Seite - 59 - in Water, Energy, and Environment - A Primer

Demand for transportation energy and associated CO2 emissions can be reduced in a number of ways. These include improving the fuel efficiency of all modes of passenger and freight transportation, fuel substitutions, improving urban environments, designing transport-conserving communities, and using telecommunications to reduce the need for commuter trips. For example, jet aircraft in service today are well over 80%more fuel efficient than the first jets in the 1960s; DOE’s Heavy Duty Vehicle Efficiency Program has developed an improved version of aClass 8 truck, called a ‘super truck’, that is 50%more efficient thanClass 8 trucks currently on the road. These heavy duty trucks use approximately 20% of US transportation fuel; in response to the OPEC oil embargo of 1973–74 the US Congress (35) established federal Corporate Average Fuel Economy (CAFE) standards for cars and other light- duty vehicles in 1975. In 2007 theNewYorkTimes called the CAFE standards ‘The most effective energy efficiency policy ever adopted by the federal government…’ and the US NationalAcademies of Sciences has called theCAFE standards ‘One of the most impressive efficiency successes in modern memory…’. Other countries have since adopted similar standards, and standards are under consideration for medium andheavy-duty vehicles. Other possibilities for reducing fuel consumption in transportation include the use of lighter, stronger, and more durable structural materials; the use of alternative liquid (alcohols, biofuels) and gaseous (compressed natural gas) fuels; hybrid vehicles (powered by both internal combustion engines and electric motors); and pure electric vehicles (EVs) powered by electricity stored in batteries or electricity generated by fuel cells powered by hydrogen. EVs offer significant advantages over traditional vehicles because electricmotors aremuchmore efficient than internal combustion engines, and the efficiency of fuel cells, which utilize a non-thermal energy conversion process, is not limited by Carnot thermodynamic efficiencies. Energyoptions 59