A Data-Driven Greenhouse Gas Emission Rate Analysis for Vehicle Comparisons

Abstract

The technology focus in the automotive sector has moved toward battery electric vehicles (BEVs) over the last few years. This shift has been ascribed to the importance of reducing greenhouse gas (GHG) emissions from transportation to mitigate the effects of climate change. In Europe, countries are proposing future bans on vehicles with internal combustion engines (ICEs), and individual United States (U.S.) states have followed suit. An important component of these complex decisions is the electricity generation GHG emission rates both for current electric grids and future electric grids. In this work we use 2019 U.S. electricity grid data to calculate the geographically and temporally resolved marginal emission rates that capture the real-world carbon emissions associated with present-day utilization of the U.S. grid for electric vehicle (EV) charging or any other electricity need. These rates are shown to be relatively independent of marginal demand at the highest marginal demand levels, indicating that they will be relatively insensitive to the addition of renewable electricity generation capacity up to the point at which curtailment occurs regularly unless the most carbon-intensive electricity sources are preferentially deactivated. We propose a simplified methodology for comparing emissions from BEVs and hybrid electric vehicles (HEVs) based on the marginal emission rates and other publicly available data and apply it to comparative case studies of BEVs and HEVs. We find that currently there is no evidence to support the idea that BEVs lead to a uniform reduction in vehicle emission rates in comparison to HEVs and in many scenarios have higher GHG emissions. This suggests that a mix of powertrain technologies is the best path toward reducing transportation sector emissions until the U.S. grid can provide electricity for the all-electric fleet infrastructure and vehicle operations with a carbon intensity that produces a net environmental benefit.

Plug‐in hybrid electric vehicles are better than battery electric vehicles to reduce CO 2 emissions until 2030

“…Production, use, and disposal of a BEV are not free of cradle-to-grave LCA CO 2 emissions. 39,40 Their emissions are larger than those of PHEVs, and FCVs, especially if these vehicles are further developed as proposed. With a grid still mostly relying on combustion fuels power plants, not only for the limited capacity of wind and solar photovoltaic plants but the almost complete lack of energy storage, 41,42 even the indirect emission of a battery recharge may be comparable with the direct emission of producing electricity on-board with high efficiency the few times range is needed.…”

“…The work promotes the sharing of the available battery capacity between PHEVs and plug-in FCVs, which may deliver the same as BEVs' energy economy working electric over the most common mode of use of the vehicle, with the production of electricity on board only in the few sporadic cases extra range is necessary. This shift allows a more economic and environment-friendly car fleet immediately, based on the current indirect emissions of electricity, 39,40 as well as the use of conventional HC fuels and renewable green hydrogen. This shift is expected to remain effective until 2030.…”

“…In the case of H 2 , both the ICE and the storage of the fuel must be modified. The recent work 40 has provided the latest, accurate, estimations of the greenhouse gas emission rate to be used for vehicle comparisons, demonstrating the PHEVs now on the market have reduced emissions vs the current BEVs even if fueled with conventional HC fuels. With the small changes proposed to the PHEVs, their advantage may only improve.…”

Battery energy storage in electric vehicles by 2030

“…While the environmental advantages of BEVs vs HTEVs and diesel ICEVs are at least controversial (worth of mention, the latest work 46 supports the view that HTEVs and diesel ICEVs are more environmentally friendly than BEVs, same as 44,45 ), this reader should accept the fact that the most energy-efficient vehicle is a plug-in HTEVs working electric on the certification cycle, which is the most common mode of operation of the vehicle. As here suggested, a much simpler plug-in series HTEVs with a slightly larger battery to better recover the braking energy and buffer the operation of the ICE, which may be small and high efficiency, is the best option.…”

Study of the Potential of Electrified Powertrains with Dual-Fuel Combustion to Achieve the 2025 Emissions Targets in Heavy-Duty Applications

“…Burton et al [159] studied the marginal emission in USA in passenger vehicles. The information from the 2019 electricity grid data was used in this study to compute the geographically and temporally resolved marginal emission rates that capture the actual carbon emissions related to the current use of the USA grid for electric vehicle charging or any other electricity need.…”