Actually, spiky supply is the least of the objections to wind power
Inconveniently, though, days-long midwinter calms across continental areas - certainly across western Europe - are a fact of life. If there were nothing but windfarms and realistic amounts of pumped storage, the lights would go out for days at a time on a fairly regular basis. Thus the existing thermal sector - or something just as powerful - would need to exist too, in a wind-grid future world.
The trouble with that is expense. Wind electricity is very expensive to begin with: only government market-meddling allows turbine farms to be built. In the UK, the costs are passed on to the consumer in the form of price rises - the Treasury pays nothing. As the government drives more wind into the market by cranking up the renewables-obligation scheme, pumped storage plant will need to appear alongside it - again, with the very large costs of the construction appearing on electricity or tax bills.
After a certain amount of renewables have been forced into the system, the thermal sector will decline to where it can no longer power the country reliably on its own - some would say we have already reached this point, in fact, as it requires only two big thermal plants to go offline unexpectedly to cause power cuts at the moment. Then, if nothing is done, the next long midwinter calm will see the lights go out - and the fridges shut off, the gas boilers' electric thermostats stop working, the trains cancelled etc etc - for days, not just hours.
In order for this not to happen, even more government action will be required in order to keep economically unviable thermal plants sitting about ready to fire up at a day or so's notice once the pumped-storage reservoirs are emptied - costing, again, a fearsome amount. In effect we will have replaced one system of powerplants - the old-time almost-all-thermal one - triplefold: thermal + wind + pumped. That would be very expensive indeed, all the more so as we are also planning to use a lot more electricity so as to replace petrol in cars, gas in homes etc.
That, in fact, is what people tend to object to about renewables - not the fact that their supply chart is so spiky, as diegocgteleline.es fondly believes, but the facts that they will be cripplingly expensive to use on a large scale in real life and will mean that the human race is always starved for energy. Affordable energy is what makes modern Westernised life so nice - it means regular washing, clean clothes, enough to eat for all, lighting, jobs outside the agriculture sector. Energy is water, information, leisure time, education. Making energy a lot more expensive makes all those things into luxuries: probably luxuries only possible for a small number of rich people, as in the sustainably-biofuelled, hydro- and wind-powered past.
Fossil fuels may well result in damaging global warming, or alternatively they may run out inconveniently soon. They absolutely definitely require the free world to truckle to nasty resource-rich governments, with associated evil effects on on foreign countries and ourselves. But none of these issues are so threatening as to justify more or less destroying modern society and remaking all of humanity as medieval (or if we're really lucky, 18th-century) eco-peasants, even if it could actually be done. Better, frankly, to have floods in fifty years and enough resources to build dykes and move populations, than spend the next twenty thousand years as hapless energy-poor primitives before being wiped out by the next ice age or spontaneous global warming* or asteroid strike. Better still, probably, to move to other kinds of thermal power and avoid all of this.
Better by far, ultimately, for the human race to strive to become independent of its mother planet for survival - to one day interact meaningfully with the vast universe around us, rather than staring into our own navels on the surface of one tiny dust-mote until some insignificant accident erases us all. Such aspirations are probably impossible even for a comparatively energy-rich fossil-burning society - something better will be needed. They are certainly impossible for a humanity powered by windmills.
Fortunately then, the Spanish wind biz are of course wrong when they say that they are now no longer marginal. Supplying 50 per cent of demand (possibly 50 per cent - this uses estimated figures, the actual metered wind output is significantly lower) in the middle of the night means nothing. Over time, Spanish wind actually supplies no more than 11 per cent of demand.
And in fact the Spanish government seems to have realised that renewables past a certain point are an expensive luxury indeed. The weekend's meaningless wind "record" comes against a background of Madrid cutting back sharply on its renewables subsidies. ®
*Yes, global warming has happened in the past without any human carbon emissions.