Offshore wind generation may still be somewhere far over the horizon in Australia, with plans for 2GW off the coast of Victoria and 1.1GW in Western Australia, but that only gives local developers more time to see what works best in other markets.

More than 20GW of offshore wind projects are operating worldwide, with the UK, Germany and China leading the field.

The big difference from onshore wind is that turbines used in offshore projects are bigger (and louder) than landed technology. Siemens Gamesa’s latest issue is a 14MW wind turbine due for commercial release later this year. A Rystad Energy analysis shows that although they are more expensive to manufacture, choosing these giant turbines actually reduces overall costs for large-scale offshore wind farms because you need fewer of them.

For every project, there is also the cost of making foundations on the seafloor, so the reduction in the number of turbines will also lead to fewer array cabling runs, which in turn reduces the installation scope.

Rystad Energy analyzed the cost of using turbines of differing sizes for the case of a 1GW offshore project. The Siemens Gamesa 14-222 DD model will leapfrog GE’s new 12MW Haliade-X prototype and become the largest turbine available. The largest turbines to be commissioned between 2020 and 2021 have capacities of up to 10MW.

Towering teenager

By deploying 14MW turbines instead of 10MW ones, the number of units required for a 1GW project falls from 100 to 72, or 28 units. Moving to a 14MW turbine from a 12MW turbine offers a reduction of nearly 11 units. Overall, the analysis shows that using the largest turbines for a 1GW offshore plant offers cost savings of nearly $US100 million versus installing 10MW turbines.

“With larger turbines come greater savings in other project segments and greater revenue generation potential over the duration of future projects, increasing the offshore wind industry’s competitiveness,” says Rystad Energy product manager for offshore wind Alexander Flotre.

Rystad assumes the cost of a turbine is about $US800,000 per megawatt for units up to 10MW, with a 2.5% premium applied for each additional megawatt for the larger units expected in the medium-term.

The analyst estimates the cost of a 10MW turbine is $US8 million, while a 12MW and a 14MW turbine would cost about $US10.1 million and $US12.3 million.

Foundations are the main components that offer opportunities for cost reductions if larger turbines are utilized, and Rystad estimates a foundation costs between $US3 million and $US4 million. “In a 10MW to 14MW switch, such cost savings could surpass $US100 million for the developer, while savings in a 12MW to 14MW scenario would likely range from $US30 million to $US50 million,” the analyst says.

Cut costs

While the use of larger turbines implies potential cost savings through fewer foundations, the added length required for array cables for 14MW turbines is likely to keep overall cable costs flat. However, the lower turbine count reduces the number of cabling runs and connection of turbines to the offshore substation, which in turn could cut installation costs.

“This example shows that while larger units are expected to drive up the cost of turbines, reductions from other segments – namely foundations – could result in cost savings of $US100 million to $US120 million on manufacturing alone, helping to offset some of the developer’s expenses,” the analyst says.

The cost to install a turbine ranges between $US500,000 to $US1 million, while the cost of foundation installation ranges from $US1 million to $US1.5 million per unit. For a 1GW project the implied savings surpass $US50 million if using 14MW instead of 10MW units, Rystad estimates. “Under similar circumstances but comparing 14MW against 12MW turbines, potential savings are beyond $US20 million.” The reduction in cabling runs and connections due to the lower number of array cables could lead to additional savings of $US5-$US15 million when using 14MW turbines rather than 12MW and 10MW.

A reduction in units can also lead to lower levelized cost of energy (LCOE). Using Equinor’s Empire Wind plant in the US as a case study, Rystad found LCOE of about $US75/MWh using 10 MW turbines, about $US71/MWh using 12MW units and $US68/MWh using 14MW turbines. “With the incremental increases in size, turbines and offshore wind plants become more economical – not just in lower upfront costs, but also in longer-term power generation potential.”