Discussion > Bogus Renewables Claim: 'equivalent to taking N thousand cars off the road'
Does your calculation include the capacity factor of the renewable source? Normally about 10% for Solar PV and 30% for wind. If not it will be about 5 and 15 cars respectively, which sounds more like it.
I like your calculation having driven the M1 at all hours and on every day of year there are a lot of cars on the road even at 2am Christmas Day.
SandyS
Yes, capacity factor was included in the 3500 tonnes of CO2 figure, along with a deduction for lifetime emissions from PV manufacture. You could also propbably make a deduction for loss of CO2 absorption by the crop that would have been growing in the field if the solar farm wasn't built. But hard to find a figure for that. Maybe a couple of tonnes per hectare (although not sure if it's all emitted again after harvest...)
Chilli
It's even more dishonest than that, Chili, although well done for unpicking the lies this far. They are not "taking cars off the road", because their calculations are based on the number of cars already on the road.
They are, at best, cancelling out the CO2 emissions of future cars on the road. Not nearly as catchy.
johanna
A common claim made in renewables planning applications goes something like:
"This development will save 3500 tonnes of CO2 per year. This is equivalent to taking 1300 family cars off the road"
This conjures an image of 1300 cars all racing along or stuck in a jam - all magically being disappeared by this wonderful new wind or solar development. That's got to be good right? 1300 cars? Worth upsetting a few nimbys, no?
After some thought I've decided this is a highly misleading claim - for two reasons:
1) The actual number of cars-worth of CO2 'taken off the road' at any one time is given by:
The renewable's CO2 saving per hour / CO2 emitted per hour by a car while driving.
A car emits about 8Kg per hour, and in this case the renewable saves 3500tonnes / 365days / 24hrs = 400Kg per hour. So the number of cars-worth of CO2 emissions offset at any moment is only 400Kg / 8Kg = 50 cars
Of course the developer is using the typical annual mileage of a car to calculate his figure: 3500 tonnes / 2.7 tonnes typical annual CO2 of a family car = 1300 cars. But this is misleading because those average cars spend 96% of their time parked with the engine off. So it's misleading to talk about them being 'taken off the road' (in the literal sense) because 96% of them are already off it.
2) Furthermore these cars aren't actually being 'taken off the road'. Their CO2 emissions have been offset. That's all. Nothing more. The noise, congestion and all other pollutants are unaffected - but the developer casually claims all those other non-existent benefits too, with the statement "This is equivalent to taking 1300 family cars off the road".
Talk about a bogus statistic!