2. 外语
  3. Usually alternating current (AC) transmission suffers lower losses than direct current (DC), and thus, AC became the industry st

Usually alternating current (AC) transmission suffers lower losses than direct current (DC), and thus, AC became the industry st

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问题     Usually alternating current (AC) transmission suffers lower losses than direct current (DC), and thus, AC 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.
    Wind power has some problems. You don’t always get it where you want it and you don’t always get it when you want it. 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. Dealing with when the wind blows is a subtler issue. For instance, 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 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. Dr Schmid calculates that a DC grid of the sort he envisages would allow wind to supply at least 30% of the power needed in Europe. Moreover, it could do so reliably—and that means wind power could be used for what is known in the jargon as base-load power supply.
    Though wind power has its opponents, too, its environmental virtues might be enough to swing things in its favour if it were also reliable. Indeed, a group of Norwegian companies have already started building high-voltage DC lines between Scandinavia, the Netherlands and Germany, though these are intended as much to sell the country’s power as to accumulate other people’s. And Airtricity—an Irish wind-power company—plans even more of them. It proposes what it calls a Supergrid. This would link offshore wind farms in the Atlantic Ocean and the Irish, North and Baltic seas with customers throughout northern Europe.
How will consumers think of a DC electricity grid?
选项 A、Not feasible yet.                                                
B、Quite economical.
C、Somewhat troublesome.                                      
D、Too bold.
答案B
解析 细节题。文章第三段指出，建设直流电电网可以节约在传输过程中浪费的电能，因此对于消费者来说这一方案是较为经济和节约的，也是可行的，因此正确答案为B。需要指出的是应区分economic和economical两个词语的区别，economic的意思是“经济(上)的，经济学的”，是宏观意义上的；而economical的意思是“节约的。俭省的”，是微观意义上的。
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