Pen y Cymoedd Wind Farm

Case study 13855

Name of Client and Location: Pen y Cymoedd Wind Farm Project, Upper Rhondda, Wynon and Afan Valleys, Wales
Project Value: £400 Million
Duration of the Project: 38 Months
Market Sector: Renewable Energy
Powersystems Fact: Powersystems your high voltage specialist partners – Powersystems Renewable Energy team have connected 27% of all U.K. land based wind farm generation

Scope of work and major design considerations:

In 2015 Natural Resources Wales (a Welsh Government sponsored body), signed a lease agreement with Vattenfall of Sweden. And its British-based subsidiary Vattenfall United Kingdom (formerly Nuon Renewables).

At the time, this was to develop what would be the UK’s highest altitude wind farm, on a site owned by Natural Resources Wales, previously the Forestry Commission Wales.


The project

The project saw the installation of 76 wind turbines with a peak power of 228 MW and planned to operate for 25 years. This was to generate up to 0.6 TWh/yr, an amount enough to power up to 140, 000 homes, with an annual consumption of 4266 kWh. The turbine manufacturer is Siemens Wind Power. During the planning process, Vattenfall (at that time: Nuon) agreed to contribute about £1.85m annually to a community fund. As well as to invest £3m in a habitat restoration scheme. 


Project facts and figures:

  • Number of turbines: 76
  • Wind turbine capacity: 3 MW
  • Total installed capacity: Up to 228MW
  • Connection to Grid:  New substation located on the Hirwaun Industrial Estate (underground cables)
  • Size of site: 4,683ha
  • Energy for 140,000 households
  • Length of onsite access tracks: 80km
  • Length of onsite cabling: 80km
  • Jobs supported: 600+
  • Total Investment in project to first generation: More than £400m
  • Annual homes equivalent production* Approximately 140,000 (enough electricity to meet the annual domestic needs of both Rhondda Cynon Taf (RCT) and Neath Port Talbot (NPT) councils combined)
Pen y Cymoedd Location of the Wind Turbines

*This figure is based on site specific data using the following calculation. Maximum installed capacity of the Wind Farm (228MW), multiplied by the number of hours in a year (8766), multiplied by the output capacity of the wind farm as a percentage (30%) [Renewable UK] divided by the amount of energy used by each UK home on average per year (4,266 kWh) [DECC].

Wind Farm project timings:

The project gained final planning permission in May 2012. The first turbine was fully completed in April 2016 and began generating electricity in autumn 2016. The final 76th turbine was installed on 2 March 201. The wind farm has been fully operational since 7 May 2017. The wind farm was officially opened in September 2017.

Wales’s largest onshore wind farm:

Pen y Cymoedd Wind Farm, is Wales’s largest onshore wind farm. Which started operating at full power, 38 months after construction started in the upper Rhondda, Cynon and Afan valleys.

The 76 turbine Pen y Cymoedd wind energy project is capable of meeting the electricity needs of more than 13% of households in Wales. It also boosts delivery of Wales’s climate change ambitions, displacing in an average year more than 300,000 tonnes of CO2 from fossil fuelled generation.

The generation site

The generation site consists of 76 Siemens SWP 3.0 direct drive wind turbines. The wind farm, with a total capacity of 228 megawatts (MW) generates at 33kV which feed into the Pen y Cymoedd Sub-Station, which steps up the voltage from 33kV to 132kV. A second sub-station some 9.2km away in Rhigos steps up the voltage from 132 to 400 kV to feed into a 400 kV National Grid substation.

The turbines were arranged in 11 Arrays of varying quantity of turbines over four regions of the site. The final region being completed and handed over operationally on 1st June 2017


What the client wanted:


Vattenfall is a European energy company with approximately 20,000 employees. For more than 100 years they have electrified industries, supplied energy to people’s homes and modernised their way of living through innovation and cooperation.

Their goal is clear: they want to make fossil-free living possible within one generation. Climate change is a global challenge and therefore requires broader solutions. Vattenfall is one of the leading companies in renewable energy production.

They help their customers to be more energy efficient, and adopt smarter technologies to create their own electricity or heating and switch to cleaner alternatives that are affordable and easy to use.

Climate smart solutions

Vattenfall took one more step towards supplying climate-smart solutions with the launch of their largest onshore wind farm at Pen y Cymoedd. And by co-locating renewable energy production with associated storage facilities. Vattenfall aims to promote the transition to a new energy system. The 22MW system believed to be the largest co-located battery and wind farm project in Wales, provides a rapid-reaction grid reliability service to the National Grid. Known as Enhanced Frequency Response. The National Grid estimates enhanced frequency response contracts will save the consumer £200m over four years.

Producing and storing energy

Inaugurated on September 28, 2017. The goal was to supply 188,000 households with renewable electricity from wind power. Pen y Cymoedd would also become the largest commercial wind farm in Wales with a co-located battery facility for storing electricity. At the inauguration, Vattenfall’s CEO Magnus Hall stressed the importance of producing and storing energy at the same site. They want to continue growing in the renewable sector to become fossil free within a generation. With Pen y Cymoedd, and the possibility to store energy. They continue to transform energy production and find new and innovative ways to help customers and partners to be climate smart.

Pen y Cymoedd providing green energy to the equivalent of 15 percent of the households in Wales

Gunnar Groebler, heading Vattenfall´s Wind Business involving investments of EUR 5 billion over five years: “Pen y Cymoedd wind farm highlights a very important step for us. Successfully completing our largest onshore wind farm underlines that we are well on track with our ambitious goals in wind power. We are very proud, that Pen y Cymoedd will provide green energy to the equivalent of 15 percent of the households in Wales.

Now we are looking forward to equipping Pen y Cymoedd with additional battery storage capacity in order to support the grid integration of renewable energy we produce here in Wales.” In March, Vattenfall and the BMW Group signed an agreement for the supply of up to 1,000 lithium-ion batteries this year. The batteries, which have a capacity of 33 kilowatt hours (kWh) each, will be packaged and installed at Pen y Cymoedd in Q4 this year and deliver enhanced frequency response to National Grid hence help to integrate renewable energy to the energy system.



Pen y Cymoedd Switching Station

How  Powersystems helped:

Powersystems involvement started with soil resistivity readings being taken at all of the 76 turbine base locations, long before the construction got underway. From this data, the earthing studies were produced and the installation designs formalised.

  • Powersystems designed and installed the 33kV distribution from Pen y Cymoedd sub-station to the turbine cable terminations
  • This involved some 312kM of 33kV single core power cables, which required 2 x fibre optic network cables and earthing cables all laid into trenches alongside access tracks
  • Followed by commissioning, energisation, SAP control and up to hand-over of all the 33kV cabling from the Primary Sub-station to 76 turbines
    • requiring some 312kM of power cables
    • 27 x 33kV Sub-stations in high security GRP enclosures
    • full fibre optic network to all turbines
    • 27 sub-stations
    • 3 Met Masts, earthing (including necessary studies) on the completed site
    • testing and energisation 900 terminations
    • 33kV terminations conducted in total
      • 94 x 3ph in-line joints
      • 194 x 3ph T connections
      • 12 x 3ph Pfisterer connections
Pen y Cymoedd Cabling

The results:

Pen y Cymoedd facts and figures

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