Offshore wind turbines are growing fast. MHI Vestas officially launched their 9.5 MW turbine with 164 m rotor diameter in June at the WindEurope Offshore Conference. For many of the participants, this was a bit of a disappointment, since they were hoping to get news of even bigger turbines. The two candidates to release such news were Siemens Gamesa and Senvion. But both were reluctant to discuss any details of their future turbine types – if any. Senvion told they are working on “something bigger”, but no dates neither exact figures were mentioned.

Husum Wind Fair 2017 will be held next week. Rumors are already circling around whether one of the two companies will show up there with a new turbine model having a double-digit generator nameplate capacity. There are grounds for such expectations, especially after Siemens Gamesa’s recent decision to integrate Adwen within the group’s offshore operations. The Adwen 8 MW prototype turbine with 180 m wing span is now in operation, and it’s pretty obvious that 8 MW is not the optimal nameplate figure for a 180-m diameter offshore turbine; the MW-figure should rather be in the range of 10 to 12 MW. And it’s equally obvious that to keep – or win back – the pole position for the coming sales negotiations, Siemens Gamesa should publish something clearly bigger than 9.5 MW, and they should do so pretty soon. If not in Husum, then perhaps in their new Strategic Plan, to be announced on 15 November.

In the latest German offshore auction earlier this year, DONG and EnBW made their winning bids based on the assumed financial figures for 13…15 MW turbines, which they expect to be on the market by 2025. Obviously, experienced offshore heavyweights won’t make their bets without having a close dialogue with the leading turbine suppliers. So, although the suppliers don’t admit it, they already have the next generation of even bigger turbines on their drawing boards.

Doubling the turbine nominal capacity makes a huge difference for the construction and operation of offshore wind farms. A turbine twice as powerful does not cost twice as much. And, more importantly, although it needs a bigger foundation, the foundation will definitely not cost twice as much. For sure, bigger turbines need bigger installation vessels with higher daily rates – but the number of installations will be halved. The result: shorter installation times per MW, more manageable weather risks, and all in all, more degrees of freedom in the construction planning. Also the number of service visits per MW will be halved, which makes a huge difference in demanding offshore conditions: Easier service planning, less downtime, and thus more kWhs per installed MW. And many, many more upsides for the project economy.

Bigger turbines can be built cost-efficiently in deeper waters, and with an increased spacing between turbines, the micrositing can be improved in terms of wake losses, soil conditions, and environmental constraints. For ice infested waters, the increasing turbine size is especially good news: as the wind loads increase, the significance of ice loads on the foundation cost decreases. Areas with more severe ice conditions located further offshore will suddenly become viable for construction. This in turn should make the public acceptance less of an issue and could thereby decrease the permitting risks.

But there are also challenges: Matching the time span of project development with the speed and uncertainty of technology development is a tricky task. How should you plan and permit your project, a process taking minimum five years and possibly up to ten years, when you don’t know how big – and thus, how many – turbines will be built once the permits are finally in place? You don’t want to end up having permits for a turbine that was phased out from production two years ago – a scenario which e.g. the French offshore developers may be facing in the future.

New offshore markets are opening up in the USA, China, India, etc. With 10 to 15 MW turbines, the zero-subsidy market is now within reach. Offshore wind may become a global and truly commercial market in 5 to 10 years. But to succeed, developers must first overcome the planning dilemma. Spatial planning and impact assessment processes should be made in a flexible manner to manage the uncertainties related to size and siting of individual turbines. Stakeholder dialogue is the key: all involved authorities and specialists should work together towards the common goal – even when shooting a moving target.

For a market characterized by long lead times from initial planning to implementation, technical revolution is not just a blessing but also a challenge. Size matters, and unfortunately not only for the better.