2. engines, which first burned wood or coal. Meanwhile, in the late 1800s,
electrically powered locomotives were developed and saw service.
Electric powered trolleys and trains were of interest because they avoided
the smoke problem, which was undesirable around cities and especially in
tunnels. The earliest trains used direct current (DC), but later versions
used alternating current (AC). In the last half of the 1900s, electric
trains entered high-speed passenger service, particularly in the case of
the Japanese “Bullet” trains and the French TGV system. In some
mountainous countries, such as Switzerland and Japan, electric traction
found widespread use. Today India hauls over 80% of passengers and
freight by electric locomotives, mostly AC powered. Electrification is
much more widespread in Europe, Japan, and India than in the U.S. The
infrastructure for electric trains is more costly, so where there are greater
distances to be covered, diesel locomotives are selected because of the
lower infrastructure costs.
Around the same time as the advent of steam powered trains, a few
impractical steam powered automobiles were built. It was not until 1886
that Karl Benz patented the predecessor of the modern automobile. Then
it was another 22 years (1908) until Henry Ford’s model T launched the
passenger car as a replacement for the horse and buggy. During the war
years, there were also some vehicles fueled with wood or other alternate
fuels.
Within transportation, passenger cars and light trucks are major energy
users, followed by public transportation (buses, trains, airlines and ships)
and freight. In describing important issues for energy management
research, the first edition of Energy Management Principles stated that
“Improvements and major new developments in transportation, (for
example, in the area of electric vehicles) are required.”4
Other than that
brief comment and a few sentences regarding the need for improving
vehicle fuel efficiency, encouraging van and carpooling, and promotion of
the use of bicycles, transportation was not considered.
At that time, a visible symbol of the importance of energy availability
was the long lines of motorists attempting to purchase gasoline during the
1973 oil embargo. When supplies resumed, public concern decreased to a
low level. Within six or seven years, the price had tripled, but people
continued to purchase gasoline because they were dependent on it for
their lifestyle. This is all the more remarkable because in the four decades
4
Smith, Craig B. (1980) p. 8, Energy Management Principles, NY: Pergamon Press.
220 Energy Management Principles
3. that have elapsed since that fateful year, gasoline prices increased by a
factor of more than ten, from around $0.35/gallon (regular grade) to as
much as $4.00 per gallon in the U.S., and higher in Europe and other
areas. People are still dependent on gasoline for their lifestyles, but energy
costs, environmental regulations, and consumer demand have been driv-
ing forces behind increased vehicle fuel efficiency.
In the intervening thirty-five years since the first edition was
published, we have seen remarkable changes in passenger vehicle
transportation energy use.
• In the U.S., Department of Transportation standards for the fuel
efficiency of passenger automobiles has increased from an average of
18 mpg in 1978 to 38 mpg in 2014 (smaller passenger vehicles).
Different standards apply to larger passenger vehicles and light trucks.
• Alternate-fueled vehicles (using natural gas) were introduced during
WWI in Europe, when vehicles with gas stored in bladders replaced
gasoline. In the 1960s, vehicles and buses using compressed natural gas
started appearing and the number has continued to grow.
• The first truly successful hybrid (Toyota Prius) was introduced in 1997
in Japan, and in 2000 in the rest of the world. By 2013 Toyota had
sold 3 million of these vehicles with a fuel efficiency of 48 to 51 miles
per gallon (20 to 22 kilometers/liter).
• The first commercially successful all electric automobile capable of a
range greater than 200 miles (the Tesla Roadster) was introduced in
2008.
• The Chevrolet Volt was introduced in 2010, initially with an
all-electric range of 38 miles, which later increased to 50 miles. Fuel
economy was reported to be 41 mpg as a hybrid.
Along the way, there have been many experimental vehicles, including
solar powered, fuel cell powered, bio-fueled and hydrogen-fueled.
RECENT TRENDS IN FUEL EFFICIENCY
During the last four decades the average fuel efficiency of passenger
vehicles has nearly doubled. From 1975 through 1988 there was a steady
improvement in mileage for new gasoline and diesel powered vehicles as
measured by the U.S. Environmental Protection Agency. As mileage
improved, there was a corresponding drop in CO2 emissions per mile.
(See Figure 10.1). This trend flattened out and then began to reverse in
221Transportation
4. 1990 until 2005, when once again vehicle efficiency improved and
emissions dropped to new lows.
Similar improvements have occurred internationally. In the European
Union, fuel consumption of new cars dropped from 7.9 liter/100 km
(29.75 mpg) in 2000 to 7.1 liter/100 km (33.1 mpg) in 2010. The specific
CO2 emission of new cars decreased by 20% during the same period,
reaching 140 g CO2/km (225 g/mile).5
Example. Effect of new fuel economy standards. A 2003 Mercury
Sable 4-door passenger car had an EPA mileage rating of 21 mpg
(combined city and highway driving) and produced 518 g/mile of
greenhouse gas emissions. This was replaced in 2008 with a Toyota Prius
that had an EPA rating of 46 mpg and 236 g/mile of greenhouse gas
emissions. Based on actual measurements, the Prius has averaged 50 mpg
over the last 7 years (75,000 miles of southern California driving.) That is
a savings of 2586 gallons of gasoline. During the period from 2008 to
2014, local gasoline prices ranged from US$ 2.50 a gallon to more than
US$4.00, with the average around US$3.00 per gallon, for a savings
on fuel cost of US$7,758. Vehicular emission reduction was 21,150 kg,
or about 21 metric tons of avoided pollution.
Improvements in vehicle fuel efficiency have come about by the use of
composites and nonmetallic components in automobile bodies to reduce
overall weight. Engine weights have been reduced. Power is required
30
25
20
15
10
5
0
1970 1980 1990 2000 2010 2020
0
100
200
300
400
500
600
700
800
FUEL ECONOMY
FUELECONOMY,mpg
CO2 PRODUCTION
CO2PRODUCTION,g/mile
Figure 10.1 Adjusted fuel economy and CO2 production.
5
European Union (2012) Energy Efficiency Trends in the Transport Sector in the EU: Lessons
from the ODYSSEE MURE Project. http://www.odyssee-mure.eu/publications/br/trans-
port-energy-efficiency-trends.html.
222 Energy Management Principles
5. to overcome rolling friction, climb grades, overcome aerodynamic drag,
and for acceleration. New design approaches have also reduced
aerodynamic drag. Engine weight and horsepower declined in the U.S.
during the period 1975 to 1983. Then, with the increased demand for
sport utility vehicles and trucks, horsepower once again increased.
For electric vehicles, the critical factor is the battery. Lead-acid
batteries have a specific energy storage capability of 30 Wh/kg. To have
enough energy for a reasonable trip (say 30 to 50 miles) requires a heavy
battery load. Another drawback is the short life of lead acid batteries
(about 3 years). The Toyota Prius uses a 53 kg nickel-metal-hydride
battery with storage capability of 1.31 kWh that has demonstrated
lifetimes in excess of ten years. The Tesla 85 kWh lithium-ion battery
has a storage capability of 150 Wh/kg, which enables the vehicle to have
a range in excess of 200 miles. Further electric vehicle development
will depend on continuing to improve battery performance and reduce
cost.
GREENHOUSE GAS EMISSIONS FROM VEHICLES
Carbon dioxide is the principal greenhouse gas, although methane (CH4)
and nitrous oxide (N2O) also contribute. Carbon monoxide (CO) is
emitted but converts to CO2 in the atmosphere. The amount of CO2
produced depends on the amount of carbon in the fuel. Since combustion
is basically combining carbon and oxygen, virtually all of the carbon in
the fuel is converted to CO2 unless the engine is running “rough” and
incomplete combustion is occurring. The U.S. Environmental Protection
Agency uses average carbon content values to estimate vehicle CO2 emis-
sions factors:
Efg 5 CO2 emissions from gasoline: 8,887 g CO2/gallon
Efd 5 CO2 emissions from diesel: 10,180 g CO2/gallon
To determine annual greenhouse gas emissions for a specific vehicle,
the following equation can be employed:
CO2 emissions=yr 5 ðEf =mpgÞ 3 D 3 1026
ðmt=yrÞ [10.1]
Where:
Ef 5 the emission factor (gasoline or diesel)
mpg 5 the vehicle fuel efficiency rating, miles per gallon
D 5 miles driven per year
223Transportation
6. Using Equation (10.1), a gasoline powered vehicle with fuel efficiency
of 25 mpg, driven an average of 12,000 miles per year, will emit 4.3 met-
ric tons of CO2 per year.
HOW VEHICLE ELECTRIFICATION CAN HELP
A study by the Electric Power Research Institute and the National
Resources Defense Council examined future scenarios that combined
new plug-in hybrid electric vehicles and improved low emission electric
power generating stations. The study considered combinations of nuclear,
wind, solar, clean coal, and combined cycle natural gas generating
stations, along with three different types of plug-in electric vehicles,
each with different range capability with a single battery charge. The
simulation included the effect of retiring older, less efficient, generating
stations and replacing them with more efficient, less polluting new types.
The study indicated that by 2050 transportation sector greenhouse gas
emissions could potentially be reduced by as much as 612 million metric
tons annually (9.4% of 2012 U.S. emissions).6
The International Energy Agency has organized an Electric Vehicles
Initiative with fifteen participating member countries. The objective is to
stimulate public/private initiatives in vehicle electrification. In 2012, the
member countries had approximately 90% of the world’s inventory of
electric vehicles (200,000, or 0.02% of the world’s 1 billion passenger cars).
The goal of the project is to increase the number of electric vehicles to 20
million (equal to 2% of all passenger vehicles) among the member countries
by the year 2020. In parallel with this effort there would be a goal to expand
the network of electric vehicle charging stations in the member countries.7
ENERGY MANAGEMENT OPPORTUNITIES
For the energy manager, the incentive to improve vehicle efficiency is
likely to be economic rather than consideration of greenhouse gas
6
Electric Power Research Institute (2007). Environmental Assessment of Plug-In Hybrid
Electric Vehicles (volume 1: Nationwide Greenhouse Gas Emissions), Electric Power Research
Institute and the National Resources Defense Council, http://mydocs.epri.com/docs/
CorporateDocuments/SectorPages/Portfolio/PDM/PHEV-ExecSum-vol1.pdf).
7
International Energy Agency. (2013) Electric Vehicles Initiative, “Global EV Outlook:
Understanding the Electrical Vehicle Landscape to 2020.” http://www.iea.org/publications/
freepublications/publication/GlobalEVOutlook_2013.pdf.
224 Energy Management Principles
7. emissions. The incentive could also stem from a corporate mandate or
goal for environmental stewardship. Any improvement in vehicle fuel
efficiency will have accompanying environmental benefits.
There are number of measures that energy managers can take to
improve transportation energy use. The following suggestions apply pri-
marily to an energy manager working for a corporation or municipality.
Low-Cost Measures
The easiest and most obvious thing to do is to pay careful attention to
proper maintenance of existing vehicles. Engine tune-ups and proper tire
inflation will help achieve optimum fuel efficiency. For deliveries, there
are many new GPS-based techniques for optimizing travel routes and
avoiding traffic delays that cost fuel.
Commuting
Policies can be established to encourage ridesharing, carpooling and use
of public transportation rather than individual automobiles. Many
companies today offer van pooling to transport employees to and from
the workplace. Some companies provide bus passes or offer financial
incentives for employees to use public transportation. Another approach
is to alter the work week to 4-ten hour days, eliminating 20% of mileage
and time spent commuting. Still another approach that is being used is
telecommuting, or allowing certain job classifications to work at home
without requiring regular attendance at the office.
Vehicles
Converting vehicle fleets to improved designs with better mileage is an
obvious first step, particularly if the vehicle fleet has older vehicles.
Conversion can reduce fuel costs by as much as 50%, going from
average fuel economy of 25 miles per gallon to as much as 50 miles per
gallon. Historically it has been noted that sales of better mileage vehicles
increase as fuel prices increase. At the time this book went to press
gasoline prices were see-sawing, first going down, then back up, due to
falling crude oil prices. This should be viewed as a temporary condition
and should not be taken as a reason to not select more fuel-efficient
vehicles.
Conversion to compressed natural gas or liquefied natural gas
(CNG or LNG) is another option that offers a reduction of 6À11%
225Transportation
8. in greenhouse gas emissions compared to gasoline or diesel engines.8
Natural gas is being used in many countries for passenger vehicles, buses,
forklifts, municipal trash trucks, and other types. Currently, natural gas
offers economies compared to diesel or gasoline fuels. Disadvantages or
limitations include the fact that fuel storage tanks take up more room and
fueling stations are not widely distributed.
Around the globe all automobile manufacturers are working on hybrid
electric vehicles, and many are starting to work on plug-in electric
vehicles. The benefit of electric vehicles could be increased if there was
a significant effort to expand the number of solar powered electric
vehicle charging stations, in order to take electric vehicles totally off the
grid.
Example. Efficiency of electric vehicles needs to consider the source
of electricity. The Tesla model S has a claimed range 265 miles with an
85 kWh battery storage capacity at 65 mph average speed, depending on
temperature, load and other factors. You would not want to run the
battery to zero, so say you retain 10% charge. Then the trip would
require 76.5 kWh. Based on 115,000 Btu/gallon of gasoline, (the equiva-
lent to 33.7 kWh on a straight energy basis), you would use the equiva-
lent of 2.27 gallons of gasoline or 116 mpg. (EPA says 90 mpg equivalent
using their test methods).This would be okay if you charged the car with
solar or wind power. Plugged into the utility grid, assume a power plant
heat rate of 10,000 Btu/kWh for an oil-fired generating station, with fuel
oil at 140,000 Btu/gallon. Then to produce 76.5 kWh requires
765,000 Btu or 5.46 gallons of fuel, so the mileage is now 48.5 mpg,
about the same as a Prius, and with a corresponding amount of
greenhouse gas emission.
Depending on range requirements, electric vehicles should be
considered for vehicle fleet upgrades. For local deliveries and commuting
requiring less than 20 to 40 miles driving per day, electric vehicles can be
charged overnight during off-peak hours using low-cost time-of-use rates.
In addition, the energy manager can use corporate or municipal buying
power to purchase better mileage vehicles, thereby encouraging
production of more efficient models. Companies can consider providing
free charging stations for electric vehicles or provide preferred parking for
employees utilizing electric vehicles.
8
U.S. Department of Energy. (2014). Natural Gas Vehicle Fuel Emissions, www.afdc.energy.
gov/vehicles/natural_gas_emissions.html. (accessed March 16, 2015).
226 Energy Management Principles
9. CONCLUSIONS
Transportation accounts for a large percentage of global energy use and of
global output of greenhouse gases. This important sector of the energy
economy is starting to benefit from efficiency improvements in conven-
tional gasoline and diesel engines, and also from new fuels (LNG, NGL,
and others, including bio-derived fuels). The rapid advances in hybrid
and electric vehicles are encouraging. Comparisons based on “well-to-
wheel” studies (raw fuel to distance traveled) include the inefficiencies of
fuel refining and electricity generation. Such studies demonstrate that to
take full advantage of electric or hybrid vehicles, solar powered charging
stations should be deployed.
227Transportation
