Vast and efficient ocean wind farms 'could power human civilisation'

Statoil's floating wind turbines surrounded by ships at dusk

But the new research suggests that if the wind energy flowing over the oceans can be converted into electric energy then, it is sufficient enough to power the human civilization.

The two authors of the study Anna Possnera and Ken Caldeira, from the Carnegie Institution for Science in Stanford, California, said that the new research is a kind of green light for the wind energy industry from a geophysical point of view. At onshore facilities, each turbine weakens the power generation potential of each additional turbine downwind of it in a phenomenon known as a "wind shadow".

Image: Offshore wind turbines.

The study found that such a enormous wind farm could capitalize on low-pressure systems throughout the winter which more efficiently combine the upper atmospheric winds with the surface level winds, producing greater yields in wind farm power generation potential.

As expected, the results showed a significant gap between land-based and sea-based wind energy.

In tapping into wind as an energy source, the United States has for decades lagged behind Europe and United Kingdom, which are home to the largest offshore wind farms in the world, including the London Array and the Netherlands' Gemini wind farm.

"The question was, is there something about the atmosphere or the ocean that allows it to bring down more wind energy to wind farms?"

Possner and Caldeira used a range of modelling tools to compare the productivity of large windfarms in Kansas, in comparison to the upscaled, theoretical open-ocean windfarms.

Wind speeds on the ocean can be as much as 70% higher than on land. This is largely due to the fact that large amounts of heat pour out of the North Atlantic Ocean and into the overlying atmosphere, especially during the winter. This contrast in surface warming along the USA coast drives the frequent generation of cyclones or low-pressure systems, that cross the Atlantic and are very efficient in drawing the upper atmosphere's energy down to the height of the turbines. "The rate of electricity generation in large wind farms containing multiple wind arrays is, therefore, constrained by the rate of kinetic energy replenishment from the atmosphere above", says the abstract of the article. Many practical factors will probably make the whole concept more complex, including the lack of technology that can capture ocean-based wind energy at that scale. It highlights the considerable opportunity for generating wind power in the open ocean, particularly the North Atlantic.

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