The size of the battery in plug-in hybrid electric vehicles (PHEVs) significantly affects their overall greenhouse gas (GHG) emissions, with a tradeoff between battery capacity, vehicle weight, operational efficiency, and emissions savings.
Influence of Battery Size on Emissions
- Battery Production “Carbon Debt”: Larger batteries have higher embodied carbon emissions due to mineral extraction and battery manufacturing, which is energy-intensive and currently powered largely by fossil fuels. This creates an upfront “carbon debt” that must be amortized over the vehicle’s lifetime mileage before net emissions benefits are realized.
- Battery Weight and Vehicle Efficiency: Increasing battery capacity adds weight, which reduces overall vehicle efficiency because more energy is needed to move the heavier vehicle. This means that beyond a certain battery size, the extra weight can diminish fuel economy gains and increase emissions during driving.
- Electric Driving Range and Charging Frequency: Larger batteries enable PHEVs to travel longer distances purely on electricity from the grid, reducing gasoline consumption and tailpipe emissions more effectively—particularly if the vehicle can be charged frequently. However, for very frequent charging (e.g., every 25 miles), smaller batteries can be more efficient and emit fewer GHGs than large batteries, as well as being less costly.
- Optimal Battery Size Depends on Use: The balance between battery size, charging patterns, and emissions is complex:
- For short distances between charging (less than 25 miles), small capacity PHEVs have lower emissions than large battery PHEVs.
- For moderate distances (30-90 miles between charges), larger batteries reduce GHG emissions but come with higher initial carbon cost and expenses.
- Frequent, reliable charging infrastructure can maximize emissions benefits of larger batteries by enabling more electric miles and less gasoline use.
- Comparison to BEVs and Conventional Vehicles: Overall lifecycle assessments show that PHEVs with smaller batteries tend to have lower lifetime emissions than full battery electric vehicles (BEVs) currently, because BEVs have much larger batteries with higher embodied carbon. PHEVs achieve lower emissions than conventional hybrids (HEVs) and internal combustion engine vehicles (ICEVs) across various grid emission intensities.
Summary
- Larger batteries reduce tailpipe emissions by increasing electric range but create more emissions during production and increase vehicle weight, which can reduce efficiency.
- Smaller batteries in PHEVs can lead to lower total lifecycle emissions when paired with frequent charging.
- The net emissions impact depends heavily on charging frequency, driving patterns, and the emissions intensity of the electricity grid used for charging.
- Currently, PHEVs with moderate-sized batteries and frequent charging tend to offer a good balance between emissions savings and cost/weight penalties.
Thus, battery size in PHEVs influences overall emissions through a balance between upfront manufacturing emissions, battery weight effects, and operational electric driving range, with smaller batteries often providing better emissions outcomes under optimal charging conditions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-battery-size-in-phevs-affect-their-overall-emissions/
