Side-splitting headline of the day: GM touts Volt with 230 mpg city rating (by using Enron accounting methods)

230 miles per gallon. Yeah - right. It's high time that people that write such tripe get a basic short course in principles of thermodynamics, especially the conservation of energy principle. You know - the whole energy can't be created nor destroyed thing. It should be a basic understanding for any writer that even wants to talk about energy. So you can have a 230 mpg car - f you use Enron accounting for the energy that must be used. I'll get to the absurd claim on a technical basis in a bit, but first, from the Detroit Free Press:

The electric-drive Chevrolet Volt is expected to get a rating of at least 230 miles per gallon in city driving, General Motors Co. announced this morning.

The results come as GM pushes to bring the new technology to market in late next year. Later this week, the company is officially announcing its battery assembly pack plant in Brownstown Township.

A mysterious, viral marketing campaign with the numbers “230” and today’s date had created speculation on the Internet that the day’s news conference could include an announcement about how many miles per gallon the electric drive Chevrolet Volt would get. In the image, the zero is a smiling electric outlet.

Henderson said the Volt will use 25 kilowatt hours per 100 miles.

The m.p.g. estimates are calculated under the U.S. Environmental Protection Agency’s draft procedure for plug-in electric vehicles. Henderson added that GM believes it will also get triple digit m.p.g. for a combination of city and highway driving. He didn’t give a highway m.p.g.

“From the data we’ve seen, most drivers could operate purely on grid electricity in a Chevy Volt,” Henderson said in a statement. “A car that gets more than 100 miles per gallon is a significant step in the reinvention of the auto industry and GM is and will continue to be a leader in that reinvention."

Mileage ratings are tricky to calculate with the Volt. In theory, some drivers would burn no gas for extended periods of time.

I've mentioned this ad infinitum in this blog especially in cases when claims are made that plug-in hybrid vehicles get 100 mpg by methods that would make accountants at Enron proud, like not counting the energy it took to fully charge those battery packs that mostly came from coal. (Another Plug-In Hybrid False Mileage/Energy Savings Claim) In that prior recent post (there are many more) here's how the numbers scam works: let's say you have a car that gets 25 miles to a gallon. You convert it into a hybrid vehicle by installing some electric motors in the wheel hub that are tied to batteries. Let's say those batteries are big enough to get you 25 miles worth of juice. Once it's gone, the engine kicks in. So your 50 mile trip used only 1 gallon of gasoline, and the claim is that you now have a 50 mile per gallon car! Viola! Except that you still only have a 25 mpg car, and that first 25 miles came from electricity derived from mostly likely coal! The efficiency of that process is even worse than if you had just burned gasoline.

What is basically happening with these ratings is that it is being gamed within the confines of the rule book. The energy it took to charge the battery in the first place is either not taken into account, or not accounted for correctly. I wrote about this before with the claim of a doubling of fuel mileage by going plug-in hybrid, but it's worth repeating here. It won't really double the cars mileage. It will just offset some gasoline with coal. Not the best trade-off in my opinion but there it is. Converting a car to hybrid may in fact save 120 million gallons of fuel per day, but that will come at the cost of using a whole lot of coal. Let's do a bit of math. Gasoline weighs 8 lb per gallon and has an energy content of 47 MJ/kg. Coal is at 30 MJ/kg. To get the same amount of electrical energy as that in 120 million gallons of gasoline, it would take about 1,840 million pounds of coal assuming a power plant efficiency of 33%! That is nearly 1 million tons of coal! Extra! That is, beyond what we are using now!

In addition, has anyone considered the enhanced electric bill one would get when plugging your car in every night? It is not only a bad idea from an environmental standpoint, it will cost more money, and has no chance of ever paying for itself. So there's the short of it...

UPDATE: From AutoBlog via Instapundit: How did GM arrive at 230 mpg for the 2011 Chevrolet Volt?

Without access to the actual method that the EPA is tentatively going to apply to plug-in vehicles (we have requests for clarification out to the EPA), all that GM's Dave Darovitz would tell us is that the number is "based on city cycles and we're not really talking in detail yet." Instead, the press release says that:

Under the new methodology being developed, EPA weights plug-in electric vehicles as traveling more city miles than highway miles on only electricity. The EPA methodology uses kilowatt hours per 100 miles traveled to define the electrical efficiency of plug-ins. Applying EPA's methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.

Frank Weber, vehicle chief engineer for the Volt, told AutoblogGreen that the EPA's method takes into account the two extremes: People who plug in every chance they get and therefore barely ever need gasoline and people who never plug in (if you're buying a Volt and never plug it in, we'd like to offer you a bridge or two. Call us). By figuring out what the average driver will do with the Volt, the EPA has declared that 230 mpg is reasonable.

What they are likely not taking into account is that the electricity is generated by burning coal. the plant is roughly 33% efficient, which isn't being taken into account. Nor is the energy required to obtain the coal, process and transport it. My problem isn't in the cost analysis, but rather the claim on an equivalent miles per gallon gasoline basis. It is not grounded in science whatsoever.

Previously:
Another Plug-In Hybrid False Mileage/Energy Savings Claim
Government report: electric cars won’t reduce carbon emissions and likely create more
UNTRUE! - Enron Accounting on the 100 mpg Hummer H3