Before the Fukushima earthquake and tsunami four years ago this month, Toyotas automotive plant in Miyagi Prefecture, north of Fukushima, had relied entirely on the Tohoku Electric Power Co. for energy. But when the disaster shut down power to its plant for two weeks, managers realized that the company needed a more secure source. The factory couldnt be independent of the electric grid, but it could manage that energy betterand supplement it.
The earthquake was a big turning point, says Atsuji Morita, a project manager for Toyota. We had this big blackout and realized we needed a new system to increase our energy security.
Thats a common theme in Japan these days. After the disaster knocked out power to much of eastern Japan, smart microgrid projects from industrial to residential changed their approach. Initially focused primarily on energy efficiency, projects have shifted the emphasis to generating energy where it is consumed and to having a diversity of power sources.
In February 2013, Toyota formed a limited liability partnership called the Factory Grid, or F-Grid, to create a smart grid that manages and provides supplemental power to seven factories (most of them owned by Toyota) within the industrial park.
F-Grid has built its own natural-gas-fired cogeneration plant, which produces 7,800 kilowatts. That plant is supplemented by 740 kW from solar panels. And, in a creative twist, the factory uses an array of old Prius batteries capable of adding 90 kW of power from energy stored during slow periods at the industrial park. In an outage, even if all other power sources fail, the Prius batteries can supply enough power to keep satellite phones and computers running for three to four days.
The microgrid is operated by a community energy management system, which polls each facility about power needs and manages distribution of energy among them. In the event of an outage, F-Grid plans to also supply power to the local disaster response center, located in a village about a kilometer away.
The need for power diversity is reflected in small, residential projects as well. Honda, for example, is developing a smart-home system in cooperation with Toshiba and the biggest home builder in Japan, Sekisui House. Honda has so far built two demonstration homes in Saitama, a part of the metropolitan Tokyo area. Although plans for the project had already been in the making, after the earthquake the project developers focus shifted to providing energy security during emergencies. That is the new meaning of smart in Japan, says Naohiro Maeda, a manager in Hondas Smart Community Planning Office. Our goal is to produce the energy on-site that we need to consume on-site.
Each homes energy system consists of rooftop solar panels, a gas cogeneration unit, a home battery unit, a hot water tank, an electric car (a Honda Fit), and an energy management system called Smart-e Mix Manager. The home battery stores energy for times when solar power is not available. Ninety percent of Japanese households use both gas and electricity, and after the 2011 disaster, natural gas came back on in many areas sooner than the electricity, according to Maeda. The cogeneration system produces electricity to power homes and heat water. Thats important, because 60 percent of household energy use in Japan is for heating, and half of that is specifically for heating water for baths and cooking, says Maeda. Daily bathing is so important in Japanese culture that the Japanese army made it a priority to set up a communal bath for evacuees after the 2011 disaster, he says.
Source: IEEE Spectrum
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14 June 2017