Doesn't the dirty back up power required when the wind stops blowing mean that the CO2 saving is wiped out?
This rather bizarre claim is increasingly common among anti-wind campaigners. Their argument runs like this:

"Because wind power is intermittent (it varies with the weather) it needs dedicated back-up for when the wind doesn't blow. This back up will be coal powered stations that have to be kept 'spinning' (ie burning) at low level so they are ready to go immediately that the wind drops. Burning like this is inefficient so the emissions they make are roughly the same as if they were actually generating electricity. Therefore wind power saves no carbon because the back-up emits the same as if there were no wind turbines in the first place."

This argument is, quite simply, wrong. The national grid has back-up on it regardless of wind power. Back-up is needed for all forms of energy generation because of unexpected increases in demand (a cold snap for example, or when the All Blacks playing Australia is televised).

It is widely accepted that only very minor levels of back-up are needed for wind - up to about 20% wind on the system (much higher levels of wind power are possible, but require a little more back-up). In terms of emissions - even if the back-up was the dirtiest option - coal power - at 10% wind power on the system only 1% of the CO2 saved by the wind would be emitted from the back-up - and 99% is saved. Coal is not the only option for back-up. Wind power and hydro are perfectly suited to each other. As New Zealand generates a remarkable energy amount from hydro dams we already have an optimal back up system. In the future a wide range of renewable energy technologies would compliment one another and offer the chance for completely secure and completely clean energy system - including both primary generation and back-up.

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