Electric Cars Have Their Flaws, Too

Tom Watkins of Montpelier, VT likes the efficiency of electric cars, but has problem with the additional electric load they will create.

Published: 13-Jan-2008

The basic laws of physics and the math of efficiencies often seem to be ignored when we get into the discussions of environmentally friendly energy. In a gasoline powered car, www.fueleconomy.gov says that only about 15 percent of the energy in the fuel actually gets used to move the car down the road. All the rest is lost to the engine and drive train inefficiencies.

An electric car can be as high as 75 percent efficient but to charge the car's battery takes energy. That involves energy conversions from chemical (crude oil) to mechanical (steam power plants) to electrical (generators) to chemical (batteries) to mechanical (vehicle motor) and can lose as much as 80 percent of the available energy in the process. Alternative fuels like ethanol and hydrogen have similar problems because they introduce additional conversion and production requirements and contain significantly less energy per unit volume that oil.

Nationwide, there are about 220 million cars, driving about 6.6 billion miles per day, burning about 125 billion gallons of gas per year. The physics of electric cars is that they get about 4 to 6 miles per kilowatt hour (kWh). A nation of electric cars would need a delivery to the car of about 2.5 trillion kWhs of additional production capability from our nation's power plants, ideally used during off-peak night hours. This would cost billions of dollars to add that much additional power production to existing energy pipelines and, where the local power plant is old or already near maximum capacity, that would create major problems.

This is not to say that electric vehicles are not a viable choice to replace internal combustion engines but we must face the fact that it takes an infrastructure perspective that includes a substantial increase in electricity production capacity.

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