Conditions for Reducing WTW CO₂ Emissions from Automobiles through the Spread of Electric Vehicles (EVs) – Identification of the Marginal Power Source for EV Charging and Calculating CO₂ Emissions from EVs

Authors

Dr. K. Hatamura, Hiroshima University, Japan

Year

2020

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 813

Summary

The spread of electric vehicles (EVs), which emit no exhaust gas while driving, is being promoted worldwide. However, a detailed life-cycle analysis shows that well-to-wheel CO₂ emissions and CO₂ produced by battery manufacturing cannot be ignored. In this paper, we focus on CO₂ emissions associated with electricity production in Japan, and compare life-cycle CO₂ emissions of EVs with those of hybrid electric vehicles (HEVs).
In order to correctly evaluate well-to-wheel CO₂ emissions, it is necessary to calculate CO₂ emissions from “a comprehensive operation of EVs”, which includes the primary energy dependent CO₂ emissions for power generation for charging EVs. Here, we apply the concept of the marginal power source as specified in the GHG (Greenhouse Gas) Protocol to calculate the CO₂ emissions when EV power demand results in changes to the configuration of the power generation infrastructure. The spread of EVs in long term can, in many cases, lead to coal-fired power generation becoming the marginal power source for EV charging demand. Under these circumstances, CO₂ emissions calculated using the emission factor of coal-fired power generation provides an estimate close to reality. As a result, it is shown that the spread of HEVs instead of EVs reduces CO₂ emissions by about 1/3. In order to achieve the same reduction in CO₂ emissions through the spread of EVs, it will be necessary to limit the number of EVs, so that over 1/3 of the total EV charging demand can be supplied using surplus power caused by renewable energy.
In Europe, although the power supply situation is different from Japan, when thinking over a long term and across the EU, coal-fired power is likely to be the marginal power source, and the same analysis performed for Japan can be applied.