Why the interst in running natural gas into fuel cells ?
Fuel cells CAN BE (not always) much more efficient than internal combustion engines either gasoline or diesel.
Note the internal combustion efficiency number are sometimes compared relative to the theoreitcal ideal Carnot cycle efficency. The Carnot cycle tends to use about 50-60% of the TOTAL energy
so using the Carnot limit as 100%, we could say a certain gasoline engine had an efficency of 45%, or a certain diesel engine had an efficentcy of 55%. This is useful for enginers comparing different engine designs at different temperatures, but it doesn't really relate to energy efficiency.
Relative to the TOTAL energy in the fuel, Fuel Cells can easily have efficencies of 50-60%, compared to gasoline combustion at 22-30% and diesel combustion at 36-45%.
For a practical car, diesels tend max out about 40%, the 45% numbers belonging to large truck and marine engines with turbo chargers with constant speeds.
Also, an electric car with fuels cells and batteries does not need to idle, and less energy is used in heating up the engine block after a cold start.
So using fuels cells and batteries to drive a car like a Mercedes Benz E320 Bluetec diesel, which gets 37 highway and 26 city, would mean really good mileage -
If we can get 56% fuel cell vs. 42% diesel for Highway
49 mpg equivalent highway.
For city driving, I would guess 46% fuel cell, and 38% diesel city driving
31 mpg equivalent city.
Including the factors for idle, warm up, and a small amount of energy recovery from regenerative braking could push this to 35+ mpg city.
This is for a large, heavy 4 door automobile. In something like a Toyota Corrolla, I would expect these numbers to be about 20% better. If the gasoline engine in the Toyota Prius was replaced with a fuel cell, there should a > 35% increase in mileage.
Natural gas cost - my current retail price for Natural gas in California on an energy equivalent basis to gasoline is about $2.86 per gallon.
>>> The current US passenger car fleet gets about 24 mpg on combined city and highway. A Fuel cell power could get 40 mpg or better. That's a big step in the right direction.
en.wikipedia.org
en.wikipedia.org
Fuel cells are considerable more efficent than combusiton engines. There's still an issue with the source of NG, of course.
IF (big IF here) we build MANY more nuclear or "clean coal" plants to make electricity instead of more plants that burn NG, that would free up lots of NG for vehicle use. Add in some plug in hybrids to further displace liquid fuel use in auto transportation, some use of biodiesel, coal to liquids, and (dare I say it) even ethanol, and we can could go from importing 2/3 of our oil to about 40%....which won't be energy independence, but would help the trade balance, and reduce the leverage Mr. Hugo Chavez has.
If we got the same level of nuclear use that France has, displaced some NG with electricty for home heating, and have about 50% of the cars be plug in hybrids or diesel, and opend up ANWR and the Eastern Gulf of Mexico, we might get our oil imports down to about 15%. That would tend to limit the world price of oil. |
