Electric vehicles good for fighting climate change?

It’s been a long time coming but electric vehicles (EVs) are now booming in political and marketing acclaim and car manufacturers are finally taking this transformation of vehicle propulsion very seriously.

One of the most important reasons for this acceleration in uptake of electric cars is the growing desire to diminish the contribution of the transport sector to climate change. But how realistic is it to put all or most of our cards on the electric car to achieve this?

In the IPPC system car emissions are calculated as so-called TTW (tank to wheel) emissions, so only direct ones from the vehicle itself are attributed to it and not those involved in producing the fuel or energy. This is logical regarding the allocation of responsibilities as it would be unreasonable to make the transport sector or in this case the car user responsible for the energy mix that was used to produce petrol or electricity.

The TTW greenhouse gas (GHG) emissions of electric cars or cars burning hydrogen or biofuels are in the IPPC methodology assumed to be zero. For electricity and hydrogen this is obvious. For biofuels this is because the CO2 emitted by the engine has been captured in nature when the biomass was growing, so the balance is neutral. That all looks very logical, but this method also somewhat distorts reality.

In fact, the electricity is produced somewhere else and this involves on average for the same energy content more release of GHG than the production of fossil fuel. Biofuel production of the first generation is even so carbon intensive that in the Renewables Directive 2009/28/EC the EU made the eligibility of biofuels dependent on the comparison of CO2 emissions in the whole chain from production to distribution and use and set a reference value for the whole chain emissions of fossil fuel.

The calculation method called Well to Wheel (WTW) includes this whole chain of production, distribution and use of the fuel. It is interesting to compare these WTW emissions for electric cars with those of cars using other fuels.

Moreover, one should also look at the difference between the two most utilized and promoted EV concepts: the plug-in-hybrid, which can drive both on electricity and fossil fuel, and the full electric battery vehicle.

In the following table the different options for a midsize car are listed as regards the TTW and WTW emissions. For this calculation it is assumed that in case of a plug-in-hybrid electric propulsion alone accounts for 35 % of all kms driven.

The values for biofuels (in this case ethanol) have been derived from the default values of Directive 2009/28/EC and in this example the car drives on a blend of 85 % ethanol (E85).

gCO2/km TTW WTW
Petrol 170 200
Plug in hybrid EV (35 % on normal electricity mix) 100 150
Plug in Hybrid (35 % on green electricity) 100 120
Battery vehicles (100 % on normal electricity mix) 0 105
Battery vehicles (100 % on green electricity) 0 10
First generation biofuel (e.g.  sugar beet ethanol) 0 120*
Second generation biofuel (e.g. waste straw ethanol) 0 35*

*Biofuels are normally in lower percentages blended into fossil fuels, but for this comparison it is assumed that the vehicle drives on E85 (85 % ethanol).

So a plug-in electric car on normal electricity emits 75 % of the normal petrol car. On green electricity 60 %. Full electric battery vehicles emit around 50 % compared to the petrol car, but the real gain is when these vehicles only use green electricity: then the emission value is just 5% of that of a comparable petrol car. Finally, it is interesting to note that driving on second generation ethanol means emitting only 17% of a petrol car’s emissions.

How realistic is it that EVs would only drive on green or carbon-free electricity?

In the EU electricity production matches usage and, when a battery car only uses the carbon-free part of production, then the coal-generated electricity is used somewhere else. This is the so-called waterbed effect.

However, there is a solution: when the batteries are only charged when intermittent renewable electricity generation (wind, sun) produces overcapacity. Using this peak production is in fact the best way to guarantee that the battery vehicle is really climate-friendly.

My conclusion is that using EVs can indeed be very good for the climate but they should be full electric battery vehicles and be connected to a smart charging system. This would create a win-win situation as for the intermittent renewable energy generation it is most important to sell in the periods of  peak production.

If this is not the case, then it may emerge as more attractive from the point of view of fighting climate change to promote and use second generation biofuels.

DNAttitudes
Show Buttons
Hide Buttons