Under a Gibbous Moon

WARNING – THE FOLLOWING POST CONTAINS MATH AND BIG NUMBERS – YOU’VE BEEN WARNED.

Recently, upon reading several articles dealing with the upcoming release of a variety of electric vehicles (EVs) onto the market I noticed that nobody was discussing a critical point: Where was all this electricity going to come from. Electrical power is, after all, a finite resource. With all the gasoline that is used in the United States, I wondered if there was enough production capacity to meet the demand of a large scale deployment of EVs.

I had no idea of the answer to this when I first started. Indeed, I initially assumed that the reason I saw no discussion on this is that there wasn’t a problem to begin with, but I wanted to see the numbers for myself. So, without further ado, here is what I found. All statistical data is based upon currently available figures (2007).

First, I needed to find out how much energy is consumed by gasoline powered vehicles in the United States. I found that approximately 390 million gallons per day¹. Gasoline has 34.8 megajoules (10⁶) (MJ) per liter or about 131.7 MJ per gallon. So with this, 390 million gallons of gasoline has about 51,363,000,000 MJ or 51.363 petajoules (10¹⁵) (PJ) of energy. To put that into terms of power production, I found that 3.6 MJ is equal to one Kilowatt-hour (KWh) of energy². Therefore, 51.363 PJ equals 14,267,500,000 KWh or 14.268 Terawatt-Hours (10¹²)(TWh).

The next step is to compensate for lost energy due to idling. It is estimated that 3.8 million gallons of gasoline is wasted in the United States by an idle engine⁵. This is approximately 1% of daily gasoline usage. Taking 1% from 14.268 TWh leaves us with 14.125 TWh.

Also, gasoline engines do not convert 100% of the available energy into useful work, they are about 30% efficient in converting energy into work³. Therfore, out of 14.125 TWh we actually will use 4.234 TWh.

Now, for the United States electrical generating capacity. The United States generated 4,157,000,000 MWh in 2007⁴. For comparison purposes, I shall move the decimal point so it reads 4,157 TWh. Dividing that by 365, I came to a daily average of 11.389 TWh.

That puts the replacement energy needs at approximately 35% over the current energy output. From 2006 – 2007, United states electrical output increased by 2.3%⁴. In the highly unlikely circumstance of no other growth in demand for electrical energy, it would take over 15 years to completely replace our gasoline fleet with and EV one and most likely it would take decades longer than this.

This leaves us with an undesirable time table for either removing dependence on foreign oil or reducing greenhouse emissions (assuming the ability for a rapid migration to renewable electrical production).

With this data, the conclusion that I have come to is that EVs are not a viable large scale alternative to gasoline powered vehicles. Due to limitations in electrical production they will only be able to fill a niche role for many more decades.

References

1. Petroleum Basic Statistics http://www.eia.doe.gov/basics/quickoil.html

2. Kilowatt Hour http://en.wikipedia.org/wiki/Watt-hour

3. Engine Efficiency http://en.wikipedia.org/wiki/Engine_efficiency

4. Electric Power Annual http://www.eia.doe.gov/cneaf/electricity/epa/epa_sum.html

5. Anti-Idling Primer http://www.thehcf.org/antiidlingprimer.html

Related (maybe) posts:

1. Fuel economy and horsepower are not a zero sum game