Emissions

2014-08-16

And now for something completely different.

Someone asked the question the other day - what's the CO2 cost of the concrete in a Wind Turbine?

You need 1000 tonnes of concrete to install a wind turbine You create a total of 410 kg of CO2 per m3 of concrete Concrete has a density of 2.4 tonnes per m3 => One wind turbine requires 416 m3 of concrete => You can attribute 170 tonnes of CO2 to the wind turbine's concrete base

Assume a turbine base lives for 20 years. Assume the turbine generates 2 MW max Assume an average utilisation of 30% => in 20 years, the turbine will generate 105.2 GWh

=> concrete production adds around 1.6 tonnes per GWh (Or 1.6 grams per kWh) to wind power.

If you make electricity using an fossil fuel power station, you create:

Coal: 910 g/kWh Gas: 390 g/kWh

(The UK average across all fuel types, including renewable and nuclear) is 470 g/kWh.

So, the effect of the concrete on CO2 emissions is negligible, compared to traditional power plants.

As an aside, if your electric car requires 120 V / 15 A for one hour to get 8 km of charge (these are the numbers for a Tesla Model S), you use 225 Wh of electricity per km at the wall socket. Given distribution, that's about 240 Wh. Or, in the UK, 112.8 g/km of CO2. Which on a petrol car is around 58 mpg.

But it's not that simple as that's only at the tailpipe and doesn't account for refining and transport. A rough figure would be 6 kWh used per gallon of petrol in refining, for example, which is all coal based in the UK

6 kWh per gallon of petrol 910 g/kWh for coal power => 5.46 kg/gallon of petrol

Assuming 58 miles per gallon of petrol (from above) => 94.1 g/mile CO2 emissions for refining petrol (consumed at @ 58 mpg) => 58.8 g/km CO2 emissions for refining petrol (consumed at @ 58 mpg)

This increases to 136.5 g/km at 25 mpg, on top of the 261 g/km the car produces. Basically, add 52% to the tailpipe CO2 to compensate for the refinery process. Plus a bit for the truck to take it to the petrol station, and the ship to take it to the refinery, and the well to dig it out of the ground.

So how many mpg does your petrol car actually have to do to match a Telsa Model S for CO2, accounting for refining (but not transport)? 88 mpg.