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solar energy, ocean energy, (tidal energy, wave energy, ocean thermal energy, ote), geothermal energy and nuclear energy belong to this category

these sources of energy which have been tapped with the aid of advances in technology to meet our growing energy needs are also called alternative sources of energy

solar energy: the energy produced by the sun in the form of heat and light energy is called as solar energy

solar radiations can be converted electricity through solar cells (photovoltaic cells)

photovoltaic cells convert solar radiations directly into electricity through silicon solar cells

solar cells arrange on a large flat sheets form a mirror solar panel

solar cookers are painted black from outside and a large glass plate to trap solar radiations by green house effect

cannot be used to make chapattis for frying as these require a temperature of 140°c or more

(maximum temperature of 100°c only can be achieved in a solar cooker) other solar devices are solar water heater and solar furnace

wind energy: when large masses of air move from one place to another then it is referred to as wind

during this process, kinetic energy gets associated with it which is referred to as wind energy

kinetic energy of wind is used in running of windmills, which are used to lift water, grind grains etc

uses of wind energy the important uses of wind energy are : it is used to drive windmills, water lifting pumps, and flour mills, etc

it is used to fly engine fewer airplanes or gilders in the air

it is used to generate electrically used for various purposes like lightning, heating, etc

hydro power plant (hydro energy): when the water flowing in a river is stored in a high rise dam and allowed to fall from the top of the dam

the water rushes down with a great force, which can be utilized to drive large water lurbine

these turbines are connected with electric generators which generate electric current

the electricity generated in this process is termed as hydroelectricity or hydel power

in fact the process involves transference of potential energy of the water into kinetic energy’ and then into electric energy

it is the most conventional renewable energy source obtained from water falling from a great height

dams are constructed to collect water flowing in high altitude river

when water is allowed to fall from a height, potential energy changes to kinetic energy which rotates the turbines to produce electricity

advantages of hydro power plant : it is readily and abundantly available everywhere free of cost

it is eco-friendly and does not produce any kind of environmental pollution

it is a renewable source as water itself is a renewable and inexhaustible resource

it is a cheap source of energy, as it does not involve any costly investment

geothermal energy: geothermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations

energy harnessed from the heat of the sun is called geo thermal energy

the magma gets collected at some depths below the earth’s surface

when underground water comes in contact these hot spots, it changes into steam, which can be used to generate electricity

advantages of geo thermal energy renewable inexpensive disadvantages of geo thermal energy only a few sites are available for harnessing energy

ocean energy: the oceans acquire almost 71% of the surface of the earth

the enormous amount of water present in them did not act as a big collector of solar heat energy, but also store large amount of it due to its high specific heat

thus, ocean water can be used as a renewable resource of energy

the main forms of ocean energy are described as under : (i) ocean thermal energy: the energy available due to the temperature difference between the deeper levels and surface of an ocean is called as ocean thermal energy, (ii) ocean tidal energy: the rise of ocean water due to the attraction of the moon is referred to as high tide and its fall as low tide

the enormous movement of water due to high and low tide provide a large amount of energy known as ocean tidal energy

this tidal energy can be utilized by constructing a tidal barrage or dam

(iii) sea wave energy: the energy obtained from the high-speed sea waves is referred to as sea wave energy

infact, these high-speed sea waves have a lot of kinetic energy associated with them, which can be used to drive dynamos which convert kinetic energy into electrical energy

(iv) energy from nuclear deuterium of oceans: the oceans water contains an unlimited amount of heavy hydrogen isotope called as deuterium which is isotope hydrogen having one neutron in its nucleus

scientists are working hard to produce energy by carrying the controlled nuclear fission of deuterium isotope

(v) energy from salinity gradient in seas: the difference in the concentration of salts in the water of the two or more seas is called a salinity gradient

this salinity gradient is now a day used to obtain energy with the involvement of suitable techniques, (vi) energy from sea vegetation or biomass: sea vegetation or biomass is another direct source of energy because the enormous amount of seaweeds present in the sea water provides an endless supply of methane fuel

bio-mass: biomass is defined as living matter or its residue and is a renewable sources of energy

the biomass includes all the new plant growth agriculture and forest residues (like bio-gases, dark, sea dust, wood savings, roots, animals dropping, etc..), carbonaceous wastes (like sewage, garbage, night-soil, etc.) biodegradable organic effluent from industries

it is the source of the conventionally used fuels that are used in our country

bio-gas: it is a mixture of gases produced during decomposition of bio mass in the absence of oxygen

bio-gas plants: animal dung, sewage, crop residues, vegetable wastes, poultry dropping, etc

advantage of bio-gas a bio-gas plant, is quite simple, can easily be built in rural areas

a small plant using dung from 3 to 4 heads of cattle is capable of supplying bio-gas for 6 hours daily for cooking purposes

bio-gas is a clean fuel that burns without smoke and leaves no ash

the main constituent of bio-gas, i.e., ethane has a higher calorific value (55 kj/g) that of petrol (50kj/g)

the spent slurry, being rich in nitrogen and phosphorus is good manure

composition of bio-gas: bio-gas is mainly composed of methane (up to 75%), c02 (25%) and traces of other gases such as nitrogen and hydrogen

whereas methane is a high-value calorific fuel, carbon dioxide is an inert gas

nuclear energy: a reaction in which, the nucleus of an atom undergoes a change to form a new atom and releases an enormous amount of energy is called as nuclear energy

there are two distinct ways of obtaining nuclear energy, (a) nuclear fission and (b) nuclear fusion

energy released when some changes take place in the nucleus of the atom of a substance is called nuclear energy

advantages of nuclear energy the alternative source of energy due to depletion of fossil fuels

from a small amount of fuel, a large amount of energy is released

environmental consequences of the increasing demand for energy : the combustion for fossil fuels produces acid rain and damages plants (crops), soil and aquatic life

the burning of fossil fuels is increasing the amount of greenhouse gas, carbon dioxide in the atmosphere

it is carried out by the bombardment of neutrons over a heavy nucleus

need for energy: the ability of a body to do work is called energy

it should be able to do a large amount of work for each unit of mass or volume

the sources of energy which have been in use since a long time are called conventional sources of energy

for example, coal, petroleum, natural gas, hydel energy, wind energy and nuclear energy are considered to be the conventional sources of energy

firewood is also a conventional source of energy but its usage is now limited to kitchens in rural india

the plants got buried under swamps and due to high pressure and high temperature inside the earth; they were converted into coal

during the days of the steam engine, coal was used in steam engines

moreover, coal was also used as kitchen fuel; before lpg became popular

the animals got buried under the ocean surface and were converted into petroleum; in due course of time

petroleum is the third major source of energy being used today

petroleum products are used as automobile fuel and also in the industries

natural gas mainly comes from the oil wells and is also a major source of energy

it takes millions of years for the formation of fossil fuels

since they cannot be replenished in the foreseeable future, they are known as non-renewable sources of energy

those sources of energy which can be replenished quickly are called renewable sources of energy

hydel energy, wind energy and solar energy are examples of renewable sources of energy

hydel energy: hydel energy is produced by utilizing the kinetic energy of flowing water

when the water falls on the turbine; the turbine moves; because of kinetic energy of water

dams can be constructed only in a limited number of places, preferably hilly areas

large areas of agricultural land and human habitation get destroyed by the cons¬truction of dams

the vegetation which is submerged underwater rots under anaerobic conditions and gives rise to large amounts of methane which is a greenhouse gas

thermal power plant: in a thermal power plant, coal or petroleum is used for converting water into steam

the steam is used to rim the turbine; to generate electricity

biomass: the material obtained from the bodies of plants and animals is called biomass

biogas: biogas is a mixture of methane, carbon dioxide, hydrogen and hydrogen sulphide

biogas is produced by the anaerobic degradation of bio¬mass in the presence of water but in the absence of air

windmills have been in use; especially in holland; since the medieval period

the kinetic energy of wind is utilized to run the turbines; which generate electricity

at present, germany is the leading country in terms of wind energy production and india comes at number five

in india, tamil nadu is the largest wind energy producing state

the largest wind farm in india is near kanyakumari; in tamil nadu; which generates 380 mw of electricity

limitations of wind energy: wind farms can only be established at those places where the wind speed is high enough and is more than 15 km/hr for most parts of the year

wind farms need to be established on large tracts of land

the fan of the windmill has many moving parts; so the cost of maintenance and repair is quite high

the initial cost of establishing a wind farm is very high

non-conventional sources of energy: energy sources which are relatively new are called non-conventional sources of energy, e.g., nuclear power and solar energy