Renewable
energy stores (1)
Wind power and solar power
Two renewable
resources for electricity generation that will never run out!
Wind Power - turbines and generators -
advantages and disadvantages of wind turbine generation
Solar Power - solar panels - solar cells -
advantages and disadvantages of using sunlight as an energy resource
Doc Brown's GCSE level Physics exam study revision notes
Wind
power - wind turbines generating electricity
The
technology of wind power
Wind turbine blades are driven by the kinetic
energy of wind movement which in turn drive a generator (electrical energy).
Energy from the wind's kinetic energy store
is mechanically transferred to the kinetic energy store of the turbine blades
and the rotor of the generator.
The kinetic energy of the rotating
generator coils is mechanically converted to electrical
energy by the magnetic field of the generator - a wire passing through a
magnetic field induces an electric current.
See
Generator effect, applications e.g. generators
generating electricity gcse
physics revision notes
Each set of turbine blades is connected to a generator to produce electricity
which can be fed into a domestic supply or, more likely, fed into the
National Grid
system.
They are sited in clusters ('wind farms') in
exposed locations on open land or out at sea (the
latter is a more expensive location to erect the turbines, but causes less
local objections!).
Locations are
chosen after a
survey is done to see if a commercial amount of wind blows!
An offshore wind farm out from Redcar on the
north-east coast of Cleveland, England
Advantages of wind power
Wind turbine technology
isn't cheap at the moment, BUT, as more are built and designs improve, they are becoming
more commercially more viable and the energy is free and maintenance costs
are low.
Free source of energy, however
unreliable, this kinetic energy store resource will never run out.
There is no pollution, though some people
feel they spoil the view of the landscape.
Costly to build, but relatively cheap to
maintain in good running order.
There is no lasting damage to the
landscape - they can be easily removed if need be.
Its convenient for small scale power
generation - illustrated below, but it needs 1000 - 2000 wind turbines to
replace a coal fired power station. Typical sites might be on 'windy' open
moorland or on the coast.
It is cheaper to build wind turbines on
land, rather than erecting out at sea, but people are more likely to object
about land-based wind turbines.

The turbine is elevated to catch more of the wind. |

A typical three bladed turbine. |

The generator is within the casing on the left,
including cog wheel gears to speed up the rotation of the generator
coils. |

The tail fin ensures maximum orientation of the
turbine blades with the wind - to maximise the kinetic energy store
output. |
Disadvantages of wind power
The initial capital costs are high, BUT
the running costs are relatively low.
(The costs of building an offshore wind
farm are greater than those for a land-based wind farm.)
It takes a great many wind turbines to generate the same amount of
electricity as a large scale power station such as those run on nuclear or fossil fuels
- large scale wind turbine farms are seen as unsightly (not in my view!).
Wind power generation is not capable of dealing with the
high energy demands of peak times eg peak travel/cooking time because,
unfortunately, you cannot suddenly increase power production at all - unless
the wind suddenly increases in speed!
Some people object to what they
see as 'visual pollution' or 'noise pollution' but at one time hundreds of
windmills were a common sight in the countryside.
Wind turbines can be unreliable - the wind doesn't always blow, but
sometimes too strongly!
It is estimated that wind turbine
electricity generation is possible for 70-85% of the time.
There are several other
problems too eg wind speed is variable and if it drops to zero, so does the
power generation.
The turbines may have to be stopped if the wind speed is
too high to avoid damage to the turbines.
Wind turbines cannot, at the moment, cope
with high electricity demands e.g. peak times in the day.
TOP OF PAGE
Solar
power cells
The technology of solar power
to generate electricity
Know and understand that
'renewable' electricity can be produced
directly from the Sun’s radiation.
The nuclear energy store of the Sun is
converted into several forms of energy.
One form is the whole range of
electromagnetic radiation.
Solar photocells can be used to
capture visible light and convert it directly into electrical energy.
You should know
that solar cells can be used to generate electricity and should be able to
describe the advantages and disadvantages of their use.
Solar cells (solar panels of photovoltaic
cells) produce 'small scale' electricity direct from sunlight energy.
Solar cells are fabricated from materials
that respond to visible and uv light energy and promote the flow of electrons i.e. they
create a potential difference causing an electrical current to flow.
You can use solar cells to power remote devices
from telephones to weather recording instruments, where it is too costly to
lay on mains electricity.
Calculator and watch batteries are easily
recharged by a
solar cell as are electric road signs.
Rechargeable cells/batteries can be
put to use later on discharging the solar charged battery.
However, all of these examples a very
small scale uses of solar powered electricity sources - but solar
cells a good in this respect for low power devices.
Note on using the thermal radiation
in sunlight:
You can also use a different type solar panel to capture the
infrared
radiation to increase the thermal energy store of water.
Solar panels can heat up water using
pipes with a dark matt surface that readily absorb the Sun's infrared
radiation (thermal radiation) increasing the thermal energy store of
the water.
The heated water can be piped to a
hot water storage tank or through radiators in the house.
Advantages of solar power
The Sun is a free energy store and non-polluting and never runs
out.
The initial manufacture and installation
costs of fitting solar panels are high, but they are getting cheaper and the
running costs are very low.
One important
advantage is that it easy to install on a small scale in remote areas not
connected to the mains electricity supply (e.g. the UK National Grid
network) - which would be a very costly affair to lay on a small scale
electrical power demand.
Solar cells are good for powering
small scale devices e.g. charging batteries in calculators.
One really good example is fitting
solar cell panels on large wings projecting out from Earth orbiting
satellites and the human manned International Space Station - the energy
is initially stored in batteries which are then able to power everything
on board - you can hardly construct a power station many kilometres
above the Earth's surface.
Lately, many people in developed
countries are putting solar panels on their house roofs to generate
electricity.
So, in developing countries, it is a most important
and convenient way of generating electricity on a local small scale in
locations far from a national electricity supply.
These are often sunny countries, but
solar cells even work on cloudy days, they are still cost effective in
the long run, but with a smaller power output from similar cells.
In developed countries it adds to the
electricity supply (National Grid) and reduces the home owners electricity
bill.
Disadvantages of solar power
Although non-polluting in itself, energy
is used in making the solar panels, but, although the technology and
installation is expensive, manufacture is getting cheaper and becoming more
energy efficient.
Once installed it is non-polluting and
runs off free energy with very low maintenance costs, but solar cells can't
work at night.
The Sun doesn't always shine!
On average, for half the day, there is no
sunlight and the sunlight itself is of variable intensity e.g. cloudy to
bright sun and of course it cannot work at night - so variable output is a
problem, but it is being widely exploited in very sunny countries from eg
Spain to African states.
Solar power is no good for a large scale
electricity supply - it is impossible to increase power output, unlike
hydroelectric or natural gas power stations.
Solar panels cannot be used to produce
electricity on the same scale as large nuclear or fossil fuelled power
station.
Keywords, phrases and learning objectives
on wind turbines and solar panels
Be able to describe and explain how a wind turbine
power plant operates to generate electricity.
Be able to describe and explain how a solar power
plant operates to generate electricity.
Be able to discuss the advantages
disadvantages of generating electricity from wind turbines and solar
cell renewable energy resources.
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