Yes, windfarms need wind to work: The danger of taking data snapshots
There’s an old parable about trying to describe a whole elephant if all you’ve ever encountered is the trunk: it’s unlikely you’d succeed. The same is true of windfarms’ ability to produce electricity. If you’ve only ever seen them on still days, it would be hard to see how they could contribute to the UK’s energy production.
The Telegraph got fixated on the elephant’s trunk this weekend. It claimed that at a given time, some of the UK’s windfarms were only producing enough power “to make a few cups of tea”. A look at the bigger picture reveals a more complex situation, however.
No wind
Windfarms produce power when it’s windy, and don’t when it’s still. Wind’s intermittent nature makes it pretty easy to find data to suggest windfarms aren’t working – it’s just a case of picking the right weather conditions.
The Telegraph looked at data from energy company RWE npower, which has a website giving live updates on its renewable energy projects’ power output. The graph below shows the amount of electricity seven of the company’s windfarms were generating when the Telegraph looked last Thursday afternoon (the blue bars). We’ve compared it to their output this morning (the red bars):
Image - windfarm data snapshot (note)
The Anglesey windfarm that was behind the Telegraph’s tea-making headline – Trysglwyn – is today producing about 15 times the amount of electricity that it did last Thursday. So if it was responsible for two boiling kettles back then – as the Telegraph claimed – around 30 were bubbling away this morning, thanks to its turbines.
But looking at energy figures in this way isn’t particularly enlightening, as it doesn’t illustrate how wind power contributes to the UK’s energy production overall.
The bigger picture
Wind power is an increasingly significant part of the UK’s energy mix. The Department of Energy and Climate Change’s (DECC) annual data shows renewable sources generated a record 11 per cent of the UK’s electricity in 2012.
A large portion of that share came from windfarms. Onshore and offshore wind power combined was responsible for 24 per cent of renewable energy generation (including heat and transport, as well as electricity). So while not all windfarms work all the time, the UK’s windfarm fleet has the potential to deliver a significant portion of low carbon power overall.
The weather conditions also affect how efficient wind turbines are, as the Telegraph points out. If there isn’t much wind, turbines generate less electricity than their calculated potential. For example, the Trysglwyn windfarm only produced 0.001 per cent of its potential six megawatts of power due to the still conditions on Thursday, the Telegraph calculates.
This is much less than the national average, however. DECC figures show UK windfarms produced about 29 per cent of their potential power on average in 2012. So the Telegraph’s chosen figures aren’t particularly representative of windfarms’ typical output.
Taking snapshots
The UK’s energy sector is pretty complex. The government has to perform a tough balancing act between making sure there’s always enough power available and cutting emissions, so taking a snapshot of a few windfarms’ output on a single day isn’t particularly useful.
DECC is legally required by the European Union to meet 15 per cent of the UK’s energy demand from renewable sources by 2020, and windfarms are key to meeting its climate change goals. Because renewable generation varies quite a lot, the government has to invest in some fossil fuel backup. This normally comes from gas plants. Increasing gas generation capacity could make the UK vulnerable to international price hikes, however.
Getting to grips with those issues means looking at the bigger picture. Otherwise all you have is a trunk, which looks kind of odd without the rest of the elephant.