Monday, November 8, 2010

Are Electric Cars "Greener"?

Potentially, maybe...but generally not so much.

Electricity as it is right now is not very green--though it is somewhat greening, and there is potential to make it more so.  At least, the biggest opponent of more widespread deployment of renewable and nuclear energy is political, not technical.  I have posited before that we are much better at overcoming technical limitations than we are at overcoming political ones, so one can assume that electricity is not greening at such a rate that the average electric car is powered by anything other than batteries charged with coal.

Cars emit a host of pollutants, most notably carbon dioxide and nitrous oxides of various forms, commonly referred to as NOx (pronounced "nocks.)"  NOx 1)contribute to acid rain, 2) react with sunlight to make ozone, which is great for blocking ultraviolet light in the stratosphere, but when produced at ground level not so good for people who like breathing easily on hot summer days, especially people with risk factors like small children, the elderly, and asthmatics.  Ozone levels in the southeast (I don't have firsthand experience with other regions) get so elevated on some summer days that prolonged outdoor exertion is considered unhealthy for most people.

Ground-level ozone is a concern for multiple reasons: high concentrations damage crop and forest tissue, and it's also a much more potent greenhouse gas that carbon dioxide.   

Here in the southeast most electricity comes from coal.  Coal-fired power plants emit carbon dioxide, sulfur oxides SOx ("socks"), and trace other things like mercury and lead.  SOx 1) contribute even more strongly to acid rain, 2) forms a layer of very fine particles suspended in the atmosphere, that are also irritating to breath in for those who are sensitive, and contribute to smog.

The good news is that SOx emissions in particular are declining thanks to a cap and trade program that's been in place since the 1990s.  Emitters buy credits, ones who have made technology improvements such as scrubbers that make their SOx emissions go below required amounts sell the extra ones, and the total number of overall credits available declines each year.  If you felt like speeding that along, you could go buy a SOx credit. (My econ teacher did that, and framed it.) Both NOx and SOx from large emitters are capped-and-traded, but obviously nobody is cap and trading the NOx that come from private vehicles.

So the trade-off between a gasoline or non-bio-diesel powered engine and a car charged with coal-fired electricity is really between more NOx or more SOx.  Carbon dioxide is gonna happen either way.  Certainly there may be a difference in the carbon dioxide released per unit of petroleum verses coal that makes one less absolutely contributory to climate change--but since coal and fuel combustion technologies alike vary strongly in their age and efficiency, and about three different varieties of coal with very different properties are regularly used by the same plants, that is a difficult and largely apples to oranges comparison.  While we're at it I suppose one should also look at life-cycle costs when considering claims of relative greenness:  the energy and environmental costs of finding, drilling for, securing, shipping, refining, shipping gasoline verses the energy and environmental costs of finding, mining, and shipping coal. I'm curious enough that maybe I'll look into that for another post, but still, apples to oranges.

Hybrid cars by contrast actually are greener, because they are tapping into an otherwise unused energy source and charging batteries with something one does while driving anyway--putting on the breaks.  That idea, tapping into otherwise unused sources, is certainly thinking along the right track toward sustainability.  I will note that my fully gasoline-powered Saturn, a product of GM, for goodness sake, regularly equals or exceeds the gas mileage of the first-generation hybrids, although they've outstripped me in recent model-years.

The advantage I do see of fully electric cars is that it takes two huge pollution problems, coal and gasoline, and turns them into one, just coal, which is theoretically much more capable of being supplemented by more environmentally sustainable production methods.  Sometimes simplifying your problems is progress--turning your oranges into apples.  The only apples to apples "green" alternative to gas combustion is biofuel, which is great when produced from used vegetable oil, but actually very un-green if made from palm-oil planted on illegally logged rain-forest.  From a climate change mitigation standpoint, we cannot afford more deforestation, and could really use some re-forestation instead.

Maybe a hybrid biofuel engine is the future.  Or crazy superconducting mag-levs, assuming room-temperature super-conduction is possible, something we have not yet observed but haven't found evidence yet either that it is impossible.

There's also the issue of American driving patterns--which is a lot of downtown, where electric or hybrid cars are doing something, anyway--but also a lot of inter-city.  People generally want cars for both capabilities, getting to work each day, visiting your sister on weekends.  Hybrids can take you inter-city no problem but don't perform much better than regular vehicles when doing so.  Electric cars don't generally have enough juice to go more than one or two hundred miles--although this could be changing.

Light passenger rail would be sweet, but way too expensive right now, and not practical at rural to suburban density levels, most common here.

By the way, your gas is pretty much exclusively 10% ethanol in North Carolina.

Fuel cells?  Still have to work out that hydrogen exploding thing.  Super efficient though, and non-emitting in the carbon dioxide department, although the method of obtaining the hydrogen is probably going to be quite carboniferous.

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