Cloud storage: Lower cost and increase uptime

Comment The Spanish wind power industry has proudly claimed that it has "set a new record" in that it delivered more than half the electricity used in all of Spain for several hours.

The "record" is less impressive than it sounds, however. It was achieved during the small hours of a Sunday morning, when electricity demand is lowest. The Spanish electricity grid organisation, Red Eléctrica, says that wind met more than 50 per cent of demand from 0300 to 0830 on Sunday morning, peaking at 53.7 per cent.

One of the most frequently raised arguments against renewable power sources is that they can only supply a low percentage of the total power because their unpredictability can destabilize the grid. Spain seems to have disproved this assertion. In the last three days, the wind power generation records with respect to the total demand were beaten twice ... there was no instability. These milestones were accomplished with the help of a control centre that processes meteorologic data from the whole country.

In fact, some people have argued in the past that the surges and dips in supply from wind, solar etc can be much steeper than most "thermal" powerplants - fossil and nuclear - can match, meaning that such plants can't be used to successfully back up a big fraction of wind on a national grid as they can't respond quickly enough to changes in the windfarms' output.

Thus, detractors of wind have argued, use of a large amount of wind would require the building of a substantial amount of faster-responding backup plant - probably "pumped storage" facilities, in which water is pumped uphill using electricity when prices are low, then later allowed to flow downhill through generator turbines when prices are high. (The price differences need to be substantial for the pumped-storage plant to pay its way, as a lot of 'leccy is wasted doing this.) Pumped storage plants cope well with short-term, spiky variations in wind whether they are storing or generating at the time; one can throttle the pumps up and down as rapidly as one can the turbogenerators.

As one might expect, given that Spanish wind was able to cope with a big fraction of demand - albeit the low demand of night-time - a large amount of pumped storage was in play. Hydro stations were never less than 6 per cent of total "demand" during the 0300-0830 period trumpeted by the wind biz, and sometimes more than 10.

Given enough pumped storage in operation, there won't be any catastrophic grid problems when large amounts of wind power are used. Wind needs pumped storage in order to stop being marginal - the use of fancy meteorological networking is comparatively unimportant.

Unfortunately wind also needs thermal power too. Pumped storage facilities able to power a nation for days are physically possible - though you'd probably have to start building them out at sea once the supply of mountain valleys ran out - but not economically possible.

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