UNTRUE! - Enron Accounting on the 100 mpg Hummer H3

I mentioned this morning a galling display of technical ignorance at the Detroit News. It regarded coverage of one aspect of the Society of Automotive Engineers (SAE) World Congress in Detroit. This was the visual on the side of one of their articles: It's not the first time I've seen this claim. in fact, I saw such a claim over at Wired Science the other day as a result of a post by Glenn Reynolds over at Instapundit. In addition, Arnold Schwarzenegger made this comment as he was the keynote speaker at the SAE Congress:

"Let me just say I love the Hummer," Schwarzenegger said. "It's a great car, and the new H2 plug-in electric hybrid gets a hundred miles to the gallon. Can you believe that? It's fantastic and this is what Detroit can produce when it puts its mind to it. This is where the action's at."

There's just one problem. It is simply not true. First, I went and checked out the fuel economy for a Hummer H3 and found this at fueleconomy.gov:16 miles per gallon combined. Now cars powered by spark-ignition engines run at around 24% efficiency, and they are maxing that out. It is partly a limitation of the actual cycle that the engine runs on (the Otto Cycle), which maxes out at around 60% efficiency (just the engine by itself) at a compression ration of about 10:1, which is high. The compression ratio can be increased a little, but only to a point as dieseling -- referring to the ignition of the fuel/air mixture prior to the spark going off -- occurs, basically throwing the timing way off resulting in engine knock and eventual damage. That 60% is under ideal conditions on paper, not the real world where there are no assumptions. The 2nd Law of Thermodynamics is a big limiter of efficiency.

Next, there are parasitic losses from the engine. The alternator, compressor for the ac systems, the oil pump, water pump, etc. all need to tap some energy out of the engine to run. In addition to all that, the heat produced from combustion is simply thrown out into the atmosphere through the radiator as it is of little use. It is the increased pressure from the combustion that makes an engine run. Then you have the losses in transmitting and converting the energy ultimately into kinetic energy of your vehicle. Thus, the end result - about 24%. (plus or minus a bit depending on make, model, engine design, etc) So if you have a 250 HP car, you're burning 1000 HP of gasoline!

That can be increased some by putting in technology outside the engine, such as regenerative brakes that collect some energy during deceleration to be used for acceleration. Plus hybrid technology, although I should note that it won't pay for itself.

So how is it that we have an article claiming a 100mpg Hummer? At 16mpg according to fueleconomy.gov, there is simply no technology that will increase the fuel efficiency that much. If you were to convert 100% of the chemical potential energy in gasoline to kinetic energy of the car, you still wouldn't get 100 mpg. So what's up with this claim?

There is one word for such a claim, and it says it all: Enron.

That's right - Enron accounting gimmicks. Here's the deal with the 100mpg Hummer: it's a plug-in hybrid. What that means is that it has a very large battery pack that charges at night. In this case, by the way, you are basically filling the car up on coal power, but anyway. When you pull out in the morning to go on your commute, the Hummer can run exclusively on battery power. Once that's depleted to a certain level, the engine kicks in and gets you the rest of the way. (it's a tad more technical than that as the engine/generator are married together rather than two separate entities, but it is of little importance here) So let's say you drive 100 miles, 80 of those miles on batteries and 20 miles on the engine. You then check your gas level and find, amazingly, that you went all those miles on such little gas! One whole gallon! Woohoo! You now have a 100mpg vehicle. Except you don't. You have just performed Enron accounting.

You see, you didn't account for the energy it took you to get that first 80 miles. You accounted that part as "free" energy when it is not. In fact, you only got 20 miles on that one gallon, pegging your car efficiency at 20mpg, not 100. If you account for the coal power needed to get that first 80 miles, you will be sorely disappointed that the efficiency, and corresponding environmental benefit, is likely lower than if you had just a gas guzzler plugging down the road the whole 100 miles. Coal plants are 35-40% efficient, plus the energy conversion to electrical, plus the transmission of that energy to your you home, then charging the batteries, then discharging the batteries through electric motors, etc. You get the gist. You will very likely fall below 24% per gasoline gallon equivalent. And you're out a lot more money for your car. Congrats! Feel better now?

As a final aside, I'll just make a comment on the Governator's comments regarding the job losses that have hit this area hard. It's bad news. Of course, Cyberdyne Systems Model T-101 was far more optimistic, even though he kicked the auto industry in the ball bearings with Californias foray into emissions regulations. Speaking at the SAE World Congress, the T-101 said this:

"The car industry is saying, 'I'll be back.' "

Message to the T-101: it's getting old dude. It was amusing back in the 80's. You're a learning computer for goodness sake! Learn something new! Speaking of Ahnold, the fact that he was the keynote speaker is interesting. As I have mentioned in a prior post about this:

The keynote speaker. The KEYNOTE SPEAKER?!?!?! Uh, wha??? Isn't this like Al Gore being the keynote to the "Coalition for Coal" convention? Why doesn't the SAE invite one of those tinfoil hat-wearing kooks who think carburetors can get 300 mpg and run on water? Like... Steven Seagal?

And now they'll also get to hear an uneducated former bodybuilding star who got to the top using steroids, who then went into movies but never actually acted, and then became the Governor of California during which he increased state spending 40% and has taken the Golden State to the brink of bankruptcy. Does that about do it? I doubt he could put together a single coherent sentence should any of the engineers at the conference challenge him on global warming or environmental issues.

What's kind of funny about the Governators' talk is that he will be, by far, the most unknowledgable and uneducated person in Cobo Hall talking to the most knowledgeable and educated people from around the world. Uh - shouldn't that be the other way around??? It should, but it is what it is...

Maybe Arnold can give us the design on that hydrogen fuel cell that is supposed to last 120 years? That was quite a laugher in T3 for us techie geeks...

UPDATE: On further thought, I suppose the idea of a 100mpg Hummer H3 is possible, as long as Congress repeals a few incomventient laws of nature. I don't put it past this Congress to try. The 2nd Law would be at the top of their list. Good luck with that one!