Part
of the problem is that a number of teams (including ProEV)
have created impressive electric powered race cars by converting
ICE designs. These electric race cars are able to go out and
turn a lap, at, or better than, their gas cousins. Building
powerful electric race cars is not a problem.
What is a problem is carrying enough energy to allow the EV
race car to do those lap time for more than a few laps.
Gasoline
is light. Batteries are heavy. If we add more batteries, the
car can no longer turn fast enough lap times.
Here is some basic math to help explain how important the
difference is:
Gasoline
contains 33.41 kWhrs per gallon (8.83 kWhrs per liter)^{[i]}.
Gasoline weighs in at about 6.073 lbs. per US gallon (.728
kg per liter).
So each pound of gasoline contains 5.50 kWhrs (12.129 kWhrs
per kilogram).
Since, when racing, the gasoline race car starts with a full
tank and ends with an empty tank, the average weight of the
gasoline carried through the race is 1/2 the starting weight.
This effectively doubles the energy per pound in gasoline
compared to batteries in racing. So this puts gasoline at
11.00 kWhrs per pound (24.258 kWhrs per kilogram) in comparison
to batteries.
However, the internal combustion engine is very inefficient.
Even Formula 1 engines only manage 30% efficiency ^{[ii]}.
This gives us 3.30 kWh per pound (7.28 kWhrs per kilogram)
usable energy in gasoline.
There are a number of types of lithium batteries. They have
different advantages and disadvantages. Wikipedia puts the
specific energy at a range of 0.0450.120 kWhrs per pound
(0.1000.265 kWhrs per kg) ^{[iii]}.
Electric
motors range around 80%99% efficient ^{[iv]}.
My experience with racing EVs indicates that they tend towards
the lower figures but let's use an optimistic 95%. This gives
us 0.0430.114 kWhrs per pound (0.0950.252 kWhr per kilogram)
usable energy in the batteries.
So, whatever the starting weight of fuel in the gasoline
race car, the electric race car needs to carry 29 to 77 times
that weight.
To illustrate how poorly suited current race vehicle designs
are for electric power, let us convert a Formula 1 (ICE) car
to electric. We assume we are able to swap gasoline engine,
exhaust pipes, and large radiators for the same weight and
performance in electric motors, controllers and smaller radiators.
The Formula 1 car starts the race with a full tank of around
55 gallons (200 liters) of gasoline. To match the weight and
thus equal the performance of the Formula 1 car during the
first few laps of a Grand Prix, our battery pack cannot weight
more than the 330 lbs. (150 kg) of fuel.
Knowing that it takes around 10 pounds (4.5 kg) of gasoline
to complete a lap at Circuit de Catalunya ^{[v]},
how may laps can our electric Formula 1 car with it's 330
lbs. (150 kg) battery pack complete?
Best case, ten pounds multiplied twentynine times give us
a required battery weight of two hundred and ninety pounds
(130 kg). We can do a single lap.
Gasoline race cars are well evolved designs that make use
of power intensive techniques to produce grip, especially
aeronautical down force. EV race cars can produce the same
power, but the weight penalty of carrying the energy, make
it a terrible design choice.
We can, and will (eventually), build electric race cars that
will be able to run races at F1 speeds. We will not get there
by doubling or quadrupling battery specific energy. We will
get there by designing electric race cars to work with the
different design challenges of batteries. For information
regarding ProEV's ideas about what this vehicle will look
like, read "Rewriting
the Rules".

^{i.}
Wikipedia
"Gasoline gallon equivalent", n.d.,
http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent
(accessed: July
6, 2013)
^{ii.} Technical
F1 Dictionary "Fuel thermal efficiency", n.d.,
http://www.formula1dictionary.net/thermal_efficiency.html
(accessed: July
6, 2013)
^{iii.} Wikipedia
"Lithiumion battery", n.d.,
http://en.wikipedia.org/wiki/Lithiumion_battery
(accessed: July
6, 2013)
^{iv.} Wikipedia
"Gasoline gallon equivalent", n.d.,
http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent
(accessed: July
6, 2013)
^{v.}
Sam, "Formula
1 2013 Round 5: Spanish Grand Prix", May 10, 2013,
http://www.racecarengineering.com/articles/f1/formula12013round5spanishgrandprix/
(accessed: July
6, 2013)
