Paul MacCready Speaks Out
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
Sunrayce 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 NASA’s
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 Lindbergh’s
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 this subject. [EDITOR'S ADDENDUM: Dr. MacCready passed away in 2007 at the age of 81.]
Ron Cogan: Given all we’ve 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: You’re noted for embracing efficiencies.
Could you explain?
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MacCready
with circa-1987 Sunraycer |
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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 year’s
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
drag…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 Propulsion’s
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 grid’s 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 recharging.”
RC: So you’re 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 government’s virtual exclusive
attention and support for hydrogen fuel cell cars, not battery-powered
ones, is decidedly strange.”
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 doesn’t balance… you
end up with bad CO2 coming from this. It is a type of fuel that’s
like fossil fuel, which can’t 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 you’d
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 vehicle efficiency?
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 doesn’t 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 you’re 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 doesn’t matter
to them. Heavier is better. But we will have to pay attention to
this as time goes on because, if you’re paying $5 a gallon
for gasoline, you care about efficiency. If you’re paying
$1 a gallon for gasoline you don’t care about efficiency.
There will still be people who don’t care about efficiency
even at $5 dollars a gallon. A couple of articles I’ve read
say that the gasoline we’re 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 we’re burning about $5 a gallon gasoline, but it’s
being paid in other ways. We don’t 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, you’ll
be able to get 300 miles from your battery and you won’t need
the other gasoline power source in your car. It won’t 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 won’t matter because
you won’t use very much of it.”
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