Chick, J. P.

Harrison, G. P.

Thomson, R. C.

English

Estimates of the greenhouse gas (GHG) emissions savings that arise from wind power replacing other types of generation are used to support wind farm developments and calculate carbon payback time. Currently these savings are approximated as the average emissions of electricity generation in the UK. However, this assumes that wind power replaces all different forms of generation equally, which is not the case. Instead, it mostly replaces electricity from coal and gas-fired stations; suggesting that actual emissions reductions are higher than current estimates. Conversely, any savings may be limited as a consequence of efficiency penalties at the power stations responding to the availability of wind power.This poster presents an analysis of detailed operational data for the National Grid in 2012, identifying the half-hourly marginal changes in GHG emissions attributable to corresponding changes in wind output. The resulting emissions savings demonstrate that wind power is replacing coal and gas, but that efficiency penalties at these power stations reduce the emissions savings to a value close to the UK average grid emissions. This work is a significant step towards a robust and reliable figure for the historical offset of wind power generation and confirms that existing carbon payback estimates are valid.<br/

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     Edinburgh Research Explorer                                      Greenhouse Gas Emissions Savings from Wind PowerCitation for published version:Thomson, RC, Harrison, GP & Chick, JP 2013, 'Greenhouse Gas Emissions Savings from Wind Power'Global Energy Systems Conference, Edinburgh, United Kingdom, 26/06/13 - 28/06/13, .Link:Link to publication record in Edinburgh Research ExplorerDocument Version:Author final version (often known as postprint)General rightsCopyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s)and / or other copyright owners and it is a condition of accessing these publications that users recognise andabide by the legal requirements associated with these rights.Take down policyThe University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorercontent complies with UK legislation. If you believe that the public display of this file breaches copyright pleasecontact openaccess@ed.ac.uk providing details, and we will remove access to the work immediately andinvestigate your claim.Download date: 20. Feb. 2015Tarong Coal-Fired Power Stationc.thomson@ed.ac.ukDO WIND FARMS REALLY REDUCE CO2 EMISSIONS?Greenhouse Gas Emissions Savings from Wind PowerR Camilla Thomson, Gareth P Harrison and John P ChickInstitute for Energy Systems, University of EdinburghImages courtesy of www.sixdegrees.org.au and Leaflet at commons.wikimedia.orgReferences: 1. Advertising Standards Authority, “ASA Adjudication on RWE npower plc”, 10th October 2007, from http://www.asa.org.uk/Rulings/Adjudications/2007/10/RWE-npower-plc/TF_ADJ_43298.aspx2. Hawkes, A.D., “Estimating marginal CO2 emissions rates for national electricity systems”, Energy Policy, vol. 38, pp 5977-5987, 20103. Elexon, “Elexon Portal – BMRA Data Archive”, Retrieved February 2013 from www.elexonportal.co.uk/bmradataarchive, 2013There is currently no reliable estimate for the reduction in GreenhouseGas (GHG) emissions attributable to wind power generation. It isnormally taken to be the average emissions of UK electricity, despiteacknowledgements that this is decreased by low-carbon nuclear energy(Fig. 1) while wind mostly replaces marginal carbon-intensive coal andgas-fired generation1 (Fig. 2). This work estimates the true emissionssavings for 2012 by carrying out a short-term marginal analysis of realdata from the National Grid, taking into account the efficiency penaltiesfor operating conventional plant at part load (Fig. 3). The method, basedon that developed by Hawkes2, examines the relationship between thehalf-hourly changes in power outputs and GHG emissions to extract therelationship between changing emissions and wind generation (Fig. 4).BackgroundConclusions• Reliable figures for the actual emissions savings of wind power willsupport carbon payback calculations and inform policy decisions.• Wind power is mostly replacing carbon-intensive coal and gas-firedgenerationResults• This analysis was based on historic generation data aggregated by fueltype, with part load curves for coal and CCGT plant developed fromdata from the Balancing Mechanism3.• With fixed values applied for the GHG intensities, the averageemissions savings were 0.72 kg CO2e/kWh for 2012 (Fig. 5)• When efficiency penalties are considered (Fig. 3) the averageemissions savings are found to be 0.51 kg CO2e/kWh for 2012.• This work does not yet include a reliable model for start-up and shut-down situations, and thus may overestimate the efficiency penalties.Fig. 2 – Total generation by fuel type, 9th December 2012Fig. 3 – Effect of efficiency penalties on GHG intensity Fig. 4 – Planar fit to estimate marginal emissions savingsFig. 1 – Comparison of GHG IntensitiesFig. 5 – Comparing monthly and average emissions savingsFurther WorkModels of the GHG emissions during start-up and shut-down need to be developed tofurther, but the efficiency penalties of operating these at partload mean that the GHG emissions savings are not as high as mightbe expected.• The actual emissions savings are higher than the value currentlyused to calculate carbon paybacks, suggesting that currentestimates are valid and wind farms really do reduceCO2 emissions.refine the results. The analysiswill then be extended to consider dataover a longer time period, to identifywhether there is a relationshipbetween the increase in windcapacity and the GHG emissionssavings.

Greenhouse Gas Emissions Savings from Wind Power

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