Wind turbines DO reduce carbon emissions

The assertion that wind turbines don't reduce carbon emissions is a myth, according to conclusive statistical data obtained from National Grid and analysed here in the Guardian for the first time. With a new wind generation record of 4,131 megawatts set on 14 September, the question of how far the UK's wind generation fleet can help in meeting our climate targets is increasingly controversial. Now it can be shown that the sceptics who lobby against wind simply have their facts wrong.

On 14 September, wind turbines connected to the National Grid produced over 80 gigawatt-hours (GWh) of electricity, just over 10% of total UK generation. This was far from being a one-off: with more than 4,000 turbines both on and offshore now connected to the grid, wind produced 48 GWh of usable electricity per day on average during September, adding up to about 6% of overall daily national electricity requirement. On many days, wind is now the fourth-largest source of UK electricity, after coal, nuclear and gas. Indeed, this figure is a significant underestimate, because about two gigawatts of wind are connected directly to local networks and so not directly visible to National Grid.

However, according to increasingly vocal critics of wind power, the intermittent nature of wind generation means we must burn more gas to provide backup. According to Telegraph columnist Christopher Booker:

"Ramping the back-up gas plants up and down would mean running them very inefficiently, and give off so much CO2 that we could end up increasing our overall emissions rather than reducing them"

Journalist and author Matt Ridley asserts that:

"The total carbon emissions saved by the great wind rush is probably below 1%, because of the need to keep fossil fuels burning as back-up when the wind does not blow. It may even be a negative number."

The climate-sceptic Global Warming Policy Foundation (GWPF) recently gave evidence to the House of Commons energy and climate changecommittee, stating:

"There is a significant risk that annual CO2 emissions could be greater under the wind scenario than under the gas scenario".

The essence of the wind sceptics' case is that a scaling up in wind power will have to be "backed up" by massive investment in gas-fired open cycle turbine (OCGT) plants, which are cheap to build but considerably less efficient than the combined cycle gas turbine (CCGT) power plants which deliver the vast majority of the UK's gas-fired electricity supply.

Their arguments are not borne out by current statistics, however. If the sceptics were right, the recent windy conditions would have seen considerable use of less-efficient OCGT as wind input to the grid ramped up and down. In actual fact, during the entire June-September period, OCGTs and equally dirty oil-fired stations produced less than one hundredth of one percent of all UK electricity. In total they operated for a grand total of just nine half hour periods in the first 19 days of the month – and these periods had nothing to do with changing windspeeds.

From analysing National Grid data of more than 4,000 half-hour periods over the last three months, a strong correlation between windiness and a reduction in gas-fired generation becomes clear. The exchange rate is about one for one: a megawatt hour of wind typically meant the UK grid used one less megawatt hour of gas-derived electricity. This means that actual CO2 savings can be calculated from the data with a high degree of accuracy – these are not guesstimates from models, but observations of real-world data. Over a year, based on the amount of electricity wind is currently generating each day, wind turbines save around 6.1m tonnes of carbon dioxide, or about 4% of the UK's emissions from electricity.. 

Read more: http://www.guardian.co.uk/environment/blog/2012/sep/26/myth-wind-turbines-carbon-emissions