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Sunday, August 14, 2011

Can We Replace Gasoline By Driving Electric Cars?

I just saw another ad for an electric vehicle.  In light of high gasoline prices, consumers and manufacturers are excited about the possibility of using plug-in hybrids and all-electric vehicles for efficient, clean transportation.  But just suppose for a moment, that the entire US motor-fuel market was converted to electric transportation.  How much power generation would be required?

Currently, the US uses about 9 million barrels per day of gasoline, or 3.3 billion barrels per year (1).   Converted to equivalent kilowatt-hours, about 4.6 trillion kilowatt hours.  By comparison, the current electrical generation capacity of the United States is about 3.9 trillion kilowatt hours (2).   Electrical demand is somewhat less, at about 3.74 trillion kilowatt hours, giving us about 5% excess capacity over demand.

So my question is: where is the electricity going to come from to power all of the new electric vehicles?  To replace gasoline transportation fuels in the United States, we would need to more than double our current electrical generation capacity, adding 117% of new capacity.  This assumes matching the efficiency of gasoline in engine performance, including losses in transmission and battery storage.

In 2010, the capital cost of new electrical generation capacity ranges from about $1000/kw to $5000/kw, depending on the type of generation (3).  To add the required 528 million kilowatts of new generation would cost a minimum of $528 billion dollars, plus associated transmission and distribution costs.

Of course, we would also need to consume an equivalent amount of fuel, to produce power for electric vehicles.  Assuming 117% of our current electrical consumption, and based on our current fuel mixture, we would need to burn about 94 million tons of coal, 2.9 million barrels of petroleum coke, and 826 billion cubic feet of natural gas per month, to provide power for the vehicles.  I will calculate the related CO2 emissions and costs later.

Of course, we will not replace the entire fleet of gasoline-powered vehicles overnight.  And there is some capacity in the existing system to absorb some electrical vehicles.  But a large scale transition to electric vehicles will require major investments in electrical generation, transmission, and distribution.  And the new generation must be a choice of large-scale generation alternatives: coal, natural gas, nuclear, or hydro; or extraordinary growth in intermittent renewable sources (solar and wind), which would require new storage technologies to make those feasible.

Critics have commented that charging vehicles could be accomplished overnight, during non-peaking hours.  This is true.  Still the magnitude of the required power, and the additional fuel consumption regardless of when vehicles are being charged, make the challenge of powering a fleet of electric vehicles truly daunting.

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