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
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• 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

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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?secti
  on/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

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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/(103124) 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

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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 site
  http//www.dti.gov.uk/

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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

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Results
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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 Espana www.ree.es
• Germany, ref EoN Netz 2005 Wind Report
  www.eon-netz.com
• Denmark, ref email from Hugh Sharman
  www.incoteco.com

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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

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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

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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.
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Region 2 Mid-Wales
2005 Capacity Factor for Mid-Wales 23.8 Total
installed generating capacity for Mid-Wales112 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
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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.
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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
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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.
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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
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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 its 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
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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 site http//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

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Annual Capacity factor by Region
North Hoyle and Scroby Sands (which are on
opposite sides of country).
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Monthly Capacity Factor by Region, 2005