Why Convert To Electric Vehicles?
OR
Evaluating Energy Storage and Conversion Schemes
L. Van Warren
© 1992-98 L. Van Warren • All Rights Reserved
Presented to:
Electric Auto Association at Pasadena City College - December 1992
revised for Honda R&D Raymond Ohio - January 1998
Introductory Assumptions
1) Continuing to pollute the air we breathe is unacceptable.
2) There are 20 million  polluting internal combustion vehicles in California alone [1].
3) Electric vehicles (EV's) produce almost no air pollution.
4) EV's have limited range compared to traditional vehicles.

Air Pollutants
 carbon monoxide: product of incomplete hydrocarbon combustion, binds preferentially and irreversibly to hemoglobin 255 times more readily than oxygen.
 hydrocarbon vapors: product of hydrocarbon use.
 lead: heavy metal, proven link to brain damage.
 ozone: irritant, product of hydrocarbon combustion.
 oxides of nitrogen: product of hydrocarbon combustion, acid rain constituent.
 sulfur dioxide: product of charging EV's from coal fired power plants, acid rain  [2].
 sulfur trioxide: product of charging EV's from coal fired power plants, acid rain.
 formaldehyde: product of methanol combustion.
 acetaldehyde: product of ethanol combustion.
 waste heat: product of all combustion.

Evaluating Energy Storage and Conversion Schemes
Using the above definitions, any proposed energy storage scheme can be assessed by answering these questions:

1) What is the specific energy of the scheme?
2) What is the specific power of the scheme, during chargeup and discharge?
3) What is the energy storage density?
4) What is the specific cost?  This includes an accounting of:
    a) the initial cost
    b) the number of times the system can be cycled
    c) the cost of disposal.
5) What is the short, medium and long term environmental impact?

Energy Definitions
specific energy: energy stored per unit mass, also called energy density.
specific power: power available per unit mass.
energy density: energy stored per unit volume.
energy cost: cost per unit of energy.
 
Specific Energy Storage of Various Storage Schemes
If we consider an idealized car traveling at constant speed on level ground, we can use the energy numbers above to calculate the range in terms of freeway miles.  These figures are most valuable for comparative purposes and can be scaled corresponding to the extent to which the system they are deployed in is optimized.
 

Energy
Storage System
Specific Energy
(kJ/kg)
Range
(miles)
Reference
Fusion
35,000,000,000
 9M
Culp [3]
Fission
500,000,000
132K 
Culp
Lithium Hydride 700°C
3,800
1000
Culp
2-cycle Aviation Engine
3,010
790
Me
4-cycle Aviation Engine
2,480
650
Me
4-cycle Auto Engine
1,440
380
DEMI
Phosphorus Combustion
1380
360
Me
Magnesium Combustion
980
 260
Me
Thermite
520
 140
Me
Silver Zinc Battery
420
 110
Hughes
Zinc Air  Battery
400
105
MATSI [4]
Sodium Sulfur  Battery
290 
 75
ANL [5]
Nickel Cadmium  Battery
200
 50
ANL [6]
Lead Acid  Battery
120
 30
ANL [7]
Flywheel
80
 20
ANL
Compressed Air
70
 18
Culp
Rubber Band
20
 5
Culp
Specific Power of EV Battery Systems
Power consumption doubles when you go from 55 to 77 mph due to the fact that aerodynamic drag increases as the square of the speed.  It is important from a design point of view therefore, to consider the specific power of the energy storage and conversion system.  Fuel cells are a good example of this.  A reasonably sized fuel cell has good energy per unit mass but poor power availability per unit mass.

Advantages of HEV's over pure EV's
The above energy arguments can be extended to compare a hybrid EV (that utilizes a small propane engine/alternator system) with a battery-only system.

My proposed HEV, the ElectricStorm™ utilizes an 7.9 kilowatt AC power producing subsystem.  This alternator subsytem weighs 330 pounds with 73 pounds of fuel.  It consumes 5.84  pounds of fuel per hour at full power and can run for 12.51 hours without stopping.  Its specific energy is 2378 kJ/kg.

The ElectricStorm™ would also carry a 550 pound, lead-acid battery pack with a specific energy of 117 kJ/kg..

By weighted summation we obtain the effective specific energy of the
965 kj/kg for the whole system.  This is better than half the specific energy of conventional vehicles with less than one quarter of the emissions.  For short trips the recharger is off, so there are no emissions at all.  The engine runs at a fixed rpm and can be optimized for that speed in power output and emissions reduction.  When you run out of charge in a pure electric car you have a problem.  When you run out of charge in a hybrid, you start the on-board recharger and "limp" home.  The level ground  "limping" speed for the ElectricStorm™ would be approximately 40 mph on level ground with no wind.
 
Footnotes:

1) Half of these 20 million vehicles are in Southern California.
2) According to Mike Kaiser 1990 Southern California power comes from:
 

2.4% oil (6% nationwide)
13% out-of-state coal 
17% natural gas
20% nuclear
44% is  purchased (gas, wind, bio, geo)
3% hydroelectric
3) Principles of Energy Conversion by Archie W. Culp Jr. McGraw-Hill 1979
4) DEMI's claims 583 kJ/kg for the zinc-air system in Chrysler Minivan.
5) Chloride claims 360 KJ/kg for the sodium sulfur system in G-Van.
6) Saft's claim of 201 KJ/kg for their STM nicad is believable.
7) This agrees well with the MATSI claim of 126 kJ/kg for the Pulsar.