Key Stage 4 & 5 fact sheet –
wind power
Wind is caused by the sun heating the atmosphere unevenly. This causes
convection currents, where warm patches of air rise and cooler air blows in to
replace them. Wind turbines are, therefore, indirectly collecting solar energy.
The UK is the windiest country in Europe, and
potentially has the largest offshore wind resource
in the world. In 2007, wind energy overtook hydro
power to become the largest renewable electricity
source in the UK, providing approximately 2% of
the UK’s electricity supply.
History
Since earliest times, humans have harnessed the
power of the wind. The Babylonians and Chinese
were using wind power to pump water for irrigating
crops 4,000 years ago, and people were using wind
power to drive boats at least 5,000 years ago on the
River Nile in Egypt.
In the early 19th century, over 10,000 windmills
were in use in Britain, mainly to grind corn (which is
where the term “windmill” comes from). Windmills
began to be used for generating electricity at the end
of the 19th century. However, during the industrial
revolution, when the cost of burning coal became
cheap, wind power became much less used in Europe.
In the 1970s there was renewed interest in renewable
energy. Wind turbine technology has developed
hugely since then, and wind is now the fastest growing
energy sector in the world! Today, there are currently
2,539 wind turbines in the UK, with an installed
Most wind turbines spin at a constant speed.
The tips of the blades of a typical wind turbine
move at approximately 140mph (64m/s).
capacity of 3,687MW (as of July 2009). That is enough
green electricity to power over two million UK homes.
Modern wind turbines are far more efficient than
old style windmills. Windmills were up to 23 metres
high, had blades of up to 22 metres in diameter and
produced up to 30kW. By comparison, the world’s
largest wind turbine, which is in Germany, has a
rotor diameter of 126 metres and a tower 138 metres
high. This turbine is rated at 6MW, and is predicted
to produce enough electricity to power about 5,000
households. However, a more typical modern 2.3MW
wind turbine will generate enough electricity to meet
the annual needs of over 1,250 households based on
annual electricity consumption per home of 4,700 kWh.
The first UK wind farm was built at Delabole in
Cornwall in 1991. Farr Wind Farm, near Inverness,
is RWE npower renewables’ most powerful renewable
energy project. It consists of 40 turbines, with a total
installed capacity of 92MW. The wind farm generates
enough electricity to meet the average annual needs
of 54,000 homes (more than half of all the homes
across the Scottish Highlands).
The Quiet Revolution is
a small-scale wind turbine
that has been designed
to work well in urban
environments, where wind
speeds are lower and wind
directions change frequently.
wind power cont…
The UK’s first large-scale offshore wind farm is
located four to five miles off the North Wales coast,
and was developed by RWE npower renewables
in 2003 (pictured). RWE npower renewables was
granted consent by the Department of Energy and
Climate Change, to develop an offshore wind farm,
with an installed capacity of up to 750MW. The
Gwynt Y Môr Wind Farm would be situated 13km
off the North Wales coast, and could be capable
of producing enough power to supply the average
needs of around half a million homes.
through the national electricity grid. (Some modern
turbines are direct drive and no gearbox is required
to drive the generator.)
A small difference in the wind speed makes a big
difference to the power output of a wind turbine. (The
power in the wind is proportional to wind speed cubed.)
The wind speed increases the higher up you go, which is
why wind turbines are so tall. The power output of the
turbine is also related to the swept area of the turbine
blades. The greater the area, the larger the amount of
power the turbine can convert from the wind.
Modern wind turbines produce electricity 70-85% of
the time, but generate different outputs depending
on wind speed. Over the course of a year, they will
generate about 30% of the theoretical maximum
output. This is known as its capacity factor.
How wind turbines work
The energy in the wind can be turned into electricity
by using a turbine to drive an electrical generator.
The wind turns the turbine blades, which turn a shaft
inside the nacelle (the box at the top of the turbine).
In the majority of wind turbines, the shaft goes into a
gearbox, which increases the rotation speed enough
for the generator, which then uses magnetic fields
to convert the rotational energy into electricity.
The electricity then goes into a transformer, which
converts it into a higher voltage for distribution
Advantages
–– Wind is a renewable resource.
–– Wind power does not contribute to climate
change or local air and water pollution.
–– Wind energy is currently one of the cheapest
ways to produce renewable energy.
–– Wind turbines can supply electricity to
remote areas where it would otherwise be
very difficult and expensive to connect to
the national grid.
–– The land underneath wind turbines can still
be used for farming.
–– When a turbine is taken down, the land can
quickly be re-instated back to a greenfield site.
Disadvantages
–– The speed of the wind is affected by many
different factors such as weather, time of day
and landscape. This makes it an intermittent
source of energy that cannot be used to
generate electricity on demand.
–– Wind turbines can be seen from long
distances (but so can lots of other methods
of producing electricity).
–– Wind farms are often located in remote areas,
so electricity distribution costs can be high.