Transportation
Transportation[edit]
Automobiles[edit]
The estimated energy efficiency for an automobile is 280 Passenger-Mile/106 Btu.[46] There are several ways to enhance a vehicle's energy efficiency. Using improved aerodynamics to minimize drag can increase vehicle fuel efficiency. Reducing vehicle weight can also improve fuel economy, which is why composite materials are widely used in car bodies.
More advanced tires, with decreased tire to road friction and rolling resistance, can save gasoline. Fuel economy can be improved by up to 3.3% by keeping tires inflated to the correct pressure.[47] Replacing a clogged air filter can improve a cars fuel consumption by as much as 10 percent on older vehicles.[48] On newer vehicles (1980s and up) with fuel-injected, computer-controlled engines, a clogged air filter has no effect on mpg but replacing it may improve acceleration by 6-11 percent.[49]
Turbochargers can increase fuel efficiency by allowing a smaller displacement engine. The 'Engine of the year 2011' is a Fiat 500 engine equipped with an MHI turbocharger. "Compared with a 1.2-liter 8v engine, the new 85 HP turbo has 23% more power and a 30% better performance index. The performance of the two-cylinder is not only equivalent to a 1.4-liter 16v engine, but fuel consumption is 30% lower."[50]
Energy-efficient vehicles may reach twice the fuel efficiency of the average automobile. Cutting-edge designs, such as the diesel Mercedes-Benz Bionic concept vehicle have achieved a fuel efficiency as high as 84 miles per US gallon (2.8 L/100 km; 101 mpg‑imp), four times the current conventional automotive average.[51]
The mainstream trend in automotive efficiency is the rise of electric vehicles (all@electric or hybrid electric). Hybrids, like the Toyota Prius, use regenerative braking to recapture energy that would dissipate in normal cars; the effect is especially pronounced in city driving.[52] Plug-in hybrids also have increased battery capacity, which makes it possible to drive for limited distances without burning any gasoline; in this case, energy efficiency is dictated by whatever process (such as coal-burning, hydroelectric, or renewable source) created the power. Plug-ins can typically drive for around 40 miles (64 km) purely on electricity without recharging; if the battery runs low, a gas engine kicks in allowing for extended range. Finally, all-electric cars are also growing in popularity; the Tesla Model S sedan is the only high-performance all-electric car currently on the market.
Street lighting[edit]
Cities around the globe light up millions of streets with 300 million lights.[53] Some cities are seeking to reduce street light power consumption by dimming lights during off-peak hours or switching to LED lamps.[54] It is not clear whether the high luminous efficiency of LEDs will lead to real reductions in energy, as cities may end up installing extra lamps or lighting areas more brightly than in the past.[55]
Aircraft[edit]
There are several ways to reduce energy usage in air transportation, from modifications to the planes themselves, to how air traffic is managed. As in cars, turbochargers are an effective way to reduce energy consumption; however, instead of allowing for the use of a smaller-displacement engine, turbochargers in jet turbines operate by compressing the thinner air at higher altitudes. This allows the engine to operate as if it were at sea-level pressures while taking advantage of the reduced drag on the aircraft at higher altitudes.
Air traffic management systems are another way to increase the efficiency of not just the aircraft but the airline industry as a whole. New technology allows for superior automation of takeoff, landing, and collision avoidance, as well as within airports, from simple things like HVAC and lighting to more complex tasks such as security and scanning.
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