Some facts about wind power

… and the arguments often deployed against wind farms

Bob Whitmarsh(Winchester Action on Climate Change)

[see Notes for added information]

Some basic facts about wind turbines• Need smooth terrain• Wind speed increases with height so big is best

• Power output depends on (wind speed)3

(good wind data is essential beforehand to estimate output)

Criticisms often levelled (incorrectly) against wind turbines (1)

• They’re inefficient (turbines convert 33% or more of wind energy into electricity; no worse than a coal-fired power station!)

• The output is variable (load factor is 25% but this can be designed for and anyway the energy is free; nationally the output is smoothed out. it is very unusual (2% of the time) for more than half of the country to have wind speeds too low to operate a wind turbine. Variability will eventually be partly tackled by ‘batteries’)

• The load factor decreases with age (Hughes 2012 claimed down from 25% to 15% in 10 years. Spurious analysis discredited by Chief Scientist of DECC; actually down from 25% to 21%)

• Turbines require stand-by back-up power generation for windless days (all power supplies require some back-up to cope with planned maintenance and breakdowns. Current UK generating infrastructure can cope until wind contribution exceeds 20%)

Criticisms often levelled (incorrectly) against wind turbines (2)

• They’re noisy (noise energy falls off as the square of distance. Windfarm at 350m is on average no noisier than highest rural background noise at night) [DoE, 1993]

• They generate impulsive sounds (only if the blades are downwind of the tower. Not in UK)

• They cause flicker which potentially causes epilepsy (Flicker only occurs under special conditions. DECC 2011 noted that ‘Researchers only identified one case of shadow flicker in the UK’! Only 1 in 2500 of the population liable to suffer epileptic seizure from flicker)

• They kill birds and bats (but birds are killed by cats, cars, buildings, large window panes etc. in far greater numbers. Little evidence of bat kill in UK)

An inconvenient factor

• Wind turbines are ‘unsightly’ (This is a subjective opinion. Anyway surveys show that people tend to get used to them c.f. pylons, telecom masts)

• Some wind turbines are visible from a great distance (true, for someone with perfect eye-sight but in many cases the actual image will be minute. A 90m diameter turbine blade viewed at a distance of 10km will look about the same size as the head of a map pin held at arms length!)

• Is ‘camouflage’ the solution? (Grey is proven to blend in better than green, brown and black against a rural background (trees, hedges, leaves etc) and also against the generally grey skyline in UK)

The good news about wind farms• Wind energy is free• Onshore wind turbines are a mature technology

which can be bought ‘off the shelf’• Onshore wind has lowest greenhouse gas

emissions per kWh compared to nuclear, gas turbine and coal-fired power stations

• Energy payback time is 6-12 months; financial payback is 7-8 years

• Provide energy which today is mostly no more expensive than nuclear, gas or coal; will become relatively cheaper as fossil fuels prices rise

• Local communities can benefit financially• Can be dismantled at end of life (20-25 years)