Fast growth in the size of turbines is often cited as a major driver of cost reduction – that growth has been incremental to date, but statements by developers and by certification bodies such as DNV GL suggest much bigger units could soon be brought to market
Fast growth in the size of offshore wind turbines has been highlighted by Vattenfall, the developer of the proposed Norfolk Vanguard offshore windfarm in the UK, which is considering using turbines of up to 20 MW for the project.
Kicking off the consultation process for Norfolk Vanguard, Vattenfall said it was considering using between 90 and 257 turbines with generating capacity of 7–20 MW each for the project.
20 MW is far larger – more than twice the size – than any turbine currently installed on any windfarm and well beyond the size and generating capacity of those currently available.
The company is not committed to using any type or size of turbine at the moment but evidently feels confident that much larger turbines will be available within the project timeframe. Norfolk Vanguard would not be up and running until the mid-2020s.
The potential of much larger, new-generation turbines has been cited as one reason that the cost of offshore wind energy is falling so quickly, enabling low and zero-subsidy bids to become established.
The Swedish energy group has published its statutory consultation plans for the 1.8 GW Norfolk Vanguard project, known as a statement of community consultation. It has also set out, in a newsletter, its latest thinking on onshore infrastructure for the windfarm.
When up and running in the mid-2020s, Vattenfall says Norfolk Vanguard will produce enough fossil-free electricity every year to meet the equivalent annual electricity demand of 1.3 million UK households, almost 5% of UK household demand.
Norfolk Boreas, Norfolk Vanguard’s sister project, is in an earlier phase of the UK’s nationally significant infrastructure planning process, and its environmental impact assessment is ongoing.
At about the same time that the Norfolk Vanguard consultation got underway, DNV GL’s renewables certification manager confirmed to OWJ that his division is reviewing multiple turbines for certification that could generate more than 10 MW of power.
Siemens and MHI Vestas Offshore Wind were mentioned as two of three manufacturers with designs currently in front of the classification society.
“They’re all 10-plus MW. You can quote me on that,” said DNV GL executive vice president Dr Kim Mørk.
However, DNV GL senior consultant Eeke Mast said getting to a projected 20 MW turbine in the next five years could be “problematic”. Ms Mast works on comparative and conceptual cost assessments on offshore windfarms in the renewables advisory section at DNV GL.
“For our economics, we don’t go for 20 [MW]. But I would always be very careful not to say we would never go to 20,” Ms Mast said.
“[In an economic sense] in terms of both weight and cost of materials, [the optimal size] would be around 15.”
“You would need some kind of disruptive technology to go to that 20 [MW].”
Dr Mørk said one of the challenges in cutting manufacturing costs was the larger turbine blades needed. He said the blades require a great deal of manual work during production, which increases cost.
The cost of energy produced by offshore wind has seen a dramatic drop recently, and much of that drop has been attributed to the increase in the size and power of the turbines being produced.
MHI Vestas’s 9.5 MW turbine launched in June, and a number of analysts are predicting the possibility for 12–15 MW turbines in the foreseeable future.
DNV GL has recently released a forecast projecting an incremental increase in size for wind turbines annually, reaching the 20 MW mark by 2023.