UK gov offers car CO2 rankings by class
Prius gets ass whupped by supergreen Polo
The UK government has set up a website advising consumers on which cars are the greenest.
The new "Best on CO2 Rankings" webpage uses What Car? magazine's system of classification, breaking motors down into the following groups: Supermini, Small family, Family, Estate, MPV, Compact Executive, Executive, Coupe, Open-top, Hot hatch, Compact 4x4, Large 4x4, Luxury and Performance.
The government seems to believe that people's first decision will always be what kind of car they want, regardless of how green that might be. Well-off urban professionals will continue to buy 4x4 offroad vehicles that they don't need and haven't the skills to use fully. Other families will continue to buy ever larger estate cars and MPVs, in order to move the burgeoning piles of junk they are supposed to have. Men young and old will continue to pay big money for unnecessary and often illegal performance levels.
But the Department for Transport seems to reckon that, having decided on a class of vehicle, people might then be willing to consider CO2 emissions; hence the web page. Say you're a young man who's just taken out an enormous crippling loan, or an older wealthier one who wants a virility-boosting toy. You select "performance", and new fast cars for sale in the UK are listed in worsening order of CO2 emissions.
So far, so routine. But then try "all vehicles", which should show the lowest-CO2 motors to be had. There still aren't any all-electric cars listed, offering zero carbon emissions (though one needs to use nuclear, solar, wind, or whatever to generate the 'leccy for this to be really true).
UK motorists can buy the controversial G-Wiz electric vehicle, but this is officially a quadricycle, not a car - and is frowned on by the DfT as unsafe - so its absence isn't surprising.
More promising fully electric rides such as the Lightning supercar, powered by the potentially game-changing "NanoSafe" fast-charge battery tech, aren't yet on sale.
OK, surely the lowest-carbon cars must be hybrids, which use batteries and motor-generators combined with ordinary engines to reduce emissions? That's the most advanced green-car tech in widespread use on the roads.
No, actually. There's a new class of ultra-low-emission ordinary cars coming, encouraged by the zero-road-tax band for vehicles rated at less than 100 grams of CO2 per kilometre. The first of these will be out shortly: the Volkswagen Polo Blue Motion diesel. It's basically an ordinary Polo tweaked for ultimate fuel economy. It pips the Toyota Prius hybrid into first place for minimal CO2 belch, avoiding even the £15 per annum road tax paid by Prius drivers. To add insult to injury, it's at least five grand cheaper than a Prius and achieves a slightly higher top speed, though slower 0-60. Auto Express say the Polo is "an excellent motorway car." On the other hand, the Prius is a bigger vehicle altogether and has doors for the back seats.
Still, if you really want to be greener-than-thou, as opposed to liking new technology, you should really get one of the new, teeny, and efficient ordinary cars rather than a hybrid. According to the government, anyway. ®
There are major issues to consider with the Dust to Dust survey which is currently being used to suggest that the Prius is more energy intensive than a Hummer.
The initial suggestion seems to go against what I would expect, so I read the report. Amongst the assumptions are that a Prius would only do around 100,000 miles in its lifetime, based upon owners doing 6000 miles per year. In addition, all of the R&D costs were put on the initial model, on the basis that it was possible that the model would fail, and so the investment energy cost has to be bourne by that one model.
Since there are now version 2 and version 3 coming along, this initial assumption can be shown to be false. Spreading this initial development cost over more vehicles would drastically change the energy requirements of the vehicle. Indeed, if the hybrid technology continues to develop, it is possible that the basic research could move into an entire sector of vehicles, with the cost per vehicle reducing dramatically.
In addition, there have been dramatic improvements in the technology leading to better fuel performance of >100mpg (http://www.autoexpress.co.uk/news/autoexpressnews/208986/toyota_prius.html)
This is not to criticise the initial report, which was examining the situation at a particular point in time. However the spin being put on it whereby a Hummer is more environmentally friendly than a Prius seems to be similar to the climate change deniers - it is easy to state something, but examining the source evidence can lead to different conclusions.
Best by far is a hybrid....
If you look at http://www.fuel-economy.co.uk/stats.shtml, you will see that the most fuel efficient car by far is a hybrid - just not a Prius. The Honda Insight gives around 20% than the next most efficient car (although they don't have data on the Polo yet). However, this is no longer on sale.
The Polo is a small car further cut down to try and get the best fuel efficiency possible. The Insight was also optimised for fuel efficiency, with excellent results. The Prius is designed to minimise the compromises of having a fuel efficient car. The next version of it is expected to give >100mpg.
The developments they are bringing in seem to be producing major changes in fuel efficiency - a nice change from the previous couple of decades.....
Consumption vs CO2
The reason consumption vs. CO2 varies is that diesel fuel contains more (hydro)carbon (and thus more energy) per unit volume compared to petrol. If you burn one litre of petrol you get 2.31 kg CO2, while one litre of diesel gives you 2.68 kg CO2. This is independent of the engine efficiency, which is a measure of how much of the chemical energy stored in the fuel you can extract as power. Higher efficiency = lower consumption for the same work.
All modern combustion engines burn virtually 100% of the fuel, if not they would never pass emission testing (where would the remaining unburnt fuel go?), so CO2 is directly related to consumption within the same fuel type.
While low on CO2 emissions, diesels also emit particulates that are allergenic and thought to be carciogenic, as well as NOx that is poisonous and contributes the the lovely brownish-yellow haze above large cities (petrol engines have virtually zero particulate and NOx emissions).
While particle filters exist (albeit at the price of increasing CO2 through decreased efficiency), a working means of catalyzing NOx is required before a diesel-powered car can be considered as "clean" as a petrol-electric hybrid.