If the unreliability of wind power really is a problem we would have seen the evidence today (3rd January 2012). Extremely strong westerly winds were predicted to deliver about 3.5 GW of electricity from turbines during most of the last twenty four hours, over 80% of the maximum capacity from the UK’s wind farms. But as has been the case several times over the last six weeks, many of the arrays stopped as excessively high wind speeds triggered automatic shut downs.
At five in the morning, Britain’s wind farms were delivering about 2.5 GW, just under 10% of total electricity need and the number was expected to go higher. The opposite happened. After five hours of steep decline as a result of unplanned closures, wind turbines managed a little over 1.0 GW, no more than about 40% of what was forecast yesterday, leaving a shortfall of about 6% of electricity supply. Did the Grid suffer? Did we come close to having the lights go out? No. As the unexpected shortage of electricity became apparent, the price for immediate delivery of power rose from about £30 a MWh to £90 and unused power stations willingly revved up to meet the extra demand.
The crucial indicator of whether the Grid was under stress barely moved: the frequency of electricity supply remained close to 50 Hertz. An unexpected loss of large amounts of power will usually result in a fall in the frequency of Grid electricity but a close look at the numbers every few seconds from 5 to 10 am shows no obvious perturbation. Grid frequency stuck to about 50 Hertz for the entire period. The electricity supply system settled down with first gas fired power stations and then coal plants from 8 o’clock meeting the unexpected gap in supply.
By ten o’clock in the morning, things had settled down. Then the next unplanned event happened. Some of the wind farms started coming back online. The amount of power generated by wind rose almost as fast as it had fallen earlier in the day. By four in the afternoon the electricity from turbines was back at nearly the same level as five in the morning. Once again, Grid stability was unchallenged. Spot prices spiked up and down as operators adjusted to the new supply but the key indicator, Grid frequency, was unaffected.
Now, at 10.30 in the evening, wind is providing about 7% of the UK’s total needs. During the last day, the country’s 3,000 turbines have averaged about 5.5% of all power. However this number has varied by a factor of three during the day, and not in any way that was remotely predictable even 24 hours ago. The average cost of electricity has probably been relatively high as spare power stations have been fired up and down to meet swings in demand but I would guess there hasn’t been a single moment of real anxiety anywhere across the UK generation and supply industry.
What continues to amaze me is that people who scorn the value of wind energy are often also the most fervent believers in free markets and their apparently magical power to match supply and demand. The UK’s electricity market is far from perfect, but it is quite robust enough to handle a near hurricane, followed by unexpected falls in wind speed. What further demonstrations that wind turbines are effective providers of electricity could possibly be required? Today’s weather might have been more of a problem had the UK had 30,000 wind turbines rather than 3,000 but as of early 2012 the freely functioning electricity market is coping very well indeed with intermittency.