Scientific sources and some math

Some additional information needs to be added to the Aug. 17 Japan Times editorial, "Ray of light amid the nuclear gloom."

The editorial mentions an estimated 23.5 gigawatts of geothermal potential in Japan. This figure is cited in the scientific paper "2010 Country Update for Japan," by H. Sugino and T. Akeno, presented at the 2010 World Geothermal Congress. In their paper, they identify many problems with accessing this geothermal potential, including lack of techniques for fully identifying the geothermal structure in the exploration phase; the time and investment needed to bring a geothermal development to fruition; and the fact that the easiest areas for geothermal power development have already been developed. They say a technical breakthrough to develop unused geothermal potential is necessary. So accessing that 23.5 GW is in no way assured.

On the solar power front, Tokyo Electric Power Co. has a new solar plant in Kawasaki, with an area of around 0.8 square kilometer. Its output is around 20 megawatts. To get the 150,000 MW Environment Ministry figure given in the editorial, we would need 7,500 more of these plants — covering an area of 6,000 sq. km. But since solar power plants have irregular output (the Tepco solar plant average output is around 12 percent of the maximum rating), the area needed to get the Environment Ministry number is closer to 50,000 sq. km, or slightly more than 13 percent of Japan's surface area. Given that such plants need to be built on flat ground, and that Japan's land is around 70 percent mountainous, we're looking at taking up almost 45 percent of Japan's nonmountainous land. We would need 50 billion solar panels (at 1 sq. meter each) to cover this area, and a lot of toxic waste is produced in the manufacture of solar panels.

With wind power, onshore turbines have to contend with lightning strikes and wind gusts; offshore ones must contend with these plus sea wave power and difficulty of access for maintenance. Moreover, wind intermittency results in an average output of 20 percent of maximum, so the actual number of turbines needed could be close to five times the number estimated based on the industry megawatt average per turbine. To avoid turbulence between windmills requires that a turbine be given around half a square meter of surface area per watt output.So, the turbines for the Environment Ministry's maximum onshore figure would use 10 percent of Japan's surface area.

In addition, both solar and wind generation would need massive power storage facilities (capacitors) to keep power for when the sun doesn't shine and the wind doesn't blow.

The editorial tells us that the cost of nuclear power does not take into account the massive subsidies given to the power industry. However, given the 2010 subsidy of ¥430 billion and the nuclear power output of 284 terawatt hours that year, the subsidy can be computed as ¥1.5 per kilowatt hour. That changes the editorial's power comparisons to the range of ¥6.3 to ¥7.7 per kilowatt hour for nuclear — compared with ¥9 to ¥14 for wind and ¥49 for solar. As for the cost of the Fukushima cleanup mentioned in the editorial, that does not rest on the shoulders of the power industry; it rests on Tepco and the government.

All things being equal, investing a sum of money in nuclear power will prevent six times more carbon dioxide emissions than an equal amount invested in solar. Expensive power will further pressure the nation's poor and make the switch to electric vehicles more difficult. Dr. James Hansen, considered by many to be the world's pre-eminent climatologist, considers investments in fourth-generation nuclear power essential for the survival of civilization. Japan, for now, should study how the Onagawa nuclear plant came out virtually unscathed by the March 11 earthquake — despite being 50 km closer to the epicenter — and apply those lessons to the rest of the nation's nuclear plants.

Plans for alternatives to nuclear power either seem infeasible or need much more research until their feasibility can be determined. If Japan starts down a nonnuclear path without doing solid scientific research beforehand, it'll be in for a lot of pain — and will probably have to rely on fossil fuels for most of its energy needs, thus contributing to global warming.

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The opinions expressed in this letter to the editor are the writer's own and do not necessarily reflect the policies of The Japan Times.