What's wrong
with this picture?
Rooftop wind turbine madness in the UK.
(Picture from Paul
Gipe's
site.)
THE ENERGY SAVINGS TRUST
•Wind turbines do work but only when
installed properly in
an appropriate location.
•There is a potential for delivering carbon savings and
energy
generation from domestic small-scale wind turbines in the
UK.
•The highest potential for successful household
small-scale
wind installations is in Scotland.
•Wind speeds are difficult to predict and highly variable.
The Energy Saving Trust recommends that potential
customers first utilise the best available wind speed
estimation tools and then, where appropriate, install
anemometry to determine the wind speed distribution.
Data gathered through the
field trial indicates that none of
the sites with building mounted turbines had
average annual
recorded wind speeds of 4m/s or greater, and only
a third of
free standing pole mounted turbines had average
annual
recorded wind speeds of 5m/s or greater. It is
therefore
likely that many sites in the UK have less of a
wind resource
than previously predicted....
No urban or suburban building mounted
sites generated more than 200kWh or £26 per
annum,
corresponding to load factors of 3 per cent or
less. In some
cases, installations were found to be net
consumers of
electricity due to the inverter taking its power
(up to 10W)
from the mains supply when a turbine was not
generating.
A
review by Paul Gipe
The Ampair perspective
Dutch small wind turbine trial suffers low wind speeds
HAWTs generally score much better than VAWTs in this test
but there are exceptions, notably the Swift (shown right)
which seems to me to be a bit of a disaster - a shame
considering what nice people they are, and near to my home
town of Edinburgh.
A new Carbon
Trust
study into the potential
of small-scale wind energy has found that small wind
turbines could provide up to 1.5 Terawatt Hours
(TWh) per year of electricity (0.4% of total UK
electricity consumption) and 0.6 million tonnes of carbon
dioxide (MtCO2) emission savings. This is based on
10% of households installing turbines at costs competitive
with grid electricity, which is currently around 12p per
kWh.
The study also indicates that for the UK as a whole, the
majority of electricity and carbon savings are available
from small turbines in rural areas - four times as much as
urban areas irrespective of costs, and considerably more
given economic drivers. This is mainly due to wind speeds
generally being higher in rural areas. Turbines in
some rural locations could provide cheaper electricity
than the grid, but it appears that in many urban
situations, roof-mounted turbines may not pay back their
embedded carbon emissions.
The report published today marks the culmination of 18
months research by the Met Office and Entec, and is partly
intended for government policy makers. It makes important
recommendations to improve existing policy measures,
including that:
• A criterion should be used in any new grant
schemes to measure likely carbon savings. This is to
help ensure grants are awarded to installations which save
reasonable amounts of carbon; and
• Higher height limits for stand-alone turbines
should be allowed under permitted development
rights. This is to help maximise the overall carbon
savings of small-scale wind energy, given the sensitivity
of electricity generation to height.
Rooftop nonsense is alive and well in France. See this
article from Paul Gipe
It's hard to know whether to laugh or cry that these guys
get public acclaim for wildly oversold nonsense.
www.wind-works.org
elena
energie
|
in the city
(updated with response from RD Swift
turbines, and my email to BWEA)
Mostly now when I see these 'Swift' turbines they are under
repair for some reason. It looks awful.
The new certification body BRE have come out with new
guidelines
for estimating windspeed on urban
sites that you can download.
These rules of thumb (see appendix suggest that the
windspeed at rooftop level is approximately 50% of what you
would expect from using the DTI (NOABL) data set that
everyone relies on. That means 1/8 of the energy
production.
The Carbon Trust have also brought
out a new
Windspeed
Estimator on line that is much
better than NOABL for built-up areas.
The
Warwick Urban Wind Trial project
has engaged in depth with the
new market for urban, building mounted wind turbines
at a critical time in market
development. By taking the customer
perspective and combining technical monitoring with
social research into the impact of installations on
public perceptions of energy efficiency and wind,
the project is providing the most thorough and complete
assessment to date of the efficacy of urban wind
systems in supporting UK energy and environmental policies.
Further
evidence from the Warwick Wind Trials shows that most
of the new generation of rooftop turbines also fail to meet
their claimed output, often only achieving 30% or
less. In many cases the inverter's standby power
consumption exceeds any power generated on urban sites.
The final
report is now available and it makes
essential reading for those who want to know about small
scale urban wind realities (as opposed to marketing spin).
"Renew-Reuse-Recycle is an online community all about what
we can do to stop or mitigate the effects of climate change.
"Some of our members have recently started logging their KWh
output on a monthly basis in a shared
Google
Spreadsheet."
Siting of small VAWT turbines in the UK
Factors affecting the success of a wind turbine are
:reliability, windspeed, swept area, cost and efficiency. I
found a Quiet Revoluiton QR5 turbine at the botanic gardens
in Edinburgh and I am checking out these criteria.
There is a good rule of thumb that says a wind turbine
should be 30 feet above any obstruction within 300 feet.
Windspeed is highly critical for energy production since the
energy depends on the cube of the windspeed. There is hardly
any wind for turbines sited below the 'canopy layer' of the
tree tops. For more details check the Carbon Trust wind
siting tool. The company state that "Please note that the
minimum recommended average wind speed for a QR5 is 5m/s."
But they were willing to sell one to go on this site, maybe
just for "demonstration purposes"?
Reliability is very important since the kilowatt hours of
energy generated will depend on the hours the turbine is
available. The QR5 is out of action so far as I am aware due
to problems with the blade attachments. Vertical axis
turbines do have intrinsic fatigue problems which along with
the problems of starting and stopping, and the problems of
putting them on proper towers have made them a poor choice
for wind energy.
The turbine is a nice size (5m high x 3.1m in diameter) but
in relation to its cost it will not produce much energy even
on a good 5 m/s site. The turbine alone costs £25,000.
It does not matter how efficient it is it can never produce
more than about 12,000 kWh per year at a 5m/s site, and the
manufacturers claim 7,500 kWh per year. A HAWT of similar
size and a fraction of the cost would do the same.
Nice ornament? Or a big waste of money, and another big
embarrassment to the small wind industry?
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E-mail me at: hugh@scoraigwind.co.uk