost of construction is very high.
• Long gestation period.
• Electricity producton is dependent on weather.

Thermal power generation constitutes about 70% of the total electrical energy generation inIndia.Thermal power stations are one of the major sources of air pollution.
Most of the countries depend on this source for generation of electricity.

The three major types of thermal power plants are:

• Steam turbine power plants.
• Gas turbine power plants.
• Diesel engine power plants.
  Steam turbine power plants use coal or gas as the fuel.In gas turbines oil or gas is only used as the fuel..In diesel power plants,the primemover is an internal combustion engine and usually diesel is used as the fuel.The advantages of thermal power plants are:
• Fuel used is easily available.
• Initial cost is less compared to hydroelectric power plant.
• Availability of power is independent of weather conditions.
• Can be installed at any place where water and transportation facilities are easily available.
  Even though the thermal power plants are advantageous in many respects still they have many disadvantages.Some of them are:
• High maintenance and operating cost.
• Produces smoke and other residues which pollute the environment.
• Difficulty in disposing the ash produced.

NUCEAR POWER PLANTS

• In nuclear power plantss,the energy generated as a result of the nuclear fission reaction is utilised for generation of electricity.The heat energy thus released is used to heat a coolant ,which in turn generates steam.The remaining functions are similar to thermal power plant.
  Advantages of a nuclear power plant are:
• The area required for installation is less.
• Less polluting when compared to coal based or gas based thermal power plants.
• Large capacity plants are possible.
• The quantity of fuel involved is less.
• Availability of power is independent of weather conditions.
  The disadvantages of nuclear power plants are:

• Requires high initial cost.
• Requires high technical knowledge for installation and operation.
• There is a risk of radiation hazard.
• The fuel is expensive.
• Disposal of radioactive wastes is difficult.
• Reactor cannot respond quickly to load variations.

SOLAR THERMAL SYSTEMS

Solar radiations contains visible light,infrared rays and small amount of ultraviolet rays.Vsible light and infrared rays can be utilised for generation of electricity.Systems which convert the heat energy from sunlight are called solar thermal systems.The other type is solar photo voltaic systems ,which directly convert the visible radiations into electricity.
The basic principle of a solar thermal electric system is to concentrate the solar radiations to a receiver using mirror reflections and the resulting heat can be used to generate electricity.The conversion of heat energy to mechanical energy may be done by a steam turbine.
Advantages of solar thermal systems:

• Renewable source and hence no fuel is required.
• There is no atmospheric pollution.
• Low maintenance cost.
• Longer life.

Disadvantages of solar thermal sytems are:

• Energy generation is possible only when sunlight is available.Suns position is always changing and hence a tracking system is required to ensure that sunlight is always reflected to the receiver.

Tides originate from the attraction between earth,moon and sun.Tidal rise and fall in the sea cost and some river banks is aregular phenomenon and it is possible to extract the energy from the water movements due to tides. The basic principle is to store the rising water in a large basin near the sea and as the tide subsides,this water can be released through a turbine to generate electricity in asimilar

manner as that hydro electric power plants.The water head available will be only a few meters and the turbines have to be designed to work with this low head.

An advantage of the tidal phenomenon is that it is predictable and occurs on a regular basis.But if power generation is done only during tidal fall ,power availability will be intermittent. This problem can be overcome by producing electricity during the tidal rise as well as the tidal fall with separate turbines.

Wave power is another source of renewable energy.It can be tried where waves of reasonable intensity is available through out the year.It has been observed that upto 70KW of power is available for every meter of wave front.The major problem with this technology is that wave power is not concentrated at one point.Also due to the intermittent nature of the waves ,it is a bit difficult to ensure steady availability of power.

GEOTHERMAL POWER PLANTS

Geothermal energy involves the production of energy from the heat of earth.There are two techniques to exploit geothermal energy:
1.To use hydro thermal sources .

2.To extract heat from the hot dry rocks.

Hydrothermal sources are found in sedimentary basins where rain water goes down to one or two kilometers below the surface of the earth and gets heated up .The hot water and steam available from these sources can be brought to the surface of the earth through boreholes.The steam available is used to drive turbines and produce electricity .Special designs for turbines are used for hydrothermal power plants since the steam pressure is relatively low and impurities may be present along with the steam.

For exracting heat from hot rocks. two separate boreholes are made which shall intersect a few kilometers below the surface of the earth.Water is sent in through one borehole.With the heat of the rocks steam will be produced and taken out through the other borehole.This steam can be used to drive a turbone .

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