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The "zero emissions" car debate.

Discussion in 'Speaker's Corner' started by Rilot, 1 Aug 2006.

  1. Rilot

    Don

    Joined: 18 Oct 2002

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    Location: Wargrave, UK

    I've been having a discussion with a collegue about pollution of vehicles and general transport issues.

    Her standpoint is that if everyone in the UK switched to electric cars tomorrow, the world would be a better place as there would be no emissions. What she fails to realise is that energy cannot be created or destroyed, it can only change it's form. Just because one may plug their car in to a wall socket at night, doesn't mean that no emissions are produced anywhere along the line.

    I was wondering just how many power stations would need to be built if the UK were to do what she suggests (assuming their was a viable electric car for us to buy). Just looking at the problems the electricity companies are facing with the increased use of home air-con units suggests that the current infrastructure would never be able to provide for a fully-electric car society.

    I was also wondering how much hydrocarbon pollutants would be produced to fully recharge an electric car for say a range of 200 miles versus the amount produced by a modern petrol engine covering the same 200 miles. I rekon the figures would not be dissimilar (assuming traditional methods of electricity production ie. non-nuclear, non-renewable). Of course I have no evidence to back this theory up however.
     
  2. Visage

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    In principle what you say is true, but power sytations are much more efficient and clean when it comes to converting hydrocarbons to electrical energy for use in a vehicle than any petrol or deisel engine, so building 100's of powers atations to fuel electric cars would be cleaner than those cars being powered 'conventionaly'.

    Though you're right, they still wouldnt be zero emissions....
     
  3. Sleepy

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    Large scale power plants are more efficient than petrol engines so there would be a reduction in emissions though I don't think it would be large enough to matter.

    Edit: too slow
     
  4. Borris

    Caporegime

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    Addressing the infrastructure point first - Brownouts / failures are due to surges (or changes) in demand, not in the level of demand. There is more than adequate infrastructure in place to cope with a higher aggregate demand (actual supply levels notwithstanding) .

    From a cost per KW perspective, electricity generation is one of the few areas that enjoys ever increasing returns to scale (most economy of scale tales off, following a cumulative normal pattern, that may even decrease), and also increased efficiency.

    Which leads me to the second point - Is it more efficient to have a centralised power supply, both at economic and environmental levels.

    I have no data to back up any assertion, but on the surface, it would seem like a fair assumption - My guess is that few things as efficient on the small scale as they are on the large. However, by the same token, maybe the electric engine is less efficient, and any previous savings are lost when transferred to actual miles travelled.

    It would be interested to see if anybody has bothered looking at this.
     
  5. Borris

    Caporegime

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    Also, seeing as the nuclear debate is around - How about the environmental effect of building the batteries, and, perhaps more importantly, disposing of them.




    [Tangent]

    This puts me in mind of electric hand driers - Are they more environmentally friendly than a paper towel? I doubt it - The energy requireed to blast that hot air at my hands is probably equivalent to burning an entire stack of paper towels, but is also not sustainable.
     
  6. Rilot

    Don

    Joined: 18 Oct 2002

    Posts: 20,668

    Location: Wargrave, UK

    I've often wondered this too.
     
  7. Visage

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    [nerd]

    As part of my degree I did a study asking exactly that question. The biggest factor is actually that paper towels merely remove water fromthe hands, wheras dryers actually have to turn the wtaer into vapour, requiring a significant energy input.

    [/nerd]
     
  8. Sleepy

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    One crude calculation done by one hung over bloke:

    No of Vehicle UK 30m

    Average mileage 10,000

    Average mpg 30 mpg (guess)

    30E6 * 10000/30 = 10,000,000,000 gallons of petrol used per year.

    burning 1 gallon of petrol ~ 145,000,000 joule

    Thus energy required per year = 10E9 * 145E6 = 1450E15J

    Averaged out over a year 1450E15/31,556,926 = 45E9 W

    In SI units 45TW

    A modern French Nuclear Power Plant outputs 1200MW (1.2TW)

    Thus 50 odd Nuclear plants would be required to provide for the electric vehicles.
     
  9. Visage

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    Ah, but you've assumed equal efficiency for petrol and electric engines.

    I dont know if they *are* equal, but it could affect the calculations quite a bit....
     
  10. Sleepy

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    good point

    Edit: This site would seem to indicate that with current battery technology real world figures indicate that they are equally efficient.
     
    Last edited: 1 Aug 2006
  11. Visage

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    http://en.wikipedia.org/wiki/Battery_electric_vehicle

    Suggests figures of 0.3 to 0.5 kWh per mile.

    So 30m vehicles @ 10k miles per year = 120 billion kWh per year = 3.8MW

    I think.....those calculations could do with double checking.