Green Car Journal Online
Dialogue > On efficiencies, energy, and why we need electric cars
Paul MacCready Speaks Out
...on efficiencies, energy, and why we need electric cars
Interview by Ron Cogan
Dr. Paul MacCready is no stranger to advanced technology vehicles. His
company, Southern California-based AeroVironment, was responsible for
building the famed GM Impact electric concept car that was unveiled at the
1990 L.A. Auto Show, as well as the GM Sunraycer solar car that preceded
it, an ultra-efficient machine that won the Australian Sunraycer in 1987.
His lifelong focus on efficiencies and the technologies that achieve them
have won him many honors, from the Lindbergh Award, Guggenheim Medal, and
Howard Hughes Memorial Award to NASAs Public Service Grand Achievement
Award and the Chrysler Award for Innovation in Design. His innovative
Gossamer Condor won the award for the first sustained, controlled
human-powered flight; the Condor now hangs in the Smithsonian Institution
alongside Lindberghs Spirit of St. Louis and the Wright Brothers 1903
Flyer. Schooled at Yale and Caltech, MacCready applies his expertise in
physics and aeronautics to surface transportation and holds strong views on
Ron Cogan: Given all weve learned about advanced vehicle technologies in
recent years, is hydrogen our best shot at creating the ultimate low
emission, high efficiency car?
Dr. MacCready: At AeroVironment, we develop land, air, and water vehicles
using various energy sources. We have made hydrogen fuel cell systems from
10 watts to 100 kilowatts and battery powered systems from a few watts to
over 50 kW. We are a flexible company that selects what works best. For the
practical role of cars, economics and efficiency strongly call for battery
power, not hydrogen/fuel cell power. Both hydrogen and batteries are energy
deliverers, not basic energy sources. For a car, using hydrogen to generate
electrical energy for powering the vehicle is about one third as efficient
as using a battery. Also, a fuel cell does not work in the reverse
direction except in very expensive units, and so cannot serve to store
energy from braking or give utility energy back for adjusting utility
levels. Every house, along with electricity, becomes an energy source for
the battery-powered car.
RC: Youre noted for embracing efficiencies. Could you explain?
Dr. MacCready: We should learn to get by on much less energy and get
energy from the permanently available resources of solar radiation, wind,
streams, waves and tides, and carefully grown crops. We can do much of
this. We can make homes and factories that are very power efficient, and we
can make cars that are very power efficient. For example, we have made a
ceiling fan that uses only one sixth the electrical energy of a typical
ceiling fan a two time improvement in blade efficiency and a three time
improvement in the old fashioned electric motor.
For cars, the choices are energy sources and travel efficiency. It is
useful to start from ultimate efficiency say a car with no drag and with
100 percent efficient propulsion. This is a nice way to start designing
cars instead of taking last years model and having to improve it. Such a
vehicle will have infinite range if we ignore the power steering, lights,
horn, etc. Backing off from the perfect efficiency picture, we can have
power coming from a lithium battery with 93 percent in-out efficiency, low
drag tires of 0.7 percent of the weight they support, low aerodynamic
say the CD equals the 0.18 that was achieved with the GM EV-1, and
realize that drag reduction devices can probably cut this down by over a
third. The car should have a 300 mile range at good speeds and acceleration.
This range has already been achieved by AC Propulsions two-person vehicle
using 6800 small lithium cells of the type used for cell phones and
microcomputers at present expensive, but clearly illustrating the point.
For car efficiency, the use of batteries which are charged from the utility
grid is rather appealing. The batteries also get a charge from regenerative
braking during stops and when descending big hills. With a two-way charging
connection to the charging grid, the car can help the utility company
continually balance the short-term variations of the grids needs plus the
long term demand for running home air conditioners on hot days. The energy
so used is recovered late at night, say midnight until 6 a.m., by normal
RC: So youre saying that from the standpoint of efficiencies, we should be
looking to battery electric cars?
Dr. MacCready: This battery-powered car is a great goal for the future,
but is a bit expensive now because of the cost of the batteries.
Incidentally, the lithium cells used would offer about 200 watt-hours per
kilogram (Whr/kg), compared to 35 Whr/kg of lead-acid cells or about 60
Whr/kg for nickel-metal-hydride cells. Lithium cells of over 50 percent
greater energy/kg can be expected in a few years. We do continuing
investigation of lithium cells for our small drone airplanes as well as
keep up with larger cells prepared for cars. Lithium cells, incidentally,
have very high power outputs as well as energy outputs.
RC: And fuel cell vehicles?
Dr. MacCready: Fuel cells do not deliver enough energy to be really useful
for cars. A vast new charging system would have to be created to supply
hydrogen fuel cell vehicles. Considering all the benefits and disadvantages
of hydrogen/fuel cell systems for standard cars, the potentials seem too
few. Efficiency is down, it only goes one direction, carrying capacity
(range) is low, complexity is high, and very expensive
and H2 leakage
represents a serious problem. The governments virtual exclusive attention
and support for hydrogen fuel cell cars, not battery-powered ones, is
RC: Then what should the government do specifically to help lead us in what
you would consider the right direction?
Dr. MacCready: They should be supporting finding a non-polluting source of
energy for movement and mobility. It should be whatever can be made
available that will be relatively inexpensive, and battery power fits this.
I think that ethanol properly made from the right crops can be a fuel that
is efficient, where it balances the CO2 of the atmosphere that it collects
and releases. But the ethanol made from corn doesnt balance
you end up
with bad CO2 coming from this. It is a type of fuel thats like fossil
fuel, which cant balance the CO2 problem. It deserves more attention and
there are other fuel sources associated with it, but not all problems have
been resolved and youd have to grow an awful lot of appropriate plants to
make this technology one that works. But it is moving along.
RC: Should we be looking at lighter or more exotic materials to increase
Dr. MacCready: There are groups working on plastic and steel. But it turns
out that by processing it properly, you can make steel much stronger than
that which is used in ordinary cars, and it doesnt cost much to do that.
So, you could make a car that is carefully designed with this new
technique, that weighs maybe two-thirds what a regular car weighs, and that
weight can save you fuel that youre consuming by cutting down on the
amount of energy needed to move.
RC: Do you feel that people really care about vehicle efficiencies?
Dr. MacCready: People buy cars for image and faster acceleration. The
weight of the car doesnt matter to them. Heavier is better. But we will
have to pay attention to this as time goes on because, if youre paying $5
a gallon for gasoline, you care about efficiency. If youre paying $1 a
gallon for gasoline you dont care about efficiency. There will still be
people who dont care about efficiency even at $5 dollars a gallon. A
couple of articles Ive read say that the gasoline were burning now has
real costs of about $5 a gallon if you attribute other things, such as some
percentage of our exercise in Iraq, to the price. If you put all the
numbers in it were burning about $5 a gallon gasoline, but its being paid
in other ways. We dont appreciate the subsidies that are going on.
RC: If you had your way, what kinds of cars would we be driving in the
short years ahead?
Dr. MacCready: The cars that this field should have for the next five to
15 years should be hybrids with enough electricity built in to provide all
your transportation for maybe a 60-100 mile range. The average driver of
such a car would operate exclusively on the battery for 80-90 percent of
the time, with the few trips farther out requiring use of the gasoline
motor to go any distance they want. As the cost of batteries goes down in a
couple of years, the price for 80 miles will be low enough so this is a
very logical direction. If you use gasoline as the other element to go long
distances and you find in five to seven years that the price of batteries
keeps going down, youll be able to get 300 miles from your battery and you
wont need the other gasoline power source in your car. It wont matter
whether you get that one or the model that goes just 80-100 miles on
battery power, with gasoline used for long distances. If the gasoline costs
$5 a gallon by then
it wont matter because you wont use very much of it.
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Felix Kramer fkramer@...
Founder California Cars Initiative
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