Slowing winds and the complications of building large windfarms
New research questions how many wind turbines can be added to large windfarms before the power they produce starts to significantly decline. This could be a problem in the UK as the government adds more onshore and offshore wind power on the way to meeting its renewable energy targets. If it’s not possible to effectively scale wind developments up, wind’s role in the future energy mix could be limited.
The new findings, recently published in the journal Environmental Research Letters, only apply to windfarms covering an area over 100 square kilometers – bigger than even the largest UK windfarm currently in operation. So the paper is most concerned with how we go about building larger windfarms in the future.
Slowing in the wind
Wind turbines slow the wind down slightly as it turns the blades to make electricity – known as a wind shadow. As more turbines are added within a particular area, the wind shadows cross over with each other and interact much more – making the whole windfarm less efficient.
And the larger the windfarm is, the less efficient it could be. Previous estimates suggest large wind developments could generate between two and seven watts per square meter. But taking account of the slowing effect, the new paper suggests that for wind installations of 100 square kilometers or more it’s more likely to be about one watt per square meter.
This isn’t much of a problem in the UK at the moment – none of its operating windfarms are that big. But it could increasingly become an issue as wind developments get bigger as the government works toward its renewable energy targets.
For instance, the London Array project currently under construction in Kent is expected to cover an area of 230 square kilometers when it’s completed. Another planned windfarm off the coast of Sussex – expected to be 167 square kilometers in size – could have the same problem. These developments could help answer important questions. Once they are up and running, we will be able to see if their readings match the paper’s modelling predictions.
If the reduced estimate is right, it has has serious ramifications for the wind industry. This is because the economic attractiveness of windfarms relies on them being an efficient source of energy – and the new data suggests they might not be as efficient as predicted.
But the paper’s authors say their findings “don’t mean that we shouldn’t pursue wind power”. Planners may need to revise their calculations on how much power is gained from adding a turbine, and think carefully about where they build, however.
Locating windfarms
One solution could be to spread the turbines out even more, preventing the wind shadows interfering with each other – but taking up a lot more space.
Windfarms can’t be built just anywhere, however. It only makes sense to build windfarms where there is a lot of wind – and where there is demand for electricity. They also need to be fairly close to electrical grids as connecting technology can’t currently stretch very far.
Working out the maximum area that could host windfarms taking into account all these constraints is a difficult but important task, the researchers say. Doing so could provide us with much better estimates of how much wind power could realistically be generated globally in the future – and how much we’ll have to rely on other sources.
Scaling up
So the new paper doesn’t necessarily mean the UK can’t still generate a large amount of electricity from wind – it’s just a question of how to do it. For now, the research indicates careful thinking is needed about how – and where – the UK’s wind sector can continue to grow.
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