The battery size in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) significantly influences their overall emissions through effects on manufacturing emissions, fuel use, and grid electricity consumption.
Battery Size and Emissions Impact
- Battery Production Emissions: Larger batteries have higher embodied carbon due to the energy-intensive manufacturing processes and the mining of critical minerals. For example, PHEVs have battery sizes roughly one-sixth that of full battery electric vehicles (BEVs), which leads to about one-sixth the emissions from battery production compared to BEVs.
- Use Phase Emissions:
- HEVs have smaller batteries that assist the internal combustion engine but rely mostly on gasoline, limiting direct emissions reductions compared to PHEVs.
- PHEVs have larger batteries that allow them to drive significant portions of miles on electric power, reducing fossil fuel consumption and tailpipe emissions. The emissions benefits increase with frequent charging and increased electric driving range.
- Charging Patterns and Battery Capacity: Studies show that smaller battery PHEVs charged frequently (every 25 miles or less) consume less gasoline and emit fewer greenhouse gases (GHGs) compared to HEVs or larger battery PHEVs. Larger batteries increase vehicle weight and can reduce efficiency, partially offsetting emissions benefits if charging is infrequent.
Lifecycle Emissions Comparison
- PHEVs generally have lower lifecycle GHG emissions than HEVs because they use grid electricity for a portion of miles, which can have zero tailpipe emissions. Even with some gasoline use (around 30% of miles), PHEVs can reduce lifetime emissions by about 46% compared to internal combustion engine vehicles (ICEVs), outperforming HEVs and often full BEVs in terms of total lifecycle emissions when the grid is not fully clean.
- The advantage of smaller batteries in PHEVs lies in their significantly reduced embodied emissions and sufficient electric driving range to cut fossil fuel use, leading to better overall emissions profiles than HEVs which have smaller batteries but no plug-in capability.
- Grid emissions impact the effectiveness of PHEVs: in regions with high grid emissions, the difference between PHEVs and HEVs narrows since electricity consumption leads to indirect emissions, but PHEVs still tend to be better.
Summary
| Vehicle Type | Battery Size | Impact on Emissions |
|---|---|---|
| HEVs | Small, non-plug-in | Lower battery production emissions but higher gasoline use; moderate overall emissions reduction. |
| PHEVs | Medium, plug-in | Higher battery production emissions than HEVs but lower due to smaller size than BEVs; significant fuel savings and reduced tailpipe emissions with frequent charging; best lifecycle emissions profile among hybrids. |
| BEVs | Large, full battery | Highest battery production emissions; zero tailpipe emissions; overall lifecycle emissions depend heavily on grid cleanliness. |
In conclusion, the smaller battery size of HEVs limits their ability to replace gasoline use, resulting in relatively modest emissions improvements. In contrast, PHEVs strike a balance by having moderate battery sizes that enable substantial electric driving and emissions reductions while minimizing battery production emissions, thereby achieving a more favorable overall emissions profile than HEVs.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-battery-size-of-hevs-and-phevs-impact-their-overall-emissions/
