Dr Sarah Myhill MB BS, Upper Weston, Llangunllo, Knighton, Powys, Wales, UK LD7 1SL
Tel: 01547550331 Fax: 01547550339 E-mail: firstname.lastname@example.org Website: www.drmyhill.co.uk
September 3rd 2008
Welsh Assembly Government
CF10 3NQ Your ref: FoI 36/ATI 2761
Dear Mr Burr,
Re: Request for Information – FoI 36/ATI 2761
Thank you very much for your letter of 18th August 2008 in response to my request for
information with respect to carbon savings on wind farms in Wales, and in particular carbon
equation undertaken for Cefn Croes.
In your reply to my letter you kindly send me a Ministerial Briefing note from Havard
Prosser, Chief Environmental Science Adviser ref MB/JD/0515/08.
I would like to put the following questions to Mr Prosser arising from the Ministerial
1. What is the evidence base for the statement that the average output of a turbine is
30% of peak capacity? My figures indicate that the figure is nearer 24.2% and that
very few wind farms in Wales achieve a load capacity of 30%.
Although the British Wind Energy Association has for years claimed that a 30% load factor
should be the basis for calculation, the BWEA’s Director of Communications wrote on
November 22, 2007, in a complaint to the BBC, that this figure is: “an arbitrary and
2. What is the evidence base for turbine lifetime being 25 years? We know historically
from turbines here in Mid-Wales that they rarely last more than 12 years.
3. What figure is Havard Prosser using for the capacity credit? This is variously
calculated by BERR at 15% and E-on at 10%. As wind generated power comes on-
line, other sources of generation have to be turned down to accommodate this. There
is a further loss of efficiency from such conventional power back ups as well as
increased wear and tear within conventional generation. What is the carbon cost of
4. What are the electricity losses in transmission between generator and consumer? This
is likely to be large and explains, of course, why most power stations are sited close
to consumers, i.e. immediately outside cities and towns. This is reflected in the
transmission costs of electricity which are much higher for sites distal to consumers
compared to sites proximal. What percentage of electricity is lost per mile of
transmission line? So if, for example, a power source generates 100MW of power,
and the consumer is 100miles away, how much power does that consumer actually
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Registered office: Upper Weston, Llangunllo, Knighton, Powys, Wales LD7 1SL
5. What is the carbon cost of grid connection? This is likely to be significant since wind
farms are necessarily sited in remote areas. For example wind farm proposals here in
SSA C Newtown South will require a 400KV connection from Oswestry. What
would the carbon cost of such a construction be?
6. What is the carbon cost of the necessary highways upgrading required to import
turbine parts at the business of manufacturing and construction of wind farms? For
example wind farm proposals here in SSA C Newtown South will require extensive
highways upgrading to import turbine parts. What is the carbon cost of such
7. With respect to Cefn Croes, you have made a calculation for loss of carbon in soils
and you come up with a figure which indicates that carbon loss from soil and peat
would be covered by the electricity generated by the wind farm in the first year of
operation. This figure is very much at variance with other comparable wind farm sites
built on peat using calculations established either by Renewable Energy Systems or
by the ECOSSE report 2007. Please, can you send me the algorithm and calculations
that you made in order to justify this figure?
8. I note that the Ministerial Briefing omits to put in the carbon cost of building and
construction. I know from the recent wind farm applications at Llandinam that it is
estimated that the carbon cost of building and construction is likely to take 3.5 years
of electricity generation to be recovered. Do you agree with this figure?
I look forward to receiving this information as a matter of urgency because it is my view that
wind farm developments are not carbon friendly.