Wubbo Ockels, a professor of sustainable engineering and former
astronaut who leads the Laddermill project, believes kites are a cheap
way to harvest the enormous energy in the wind at a kilometre or more
above the ground, where winds carry hundreds of times more energy than
on the ground. 'We need to use all the energy supplies that are offered
to us by nature, we need diversity and kites are ... intriguing and
fascinating,' he said.
Ockels is not alone. Google.org, the philanthropic arm of the
Californian web-search company, invested $10m (about £5m) last year in
a US kite company called Makani, one of the first awards as part of the
organisation's Renewable Energy Cheaper than Coal programme.
The aim of both teams is to tap into high-altitude wind, which is an
energy source that is more abundant and reliable than the ground-level
wind on which normal turbines depend.
Ken Caldeira, a climate scientist at Stanford University's Carnegie
Institution, has estimated that the total energy contained in wind is
100 times the amount needed by everyone on the planet. But most of this
energy is at high altitude.
The blades of modern commercial windmills sit around 80 metres from the
ground, where the wind speed is almost five metres per second. At 800
metres, however, wind speed rises to seven metres per second,
potentially generating considerably more energy.
It would be virtually impossible to build a standard turbine to take
advantage of the wind at 800 metres, but kites could easily get to
these heights. Furthermore, thanks to the high-speed jet stream,
countries such as the UK, the Netherlands, Ireland and Denmark are
particularly suited to flying kites.
'Pretty much anywhere in the UK you could run a kite plant
economically, but you couldn't run a wind turbine economically,' said
Allister Furey of the University of Sussex, who develops computer
control mechanisms to maximise the power generated from kites.
A kite generates power by pulling on a string attached to generators on
the ground. When it has reached its maximum height, it is reeled back
down to repeat the process.
Using computer models, Furey has worked out that flying kites in a
figure of eight pattern means the air flowing over them travels even
faster than the ambient wind speed. When a kite needs to be reeled in,
it is angled so that it falls out of the sky like a glider, without the
need for much power. Ockels's system uses these flying patterns to
maximise the power the kites can generate. He is also looking at
extending his basic prototype to use multiple kites that yo-yo: when
one goes up, another goes down. Ockels estimates that kites could
generate power at less than 4p per kilowatt-hour, which is comparable
to coal power and less than half the cost of electricity from wind
turbines.
'The first systems will be community scale that could power a large
farm and sell some electricity back to the grid,' said Furey. 'Once the
technical issues have been sorted out, you can scale them up to the
level of a coal-fired plant. All you have to do is multiply the number
of kites and you can have a farm as big as you want.'
There are many ideas for commercial-scale demonstration projects. An
Italian company, Kitegen, has come up with a theoretical design for a
system that could generate a gigawatt, as much power as a standard
coal-fired power station. Its idea involves flying 12 sets of lines
with four 500-sq metre kites on each.
A spokesman for the British Wind Energy Association welcomed the idea
of devices that could harness the power of jet streams and
higher-altitude winds, saying: 'There is a vast potential that could be
harnessed with the technology now available.'
Nick Rau, energy campaigner at Friends of the Earth, agreed. 'We could
easily supply our electricity demand from offshore, even with other
demands on sea such as shipping, fishing and defence radar. These new
[kite] technologies allow us to go further offshore and avoid other
problems. We have an abundance of renewable energy and there are a lot
of visionary technologies coming along so that, in future, the sky's
the limit.'
How quickly technology will make it to market depends on how much
investors are willing to put in. Ockels said that commercial systems
could be operational within five years if the money was made available;
otherwise the technology could languish in the lab for a decade or
more.
'The Google prize is nothing compared to taxpayer money flowing into
energy research. If you take sustainable energy seriously, the money
flow to sustainable energy should also be serious.'
Transcript
Courtesy: The Guardian
VOICEOVER: Dutch scientists have successfully demonstrated a plan which
could harness renewable energy from the wind. By flying a
10-meters-square kite tethered to a generator, a team at the Delft
University of Technology produced ten kilowatts of power. The early
experiment generated enough electricity to keep ten family homes
running. The researchers already have plans to test a 50-kilowatt
version of their invention, called Laddermill, eventually building it
to a proposed version with multiple kites that they claim could
generate 100 megawatts—enough for 100,000 homes. The blades of modern
commercial windmills sit around 80 meters from the ground, where the
wind speed is almost five meters a second. At 800 meters, however, wind
speed rises to seven meters a second. But because the amount of power
available from the wind is related to the cube of its speed, blades at
the higher altitude could potentially generate four times the
electricity. It would be virtually impossible to build a standard
turbine to take advantage of the wind at 800 meters, but kites could
easily get to these heights. Furthermore, thanks to the high-speed jet
stream, countries such as the UK, the Netherlands, Ireland, and Denmark
are particularly suited to flying kites.
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