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/disadvantages

Solar Power - solar panels - solar cells - advantages/disadvantages

See also

(2) Hydroelectric power and geothermal power, advantages and disadvantages

(3) Wave power and tidal barrage power, advantages and disadvantages

and Renewable energy - biofuels & alternative fuels, hydrogen, biogas, biodiesel gcse chemistry 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.

Solar power cells

The technology of solar power

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: (need diagram)

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.

• Check out your practical work you did or teacher demonstrations you observed, all of this is part of good revision for your module examination context questions and helps with 'how science works'.

  • investigating the effect of changing different variables on the output of solar cells, eg distance from the light source, the use of different coloured filters and the area of the solar cells,

  • planning and carrying out an investigation into the effect of changing different variables on the output of model wind turbines, eg the number or pitch of the blades, the wind velocity,

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