Editor's Note: We are posting this feature from our September 2006 issue in light of the Obama administration's renewed focus on how to power the country without overloading the atmosphere with greenhouse gases.
If we are honest, most of us in the world’s richer countries would concede that we like our transportation systems. They allow us to travel when we want to, usually door-to-door, alone or with family and friends, and with our baggage. The mostly unseen freight distribution network delivers our goods and supports our lifestyle. So why worry about the future and especially about how the energy that drives our transportation might be affecting our environment?
The reason is the size of these systems and their seemingly inexorable growth. They use petroleum-based fuels (gasoline and diesel) on an unimaginable scale. The carbon in these fuels is oxidized to the greenhouse gas carbon dioxide during combustion, and their massive use means that the amount of carbon dioxide entering the atmosphere is likewise immense. Transportation accounts for 25 percent of worldwide greenhouse gas emissions. As the countries in the developing world rapidly motorize, the increasing global demand for fuel will pose one of the biggest challenges to controlling the concentration of greenhouse gases in the atmosphere. The U.S. light-duty vehicle fleet (automobiles, pickup trucks, SUVs, vans and small trucks) currently consumes 150 billion gallons (550 billion liters) of gasoline a year, or 1.3 gallons of gasoline per person a day. If other nations burned gasoline at the same rate, world consumption would rise by a factor of almost 10.
As we look ahead, what possibilities do we have for making transportation much more sustainable, at an acceptable cost?
Our Options
Several options could make a substantial difference. We could improve or change vehicle technology; we could change how we use our vehicles; we could reduce the size of our vehicles; we could use different fuels. We will most likely have to do all of these to drastically reduce energy consumption and greenhouse gas emissions.
In examining these alternatives, we have to keep in mind several aspects of the existing transportation system. First, it is well suited to its primary context, the developed world. Over decades, it has had time to evolve so that it balances economic costs with users’ needs and wants. Second, this vast optimized system relies completely on one convenient source of energy—petroleum. And it has evolved technologies—internal-combustion engines on land and jet engines (gas turbines) for air—that well match vehicle operation with this energy-dense liquid fuel. Finally, these vehicles last a long time. Thus, rapid change is doubly difficult. Constraining and then reducing the local and global impacts of transportation energy will take decades.
We also need to keep in mind that efficiency ratings can be misleading; what counts is the fuel consumed in actual driving. Today’s gasoline spark-ignition engine is about 20 percent efficient in urban driving and 35 percent efficient at its best operating point. But many short trips with a cold engine and transmission, amplified by cold weather and aggressive driving, significantly worsen fuel consumption, as do substantial time spent with the engine idling and losses in the transmission. These real-world driving phenomena reduce the engine’s average efficiency so that only about 10 percent of the chemical energy stored in the fuel tank actually drives the wheels. Amory Lovins, a strong advocate for much lighter, more efficient vehicles, has stated it this way: with a 10 percent efficient vehicle and with the driver, a passenger and luggage—a payload of some 300 pounds, about 10 percent of the vehicle weight—“only 1 percent of the fuel’s energy in the vehicle tank actually moves the payload.”
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2 Comments
Add CommentCombustion engines may be adapted to use hydrogen and/or gasoline using a double injection system. Operation can change from hydrogen to gasoline when no hydrogen pump is on the road. BMW, GM and others have such cars. China and India, desperate in need to reduce dependence on oil, are highly interested on the global Hydrogen initiative, using solar energy according to Kosuke Kurokawa and the global grid according to Fuller.
Reply | Report Abuse | Link to thisKarl Heinz Wilm
www.desertenergyproject.net/Global_Initiative.pdf
"First, it is well suited to its primary context, the developed world. Over decades, it has had time to evolve so that it balances economic costs with users needs and wants. Second, this vast optimized system relies completely on one convenient source of energypetroleum"
Reply | Report Abuse | Link to thisIf you start with false assumptions about the "optimization" of current transport systems, the problem can never be solved. Our current system of provision of vast areas of subsidised car parking, and roads are not based on empirical research. Users needs and costs cannot be addressed when they have no choice or knowledge of how their money is spent. Vast sums of money are wasted building infrastructure which is worse than useless, it is not efficient in terms of time, economics, space and land use not to mention the negative health effects of a life spent sitting on a car seat.