Harnessing the wind

Offshore wind turbines

 

Wind power is one of the key technologies for humanity’s future energy needs. And one of the best places to exploit it is offshore, where the wind is more reliable and where there are fewer objections to big wind farms.

While seas and oceans cover about 70% of the Earth’s surface, there are limits to the amount of this vast area that can be used to produce wind power with today’s technology. The reason is that existing wind turbines have to be fastened to the sea floor, limiting their deployment to shallow areas of the ocean.

This problem has been the focus of UK and CHN CORE, the UK and China Centre for Offshore Renewable Energy. Chaired by the UK’s Lars Johanning, Professor of Ocean Technology at the University of Exeter, its further UK partners included Imperial College London, Oxford University and the University of Strathclyde. UKRI’s NERC and EPSRC research councils distributed UK development money from the Newton Fund for research and innovation, and observed the projects. 

The three-year programme, which involved five projects, will end in January 2021. The UK spent £4 million on CORE and the principal Chinese partner, the National Natural Science Foundation of China (NSFC), contributed £1.5 million. 

The programme was inspired by the surprising realisation that as Johanning puts it, we may “run out of seabed.” He explains: “Today we can site an offshore wind farm in 30m of water. It may be possible to extend that to 50m.” This is the limit beyond which it becomes difficult to fix or otherwise stabilise a big wind turbine to the seabed. And as Johanning says; “There are other stakeholders with an interest in the sea [at these depths], including shipping, fisheries and the military. Being able to use deeper water will vastly increase the area available for wind generation.”

The UK and China both have long coastlines, making them natural users of offshore wind power. And each has a commitment to renewable energy as part of the process of decarbonising their economies. In addition, many of China’s cities have an acute problem with local air quality. Coal-burning power stations are a major contributor to this pollution, and the need to close them is a further incentive for investment in wind power. 

To extend the area of ocean that can be used for wind power, it will be necessary to mount wind turbines on floating platforms. This raises big engineering challenges, since these turbines are big, rotating machines unlike anything now seen in the open ocean. And while floating platforms have long been used by the oil and gas industry, this technology cannot be transferred directly to wind generation. 

One focus of the CORE research has been to prove the viability of floating offshore systems by modelling ways in which existing small platforms could be scaled up and used in actual offshore environments. In addition, more innovation will be needed to get costs down. Floating offshore wind may eventually be able to produce electricity for about 4.5p per unit, which Johanning points out is “less than oil, coal or nuclear,” once the technology has been developed and scaled up. 

Both the UK and China have invested heavily in today’s offshore wind technology. But for both partners, the shift to floating wind farms is an important next step. Johanning says that the CORE research is now being built into Chinese energy policy, within a five-year plan to introduce more low-carbon offshore renewables.

Atmospheric effect

Replacing today’s fossil-fuelled power generation with renewables is a massive undertaking. And while we largely understand the environmental effects of carbon emissions on the atmosphere, it is now becoming important to grasp the environmental consequences of big renewable  energy projects.

Part of the CORE programme (Fengbo Wind) was intended to look at these impacts. Johanning says: “It is important to understand the complex interactions between the individual wakes of single wind turbines in a farm and the combined atmospheric turbulence that results, to inform and optimise design. Furthermore, we need to understand the possible effects in the atmosphere to avoid significant environmental impacts.” Johanning says that this part of this programme was carried out by models running on a Chinese supercomputer.

The wider aspect of the programme involved modelling the atmosphere, the oceans and the interaction between them, in order to see the possible effects of integrating large-scale offshore renewables into the energy mix, and their contribution to addressing global climate change.

However, the use of floating wind turbines can also bring socio-economic gains. Another CORE project (Inno-MPP) looked at the possible integration of the aquaculture industry into massive offshore structures wind installations. “That would make this technology [economically] useful in two different ways,” says Johanning. 

He adds that working with Chinese partners has been a positive experience. “It was very interesting to see the cultural differences between Europe and China,” he says, “but there was never a problem with working together in research and development. It was possible to exchange all the information we needed in order to be innovative, and knowledge flowed in both directions.” 

The CORE research programme has attracted the attention of China’s large windpower industry. Johanning says that companies such as MingYang WindPower and Goldwind, which are among the world’s biggest manufacturers of onshore and offshore wind turbines, showed interest at a recent outreach event and were partners in the CORE projects.

Despite the end of the CORE programme, Johanning has a five-year agreement with his Chinese partners to continue this research. He anticipates that the positive collaboration that has taken place to date will continue.

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