Automotive Engineering - June 2021 - 30

READER
FEEDBACK
Solar power is the solution for EVs
The current enthusiasm for electric vehicles is based on the
premise that they will reduce air pollution. However: We could
put one gallon of fuel in a compact diesel vehicle and go 40
miles. Or, the same gallon of fuel could be used in an electric
power plant to run a small electric vehicle 28 miles. This
means that it will take 50% more fuel to travel the 40 miles,
and this will produce 50% more air pollution.
We submit the following technical explanation of how this
situation exists, using the overall systems efficiency to make
this comparison. See the accompanying table for Efficiency
values. For comparison, let's say the energy value of a gallon
of diesel is 33 kW-h and an average compact car delivers 4
miles per kW-h.
A) Existing Diesel Power
Conventional diesel-powered compact vehicles get about 40
miles per gallon. These vehicles would use 10 kW-h for the 40
miles and therefore be 30% efficient. Note that this is total
system efficiency.
Energy grid-to-vehicle efficiency
B) A gallon of fuel burned in a power plant will deliver 12
kW-h of electrical energy because the plant operates at 35%
efficiency.
C) Transferring this electrical power to the vehicle's charging
location is done at 85% efficiency, but this negative reduces
the power available to the car to 30% or 10 kW-h because of
line losses.
D) Electricity from the power plant is transmitted at a very
high voltage and it is on the alternating-current (AC) format.
Operations
A Gallon petroleum
B Gallon diesel
C Transfer power
D Transfer power
E Convert to DC,
reduce voltage,
feed to battery
F Motor
Correcting the voltage and converting it into the direct-current
(DC) format and feeding it into the EV battery will reduce
the efficiency to approximately 25%.
E) The electric motor in the vehicle is about 85% efficient so
the total system efficiency will be about 20%. This results in
about 7 kW-h of energy for a driving range of about 28 miles.
If the electric vehicle can only go 28 miles on a gallon of diesel
and the diesel vehicle can go 40 miles on the same gallon, it
will take 50% more petroleum fuel to drive the same distance.
Using more fuel will result in more air pollution and CO2.
If the interest in switching to electric vehicles is to reduce
air pollution, why are industry and governments taking a path
that will increase air pollution?
Alternative Solutions
Electricity can be generated from sources other than fossil
fuels to make steam to drive their generators. Wind, hydro
and nuclear systems are also used but they currently amount
to about 10% of the total U.S. national needs due to geographic
limitations.
The obvious solution for generating more electricity is
through solar cells. This method can be used in a variety of
ways. The obvious way is for each EV to have its own solar
generating panels. This would provide the vehicle owner
with most of the electric energy required for daily travel. It
would be pollution free and cost the owner nothing to operate.
The cost of the panels could be part of the vehicle loan.
(The electricity produced by power plants would still be
needed when the car might need a quick boost when on
longer trips.)
Operational
Efficiency %
100
30
35
85
85
85
Net
Efficiency %
100
30
35
30
25
20
Operational
Energy kW-h
33
10
12
10
8
7
Total Miles
*****
40
*****
*****
*****
28
Herb Adams and George Kraus
READERS: Let us know what you think about Automotive
Engineering magazine. Email the Editor at Lindsay.Brooke@
sae.org. We appreciate your comments and reserve the
right to edit for brevity and clarity.
30 June 2021
Mr. Adams is a graduate of General Motors Institute (GMI) and
a former head of the Pontiac Advanced Design department.
Mr. Kraus, a graduate of Fairleigh Dickenson University, has 40
years' experience in energy management and development of
energy-efficient HVAC products.
AUTOMOTIVE ENGINEERING
Automotive Engineering - June 2021

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