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Created
by Andy Dervill
Science teacher at
Broadoak Community School England
Web site www.darvill.clara.net
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Coal, Oil and Gas are called "Fossil Fuels"
Introduction How it works More details Advantages Disadvantages Is it renewable?
Introduction
Coal,
oil and gas are called "fossil fuels"
because they have been formed from the organic remains of prehistoric
plants and animals.
Find out more
about how they formed at www.energyquest.ca.gov/story/chapter08.html
At the time
this page was written, they provided around 66% of the world's
electrical power, and 95% of the world's total energy demands
(including heating, transport, electricity generation and other
uses). |
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How
it works:
Coal is crushed
to a fine dust and burnt. Oil and gas can be burnt directly.
More
Details:
Coal provides
around 28% of our energy, and oil provides 40%. Mind you, this
figure is bound to have changed since this page was written, so
check the figures if you want to quote them.
Burning coal
produces sulphur dioxide, an acidic gas that contributes to the
formation of acid rain. This can be largely avoided using "flue
gas desulphurisation" to clean up the gases before they are
released into the atmosphere. This method uses limestone, and
produces gypsum for the building industry as a by-product. However,
it uses a lot of limestone.
More
details on 'clean coal technology' from BBC News web site...
Crude oil
(called "petroleum") is easier to get out of the ground
than coal, as it can flow along pipes. This also makes it cheaper
to transport. |
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Natural
gas provides around 20% of the world's consumption of energy,
and as well as being burnt in power stations, is used by many
people to heat their homes.
It is easy to transport along pipes, and gas power stations produce
comparatively little pollution.
Other
fossil fuels are being investigated, such as bituminous sands
and oil shale. The difficulty is that they need expensive processing
before we can use them; however Canada has large reserves of 'tar
sands' , which makes it economic for them to produce a great deal
of energy this way.
Find out more at www.eia.doe.gov/emeu/cabs/canada.html |
The steam
that has passed through the power station's turbines
has to be cooled, to condense it back into water before it can
be pumped round again. This is what happens in the huge "cooling
towers" seen at power stations.
Some power
stations are built on the coast, so they can use sea water to
cool the steam instead. However, this warms the sea and can affect
the environment, although the fish seem to like it. |
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Advantages
- Very large
amounts of electricity can be generated in one place using coal,
fairly cheaply.
- Transporting
oil and gas to the power stations is easy.
- Gas-fired
power stations are very efficient.
- A fossil-fuelled
power station can be built almost anywhere, so long as you can get
large quantities of fuel to it. Didcot power station, in Oxfordshire,
has a dedicated rail link to supply the coal.
Disadvantages
-
Basically,
the main drawback of fossil fuels is pollution.
Burning any fossil fuel produces carbon dioxide, which contributes
to the "greenhouse effect", warming the Earth.
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Mining
coal can be difficult and dangerous. Strip mining destroys large
areas of the landscape.
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Coal-fired
power stations need huge amounts of fuel, which means train-loads
of coal almost constantly. In order to cope with changing demands
for power, the station needs reserves.
This means covering a large area of countryside next to the power
station with piles of coal.
Is
it renewable?
Fossil
fuels are not a renewable
energy resource.
Once we've burned them all, there isn't any more, and our consumption
of fossil fuels has nearly doubled every 20 years since 1900.
This is a particular problem for oil, because we also use it to make
plastics and many other products.
Ok,
you could argue that fossil fuels are renewable because more
coal seams and oil fields will be formed if we wait long enough. However
that means waiting for many millions of years. That's a long time -
we'd have to wait around for longer than the time that humans have existed
so far! As far as we today are concerned, we're using it up very fast
and it hardly gets replaced at all - so by any sensible human definition
fossil fuels are not renewable.
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