ENERGY : The energy shortage that we all have felt in the last decade has been a result of rapidly decreasing supplies of fossil fuels I.e coal, oil and natural gas. Like other environmental resources, energy resources can also be classified as :
Inexhaustible resources : Inexhaustible resources includes solar energy, fall in water (hydro power), wind, ocean, thermal gradients, waves, tides, currents, geothermal a biomass.
Exhaustible resources : Fossils fuels like coal, oil and natural gas are exhaustible sources of energy.
- Fossil fuels : Coal, oil and gas are the fossil fuels 95% of our daily energy requirements are met from these resources. They are called fossils fuel because they are the remains of plants and animals of past which became buried due to environmental hazards and were fossilized in deeper layers of earth a sea. Pakistan has reservoirs for gas, oil and coal. Extensive drilling for oil is being carried out in various regions of Pakistan.
- Fossils fuels are present in earth in fixed and limited quantities and they will exhaust sooner or later, effecting the standard and life style of the future citizens. Thus, this source be used properly and search for other sources of energy also be carried out.
- Hydroelectric power : Rain is a renewable energy source, which gets its energy indirectly from sun. Rain that falls on high areas such as mountains possesses large amount of gravitational potential energy. As rain water falls it gains speed and its kinetic energy increases. The kinetic energy of falling water is harnessed to turn turbines fixed at the base of dams. The turning turbines will then drive generator to produce electricity, which is known as hydroelectric power or electricity. It is cheapest and non pollutant source of energy, which man must exploit more for its benefit and for keeping environment safe.
- Tidal power :Tides are mainly caused by the gravitational pull of the moon to a lesser extent and the gravitational pull of sun on the water in sea and ocean. The changing tides drive water towards or away from the land. The difference in height of the water at high and low tides is made use of in a tidal power station to generate electricity. A tidal power station consists of a long barrier called a tidal barrage. The flow of water across the barrage turns its turbines, which in turn drive the generators to produce electricity.
- Wind power :Wind is moving air. It is caused by sun heating different parts of the earth surface unevenly. As warm air rises, cooler air flows as wind to take its place. Different temperature at different places has created various high and low pressure regions. Wind blows from area of high pressure 0 area of lower pressure. Modern windmills stop working when the wind stops blowing. For windmill to work efficiently, they have to be built in large number at different location with strong and steady winds, for continues supply of electric / mechanical energy.
- Nuclear energy : Nuclear energy is obtained from nuclear fuels by nuclear fission. In nuclear power station, large amount of heat is generated by nuclear fission, which takes place in a nuclear reactor. The heat energy is then used to convert water into steam, which drives stream turbines for generating electricity. Nuclear power station does not produce waste gases, which pollute the air unlike those using fossils fuels. However, each nuclear power station only can last for about 30 years and strict safety measures have to be taken to avoid radiation pollution.
- Geothermal energy : Volcanoes, not springs and geysers allow the escape of hot substance from the inside of the earth. The natural heat trapped underground is called geothermal energy. Hot waster or steam carrying geothermal energy comes up to the surface in some parts of the world such as New Zealand and Ice Land. Geothermal energy is free and can last for a long time. Sites of geothermal energy are usually located in areas far away from their consumers. This makes the harnessing of geothermal energy at these sites impractical. Furthermore, harmful substance such as boron and oxides of sulphur are also released together with the hot water or stream.
- Solid waste : Conservation of waste materials like trash, paper, organic, manure, plastic material, cans. Agriculture and industrial waste etc. By hydrogenation, pyrolysis (destructive distillation) or bio conversion can provide oil and gas and also their threat as source of pollution of land and water can be countered.
Ocean thermal gradient : In oceans, especially in tropical regions, temperature of surface water is about 25oC and that at the depth of few hundred meters only 5oC. This develops an ocean thermal gradient and heat is conducted from region of higher to lower temperature. Man has developed the technology to use this thermal gradient to drive a turbine for electricity generation, but this may also disturb the marine.