Well-to-Wheel
By: Savas Kalfas
Tags: Automotive, Electric Car, Green Energy, Electromobility, Emissions

How much “green” electric cars really are?

Word has it that electric vehicles (EV) are zero-emissions vehicles (ZEV) as they do not use carbon-based fuels (petrol or diesel) like ordinary automobiles do. Well, does the ZEV tag represent a true scenario or a somewhat misleading accolade?

In effect, EVs do not emit carbon dioxide from their tailpipes simply because there is no internal combustion engine and no exhaust. As a result, as power is being transferred from the energy source (battery) all the way to the wheels, yes, EVs are zero-emissions vehicles.

What it takes to charge EVs though? Is it a clean process?

Before answering the above questions let’s examine the carbon footprint of a conventional vehicle. First, it is important to note that as fuel is being supplied from oil wells to fuel tanks and then burned by internal combustion engines, one has to add all indirect and direct emissions being emitted by producing, storing, transporting, and burning fuels.

The most obvious observation is that in conventional cars the transfer of energy from the reservoir to wheels (aka Tank-to-Wheel) is not a clean process. As the engine runs, fuel burns and the car directly produces emissions.

Equally obvious is that petrol and diesel automobiles need to refill at gas stations. What is less clear to see though is that bringing fuel from oil wells to oil refineries and then to gas stations (a process aka Well-to-Tank) involves additional indirect emissions and energy losses during oil extraction, storage and transportation.

Well-to-Tank emissions are also known as upstream or indirect emissions. They are being recorded throughout the energy path of production, processing and delivery of fossil fuels.

To illustrate how these direct and indirect emissions add to the equation, the following table summarises all the stages involved when measuring a conventional vehicle’s emissions:

Tank-to Wheel average: 118 g CO2/km

Well-to-Tank average: 29 g CO2/km

Well-to-Wheel average: 147 g CO2/km

Thus, Well-to-Wheel emissions is the ultimate pollution criterion for conventional vehicles since it is the aggregate sum of all the intermediate steps that bring fuel from oil wells to motor wheels -not only what the car emits at the time of travel.

What is the case with EVs and upstream emissions?

In the case of electromobility, electric vehicles need a charger in order to bring energy from the source (the power grid) all the way to the battery (the fuel tank equivalent). This is why EVs are also referred to as plug-in cars -that is, you need to use a power cord and plug the car in order to connect it with the electricity network. How clean is that stage though?

If you live in France and drive an EV you are far “greener” than a Greek electric car driver. In the land of Asterix, nuclear power is the largest electricity source whereas in the land of Greek Gods coal is king… In other words, as Greece largely depends on carbon for electricity production, upstream emissions in Greece are higher relative to France -where energy production is clean thanks to the nuclear plants. At the same time, the very same electric car is credited with more emissions in Greece and thus becomes dirtier -clearly debunking the zero-emissions reputation of EV’s.

As a natural conclusion, the end result of your decision to “go green” and drive an EV very much depends on the political and economic decisions of each country about its energy mix. You might be ready to make a statement that you care about the environment, you might be a fashion victim or be an early adopter just willing to innovate.

In terms of emissions, -no matter who you are and what you want, the outcome of your choice to go electric reflects your country’s power infrastructure and energy sources -definitely not your motives or desires…

Beyond politics, the Well-to-Wheel criterion not only exposes electric cars to a scrutiny about the political correctness of EV’s vis-a-vis their zero-emissions halo, it also creates a framework in order to assess the variably cleaner role of electromobility relative to traditional propulsion technologies.

To illustrate, a recent study showed that in some EU countries electric cars account for more greenhouse gas (GHG) emissions relative to diesel or petrol vehicles (Cyprus, Estonia, Greece, Latvia, Malta, Poland). Some other countries (Bulgaria, Chech Republic, Germany, Ireland, Nederlands, UK) come near to the diesel emissions EU average of 145g CO2/km. The only notable exceptions are Finland, France, and Sweden -where nuclear energy accounts for 30%, 75% and 40% of the energy mix, respectively.

The table below presents the study’s authors and the levels of GHG emissions from the use of EVs in each EU member state.

Greenhouse gas (GHG) emissions from electric vehicles in the EU - SOURCE: Moro Alberto, Lonza Laura. Electricity carbon intensity in European Member States: Impacts on GHG emissions of electric vehicles (2018). PERGAMON-ELSEVIER SCIENCE LTD, ISSN: 1361–9209

Despite that the study’s findings might create some scepticism about the green characteristics of electric cars, the analysis clearly shows that, on average, electromobility can produce between 40% and 50% GHG emission savings relative to gasoline and diesel powered vehicles, respectively.

The advantages of electromobility are further confirmed in the below table. As Well-to-Tank (WTT) data reveal, although indirect CO2 emissions from Battery Electric Vehicles (BEV) are twice as high as those from cars burning carbon fuels (petrol, diesel and compressed natural gas), the Well-to-Wheel (WTW) performance of BEVs keeps overall emissions significantly lower than conventional vehicles. This is a clear advantage which stems from the Tank-to-Wheel point of view -in that EVs produce zero emissions while they move.

Source: gmobility.eu

Conclusion

Thanks to the Well-to-Wheel methodology we can definitely praise the technological superiority of electric vehicles and highlight their important role in the global effort to curb GHG emissions. Although each country’s electricity carbon intensity dramatically increases or decreases the carbon footprint of EVs, this article clearly showed that -on average- electromobility is a cleaner solution that conventional technologies.

In addition, the Well-to-Wheel efficiency measure gives us valuable insights when comparing the greenhouse gas performance between conventional and electric vehicles. Most importantly, WTW is a safe standard in order to compare emissions of all available motoring technologies. In today’s crucial transition of the auto industry’s carbon-based solutions to efficient and clean propulsion methods, WTW can help policymakers, manufacturers and consumers realise the significance of building a sophisticated infrastructure network that will accelerate the adoption of electromobility and transform the current role of the motor car as a major polluter -responsible for 60.7% of total CO2 emissions from road transport in Europe.