Reply To: General thought on old coal mines.

[Glenn Millam]

nemmart wrote: Why not just power the airplane with FF’s? Just checked some numbers. A 747 burns on average a gallon a second during flight. Jet A has roughly the same energy per weight as gasoline which has 121 MJ per gallon. Therefore a 747 uses 121 MW/hr, which means 20 FFs to produce the juice.

You wouldn’t want to put FFs on an airplane. X-ray shielding alone will make the weight prohibitive.

Also, don’t confuse joules and watts.

As for your numbers… are you sure you are factoring in the jet engine’s efficiency? When using any fuel to power an engine, it is not just the total amount of potential energy in the fuel that matters, but the efficiency of the engine in extracting useful energy from the fuel.

Jet engines are not terribly efficient at extracting energy from fuel. In fact, most fossil fuel based engines aren’t. Car engines get about 20% efficiency. So if you put a gallon of gas in a car, with a total energy of 130 MJ, you end up only getting 26MJ of useful energy out of it. The rest is wasted.

In terms of cars, the efficiency and local nature of FF would make it a great solution for powering electric cars. Part of the argument about electric cars is that the sources we currently have of producing and transmitting electricity gives only about 33% efficiency, thus making an electric car about 25% fuel efficient. If we had FF, with its potential 80%+ efficiency and ability to have the plant closer to the end user, you could see a dramatic increase in the efficiency of the drive to work. This, of course, depends on a lot of problems to be overcome. Not only does FF have to work, but you need a better battery than current technology.

And that’s just cars. With planes, you need to have weight in consideration. To make a good electric airliner, you would need a phenominal battery technology that is light, stable, incredibly energy-dense, and won’t randomly catch on fire or arc lightning about the cabin. I think carbon-based fuels will be used in airplanes for a long time. But that’s OK, because if the only thing we are using fossil fuels for are airplanes, then the oil reserves of the planet will last a long, long time.

And, you could always take one of these instead.