Science Forums 2

[CraigD]

Moderation note: The first 12 posts of this thread were moved from the Community polls thread “to bailout, or not to bailout”, because they are a discussion of electric car and electric power engineering, not a discussion of the pros and cons on government bailouts of businesses.

Originally Posted by C1ay

I think vehicle development, be it private or not, is a small part of the problem of accomplishing the dream of converting our transportation infrastructure to an electrical energy source. If one calculates the amount of chemical energy currently used across the nation from petroleum fuels to find the amount of electrical energy that would be required to replace it they will find our electrical generating capacity and the distribution capacity of the power grid is but a tiny fraction of what it would need to be. The average megamart fuel station today would need to be a mini-nuclear facility to charge the same numbers of cars they see today with an equivalent amount of energy as they currently get with a fillup of gasoline.

I don’t think this is accurate. Although a bit off-topic, I think this is an important enough issue to discuss here.

According to this US DOE summary, of 101600 trillion BTUs total energy consumed in the US in 2007, 29096 was used in transportation (29%) which includes passenger cars, busses, trucks, trains, and aircraft), while 40567 (40%) was used to generate electricity. So, assuming that all transportation could be reengineered to use generated electricity (an unrealistic assumption, see below), the increase in demand for generated electricity would be about 70%, about the same as the increase that occurred between 1979 and 2007.

A large car gas tank hold about 90 L (24 gallons), about 2.3 GJ energy (). A typical US residential home (mine, for example) can deliver at a single outlet about 8800 W (the “dryer” circuit, 40 A at 220 V, limited by a breaker). So, ignoring transmission and other inefficiencies, without substantial rewiring, a typical home can deliver electric energy equivalent to a tank of gas in about 260000 s, about 3 days.

The tanks at typical neighborhood gas station hold about 60000 L (15000 gallons) of fuel, with an energy density of about 25 MJ/L, for a total energy of about 1.5 TJ (). A small nuclear reactor, such as those used on small warships and submarines, (eg: a US naval D2G reactor) generate about 150 MW power. So a small nuclear reactor delivers the energy stored in a neighborhood gas station in about 10000 s, about 2 hours 46 minutes.

There are certainly large scale engineering and planning issues that must be addressed if many vehicles are made to use stored electric power rather than fossil fuel, but I don’t think these issues are overwhelming. The big problem is not, I think, electric generation and delivery, but battery or other storage energy density. At present, a major class of vehicles, aircraft, can’t practically be made to run on stored electricity (see “Airframe design, and some daunting numbers for electric airliners”).

On a practical note, having a rechargeable electric car of the kind available today (or from 1997 to 2003, when the EV1 was in use) means you don’t recharge at fuel stations, but either at home, or in specially equipped parking places. Batteries take to long to charge to “wait at the pump” as we do when filling our fuel tanks.