It's not just weirdo lefties.
Where the wind blows
Jul 26th 2007
From The Economist print edition
A grandiose plan to link Europe's electricity grids may recast wind power from its current role as a walk-on extra to being the star of the show
by Stephen Jeffrey
PLUG in your toaster—or your television or your vacuum cleaner—and the electricity that surges through it is an alternating current. The question of whether the world would be powered by direct current (DC), in which electrons flow in one direction around a circuit, or by alternating current (AC), in which they jiggle back and forth, was decided in the 1880s. Thomas Edison backed DC. George Westinghouse backed AC. Westinghouse won.
The reason was that over the short distances spanned by early power grids, AC transmission suffers lower losses than DC. It thus became the industry standard. Some people, however, question that standard because over long distances high-voltage DC lines suffer lower losses than AC. Not only does that make them better in their own right, but employing them would allow electricity grids to be restructured in ways that would make wind power more attractive. That would reduce the need for new conventional (and polluting) power stations.
AC/DC/PC
Wind power has two problems. You don't always get it where you want it and you don't always get it when you want it. According to Jürgen Schmid, the head of ISET, an alternative-energy institute at the University of Kassel, in Germany, continent-wide power distribution systems in a place like Europe would deal with both of these points.
The question of where the wind is blowing would no longer matter because it is almost always blowing somewhere. If it were windy in Spain but not in Ireland, current would flow in one direction. On a blustery day in the Emerald Isle it would flow in the other.
Dealing with when the wind blows is a subtler issue. In this context, an important part of Dr Schmid's continental grid is the branch to Norway. It is not that Norway is a huge consumer. Rather, the country is well supplied with hydroelectric plants. These are one of the few ways (but not the only way, see article) that energy from transient sources like the wind can be stored in grid-filling quantities. The power is used to pump water up into the reservoirs that feed the hydroelectric turbines. That way it is on tap when needed. The capacity of Norway's reservoirs is so large, according to Dr Schmid, that should the wind drop all over Europe—which does happen on rare occasions—the hydro plants could spring into action and fill in the gap for up to four weeks.
Put like this, a Europe-wide grid seems an obvious idea. That it has not yet been built is because AC power lines would lose too much power over such large distances. Hence the renewed interest in DC.
Westinghouse won the battle of the currents in the 1880s because it is easier to transform the voltage of an AC current than of a DC current. High voltage is the best way to transmit power (the higher the voltage, the smaller the loss), but high voltage is not usually what the user wants. Power is therefore transmitted along high-tension AC lines and then “stepped downâ€
This is not legal advice.
