IEEE Spectrum January, 2014 - 44

fUn faCts: Ordinary car noise: 70 decibels;
bus: 90 dB; Formula E: 80 dB; Formula One: 150 dB

the Green Guts of this year's
Formula e cars all come from
mclaren automotive.

In fact, it's the same system
McLaren supplies to all the
cars in the U.S. Indycar series,
although here it will run different
software. The electrical traction
systems run at 800 volts,
generating enormous amounts
of heat. It is channeled away from
the cars via water cooling and
lightweight heat sinks, says Peter
van Manen, managing director of
McLaren Electronic Systems.
A Formula E race will last
about an hour, with 10 teams
each fielding two drivers. The
cars will generally be allowed to
use no more than 134 kilowatts
of power (180 horsepower).
A certain number of times
in the race, however, they
will be permitted to boost to
200 kW, reaching speeds of
up to 220 kilometers per hour
(137 miles per hour).
The cars will race until
their batteries are exhausted-
about 20 minutes. And then
you'll see by far the strangest
thing about this race: Rather
than swap out the batteries,
the drivers will swap cars.
Each driver will get out, run
100 meters down the pit lane to
the team's garage, jump into the
fully charged spare car and race
for another 20 minutes while
the first car recharges. Then the
driver will make another pit stop,
run to the first car, and complete
the race. Power management will
therefore be a paramount skill,
as it was in the early days of flight.
Inductive battery charging
across an air gap, via coils
embedded in the road, would
eliminate the need for car
swapping and allow for lighter
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nORTh aMERICan

batteries. Indeed, FEH has
plans to use such a system,
developed by HaloIPT, a New
Zealand company acquired two
years ago by the cellphone firm
Qualcomm. This year, though,
the inductive charging will be
static, with just one pad on the
ground, and it will be used only
for a safety car, which is sent out
in front of the other cars to limit
their speed.
Another rule for this year only:
Each car will run on a single
electric motor developed from
the unit McLaren designed for
its latest street car, the P1 hybrid.
Weighing just 26 kilograms,
the motor spins at 17 500 rpm,
similar to the revs of a Formula
One V8, and develops 200 kW.
That gives a power-to-weight
ratio of 7.7 watts per gram, the
highest of any automotive power
plant in the world, says van
Manen. And although Formula
E cars are slower than Formula
One cars, they'll achieve far
greater acceleration because
of the instant availability of full
torque with electric propulsion.
The cars have also been
designed to generate current for
the battery during braking.
The series will start in Beijing
on 20 September and continue
on to Putrajaya, Malaysia;
Hong Kong; Punta Del Este,
Uruguay; and Buenos Aires
before reaching Los Angeles
on 14 February 2015 and Miami
on 18 April. Then comes Monte
Carlo, Berlin, and London,
where the series will finish on
27 June.
So will Formula E be the
spectacle that the organizers
hope for? Well, shutting down
the center of a city does tend
to attract attention. But one
complaint is that the experience
of motor sports is so tied up
with that sensory overload of
noise and odor that the quiet of
an electric motor will render it
sterile. Still, that hasn't stopped
audiences from thrilling to the
instant acceleration of electric
motorcycle racing, which has
had its own TTXGP racing series
since 2009.
Besides, electric cars have
a noise all their own. It's the
sound of the future.
-st ua rt nath a n
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SPECTRUM.IEEE.ORG

illustration by

Eddie Guy
http://SPECTRUM.IEEE.ORG
Table of Contents for the Digital Edition of IEEE Spectrum January, 2014
