18 Dec 17

Are EVs really greener than conventional cars?

This question has been raised several times – and yields very different answers depending on whom you ask it. In fact, the answer is usually ‘yes, but’. Much depends on the sourcing of the power used to charge the batteries.

Less pollution, even with “grey” power

A study by the European Climate Foundation (ECF), performed with the cooperation of several NGOs, Renault and battery manufacturer Saft, confirms what others have concluded: the energy mix is decisive in drawing up the balance. Previously, Brussels University (VUB) and Mobi found that EVs almost always have a smaller carbon footprint, even when they use ‘grey’ electricity.

According to the ECF study, an electric city car emits up to 70 percent less greenhouse gases over its entire life than a comparable petrol-powered model, on the condition that the electricity used is green and that the batteries are recycled at the end of the lifecycle. If you look at a compact car, the advantage equals 57 percent compared to a comparable diesel model.

Integral part of a smart grid

Moreover, the biggest advantage of electric cars over diesel cars is that they do not emit NOx or particulate matter (PM). Also, batteries of electric cars and plug-in hybrids can be put to good use as energy buffers for the power grid (V2G, or vehicle-to-grid), levelling out peaks and troughs in both demand and supply.

In fact, the smart grid can even extend the life of a lithium ion battery and decrease degradation. Until now, many believed the opposite was true, but research performed by WMG, International Digital Laboratory, The University of Warwick and Jaguar Land Rover, yields a tantalising conclusion: “An EV connected to this smart-grid system can accommodate the demand of the power network with an increased share of clean renewable energy, but more profoundly that the smart grid is able to extend the life of the EV battery beyond the case in which there is no V2G.”

Don't write off diesel just yet

But not everyone is convinced of the overall greenness of EVs. Uniting stakeholders in the oil industry, Fuels Europe claims that with the upcoming Euro 6d emission standards, diesels will be absolutely clean by 2020, tackling the NOx and PM problem.

Regarding NOx emissions: today's Euro 6c diesels struggle to comply with the RDE test (Real Driving Emissions). It basically verifies whether a new model meets the emission standards both in theory (lab conditions, measured under WLTP) and in practice (on the road). The Euro 6d standard will push OEMs to close the gap between lab and real-world, making diesels as clean as petrol engines whilst emitting less carbon dioxide. 

The truth about brake pads

As far as particulate matter is concerned, a study performed by Aeris Europe (and ordered by Fuels Europe) projects that if we were to replace all diesels by EVs by 2030, the level of PM2,5 (i.e. particles with a diametre of less than 2.5 µm) would drop to 2,500 tonnes. If by that year, all diesels would be Euro 6d compliant, the PM25 emissions would equal 3,000 tonnes. The source of particulate matter would primarily be brake pads and tyres – an issue that today is entirely ignored by OEMs and legislators.

In this respect, EVs have a considerable advantage: most of the braking is not done by brake pads being pushed against the brake discs, creating friction and launching particles in the surrounding air, but by putting the electric motor in "reverse mode". This "regenerative braking" convertes kinetic energy into electric power, which is stored in the battery pack.


Authored by: Dieter Quartier