The effect of plug-in hybrid electric vehicle charging on fuel consumption and tail-pipe emissions

Ahmet Mandev,Patrick Plötz,Frances Sprei

doi:10.1088/2515-7620/ac1498

Abstract

Plug-in hybrid electric vehicles (PHEV) have an electric motor and an internal combustion engine and can reduce greenhouse gas emissions (GHG) from transport. However, their environmental benefit strongly depends on the charging behaviour. Several studies have analysed the GHG emissions from upstream electricity production, yet the impact of individual charging behaviour on PHEV tail-pipe carbon emissions has not been quantified from empirical data so far. Here, we use daily driving data from 7,491 Chevrolet Volt PHEV with a total 3.4 million driving days in the US and Canada to fill this gap. We quantify the effect of daily charging on the electric driving share and the individual fuel consumption. We find that even a minor deviation from charging every driving day significantly increases fuel consumption and thus tail-pipe emissions. Our results show that reducing charging from every day to 9 out of 10 days, increases fuel consumption on average by 1.85 ± 0.03 l/100 km or 42.7 ± 0.8 gCO2 km−1 tail-pipe emissions (± on standard error). Charging more than once per driving day has less impact in our sample, this must occur during at least 20% of driving days to have a noteworthy effect. Even then, a 10% increase in frequency only has moderate effect of decreasing fuel consumption on average by 0.08 ± 0.02 l/100 km or 1.86 ± 0.46 gCO2 km−1 tail-pipe emissions. Our results illustrate the importance of providing adequate charging infrastructure and incentives for PHEV users to charge their vehicles on a regular basis in order to ensure that their environmental impact is small as even long-range PHEVs can have a noteworthy share of conventional fuel use when not regularly charged.

Highlights

Greenhouse gas (GHG) mitigation is strongly needed in the transport sector to limit global warming as stated in the Paris agreement
Given inset in figure 3, if we control for daily vehicle kilometres travelled (VKT) and look at the isolated effect of additional charging, we observe more clearly that an increase from 0% to 10% driving days with additional charging can result in a reduced observed mean fuel consumption of approximately 1 1⁄4 l/100 km or 29 g tail-pipe CO2 per km
We choose to focus only on tail-pipe emissions and do not include in our analysis emisssions from the grid that might vary depending on charging time.While the overall emissions of the Plug-in hybrid electric vehicles (PHEVs) are important, we find that less attention has been given to the tail-pipe emission and fuel consumption of PHEVs

Summary

Introduction

Greenhouse gas (GHG) mitigation is strongly needed in the transport sector to limit global warming as stated in the Paris agreement. Plug-in hybrid electric vehicles (PHEVs) are plug-in electric vehicles (PEV) that can use electricity as well as conventional fuel for propulsion (Bradley and Frank 2009). Their potential to reduce local and global emissions strongly depends on their real-world usage and the share of kilometres driven on electricity, the so-called utility factor (UF) (Chan 2007, Jacobson 2009, Flath et al 2013). PHEV are one third of the global PEV fleet or about 9 million vehicles on the road (by the end of 2020) and still increasing (IEA 2021). PHEV are both relevant in the current global PEV fleet and in terms of market shares in major vehicle markets.

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Discussion

Conclusion