Editor's Note: This is part of the IEEE Spectrum special report: Fukushima and the Future of Nuclear Power.
26 October 2011—On 11 March, when the 9.0-magnitude earthquake struck off the northeast coast of Japan and triggered one of the deadliest tsunamis the world has ever seen, the bustling port city of Sendai was directly in harm’s way. The port was destroyed, the airport was swamped, and waves reportedly rolled 8 kilometers inland, killing hundreds of people. While downtown Sendai escaped heavy structural damage, activity in the city ground to a halt. Every traffic light and office lamp went dark after the wall of water knocked out the electricity grid for the entire city. In some areas, the outages would last for weeks.
But in one small section of the city, the lights stayed on. At Tohoku Fukushi University, in the northwest part of town, the laboratories’ servers kept on humming, the clinic’s MRI machines didn’t lose a tesla, and the hospital’s lights and equipment operated without a hitch. These facilities were the beneficiaries of an experimental microgrid project fed by three types of energy generators—fuel cells, solar panels, and natural gas microturbines. Because the project also uses the thermal exhaust from the gas turbines and fuel cells to heat the buildings, the hospital’s patients were kept warm through northern Japan’s cold March nights.
The project was intended to demonstrate a microgrid’s potential to improve power-supply reliability. It seems safe to say that its performance in the wake of the Great East Japan Earthquake provided ample proof.
The Sendai microgrid is a small distributed energy system with a total output of only 1 megawatt, but its setup yields certain advantages that make up for its diminutive size. For example, the microgrid’s power sources are close to its customers; this arrangement decreases energy losses during transmission and allows for the distribution of heat as well. And although the microgrid is connected to the larger "macrogrid," its independent energy sources make it less vulnerable to problems in the larger system.
The resulting reliability makes microgrids attractive to customers such as hospitals—which need a guaranteed, uninterrupted flow of power—while allowing utilities to avoid costly across-the-board improvements.
"Today, people have no options," says Keiichi Hirose, the head of the Sendai microgrid project. "The idea is to provide some options for electricity." In the Sendai system, customers pay different rates depending on the level of reliability they need.
The Sendai project was proposed and carried out by NTT, Japan’s largest telecom company, with initial funding from a government R&D agency. But even after the government’s four-year funding commitment came to an end in 2008, NTT decided to keep the microgrid alive and operational. Hirose, a senior research engineer with NTT Facilities, says the company is experimenting with distributed energy because it is looking for new ways to power its massive data centers.
The power center that forms the heart of the microgrid is noisy and industrial but oddly homey. The tops of the natural gas turbines’ cooling towers are covered with green nets to keep out cherry blossom petals from a row of trees that flower spectacularly each spring. The control room, packed with computers and ranks of batteries for energy storage, is housed in an undistinguished metal building. Still, workers trade shoes for slippers when they go inside.