Wind power - helping keep the lights on

Simon Bullock

16 November 2012

This month UK wind generation hit a new record of 4.2 Gigawatts - great news for the UK's renewable electricity future.

With predicted increases in both offshore and onshore wind capacity, by 2020 this figure could quadruple - more good news I say. But some people worry that, because wind's output is variable, will the electricity system be able to cope with sudden drops in wind generation?

This article looks at UK's electricity generation data to see where there might be problems. I deliberately picked January 2012 - a month where demand was very high, and where there might have been trouble with wind: for example a high-pressure system lasting for several days.

Here's the data for wind:

Sure enough, there was a big fall in wind power for one 5 day stretch, and other days where power was also low. On other days, generation often topped 3GW - displacing more polluting power generation. Wind power never went to zero, but it did go very low.

So, was this a problem? Here's the same graph, but with total electricity demand in as well:

It's really clear that the rises and falls in demand are far greater and steeper than they are for wind. Even by 2020, when the blue line might be expected to be 4 times larger, wind variability is a minor issue for the grid to cope with, compared with variability in total demand. The UK grid already copes fine with much higher variabilities in power, than that posed by the variability of wind, every day of the year.

This though is a snap-shot of the whole month. What about sudden drops in wind power? Can the system cope then?

In January the biggest fall in wind power in any 5 minute period was at 15:55 on 25^th Jan: when there was a 288 MW drop. This coincided with a rise in overall demand of 290 MW:

This does not look so terrible. And here is the same graph, with the other main generation types thrown in. Wind's drop barely registers:

But what about sustained drops in wind? The biggest daily drop in January was 7am-7am on the 12^th-13^th Jan. Wind power fell steadily from 2.5 GW to 0.5 GW:

Again though, this fall is dwarfed by the variations in total demand and the related variations in other forms of generation to cope with these demand changes. For example gas generation rose by 4 GW in one hour on that same day - a rate 48 times faster than wind's fall:

Even with quadruple the wind in the system, the above graphs would have wind generated falling from around 10GW to 2 GW - way lower than the daily variations in demand the system already manages. And by 2020 we can expect two improvements also for how we manage wind- better forecasting of future wind generation, and greater spread of wind-farms, smoothing out fluctuations in generation.

These graphs are clearly just a snap-shot - numerous far more detailed studies have shown that the UK can cope easily with the levels of wind planned to 2020, using the existing grid - for example reports and statements by Poyry, National Grid and Imperial College - both in terms of sudden drops in output, and for days-long periods with low output.

Wind variability is after all just one of the many issues the grid copes with: there's the Coronation Street spike when demand rises, and sudden losses of a nuclear plant or coal plant's output - for example Heysham 1 nuclear Reactor 2 shutting down on 12^th October this year after a cooling pipe leak, losing 600MW in 5 minutes, and larger 1000MW rapid nuclear shut-downs at Sizewell on 18^th July and 2^nd March this year.

Beyond 2020, it will make sense to invest more in a variety of upgrades to how we balance the electricity network - as the share of renewables of all types increases. Building more interconnectors to trade electricity with the EU and Norway, investing in energy storage, "demand-side" response and smart grids: these all have a vital role to play. But although moving to a clean electricity system will be complex, it's a job for which the solutions exist, and where the UK has the engineering expertise to deliver them.

We can have a green electricity system that keeps the lights on - we just need to get on with it.