The CO2 impact of electric vehicles based on charging habits

A new methodology has been devised that quantifies the carbon dioxide (CO2) impact of electric vehicles based on charging habits.

The work is the work of researchers from the Polytechnic University of Valencia (UPV) in Spain, belonging to the CMT-Thermal Engines Institute.

In their study, they have compared the CO2 emissions of electric, hybrid, and thermal engine vehicles, through computational modeling, and taking into account different vehicle segments and driving cycles. And the results show that the CO2 emissions of electric vehicles due to their recharging double or even triple their value if the analysis of marginal emissions is applied, instead of making estimates with average values ​​of emissions associated with electricity generation. The difference between the two methods is that the marginal analysis takes into account the instantaneous impact of a given load on CO2 emissions from the electricity production system.

“CO2 emissions from the life cycle of an electric vehicle in Spain, without taking into account those associated with the recycling process, are currently of the order of 100 g/km, and could exceed 130 g/km in 2030 if The Spanish electricity production system does not increase its percentage of renewable sources. These values ​​are lower than the 188 g/km and 242 g/km obtained for a non-plug-in hybrid and non-hybrid vehicle, respectively, but it must be taken into account that there is no zero emission technology, contrary to what is often The aim is to make the public believe”, points out Antonio García, a researcher at the CMT-Motores Térmicos of the UPV.

To carry out this study, the UPV team took CO2 emissions data provided by Red Eléctrica Española, with which they evaluated the CO2 impact of different propulsion systems in passenger cars in various segments. The analysis was carried out both from the tank to the wheel, that is, the CO2 emitted from the vehicle itself, and from its complete life cycle, which includes the CO2 generated to obtain and transport energy to the recharging points (either electric or fossil fuel).

Research team members. (Photo: UPV)

As Javier Monsalve, co-author of the study and researcher at CMT-Motores Térmicos, explains, the Spanish electricity production system prioritizes the use of renewable sources -they cover 15% of the total annual demand-, to subsequently satisfy the rest of the demand, making use of the lowest cost generation source at that time (biomass, coal, combined cycle and thermal).

“The sources of electricity generation active at any given time vary depending on the instantaneous demand for energy, so in order to accurately quantify the impact on CO2 associated with recharging an electric or hybrid vehicle, the moment in which the which connects to the network. To do this, we have analyzed data from the Red Eléctrica Española (REE) database, which provides instantaneous data on electricity generation and CO2 emissions, with a time scale of 10 minutes”, explains Monsalve.

To limit the scope of the study, the team from the CMT-Motores Térmicos of the UPV carried out the calculations assuming a complete recharge of 6 h, which can start at any time of the day. In turn, they considered two instantaneous power demand scenarios, one representative of the current vehicle fleet, where few electric vehicles are connected to the grid at the same time, and another representative of 2030, where 1 million vehicles could hypothetically be connected to your recharge at the same time. “We have to assimilate that there is no such thing as a carbon-neutral transportation technology. If we want to minimize the impact of the transport sector, we must be aware of the real emissions of each technology. With this, more effective charging strategies can be designed, for which a giant advance in the interconnection of systems is required. At the moment, the electric vehicle is still in the phase of acceptance by users, given that there are currently more important problems such as the scarcity of charging points and the short driving range”, explains García.

The results analyze the scenario of Spain, but the methodology developed by the CMT-Motores Térmicos team of the UPV can be extended to other regions of the world.

The study is entitled “Carbon footprint of battery electric vehicles considering average and marginal electricity mix”. And it has been published in the academic journal Energy. (Source: UPV)