In reply to Removed Userrabthecairnterrier:
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> Basically, as wind is intermittent, it cannot provide baseload generation, neither can it respond to demand, which begs the question of what it actually IS for. There is also the issue of cost: the "fuel" for wind may be free, but as 100% backup capacity is required the consumer has to pay the capital cost twice over - once for the windfarms, once for the gas (or whatever else). At a time of rising fuel poverty this is a serious issue for many.
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It's one of the myths put about by opponents of wind power that wind needs 100% back up. This quite simply isn't true. Wind does need back up (or reserve, to use the correct terminology) but so does all generation - there is always reserve generation allocated for potential failure. And it's not the case that this reserve generation is always running - there are different types of reserve generation, and among the ways they are differentiated is by the speed of response. Nuclear is very slow, whereas gas (and to a lesser extent coal) are quicker to respond, and are more often used as reserve generation.
Intermittency is an issue. One of the ways to deal with this is accommodated within our current balancing mechanism, which matches supply and demand. The balancing mechanism works on half-hour slots, and generators are asked to submit bids to supply amounts of electricity over a 24 hour period, split into half hour slots. The National Grid then selects, or dispatches, the required generation, based partly on price, but also on location of generation (particularly with respect to other dispatched generation). So, if a wind generator knows it's not going to be windy, they don't bid for any slots, and a different generator is dispatched for that slot. This is not very different to a conventional generator opting out of slots, for a variety of reasons, such as maintenance downtime. Alternatively, if the wind generator knows there will be a good steady wind, they will bid and be allocated if their bids meet the National Grid requirements. There are financial penalties for supplying more or less than the bid amounts, so a good deal of care goes into the bids.
At any time, we need to have a surplus of generating capacity, to meet unusual demand and to prevent grid failure in the event of a power station failure. Another benefit of a decent surplus is the ability to pick and choose the most suitable generation at a given time. Of course, there is a cost to having this surplus capacity, and that has always been the case. I'm not sure what the position is now, but it was the case a few years ago when the amount of surplus capacity was decreasing to dangerously low levels, but that was more as a result of failure to replace aging conventional power stations. The intermittency of wind also contributes to the cost, and the cost varies according to the amount of wind generation available - at low levels (less than 5% of total electricity requirement), the costs are also low, but at higher levels, above 10%, they do start becoming significant. At this point, one question that needs to be asked is whether this is a cost that society is willing to pay in order to reduce carbon emissions.