ONE reason for Japan’s reliance on nuclear power—with all its attendant difficulties of building reactors safely in an earthquake zone—is its lack of indigenous energy sources. Yet it does have one that seems under-exploited, namely the wind. According to a report published in 2009 by the Global Wind Energy Council, Japan, which generates 8.7% of the world’s economic output, has just 1.3% of its capacity to make electricity from the air. The world’s third-largest economy, then, is 13th in the world’s windpower league table.
According to Chuichi Arakawa, a mechanical engineer at the University of Tokyo, that is because Japan has too much of the wrong sort of wind. First, the typhoons which regularly strike the place are simply too powerful. (In 2003, for example, such a storm crippled six turbines on Miyakojima, near Okinawa.) Second, the regular winds that blow through the country are less useful than they might be because Japan is so mountainous. Engineering considerations require that a turbine be erected perpendicular to the Earth, regardless of the slope of the local hillside. But if that ground is, indeed, sloping, it means that the wind (which tends to follow the ground when it is close to the surface) hits the blades of the turbines at an angle instead of face on. That makes the whole process of power generation less efficient.
Help, though, is on the way. Engineers at Fuji Heavy Industries (FHI), a large manufacturing company, have come up with a turbine they think can withstand the sort of battering that brought down those on Miyakojima, and also turn the irregular mountain winds to advantage.
The crucial differences between FHI’s new turbine and a traditional one are in the location and setting of the blades. In a traditional turbine the blades are in front of the pole and also of the nacelle—the structure that houses the generator. In addition, the plane of the blades is parallel to the pole, so that a ground-hugging wind hits the blades face on. This is known as an upwind design.
By contrast, FHI has opted for a downwind design, which puts the blades behind both nacelle and pole. This allows the rotor plane to be tilted so that it faces directly into winds blowing up the hill without snagging on the pole. According to Shigeo Yoshida, who is in charge of research for the project, that makes the arrangement 5-8% more efficient in these circumstances than an upwind turbine would be.
As a bonus, the downwind design is less temperamental in high winds. That is because the blades, being behind the pole and at an angle to it, can be given more freedom to yaw about than they would have in an upwind turbine. This puts less strain on them than if they were fixed.
So far, 25 downwind turbines have been constructed in Japan, and dozens more are in the pipeline. Windpower will never, of course, replace the day-in-day-out reliability of nuclear or other thermal forms of electricity generation. But, as Japan has recently been reminded, it is never a good idea to put all of your eggs in one basket.