Cleantech
Five Ways to Cheaper Offshore Wind – and More Clean Energy

The cost of black energy has now got ‘green’ competition. Solar power and onshore wind are already cheaper than fossil alternatives and according to DONG Energy, offshore wind must follow the same development. DONG Energy aims to make clean energy from offshore wind turbines at least as cheap as black energy from fossil fuels in ten years. The Danish energy company, which is among the global leaders within offshore wind power, gives five specific examples of how that is going to happen.

1. Wind turbines growing by leaps and bounds

The larger the wind turbines are, the more energy they produce each time they rotate. This means that we can harness more offshore wind in a more cost-effective manner. Since 1991, when DONG Energy built the world's first offshore wind farm in Vindeby, off the coast of Denmark, wind turbines have grown almost fourfold in size. Back then, the wind turbines had a height of 35 metres, an equivalent rotor span and a capacity of 0.45MW. By comparison, DONG will build an offshore wind farm in the UK next year with 113-metre tall wind turbines with a rotor span of 164 metres and a capacity of 8MW. This rotor span more or less corresponds to the diameter of the Colosseum in Rome.

"Larger wind turbines are good news for the environment. The larger the wind turbines, the more kilowatt-hours will be fed into the sockets for each blade rotation," says Jesper Skov Gretlund, Project Manager in DONG Energy's Research & Development department. “With today's experience and technology, we can build and operate offshore wind turbines which are far more efficient than in the past, and that can help bring down the cost of electricity from offshore wind.”

Since the first offshore wind turbine saw the light of day in 1991, wind turbines have grown nearly fourfold in size. Photo: DONG Energy

2. Less steel makes for less expensive foundations

It requires solid steel foundations to anchor offshore wind turbines safely in the seabed. But steel is expensive. Therefore, good savings can be made if the foundations can be made smaller. In cooperation with a number of business partners, DONG Energy has completed the research project, PISA (Pile Soil Analysis), and tested 28 different pile foundations in different soil conditions. The study of the piles, which varied in size, type and amount of steel, gave an interesting result.

3. Easier inspection with intelligent cameras

Building offshore wind farms costs money. And the same goes for service and maintenance of the wind farms once they have been constructed. Here, too, DONG is working to reduce costs. For example, new technology has made it easier and cheaper to inspect offshore wind turbines. Previously, specially trained technicians had to crawl out onto each blade and examine each turbine in detail to see if they were damaged or defective. It was a very demanding and hazardous work, which only made it possible to inspect one single wind turbine per day. Today, DONG has developed a method using state-of-the-art equipment to take pictures of the wind turbine blades from a distance.

"When performing inspections today, we can use the intelligent cameras, which will take 200 to 250 pictures of each blade,” Gretlund explains. “Doing it that way, a team of two will be able to do inspections of three turbines per day."

4. Larger ships equals less time at sea

Normally, it is not an advantage to sleep at work. But with the new SOVs (service operation vessels), a longer stay offshore will help reduce the costs for transport and non-productive man hours.

Before, technicians were transferred back and forth to the offshore wind farms every day. It created disturbances in the work process and cost a lot of transport time. To optimise the work process, DONG has recently invested in two SOVs, which, in addition to the crew cabins, can accommodate 40 wind turbine technicians. The vessels sail out to the wind farms where they drop anchor and function as a base for the technicians. The vessels are a kind of floating hotels where the technicians eat, sleep and relax close to their temporary workplace at sea.

5. No reinventing the wheel

According to DONG Energy, standardisation is a fifth and decisive factor that will make offshore wind power cheaper than black energy.

"Offshore wind is still a young industry, but after 25 years, we've established a routine so that we don't have to reinvent the wheel every time we're going to construct an offshore wind farm,” Gretlund says. “Today, we can execute both better and cheaper than before, and that development will become even more successful in future once standardisation kicks in for good."

In short, it is about constructing offshore wind farms in areas where the soil and wind conditions are similar to those the company is already familiar with. Also, the wind turbines are to an increasingly larger extent built with standardised components produced by suppliers in a competitive market. In this way, the cost of spare parts and service is brought down - exactly as we know it from car repair shops.

Following the same standardised recipe each time a new offshore wind farm is to be built lowers the cost of electricity. Photo: DONG Energy

Firmly on track

The plan to generate green energy from offshore wind power at the same cost as black within the next decade is ambitious, but not unrealistic. In 2012, DONG set a target of reducing costs for the construction of offshore wind farms by 35-40 percent by 2020. And the company is well on the way to reaching this target. But according to Gretlund, there are many factors involved in realising this goal.