It is likely that the use of biomass-based fuels will steadily grow. But given the uncertainty about the environmental impacts of large-scale conversion of biomass crops to fuel (on soil quality, water resources and overall greenhouse gas emissions), this source will contribute but is unlikely to dominate the future fuel supply anytime soon.
Use of natural gas in transportation varies around the world from less than 1 percent to 10 to 15 percent in a few countries where tax policies make it economical. In the 1990s natural gas made inroads into U.S. municipal bus fleets to achieve lower emissions; diesels with effective exhaust cleanup are now proving a cheaper option.
What about new propulsion system technology? Likely innovations would include significantly improved gasoline engines (using a turbocharger with direct fuel injection, for example), more efficient transmissions, and low-emission diesels with catalysts and particulate traps in the exhaust, and perhaps new approaches to how the fuel is combusted might be included as well. Hybrids, which combine a small gasoline engine and a battery-powered electric motor, are already on the road, and production volumes are growing. These vehicles use significantly less gasoline in urban driving, have lower benefits at highway speeds and cost a few thousand dollars extra to buy.
Researchers are exploring more radical propulsion systems and fuels, especially those that have the potential for low life-cycle carbon dioxide emissions. Several organizations are developing hydrogen-powered fuel cell vehicles in hybrid form with a battery and an electric motor. Such systems could increase vehicle efficiency by a factor of two, but much of that benefit is offset by the energy consumed and the emissions produced in making and distributing hydrogen. If the hydrogen can be produced through low-carbon-emitting processes and if a practical distribution system could be set up, it has low-greenhouse-emissions potential. But it would take technological breakthroughs and many decades before hydrogen-based transportation could become a reality and have widespread impact.
Hydrogen is, of course, an energy carrier rather than an energy source. Electricity is an alternative energy carrier with promise of producing energy without releasing carbon dioxide, and various research teams are looking at its use in transportation. The major challenge is coming up with a battery that can store enough energy for a reasonable driving range, at an acceptable cost. One technical barrier is the long battery recharging time. Those of us used to filling a 20-gallon tank in four minutes might have to wait for several hours to charge a battery. One way around the range limitation of electric vehicles is the plug-in hybrid, which has a small engine onboard to recharge the battery when needed. The energy used could thus be largely electricity and only part engine fuel. We do not yet know whether this plug-in hybrid technology will prove to be broadly attractive in the marketplace.
Beyond adopting improved propulsion systems, a switch to lighter-weight materials and different vehicle structures could reduce weight and improve fuel consumption without downsizing. Obviously, though, combining lighter materials and smaller vehicle size would produce an even greater effect. Maybe the way we use vehicles in the future will differ radically from our “general purpose vehicle” expectations of today. In the future, a car specifically designed for urban driving may make sense. Volkswagen, for example, has a small two-person concept car prototype that weighs 640 pounds (290 kilograms) and consumes one liter of gasoline per 100 kilometers (some 240 miles per gallon—existing average U.S. light-duty vehicles use 10 liters per 100 kilometers, or just under 25 miles per gallon). Some argue that downsizing reduces safety, but these issues can be minimized.
Promoting Change
Better technology will undoubtedly improve fuel efficiency. In the developed world, markets may even adopt enough of these improvements to offset the expected increases in the number of vehicles. And gasoline prices will almost certainly rise over the next decade and beyond, prompting changes in the way consumers purchase and use their vehicles. But market forces alone are unlikely to curb our ever growing appetite for petroleum.
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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.