By David Craik

As the number of offshore wind farms ramps up over the next few years, optimised wind farm design and layout will be pivotal to minimising operations and maintenance costs.

Mark Leggett, managing director of cable O&M group Global Marine Energy Systems, says that what seems such an obvious element in a wind farm project is currently only given limited consideration.

“The emphasis on O&M in a farm’s initial design can be improved. At present, each wind farm is looked at on a bespoke basis,” he states. “Investors and developers need to take a much more holistic approach about how portfolios of farms can be better connected and how their technologies can be more standardised.”

Leggett says he is currently engaging the industry through a series of seminars, in a bid to draw attention to the importance of O&M considerations in the early stages of wind farm design. He says progress is being made and that more consideration will be given as capacity increases and developers and suppliers become more concerned about mitigating long-term maintenance costs.

Developer Mainstream Renewable Power is one industry player already making waves in this area.

Lifecycle model

Joe Dalton, Mainstream Renewable Power’s operations manager, says the company is creating an ‘integrated life cycle cost model’ which would include O&M being factored into the overall life cycle of a wind farm project from day one.

“When you look at farshore farms in particular then O&M costs must be considered from the start of a project. It must be designed for maintainability and reliability,” he states. “The technology will be completely different in farshore farms than those in previous rounds and areas such as the accessibility of the turbines and shift arrangements for personnel will need a bigger focus.”

This, he argues, includes farshore farm designers having to consider fixed platforms and jack-up vessels to help O&M as well as single vessels.

“It will be a multi-pronged approach including a complete review of all present and future turbine component technology,” he explains. “Innovations such as electrical equipment located at the base of a tower so it is not subject to high levels of vibration should be embraced in the initial design of turbines in a farm. Air conditioning technology to keep the right components dry should also be looked at.”

The layout of farms, where and how turbines are located in relation to each other, will also be crucial to ensure travel time to turbines is not too lengthy for O&M purposes and to minimise the impact of turbulence on their performance.

However Dr Axel Birk, vice president business development offshore at REpower, points out that turbine manufacturers have little influence on how turbines are positioned because this depends on the specific conditions on site such as the wind and the seabead.

What REpower can control, however, is how it works with its customers and wind farm owners to improve maintenance and performance. Birk says: “We are using jack-up platforms for the installation as well as for service and maintenance work. What we try to achieve is that 2 boat landings per turbine becomes a standard. This would ensure that when you land with your ship that you avoid waves and dangerous currents.”

Safety and performance hotspots

He adds that building wind farms further out to sea presents new challenges and opportunities when it comes to design.

“The maintenance of these farms can be optimised with the use of a service platform and an automatic boat landing system which reaches over the tide area,” he states. “At present as a service technician you have to climb up a ladder from the ship and step on wet areas like slippery stairs. With a service platform which docks on the dry area you can improve safety.”

Array cable layouts should also be optimised in the design to mitigate against the loss of transmission supply.

“We need to raise the importance of cable installation in general because even though it is a fairly small capital part of a project its vulnerability can really affect overall costs. We need to look at the position of the sub-stations and sharing routings,” says Global’s Leggett. “We also need more standardised engineering in particular long pull cables and J-tube seals.”

Supplier strategies

Dalton of Mainstream wants to take the theme of standardisation even further.

“We have to demand higher standards from wind turbine suppliers and certain proprietary technology will have to be shared if we are going to make wind farms more efficient,” he argues.

“Some companies have a technological edge and we are calling for them to share this throughout the sector. Some have asked for patents on positive overpressure technology in wind turbines but this hasn’t been patented in other sectors. We need to get smart as an industry and as a developer we will make certain demands of our suppliers in future wind farm designs.”

That means finding suppliers who can offer higher reliability, minimise maintenance and offer “cunning technology”.

The race to meet more optimised designs is underway.

To respond to this article, please write to the Editor: Rikki Stancich

Image credit: Vestas