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looked to such traditional designs for ways to save energy. Since
the city will depend almost entirely on electricity from solar power,
which is five times the price of electricity from the local grid, the
city needs to be roughly five times as energy e cient as compet-
ing developments nearby.
One of the first things Evenden did was subtract cars: with the
highways gone, the city's buildings could be separated by pas-
sages just 7 to 12 meters wide, close enough to shade each other
yet far enough apart to let in indirect light. That's a cheap way to
reduce the need for not only air conditioning but electric light-
ing, the largest drain on electricity in commercial buildings. Insu-
lation is cheap, too: in the Masdar Institute, Evenden plans to
use 30-centimeter-thick insulation to keep out the heat. He's also
incorporating "skins" of copper foil that reflect light and conduct
heat away from the buildings. The foil will be protected from the
desert dust by a self-cleaning Teflon-like plastic. To reduce the
need for energy-intensive desalination, Evenden's design will
cut water consumption by 75 percent through recycling, low-flow
fixtures, and waterless urinals.
A small fraction of the energy that's still needed to run the
city will come from waste-based fuel and perhaps geothermal
power. The rest will come from the sun---but not all of it through
expensive photovoltaics, which convert sunlight into electricity.
Much cheaper devices that concentrate heat from the sun will
heat water and run a type of air conditioner called an absorption
chiller. (This is the same kind of technology that is used now in
In theory, it should all work. But in practice, even much less
ambitious projects have failed. Oberlin College's Lewis Center
features many of the same elements of energy-e cient design:
thick insulation, natural ventilation with heat exchangers, plenty
of windows to o set the need for electric lighting, and heat pumps
rather than conventional furnaces. A 60-kilowatt array of solar
panels on its roof was supposed to produce as much electricity
over the course of a year as the building consumes. Yet the build-
ing initially used too much energy, and the solar panels were not
adequate. To achieve zero net energy, the college had to install an
extra solar array nearby, more than tripling the total power produc-
tion. It added over a million dollars to an already expensive build-
ing, estimates John Scofield, a physics professor at Oberlin who
has published a detailed analysis of the building's performance.
In general, architects find that predicting how energy-e cient
systems will interact gets much harder as buildings get bigger. In
buildings designed to take advantage of natural light, for example,
designers can install sensors to automatically switch bulbs o
when enough light comes in from outside. But lights turning on
or o in one sensing zone may a ect the sensors in another. In
some buildings this has created a feedback loop that makes lights
cycle on and o annoyingly.
Neighboring heating and cooling zones can also a ect one
another to create complex and unpredictable feedback loops,
especially as the number of zones increases. United Technolo-
gies' J. Michael McQuade recalls what happened when his com-
pany designed what was supposed to be an intelligent heating,
ventilation, and air-conditioning management system for a new
building in Paris. The system was designed to coördinate 3,000
di erent zones. "When that building was first put together, it was
a significant energy consumer, and it took a revamp of the inte-
grated control systems to get it right," McQuade says.
If zero-emissions buildings are to be economical, Scofield says,
the designs will have work from the start. "If you don't get it right,"
he says, pointing to the fiasco at Oberlin, "every correction you
make is so much more costly than getting it right the first time."
Masdar City will be raised on concrete stilts to make room for a
personal rapid-transit (PRT) system that will replace buses and
trains with smaller vehicles designed for four people. Masdar's
planners expect the system to use less energy than conventional
mass transit, and they say it will be more convenient, too.
In a PRT system, several small vehicles, often called pods,
are kept waiting at each station. An individual or a small group
boards one and selects a destination; the pod proceeds automati-
cally to the destination without stopping. In a typical design, each
vehicle resembles a battery-powered golf cart, only it's completely
enclosed and somewhat bigger---and it lacks a steering wheel. The
vehicle follows a track, which is connected to stations by on-ramps
and o -ramps, and a computer controls how the pods enter and
exit the stations: the ramps allow individual pods to make stops
while others continue along the main track at top speeds. Simu-
lations suggest that the systems could run with as little as half a
second between vehicles.
But although PRTs look promising, they haven't caught on.
That's in part because an early PRT-like system built in the 1970s in
Morgantown, WV, gave the idea a bad name, says Jerry Schneider,
an emeritus professor of urban planning and civil engineering at
the University of Washington in Seattle and a longtime advocate
of PRTs. "People would get on the vehicles and they wouldn't stop,"
Schneider says of the system, a transit line with automated cars
for about 20 people. Technology has improved since then, he says,
but there hasn't been a significant real-world demonstration of
the updated systems.
Two demonstration programs are on the way. The first, which
will transport passengers to a new terminal at Heathrow Interna-
tional Airport near London, will open later this year. Tests of that
system are already under way. And the first stage of the system at
Masdar City, to be built by the Dutch firm 2GetThere, is scheduled
to be in place for the opening of the Masdar Institute this fall.
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