Offshore wind industry to increase array voltage

Companies in the offshore wind industry have announced plans to increase voltage of the power cables in arrays from 66kV to 132kV.

They said the rise in voltage will improve the efficiency of electricity collection, facilitate the deployment of larger, more powerful turbines, and lower costs and environmental impacts by reducing the length of cables.

The decision to increase voltage of offshore wind farms to 132kV was result of a project by the Offshore Wind Accelerator (OWA) – the Carbon Trust’s flagship research and development programme.

The High Voltage Array Systems (Hi-VAS) project began in 2020 and involved more than 70 organisations including suppliers, energy systems operators, marine planners, policy maker and regulators. Among the partners on the project were Orsted, Equinor, RWE, Scottish Power Renewables, Shell, SSE Renewables, Vattenfall, Total Energies, EnBW and Ocean Winds.

Based on their input, the project conducted a series of engineering studies to assess a range of possible array voltages and how they would affect wind farm design. Of the voltages considered, 132kV was found to have the best cost-benefit ratio and the lowest risk profile.

The last voltage shift began in 2010 when the OWA, in collaboration with nine leading offshore wind developers, drove the change from 33kV to 66kV, enabling the installation of turbines in the 8-12MW range.

The Carbon Trust said the jump to 132kV is expected to bring significant costs savings, amounting to between £32 million and £50 million for a 1,200MW wind farm.

Given the “dramatic” savings of offer, the organisation emphasised the urgency of bringing 132kV technologies to market, saying “it is critical no time is lost”. It said the first 132kV wind farms are expected to be operational by the end of the 2020s at the earliest, but even this timing is dependent upon significant proactive work by developers and the supply chain.

Stephen Loft, electrical department manager at Scottish Power Renewables, said: “In order to provide cheaper green energy to everyone quicker, doubling the voltage of our wind farm cables is essential.  The global offshore wind industry will benefit immensely from increasing the voltage to 132kV.

“Doing so will unlock cost savings by reducing cable lengths and reducing electrical losses.  Further, it will enable the next generation of wind turbines to be brought to market, which will provide step-change cost savings for the industry. Reducing cable length offshore will also reduce the environmental footprint of offshore wind farms.”

Jan Matthiesen, director of offshore renewables and maritime decarbonisation at the Carbon Trust, said: “The Hi-VAS project is a great example of the Carbon Trust’s collaborative R&D approach.  It shows that building consensus amongst the major global offshore wind farm developers can quickly and efficiently create de facto standards in the industry, giving great clarity to the supply chain.

“This in turn allows the global offshore wind industry to rapidly uptake technological step changes, which is necessary to accelerate offshore wind development and meet net zero climate targets globally.”