Sunday, September 14, 2008

HOW TO REDUCE VEHICLE FUEL CONSUMPTION 75% WITH CURRENT TECHNOLOGY

Low Tech Magazine - If we cut the average speed of all vehicles by half, fuel consumption would decrease by a whopping 75 percent. . .

Engineers treat velocity as a non-variable, while in fact it is the most powerful factor to save a really huge amount of energy - with just one stroke, at minimal cost, and without the need for new technology. Lower speeds combined with more energy efficient engines, better aerodynamics and lighter materials could make fuel savings even larger.

Air resistance (drag) increases with the square of speed, and therefore the power needed to push an object through air increases with the cube of the velocity. If a car cruising on the highway at 80 km/h requires 30 kilowatts to overcome air drag, that same car will require 240 kilowatts at a speed of 160 km/h.. . .

Drag can be partly offset by better aerodynamics: a boxy car like the Volvo 740 has a drag area that is almost twice that of the most aerodynamic standard car, the Honda Insight. The Volvo needs almost two times the engine power of the Honda when driven at 120 km/h.

Yet a Volvo 740 driving at 60 km/h will face less than half the drag and will need 4.6 times less energy power than a Honda Insight driving at 120 km/h. When compared to velocity, the potential of aerodynamics is limited. . .

The blindness for the importance of speed leads to doubtful conclusions, like the environmentally friendly label of high speed trains. The French TGV that set the most recent speed record at 575 km/h for wheeled trains in 2007 has an engine output of 19,600 kilowatts. A contemporary "slow" train like the Siemens ES64 with a top speed of 240 km/h has a maximum power output of 6,400 kilowatts.

Travelling 1,000 kilometres, the "slow" train will consume 26,240 kilowatt-hours (over 4.1 hours) while the fast train will consume 33.320 kilowatt-hours (over 1.7 hours). . . .

A decrease of 75 percent in fuel consumption is not peanuts. More than 60 percent of world oil production is used for transportation, which means that total oil production would be almost halved. In combination with more efficient engines, better aerodynamics and lighter materials a 75 percent reduction of oil production is not unrealistic.

Yet, when the International Energy Agency argues that the average car sold in 2030 would need to consume 60 percent less fuel than the average car sold in 2005, it claims: "With current technologies, only plug-in hybrids are capable of this".

This statement is wrong. We could lower the fuel consumption of cars (and other vehicles) by at least 75 percent, we could do it today, and we can do it with present technology.