Thursday, 5 November 2015

The untold story of how windfarms help keep the lights on

The UK press has been full of stories implying that wind power is to blame for the National Grid having to call in expensive demand shedding measures recently to keep the lights on. What they will not tell you is how often wind power saves the UK consumer large amounts of money because the National Grid does not have to buy in expensive reserves of power. Also they do not tell you that wind power in fact has quite a substantial contribution to effective firm power station capacity.

It is all very well repeating over and over again that the wind sometimes doesn't blow very strongly, but that doesn't tell you how to keep the lights on. Put simply, the chances of there being challenges to keeping enough electricity generation to meet demand at any point in time depends on a combination of factors being present; not just there being not much wind, but also that there are unexpected failures in power stations, unexpected high demand and unavailability of other power or demand side reduction options at any given time. Usually wind power will be slaving away saving the the need to buy in more reserves of power or demand side management during those winter days and nights when our electricity system is challenged. But we don't hear about this.

It would be as ludicrous to dismiss wind power's contribution to providing firm capacity as it would to insist that a particular power station can be guaranteed to be online all of the time. Indeed, a difference is that low wind power production may be usually more predictable than power stations going offline through breakdowns.

In fact, buried deep inside regulatory reports there is official recognition that wind power does have substantial equivalent firm capacity. As can be seen in OFGEM's electricity capacity assessments. See the 2014 version at

OFGEM defines:'Equivalent Firm Capacity of wind (EFC): the average contribution of wind power to the de-rated margin. It is the quantity of firm capacity (ie always available) required to replace the wind generation in the system to give the same level of security of supply' (pages 26-27)

In fact OFGEM's models indicate that the 'wind equivalent firm capacity factor'  varies in its models from 14.8 per cent to some 25.9 per cent depending on the scenarios modeled for a range of years.

Now that is quite substantial (ie a mean of around 20 per cent). According to the UKWED database there are currently around 13.5 GWe of wind power installed in the UK.

Hence, in effect, averaging out the mean of the models assessments of equivalent firm capacity provided by wind, wind power adds the equivalent of  2.7 GWe of firm capacity to UK generating capacity. That, by the way, is rather more than the equivalent of around two and a half Sizewell B nuclear power stations.

We hear a lot about how the Government is throwing huge sums of money into something called a capacity mechanism to produce very inefficient outcomes. What I'd like to see, (among a lot of other things!) is a calculation of how much the electricity consumer is saving through the equivalent firm capacity that wind power is providing, which is likely to be quite large! That, of course, is apart from providing a lot of cheap clean energy.


  1. 2.7 GW of "Equivalent Firm Capacity" is not much use during a period of cold winter weather dominated by a blocking High in which wind output is very low for several days or weeks.

    Two and a half Sizewell Bs would be very useful at such times, and would probably cost around the same as the current wind capacity.

    Energy politics 101: No government would survive a cold winter with power cuts, so no government should put too many eggs in the wind basket, or be taken in by statistical quantities with inappropriate words like "Firm" in the name.

    1. Well by the same token Sizewell B is useless when it breaks down - which it has done causing havoc to the electricity system - in contrast to wind power whose fluctuations are predictable to a high degree a long time in advance. I salute your optimism on costs of of nuclear power but reality says something very different - wind power contracts are issued by the government for a lot lower prices than for Hinkley C despite the fact that they are for only 15 years compared to 35 years for Hinkley C and the wind power schemes do not get the billions of pounds of loan guarantees offered to the Hinkley project!