SPECIAL TO THE ASAHI SHIMBUN
2011/07/01
Yasuhiro Hayashi (Photo by Kazuhiro Yokozeki)Some people probably think it is possible to reduce Japan's dependence on nuclear power simply by aggressively promoting the use of renewable energy sources like solar and wind power.
But these natural, alternative energy sources have a serious drawback. The amounts of electricity generated with these sources are greatly affected by natural conditions, such as hours of sunlight and wind velocity. In other words, these are very unstable sources of electricity.
Quality control is vital for a dependable power supply. Electricity utilities in eastern Japan, for instance, need to keep the outlet voltage of their electricity supplies between 95 volts and 107 volts and their frequency between 49.8 hertz and 50.2 hertz, while balancing their power generation with changing consumption.
If large amounts of electricity generated with unstable renewable energy sources are fed into the grid, they will cause wild fluctuations in power output, making it difficult to maintain the quality of electricity supplies.
The ongoing research on smart grid technology could lead to a realistic solution to this problem. The goal is to develop technology to link the electrical grid to an information network in a way that allows efficient control of power supply and consumption.
Storing electricity for household use has long been a tough technological challenge. But the widespread use of electric vehicles would offer a convenient way to solve the challenge because electricity could be stored in the batteries of the vehicles.
Used batteries for electric vehicles can be diverted to use at homes. It is also possible to store electricity in the form of thermal energy by using a heat pump water heater for household use.
If a smart meter--an electrical meter that can track electricity consumption in real time and send that information back to the utility--is installed in households, it will be possible for each household to store electricity and thermal energy while PV power output is high and use the stored energy for home consumption when output is low.
The core function of the smart grid is to allow flexible storage and use of electricity in response to the changing balance between power output and consumption.
The technology can be a remedy for the problem of output fluctuations of power generation using natural energy sources as well as curb overall electricity consumption during peak demand hours.
Until now, electric utilities have been forced to spend huge sums of money to build facilities like nuclear power plants to have reserve capacity for peak demand. The smart grid will also help them cut their capital investment.
If electricity rates are set to vary according to changes in power output, households will be benefited by, for example, storing electricity during the hours when the rates are low. In short, the smart grid system combined with electricity storage devices would provide for smart energy saving without pain.
But smart grid technology will not be a cure-all. How much power from renewable energy sources can be fed into the grid and how sharply power consumption can be slashed during peak hours depend on the entire network's capacity of storing electricity.
Fortunately, Japan has cutting-edge technology for both storage batteries and heat pump water heaters. I believe that Japan will be able to achieve technological innovations.
In order to promote these innovations, the government should increase the use of renewable energy sources and promote smart grid technology to cover the supply from the nine nuclear reactors that will be built by 2020 under the government's basic energy development plan.
That would be a realistic first step toward lowering Japan's dependence on atomic energy.
(This article was compiled from an interview by Hiroyuki Ota.)
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Yasuhiro Hayashi is director of the Research Institute of Advanced Network Technology, Waseda University. Born in 1967, Hayashi is an expert in electrical energy systems. He heads an advisory panel on the smart meter system for the Ministry of Economy, Trade and Industry. His published works include "Sumaato Guriddo Gaku" (Research of smart grid).
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