UK wind farm performance 2005, based on Ofgem ROC Data

1. UK wind farm performance 2005, based on Ofgem ROC Data Authors: J. Oswald M. Raine H. Ashraf-Ball E. Murphy 1st Nov 2006

2. Contents ROCs & Ofgem Capacity Factor and Installed Capacity Data sets Wind turbine characteristics Results UK Annual Capacity Factor, 2005, compared to Spain, Germany and Denmark Map of annual wind turbine Capacity Factor Regional Analysis 2005 Annual Capacity factor by Region Monthly Capacity factor by Region Regional contribution to UK monthly wind total

3. ROCs & Ofgem • ROCs are the Renewable Obligation Certificates granted for each MWh of electricity produced by an accredited renewable generator in the UK. The accreditation and management of the ROC system is carried out by Ofgem. Each ROC has a value to its owner and can be sold or traded. The average value of each ROC since 2002 has been £45.50/MWh, ref Non-Fossil Purchasing Agency Ltd http://www.nfpa.co.uk/ • Ofgem publish the ROCs claimed by renewable generators in their ROC register and this can be accessed through their web site at • http://www.ofgem.gov.uk/ofgem/work/index.jsp?section=/areasofwork/renewrocregister • However, it is difficult to access a summary of this data and the work here aims to present this data in a fair and concise way and then draw conclusions on the performance of the established wind industry in the UK • Date of download • For the purposes of this summary all ROC data for stations over 50kW was downloaded from the ROC register in May 2006. This provided a complete set of ROCs 2005. • Duplicate entries • Ofgem advised us that some accredited sites split their monthly ROCs for commercial reasons. They advised us to sum the monthly ROC values for these sites to obtain the total ROCs claimed for the site

4. Capacity Factor & Installed Capacity • Capacity factor (or load factor) is the proportion of energy produced over a time period compared to the energy produced if operating continuously at full power • CF in a month = MWh produced in month / (number of hours in month * Installed Capacity) • e.g. for a 10 MW wind farm operating in January which produced 3000 MWh • CF = 3000/(10*31*24) = 40.3% • Capacity Factor is an easy way to summarise and compare the effectiveness of different wind farms. • The UK has the highest CF in Europe as it is located in the windiest place, as shall be illustrated • Installed capacity • The installed capacity for each wind farm was obtained from the Ofgem list of accredited RO generators which was downloaded from Ofgem web site in May 2006. This gives the latest installed capacity for each site which may not have been the installed capacity earlier in the year as wind turbines are sometimes added, removed or altered. It was not possible to obtain the historical levels of installed capacity and so calculations of capacity factor have been based on the latest installed capacity and then best endeavours have been made to cross check the installed capacities with generators

5. Good and imperfect data sets • The wind farm data has been grouped into two data sets • The ‘Good data set’ which contains wind farms with 12 months of ROC values for 2005 (shown on the map as green dots). This data has been used for all further analysis. There are 93 out of a total 163 wind farms in this set. • The ‘Imperfect data set’ which contains wind farms which do not have 12 months of ROCs for 2005. (shown as red dots). They are typically new wind farms. These wind farms have been discarded from the annual 2005 analysis • UK offshore data • There are two significant offshore sites, North Hoyle (off North Wales) and Scroby Sands (off Great Yarmouth). These are interesting and are included as their own region, even though they are on opposite coasts. Data taken from summary reports obtained from DTi web sitehttp://www.dti.gov.uk/

6. Wind turbine basics • The power in the wind is given by • Note that power is a cubic function of wind speed. This makes power very, very sensitive to speed • A wind turbine takes only a proportion of this wind power • Above 13 to 15 m/sec the turbine blades are feathered to spill the wind. This gives the flat power characteristic shown • Above 25 m/sec the forces on the wind turbine become unacceptable and all the wind is split and the turbine shutdown in a controlled manner • Doubling wind speed from 5m/sec to 10 m/sec increases power from 6% to 73% of rated output, a 12 fold increase. • This is illustrates how sensitive power is to wind speed. Wind speed is related to the location of the turbine is • Cliff tops are better than valleys • Open flats are better than built up areas • Scotland is windier than England

7. Results

8. UK Annual Capacity Factor, 2005, compared to Spain, Germany and Denmark • The derived average UK capacity factor for 2005 is 28.4% • This is based on the ‘good data set’ which uses only wind farms with 12 months of returns and the installed capacity as published by Ofgem • By comparison, the DTi figure for 2005 on an ‘unchanged configuration basis’ is 28.2%, • Ref: Table 7.4, Digest of United Kingdom Energy Statistics 2006, URN No: 06/87 • These are higher than Spain, Germany and Denmark • Spain, ref: Red Electrica de Espanawww.ree.es • Germany, ref: EoN Netz 2005 Wind Reportwww.eon-netz.com • Denmark, ref email from Hugh Sharman www.incoteco.com

9. Annual Capacity Factors • The annual capacity factor has been calculated for each wind farm in the good data set • They are summarised on the attached map. • Green dots had annual 2005 capacity factors exceeding 28% • Blue dots had annual 2005 capacity factors between 23 and 28% • Red dots had annual 2005 capacity factors below 23% • The capacity factor for every wind farm (in both the good and imperfect sets) have been determined by month and are reported and available on the REF web site at wwwREF1pagesummaries

10. Regional wind analysis results - 2005 Clusters of wind farms have been grouped into eight convenient ‘regions’ to allow understanding of performance across the country. The capacity factor for these wind farms is compared for 2005

11. Region 1 - Cornwall Region 1 - Cornwall Bears Down Reservoir - best performing site 2005 Capacity Factor for Cornwall: 24.1% Total installed generating capacity for Cornwall: 42 MW 2005 Capacity Factor UK: 28.4% Total installed generating capacity UK (in good data set) : 902 MW Capacity factor variations are consistent across this region.

12. Region 2 – Mid-Wales Region 2 – Mid-Wales 2005 Capacity Factor for Mid-Wales: 23.8% Total installed generating capacity for Mid-Wales:112 MW 2005 Capacity Factor for the UK: 28.4% Total installed generating capacity UK (good data set): 902 MW This line represents a single wind turbine at the Centre for Alternative Energy. This is a 75kW Vestas turbine. Small wind turbines (say below 400 kW) use less advanced aerodynamics and control and are therefore have lower capacity factors

13. Region 3 – Yorkshire Dales Ovenden Moor – best performing site Region 3 – Yorkshire Dales 2005 Capacity Factor for Yorkshire Dales: 24.9% Total installed generating capacity for Yorkshire Dales: 27 MW 2005 Capacity Factor UK: 28.4% Total installed generating capacity UK (good data set): 902 MW Chelker Reservoir uses WEG300 units installed in 1992 (300 kW ). Turbines of this age are likely to have low efficiency and low availability. Other operators have replaced WEG300 units.

14. Region 4 – Cumbria Lowca – best performing site. The average 2005 capacity factor is, 34.5%, which is almost 1.5 times the capacity factor at Siddick which is only 2.3km away. This may be because Lowca is on top of a 50m cliff overlooking the sea whereas Siddick is lower down on the beach front. Region 6 - Cumbria 2005 Capacity Factor for Cumbria: 25.9% Total installed generating capacity for Cumbria: 48 MW 2005 Capacity Factor for the UK: 28.4% Total installed generating capacity UK (good data set): 902 MW

15. Region 7 – Durham and South Northumberland Region 5 – Durham and South Northumberland Hedley Hope – best performing site. On a ridge between 2 valleys. 2005 Capacity Factor for Durham: 24.0% Total installed generating capacity for Durham: 10MW 2005 Capacity Factor for the UK: 28.4% Total installed generating capacity UK (good data set): 902 MW Blyth Harbour is on the coast, near to another, much better performing wind farm. This site was built in 1992 and is relatively old. (300 kW, Windmaster units, 30m hub height) This site is at the GSK pharmaceutical plant in Barnard Castle, in a relatively built up area. It employs second hand turbines.

16. Region 5 – Southern Scotland Region 6 – Southern Scotland Hare Hill has a capacity factor which is around 1.5 times the capacity factor at Gallow Rig which is a site at a similar location. It is not known why. 2005 Capacity Factor for Southern Scotland: 31.5% Total installed generating capacity for Southern Scotland: 230 MW 2005 Capacity Factor UK: 28.4% Total installed generating capacity UK (good data set): 902 MW

17. Region 4 – Caithness, Orkney and the Shetlands Region 7 – Caithness, Orkney and the Shetlands Shetland has exceptionally good wind resource with an annual capacity factor double the UK average 2005 Capacity Factor for Caithness, Orkney and the Shetlands: 33.0% Total installed generating capacity for Caithness, Orkney and Shetlands: 62 MW Spurness is a new wind farm officially opened in March 2005. This may account for it’s low CF at the beginning of the year. Fair Isle has two very small wind turbines, one of 60kw and one of 100kw. The 60kw turbine was commissioned in 1982 and so is very old. 2005 Capacity Factor UK: 28.4% Total installed generating capacity UK (good data set) : 902 MW

18. Region 8 – Offshore 2005 Offshore Capacity Factor: 32.6% Total offshore installed generating capacity: 120 MW 2005 Capacity Factor for the UK: 28.4% Total installed generating capacity UK (good data set): 902 MW Average = 36.2% Average = 29.0% • North Hoyle and Scroby Sands are relatively new and began generating in Spring/Summer of 2004. North Hoyle is off north Wales and Scroby Sands is on the opposite coast, off Great Yarmouth. • Information has been obtained on their performance from the summary reports published on the DTi web sitehttp://www.dti.gov.uk/. This shows that availability was low and analysing this data shows that had availability been 90% in 2005 then capacity factors would have been 39.2% at North Hoyle and 31.9% at Scroby Sands

19. Annual Capacity factor by Region North Hoyle and Scroby Sands (which are on opposite sides of country).

20. Monthly Capacity Factor by Region, 2005