Fuels of the Future for Cars and Trucks
Dr. James J. Eberhardt
Energy Efficiency and Renewable Energy
U.S. Department of Energy
2002 Diesel Engine Emissions
Reduction (DEER) Workshop
San Diego, California
August 25 - 29, 2002
Fuels of the Future for Cars and Trucks
Dr. James J. Eberhardt
Energy Efficiency and Renewable Energy
U.S. Department of Energy
2002 Diesel Engine Emissions
Reduction (DEER) Workshop
San Diego, California
August 25 - 29, 2002
2
What Energy Source Will Power Engines of the Future?
q
Presently we know of no energy source which
can substitute for liquid hydrocarbon fuels.
q
No other fuels:
Ø
Are so abundant
Ø
Have such a high energy density
Ø
Have such a high power density
Ø
Store energy so efficiently and conveniently
Ø
Release their stored energy so readily
(rapid oxidation/combustion)
Ø
Have existing infrastructure
Ø
Are so easily transported
3
Potential Energy Carriers
q
Currently, we see only 2 potential non-carbon
based energy carriers that have the requisite
volume needed to replace petroleum fuels
Ø
Hydrogen
Ø
Electricity
4
Energy Density of Fuels
Thousand Btu per ft
3
F-T
Diesel
Liquid H
2
1058
990
922
683
635
594
488
270
266
68
16
950
0
200
400
600
800
1,000
1,200
Diesel
Biodiesel
LPG
Ethanol
CNG (@ 3626 psi)
CNG
(@ 3626 psi)
Diesel Fuel
LNG
Compressed
Hydrogen
(@ 3626 psi)
Methanol
Gasoline
Ethanol
NiMH
Battery
Propane
Biorenewable
Diesel
5
Percent of Diesel Fuel Energy Density
Energy Density of Fuels
Normalized to Diesel Fuel
89.8%
87.2%
56.2%
46.1%
25.5% 25.1%
6.4%
1.3%
64.6%
60.0%
100.0%
93.6%
0.00
0.20
0.40
0.60
0.80
1.00
1.20
Diesel
Biodiesel
LPG
Ethanol
CNG (@ 3626 psi)
NiMH
Battery
F-T
Diesel
Liquid H
2
CNG
(@ 3626 psi)
Diesel Fuel
LNG
Compressed
Hydrogen
(@ 3626 psi)
Methanol
Gasoline
Ethanol
Propane
Biorenewable
Diesel
6
0%
10%
20%
30%
40%
50%
70%
Conventional ICE
Fuel Cell-Stored Hydrogen
Today's Capability
Projected Capability
(2004)
Peak Thermal Efficiency (%)
Fuel Cell-Methanol
Reformer
Fuel Cell-Stored
Hydrogen
Compression-Ignition
Direct-Injection ICE
Gas Turbine
Conventional Spark
Ignition ICE
Heavy Duty
DI -Diesel Engine
60%
Gasoline Direct
Injection
Comparison of Energy Conversion Efficiencies
Homogeneous Charge
Compression Ignition*
* HCCI research focus: operate well across the load-speed map and extend the operating range to higher loads
7
Vehicle Range Limitation -
Challenge To Be Overcome By Alternatives
0
20
40
60
80
100
Comparison of Miles Driven
(Same Volume of On-Board Fuel)
Diesel Engine-
Conv. Diesel Fuel
Diesel Engine-
F-T Diesel
Direct Injection
Engine- Gasoline
Adv. NG Engine-
CNG (3,600 psi)
Fuel Cell-
Hydrogen (3,600 psi)
Fuel Cell - Gasoline
Today's Capability
Projected Capability
(2004)
8
The Defining Characteristic: Car versus Truck
Car: A vehicle designed for a payload (people)
which
never
exceeds its unloaded weight
Heavy Truck: A vehicle designed for a payload
which
routinely
exceeds its unloaded weight
9
Truck Classification (by Gross Vehicle Weight)
CLASS 1
6,000 lbs. & Less
CLASS 2
6,001-10,000 lbs.
CLASS 4
14,001-16,000 lbs.
CLASS 5
16,001-19,500 lbs.
CLASS 6
19,501-26,000 lbs.
CLASS 8
33,001 lbs. & Over
CLASS 3
10,001-14,000 lbs.
CLASS 7
26,001-33,000 lbs.
10
Vehicle Type
Common GVW
(lbs)
Unloaded
Weight (lbs)
Payload (lbs)
Payload to
Unloaded Weight
Ratio (%)
Family Sedan – 5
passengers
3,400
~ 3,100
~ 1,000
(5 x 200 lb)
32
Light Truck
5,150
4,039
1,111
28
Class 2b Truck
8,600
4,962
3,638
73
Class 3 Truck
11,400
5,845
5,600
96
Class 4 Truck
15,000
6,395
8,605
135
3-axle single unit
truck
50,000 to 65,000
~ 22,600
27,400 to 42,400
121 to 188
4-axle single unit
truck
62,000 to 70,000
~26,400
35,600 to 43.600
135 to 165
5-axle tractor semi-
trailer
80,000 to 99,000
~ 30,500
49,500 to 68,500
162 to 225
Cars and Light-Duty Trucks vs. Heavy-Duty Trucks
11
Volume of Fuel Needed for Equivalent Range
(1,000 mile range)
Diesel Fueled – Two (one on each side) 84 gallon tanks (23 ft
3
)
Fuel Cell/Hydrogen Fueled – Two 1,180 gallon tanks (316 ft
3
)
at 3,600 psi (Each tank approximately: L = 150”, D = 48”)
Loss of revenue
cargo space!
12
Space and Weight Estimates for HV Batteries
Cargo Space in trailer is typically 6,080 ft
3
Front Axle Capacity is 12,000 lb, Rear Axle Capacity is 38,000 lb
Assumptions: Truck: 310 HP, 6 mpg fuel economy, 45% average engine thermal efficiency, Batteries: Spec. Power 241
W/kg, Energy Density: 143 Wh/l, Spec. Energy 121 Wh/kg
85%
(% of total capacity)
5.9%
(% of cargo)
(lb)
(ft
3
)
42,635
358
Range -
500 miles
Battery Weight
Battery Space
Performance
LMP Batteries
13
q
Sodium borohydride (a salt) is dissolved in water where it stays
until gaseous hydrogen is needed
q
When H
2
is needed, the solution is pumped over a catalyst
q
The H
2
gas comes out and leaves behind sodium borate
(another salt) which remains dissolved in water and goes to the
spent fuel tank.
q
NaBH
4
2H
2
O
Na 23
2O 32
We have to carry 73.8kg
B 10.8
2H
2
4
for every 8kg of Hydrogen
4H
4
which is about 11% by weight
37.8
36
or <50% that of methane, CH
4
A Compact and Portable Way to Store
Hydrogen for the Fuel Cell Car?
NaBH
4
+ 2H
2
O 4H
2
+ NaBO
2
catalyst
14
NaBH
4
+ 2H
2
O 4H
2
+ NaBO
2
catalyst
q
Sodium borohydride is derived from borax, which is abundant
and widely available
q
Sodium borate is a common, non-toxic household item used in
detergents
q
Sodium borate can be recycled into new sodium borohydride
q
To recycle sodium borate into new sodium borohydride requires
reduction reaction in a kiln at 900
o
C under highly corrosive
environment
q
Coke or methane (CH
4
) is needed
CH
4
+ NaBO
2
900C
NaBH
4
+ CO
2
q
It takes more energy to make sodium borohydride than the
energy released (or recovered) in the fuel cell
A Compact and Portable Way to Store
Hydrogen for the Fuel Cell Car?
Claims
The Rest of the Story
15
Volume of Fuel Needed for Equivalent Range
(1,000 mile range)
Diesel Fueled – Two (one on each side) 84 gallon tanks (23 ft
3
)
Fuel Cell/H
2
from NaBH
4
in Water –
Twenty-six 84 gallon tanks (13 tanks containing
NaBH
4
/water solution weighing 15,058 lbs.; 13 tanks for spent fuel).
Batteries not included
(but required for fuel cell-hybrid configuration).
Loss of revenue
cargo space!
13
16
q
Hydrocarbon fuels need to be reformed on
board the vehicle to produce H
2
q
Furthermore, water gas shift is necessary
to convert the energy content in the
carbon-carbon bonds to H
2
q
Powertrain hybridization may be required
for heavy vehicle acceleration
To Enable Replacement of Petroleum as Primary
Energy Carrier for Ground Transportation
Fuel Cells for Heavy Vehicle Propulsion:
Practical Considerations
17
25
30
35
40
45
50
55
60
65
70
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Carbon Monoxide
Hydrogen
Percent of Energy in Reaction Products
C
n
H
2n+2
+ (n/2)O
2
nCO + (n+1)H
2
-
)
H
Energy Embodied in Carbon-Carbon Bonds Increases
with Hydrocarbon Molecular Weight
18
On-Board Reforming of Hydrocarbons to
Produce Hydrogen for the Fuel Cell
Partial oxidation of a hydrocarbon into CO and H
2
C
n
H
2n+2
+ (n/2)O
2
nCO + (n+1)H
2
-
)
H
Water-gas shift reaction of CO to produce more H
2
(also produces CO
2
)
POx
Steam
CO + H
2
O +
)
H
H
2
+
CO
2
19
q
Major technological breakthroughs are needed if
hydrogen fuel cells are to displace the diesel engine
Ø
Electrolytic/water “splitting” hydrogen production
(renewable, nuclear)
Ø
Low pressure on-board gaseous fuel storage OR
on board highly efficient hydrocarbon fuel reformer
Ø
Greatly reduced catalyst loading in fuel
stack/reformer (cost reduction)
q
Major technological breakthroughs are needed if
electrical energy is to displace the diesel engine
Ø
Electrical generation from non-fossil resources
(renewable, nuclear)
Ø
On board high energy/high power density electric
storage
To Enable Replacement of Petroleum as Primary
Energy Carrier for Ground Transportation
Research Breakthroughs Are Needed
20
DOE’s FreedomCAR and Truck Partnerships
“While FreedomCAR is concerned with light-duty
vehicles, we are also working with trucking industry
partners on a revitalized 21
st
Century Truck Initiative.”
“Unlike FreedomCAR, which is focused on
hydrogen powered fuel cells, this 21
st
Century Truck
Partnership will center on advanced combustion
engines and heavy hybrid drives that can use
renewable fuels.”
“The new technologies in these engines and drives
could, in effect, result in heavy truck transportation using
dramatically less diesel fuels and throwing off virtually
no emissions of NOx or soot.”
-
Remarks of Energy Secretary Spencer Abraham at the 13th Annual
Energy Efficiency Forum, National Press Club, June 12, 2002
21
Heavy-Duty Diesel – Increasingly
Dominant Engine for Heavy Vehicles
q
Improved fuel quality
q
Combustion technology
Ø
DI rate shaping/electronic controls
Ø
HCCI (part load)
q
Aftertreatment technology
q
Hybridization
Future Liquid Fuels Strategy?
In-cylinder Processes
Diesel Engine
Fuel Quality
Exhaust Treatment
l
Common
Diesel Fuel
Specification
l
Uses
Existing
Infrastructure
Efficient Low
Emission Heavy
Vehicles
Clean Diesel
Fuels/Blends
Advanced High-
Efficiency Clean Diesel
Engine Technologies
High-efficiency clean diesel-cycle engines utilizing compression
ignitable clean fuels/blends derived from diverse feedstocks
Multiple
Alternative
Feedstocks
Synthesis gas
route to:
Conventional
petroleum
refining
Liquid Fuels
•
Coal
•
Biomass
•
Natural Gas
•
Petroleum
Locomotive
Construction/
Farming Vehicles
Heavy Truck
23
Fischer-Tropsch Fuel Production
New Fischer-Tropsch production with partial oxidation
and Cobalt-based catalysts reduces CO
2
formation
Fischer-Tropsch Reaction
New Syngas Production
H
2
/CO ratio
near-ideal
H
2
/CO ratio
non-ideal
CO + H
2
Co catalyst (H
2
C-)
n
+ H
2
O
(g)
+ heat
steam reforming CH
4
+ H
2
O Co-based 2H
2
+ CO
catalytic partial oxidation CH
4
+ 1/2 O
2
CO + 2H
2
+ heat
24
q
Low sulfur diesel fuel (15 ppm)
q
Low sulfur gasoline (30 ppm)
q
Niche fuels in heavy-duty market
Ø
Natural Gas (as gas - CNG) – local delivery
fleet vehicles
Ø
LNG (long haul fleet vehicles)
Ø
Biodiesel (B20) (long haul vehicles, marine
applications)
q
Natural gas derived liquids
Ø
Fischer Tropsch (blendstock for petroleum
Diesel fuel)
q
Ethanol as replacement oxygenate for MTBE in
gasoline
Fuels for the Next 10 Years
Dominant
25
Summary
What Will Be the Fuels of the Future?
q
In the Near Term
Ø
Low sulfur gasoline and low sulfur diesel
q
In the Mid to Long Term
Ø
Hydrogen from safe on-board storage appears
promising for light-duty vehicles (FreedomCAR)
Ø
Breakthroughs are necessary in the economical
production and intermediate storage (e.g., CH
3
OH,
NaBH
4
) of hydrogen for light-duty vehicles
q
For the Foreseeable Future (Next 10 - 25 years)?
Ø
With no alternative yet identified, it appears that
hydrocarbon-based fuels (from a variety of
feedstocks) will be the future fuels for heavy-duty
vehicles