SULEVs, Plug-In Hybrids and Oil Independence

Super-ultra low emission BMW 325i may be cleaner than a grid-charged plug-in hybrid, but its not just about the emissions, argues EV World publisher

Published: 04-Feb-2005

Okay, I admit it. I'd love to own a "Beemer". I know, I know it's an ICE that burns gasoline, but then so does my Honda Insight that consumes half the fuel the Beemer would and therefore emits half the carbon dioxide. But if I were to compare the two cars in terms of their hydrocarbon emissions -- the stuff that makes smog and aggravates asthma in kids -- the new BMW 325i SULEV will actually be significantly cleaner, thanks to its Boysen-developed exhaust system. While my Insight is rated an ULEV or "ultra-low emissions vehicle", the 325i SULEV model -- available only in California and states that have adapted its standard -- is a "super-ultra low emission vehicle" by California EPA standards, which are the world's toughest.

To give you a sense of the difference between ULEV and SULEV, take a look at the graph below, which was sent to me by my UK correspondent and Low-Carbon Car system developer, Chris Ellis. The chart comes out of the August 2004 issue of Auto Technology in an article entitled, "The Exhaust System of the BMW 325i SULEV/PZEV". It's the first really good explanation (a picture is worth a thousand words) of the various tiers of emission control standards.

As the chart shows, achieving SULEV standards is no mean feat for any carmaker through whose veins the black blood of oil runs so thickly. Chris' point in sending me the article was to reinforce his view that SULEV/PZEV (partial zero emission) vehicles may, in fact, be cleaner than battery electric cars -- or plug-in hybrids -- charged from the power grid when the total emissions of the power plant are taken into consideration. This is especially important in parts of the world like America and China where so much of the electricity is generated from dirty coal-fired power plants.

EV advocates will quickly counter that battery electric cars charged from solar panels or wind energy generate no emissions and that's true, as long as you don't count the emissions generated to fabricate and install the PV system or wind farm, but then at some point the whole well-to-wheels emissions and efficiency thing sort of gets ridiculous. And lest a few electric car zealots jump on Chris' case, I should point out that he's a huge advocate of plug-in hybrids, He's working on an exciting kinetic energy storage system that might just turn the whole plug-in hybrid debate on its head, but I can't say more than that.

I should also point out that SULEV technology is a dramatic development -- Chris estimates that if all cars in North America were SULEVs, the fleet would be cleaner than an all-electric battery fleet charged from the grid -- it does have its Achilles heel. In order to be rated SULEV, a manufacturer must demonstrate that the exhaust system will do its job for 15 years or 150,000 miles, that 50% longer and further than ULEV. The trouble is, the technology is so new, that no one actually has 15 years of data on it.

Here's what Auto Technology wrote in their conclusion to the article.

"The requirement of the SULEV standard to meet the emission limit values for 15 years or 150,000 miles goes far beyond that of the ULEV standard, which prescribes a period of 10 years or 100,000 miles. The problem of representing such long guarantee periods within a relatively short testing phase is exacerbated by the fact that engineers have hardly any experience regarding the durability of exhaust systems over such long periods of time or mileages.

"Most of the tests in the vehicle and on the engine test stand are designed to reproduce, in an intensified manner, the entire range of loads that are to be expected during the vehicle’s lifetime. In order to take account of the stricter requirements in the tests, the test programme had to be extended and the test conditions had to be made more severe, in some cases drastically. In addition, special component tests with specially manufactured "bad samples” were carried out. These tests took up to three times the amount of time normally required."

Will a 14 year-old SULEV be as clean as it was when it was new? It's doubtful; and its a problem that simply doesn't exist with an EV. And then there's all that imported oil it consumes and carbon dioxide it emits.

Ellis concluded, "Consequently, in the near term the valid argument for plug-in (hybrids) is not about emissions, it's mainly for 'oil-independence'".

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