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Old Wednesday, February 13, 2008
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Default Sources and Resources of energy

Energy crisis
We often hear about the global energy crisis .But if energy is always conserved,
How can it be running out?
The problem is that as we ‘use’ energy in our daily lives it is all eventually transferred to internal energy in our surroundings .It is then almost impossible to transfer back to any form.
For example , our car are powered by the chemical potential energy stored in petrol.The engine transfers some of this to kinetic energy but the rest is ‘wasted’ as heat.As the car comes to a stop its kinetic energy is transferred to heat due to friction at the brakes and between the tyres and the road .The heat generated is all eventually transferred to the surrounding air.
So energy is not being used up , but it is being dissipated in the environment .This is why we need to conserve our limited supplies of fossil fuels and nuclear fuels .The energy stored in these can be converted into wide range of useful forms.
As these high grade energy sources run out , we will need to make more use of ‘renewable’ sources such as biomass , solar , geothermal , wind , wave tidal and hydro-electric power.


Sources of energy

Most power stations burn fossil fuels (coal , oil and gas) but 20% produce electricity using nuclear fuel.
Why are fossil fuels and nuclear fuel called non-renewable enrgy source?
The reserves of these fuels are limited and one day they will run out . It is estimate that the known reserves of gas , oil and nuclear fuels will last between 40 and 60 years . Coal has longer - about 200 years.
Burning fossil fuels releases vast amounts of carbon dioxide (green house gas) leading to global warming.Sulphur dioxide is also released , causing acid rain.Nuclear power produces highly radioactive waste.
So why do we rely so heavily on non-renewables?
These power stations are able to generate electricity at all times. Fossil fuel power stations are relatively cheap to build and their power output is high - typically around 2000MW.Nuclear power stations are costly to build (and to dismantle) but fuel is relatively cheap and power output is high.

How is fossil fuel formed?

Fossil fuels were formed from the fossilized remains of tiny plants and animals that lived long ago. Most electricity used in the world is generated from power plants that burn fossil fuels to heat water and make steam. The highly pressurized steam is directed at turbine blades to make them spin.

What are the forms of fossil fuels?

Coal is a hard, black, rock-like substance made up of carbon, hydrogen, oxygen, nitrogen, and sulphur. There are three main types of coal: anthracite, bituminous, and lignite. The precursor to coal, called “peat,” is still found in many countries and is also used as an energy source. Coal is found in many parts of the U.S. and throughout the rest of the world.
Oil is a liquid fossil fuel, sometimes also called petroleum. It is found underground within porous rocks. To obtain oil, companies drill down to deposits deep below the earth’s surface using oil rigs. More than half of all the oil we use in the U.S. comes from outside our country—most of it from the Middle East.
Natural gas is made up primarily of a gas called methane. Methane gas is highly flammable and burns very cleanly. Natural gas is usually found underground along with oil. It is pumped up and travels through pipelines to homes and businesses. Natural gas supplies are abundant from sources in the U.S. and Canada.

How does nuclear power works?

Nuclear power uses heat released from splitting atoms to convert water into steam that turns turbines. Nuclear power plants rely on uranium, a metal that is mined and specially processed. Fuel rods containing uranium are placed next to each other in a machine called a nuclear reactor. The reactor causes the uranium atoms to split and in so doing, they release a tremendous amount of heat.

What are the disadvantages?

At each stage of the process various types of radioactive waste are produced. This waste is poisonous and can cause harm to people and the environment coming into contact with it.

Energy resources

Hrydroelectricity and tidal power
Nowadays there are many hydro-electric power stations, providing around 20% of the world's electricity. The name comes from "hydro", the Greek word for water
A dam is built to trap water, usually in a valley where there is an existing lake. Water is allowed to flow through tunnels in the dam, to turn turbines and thus drive generators.
Notice that the dam is much thicker at the bottom than at the top, because the pressure of the water increases with depth

What are the advantages?

This is clean way of generating electricity for mountainous regions such as scoltland and wales.once the station is built, the water comes free of charge, and there is no waste or pollution.
Electricity can be generated constantly.

What are the disadvantages?

Although there are many suitable sites around the world, hydro-electric dams are very expensive to build.

Tidal power
The tide moves a huge amount of water twice each day, and harnessing it could provide a great deal of energy .Although the energy supply is reliable and plentiful, converting it into useful electrical power is not easy.
There are eight main sites around Britain where tidal power stations could usefully be built, including the Severn, Dee, Solway and Humber estuaries.
Only around 20 sites in the world have been identified as possible tidal power stations.

What are the advantages?

Hydroelectric schemes produce no pollution
Once you've built it, tidal power is free.
It produces no greenhouse gases or other waste.
t needs no fuel.
It produces electricity reliably.
Not expensive to maintain.
Tides are totally predictable.
Offshore turbines and vertical-axis turbines are not ruinously expensive to build and do not have a large environmental impact

what are the disadvantages?

The ecology of the area can be disrupted by changing the natural flow of water.
Only provides power for around 10 hours each day, when the tide is actually moving in or out.


Biomass
New power stations that burn renewable biomass such as wood , straw , animal waste and specially grown crops such as willow are already producing electricity .Many more are planned

Doesn’t this produce the “green house gas”carbon dioxide?

No , because the amount of gas released by the burning is equal to the amount absorbed by the growing plants in photosynthesis.
Rooting plants and animal waste also produce methane gas,If they rot in a tank called a digestor the gas can be piped away and used as fuel.Methane can also be collected from land fill sites used to tip domestic rubbish.These plants are small , but they can make a useful contribution.

What are the advantages?

It makes sense to use waste materials where we can.
The fuel tends to be cheap.
Less demand on the Earth's resources.

What are the disadvantages?

Collecting the waste in sufficient quantities can be difficult.
We burn the fuel, so it makes greenhouse gases.
Some waste materials are not available all year round.

Wind and wave energy
The Babylonians and Chinese were using wind power to pump water for irrigating crops 4,000 years ago, and sailing boats were around long before that.
Wind power was used in the Middle Ages, in Europe, to grind corn, which is where the term "windmill" comes from.
A large aerogenerator can produce up to 7MW of power from the kinetic energy of the wind.A typical wind farm consists of about 20 machines covering 3 or 4 square kilometers of land.
The sea provides us with another source of energy , the kinetic energy of the waves can be captured by floats and used to generate electricity .How ever 20km of floats would produce only as much as energy as small power station.

The Sun heats our atmosphere unevenly, so some patches become warmer than others. These warm patches of air rise, other air blows in to replace them - and we feel a wind blowing.We can use the energy in the wind by building a tall tower, with a large propellor on the top.

What are the advantages?

Wind is free, wind farms need no fuel.
Produces no waste or greenhouse gases.
The land beneath can usually still be used for farming.
Wind farms can be tourist attractions.
A good method of supplying energy to remote areas.

What are the disadvantages?

The wind is not always predictable - some days have no wind.
Suitable areas for wind farms are often near the coast, where land is expensive.
Some people feel that covering the landscape with these towers is unsightly.
Can kill birds - migrating flocks tend to like strong winds.
However, this is rare, and we tend not to build wind farms on migratory routes anyway.
Can affect television reception if you live nearby.
Can be noisy. Wind generators have a reputation for making a constant, low, "swooshing" noise day and night, which can drive you nuts.
Having said that, as aerodynamic designs have improved modern wind farms are much quieter. A lot quieter than, say, a fossil fuel power station; and wind farms tend not to be close to residential areas anyway. The small modern wind generators used on boats and caravans make hardly any sound at all.

Geothermal energy

The inside of the earth is very hot due to radioactive decay .Bore-holes can be drilled down into the hot rock and cold water is forced down the holes .The water is heated by the rock and returns to the surface as steam
This steam is then used to turn turbines to generate electricity .

What are the advantages?

Geomthermal plants are clean , since they produce only steam .
The power stations do not take up much room, so there is not much impact on the environment.
No fuel is needed.
Once you've built a geothermal power station, the energy is almost free.
It may need a little energy to run a pump, but this can be taken from the energy being generated

What are the disadvantages?

The installation cost are high and the power out put is low.
The big problem is that there are not many places where you can build a geothermal power station.
You need hot rocks of a suitable type, at a depth where we can drill down to them.
The type of rock above is also important, it must be of a type that we can easily drill through.
Sometimes a geothermal site may "run out of steam", perhaps for decades.
Hazardous gases and minerals may come up from underground, and can be difficult to safely dispose of.

Solar energy
The earth receives an enormous amount of energy directly from the sun each day ,around 1,4KW per square metre of its surface and the sun is 150 million kilometres away.
There are main ways to use solar energy:
Solar Furnaces
Solar Furnaces use a huge array of mirrors to concentrate the Sun's energy into a small space and produce very high temperatures.
There's one at Odellio, in France, used for scientific experiments.
It can achieve temperatures up to 33,000 degrees Celsius.

Solar water heating
Heat from the Sun is used to heat water in glass panels on your roof.
This means you don't need to use so much gas or electricity to heat your water at home.Water is pumped through pipes in the panel.
The pipes are painted black, so they get hot when the Sun shines on them.

Solar Cells
Some homes have solar panels on the roof to provide hot water.Solar photo-voltaic cells(PV cells) convert sunlight directly into electricity.In a sunny climate, you can get enough power to run a 100W light bulb from just one square metre of solar panel.This was originally developed in order to provide electricity for satellites, but these days many of us own calculators powered by solar cells.

What are the advantages?


Solar energy is free - it needs no fuel and produces no waste or pollution.
In sunny countries, solar power can be used where there is no easy way to get electricity to a remote place.
Handy for low-power uses such as solar powered garden lights and battery chargers

What are the disadvantages?

Doesn't work at night.
Very expensive to build solar power stations.
Solar cells cost a great deal compared to the amount of electricity they'll produce in their lifetime.
Can be unreliable unless you're in a very sunny climate.
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