Bat and blade
New Scientist|John Etherington, Llanhowell, Pembrokeshire|June 9, 2007
New Scientist's report on the large number of bats succumbing to wind turbines reinforces a common misperception - that the blades move slowly (12 May, p4). It is true that the blades of older, small wind turbines rotated rapidly and so would appear to a bird or bat as a semi-solid disc to be avoided. Modern 2-megawatt wind turbines make an apparently lazy 10 to 20 revolutions per minute, but the blades are around 40 metres long. Simple geometry shows that the blade tips travel at between 150 and 300 kilometres per hour. For a bird or bat in misty weather, these aircraft-sized blades appear from nowhere at intervals of between 2 and 4 seconds, a scenario that even a fighter pilot would find alarming.
New Scientist's report on the large number of bats succumbing to wind turbines reinforces a common misperception - that the blades move slowly (12 May, p4). It is true that the blades of older, small wind turbines rotated rapidly and so would appear to a bird or bat as a semi-solid disc to be avoided. Modern 2-megawatt wind turbines make an apparently lazy 10 to 20 revolutions per minute, but the blades are around 40 metres long. Simple geometry shows that the blade tips travel at between 150 and 300 kilometres per hour. For a bird or bat in misty weather, these aircraft-sized blades appear from nowhere at intervals of between 2 and 4 seconds, a scenario that even a fighter pilot would find alarming.
New Scientist's report on the large number of bats succumbing to wind turbines reinforces a common misperception - that the blades move slowly (12 May, p4).
It is true that the blades of older, small wind turbines rotated rapidly and so would appear to a bird or bat as a semi-solid disc to be avoided.
Modern 2-megawatt wind turbines make an apparently lazy 10 to 20 revolutions per minute, but the blades are around 40 metres long.
Simple geometry shows that the blade tips travel at between 150 and 300 kilometres per hour.
For a bird or bat in misty weather, these aircraft-sized blades appear from nowhere at intervals of between 2 and 4 seconds, a scenario that even a fighter pilot would find alarming.