The Case against Windfarms

The Case Against Windfarms is an authoritive, referenced document written by Dr John Etherington ( © Dr JR Etherington).

The views expressed are those of the author, who is a professional environmental scientist, formerly Reader in Ecology at the University of Wales. It is freely offered for reproduction or other use providing it is acknowledged. Our website contains the complete document, which consists of 18 Sections, 2 Appendices and References/Notes. The full list is shown on the Home Page, and also at Case Sections

The website also contains a web page devoted each separate section, of which this is one. These pages start with a copy of the relevant section of the full report, followed by links to a series of articles, news items, research papers and reports which are relevant to that topic. Note that these items have been compiled by Country Guardian and are not part of Dr Etherington's paper

5. Calculating CO₂ emissions and saving

Saving of CO₂ emission by individual onshore wind turbines

One megawatt of wind power installed capacity generates 0.3 MW assuming a generous load factor of 30%.

 The annual electricity yield of this would be 0.3 x 365 x 24 = 2,628 MWh/y

 According to BWEA, if this electricity displaces 'dirty coal' generation it will save 0.86 tonne CO₂ /MWh  (http://www.bwea.com/edu/calcs.html ) so the 1.0 MW of installed capacity would save: -

 2628 x 0.86 = 2,260 tonne CO₂ /year.

 Both DTI and the Sustainable Development Commission utilise a much lower factor for CO₂ emission per MWh – also upheld by a recent Advertising Standards Authority (ASA) adjudication.

 The more truthful value for saving of CO₂ emission is based on the current generating mixture of fuel used to produce electricity (gas firing is much less CO₂-dirty than coal and nuclear power emits no CO₂) (Etherington 2003).

 DTI

 In a letter to an MP representing Humberhead Against Turbines (2005), Mike O’Brien (Energy Minister at time) agreed that: “it would be appropriate to use an average generating mix when calculating CO₂ savings from a wind turbine. This is consistent with DTI Wind Energy fact sheet 14.” Mike O’Brien’s letter and notes were presented in evidence at the Whinash Inquiry (2005) and are thus in the public domain.  

 The current “average generating mix” gives about 0.43 tonne CO₂ /MWh, just half of the saving claimed by BWEA (DEFRA  Fuel Conversion Factors http://www.defra.gov.uk/environment/business/envrp/gas/05.htm).

 ASA

 An adjudication of 21 December 2005 against Renewable Energy Systems (RES) concluded “although an emissions factor of 860g CO₂/kWh might have been a reasonable figure for RES to use to calculate the reduction of CO₂ emissions at the present time, it was not a reasonable figure to use for calculating the reduction over a period of as long as 25 years without some qualification to indicate the uncertainties about future fuel generating mix.” 

Sustainable Development Commission (SDC)

The SDC’s report Windpower in the UK (see November 2005 corrected edition) also suggest that future projections of saving must be based on a lower figure than BWEA’s 0.86 tonne CO₂ /MWh

 “There are large differences between the CO2 emissions associated with coal (243 t C/GWh) compared to natural gas (97 t C/GWh), with none associated to nuclear power.” [these two factors convert to 0.89 t CO₂ /MWh and 0.36 t CO₂ /MWh ]

 SDC continues: - for the purpose of this report, it has been assumed that wind output will displace the average emissions resulting from gas-fired plant… it is the figure that the DTI use and is used here so that the carbon benefits of wind power are not overestimated."

 “The figure that the DTI uses” is currently 0.43 t CO₂ /MWh (see above)

 Thus, calculated on current generating-mix, 1.0 MW of installed windpower capacity displaces no more than: -

 2,628 x 0.43 = 1,130 tonne CO₂ /MWh

 Because of the rather ‘reserved’ wording of the ASA adjudication it is wise only to use the 0.43 tonne CO₂ /MWh to estimate saving over the whole life of the 'farm' (20 to 25 years).

Payback time for energy and CO₂

Generally speaking the wind power industry has correctly observed that a wind turbine pays back the energy consumption of its construction and the accompanying CO₂ emission within a few months (DWTMO 1997).

 The cash cost of a wind turbine is a very different matter and arguably without enormous subsidy a wind turbine cannot pay back its financial cost in a reasonable time-frame. This is because a large proportion of the cost derives from value additive operations such as the complex engineering of the drive train and generator and the specialist fabrication of blades which are expensive but do not consume much energy – which is largely absorbed in the smelting of iron and its conversion to steel and to a lesser extent, manufacture of other metals..

 In the case of wind ‘farms’ on deep peat, especially if site operations such as road construction cause drying of previously waterlogged peat, there may be substantial CO₂ emission from its oxidation. This has been specifically observed by the Environmental Management Committee at Cefn Croes which wrote: - “… oxidation of exposed peat was leading to a huge loss of carbon to the atmosphere, and mitigating the impacts of the Wind Farm from a Global Warming perspective.” Despite this, even if serious peat oxidation occurs, the displacement of fossil fuel electricity by wind turbines will outweigh the construction energy and carbon emission within a year or two.

Extra CO₂ from backup

 It is remarkably difficult to calculate the amount of CO₂ which is liberated from power stations which backing-up renewable electricity generation. This amount must be subtracted from the theoretical saving of CO₂ emission.

 Wind power is supported by thermal generation which is operating below peak generation and can be ramped up to cover losses of generation when the wind. This causes fuel inefficiency and emission of extra CO₂ per unit of electricity generated by the backup.

 At the present the backup is taken from the existing reserve capacity used as insurance against plant and transmission failure. The wind power industry, unfairly, has argued that because the backup is pre-existing, there are no CO₂ costs.

Be that as it may, it is not a situation which will persist. Once the demands of wind power for cover for its full installed capacity are sufficient to call upon a large proportion of existing reserve it will be necessary to build dedicated backup and it is this requirement that prompted the Irish National Grid, ESB (2004) to conclude, as previously quoted,  that: -

“As wind contribution increases, the effectiveness of adding additional wind to reduce emissions diminishes…The cost will be very substantial because of the back up need.”

 At least some power engineers have attempted to calculate CO₂ costs in these circumstances (Bass & Wilmott 2004). They claim, for a worst-case scenario, that their analysis “suggests that the current ‘Dash for Wind’ could actually make the situation worse.”

 Relevant articles, news items, papers, reports

Green Places - Summer 2005

Angela Kelly wrote this article for the magazine Green Places

Report doubts future of wind power and The Menaced Landscape

Two articles from The Guardian, 26 October 2005

When the wind blows

Article by Angela Kelly in the Faculty of Building Journal, October 2000

REDUCTION IN CARBON DIOXIDE EMISSIONS: ESTIMATING THE POTENTIAL CONTRIBUTION FROM WIND-POWER

A Report by David White, BSc, C Eng, F I Chem E: Commissioned and published by the Renewable Energy Foundation December 2004