IEEE Spectrum - North American - March 2015 - 17

yoshikazu tsuno/aFP/Getty iMaGes

multiple input, multiple output:
The Kashiwanoha smart-city project uses energy
from electric-vehicle batteries, biogas, storage
batteries, solar panels, and the grid.

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 diversit y 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 Honda's Smart Community Planning
Office. "Our goal is to produce the energy
on-site that we need to consume on-site."

Each home's 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. That's
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.
The shift to emergency energy also happened in a smart-city project, called Kashiwanoha, on the outskirts of Tokyo. The
project is backed by the real estate developer Mitsui Fudosan, Hitachi, and Sharp,
in cooperation with local government, the
University of Tokyo, and Chiba University.
This smart city has been in development

for several years as a retail and business
area. Last summer, the project started
offering apartments and condos.
Kashiwanoha uses a wide variety of
power sources, although it still draws
most of its power-some 90 percent-
from the electricity grid. The high-rise
apartment buildings take advantage
of natural hot springs beneath them to
create a communal bathing area on the
third floor. Water for the residences is
heated using biogas generated from food
waste. The town uses a bank of Hitachi
lithium-ion batteries that can store up to
3,800 kilowatt-hours' worth of energy,
collected from the solar panels that are
distributed on rooftops throughout the
city and purchased from the grid at night,
when rates are cheaper. There are a few
small-scale wind turbines scattered
throughout the development as well.
The facility has a gas cogeneration
engine to provide power and heat in
emergencies, and it keeps a supply of oil
on hand in case the gas supply is interrupted, says Kiyoko Hama, a representative from Mitsui Fudosan and a member
of the Kashiwanoha urban planning and
development department. Communal
electric vehicles can also be used to store
electricity. All told, in an emergency
there would be enough auxiliary energy
to meet 60 percent of normal residential power requirements for three days.
The city optimizes energy use through
an energy management system. Residents can monitor energy use through
an app on their tablets or phones. The
development even encourages residents,
like 56-year-old Ryoji Iwasawa, to reduce
usage by rewarding them with points
they can use to shop at the mall across
the street. It's not like they need that
much of a push to cut down on their
usage, however. "We've all become more
cognizant of our energy use since Fukushima," says Iwasawa. -tam harbert

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Table of Contents for the Digital Edition of IEEE Spectrum - North American - March 2015