The emissions intensity of the electric grid significantly impacts the overall efficiency and environmental benefit of plug-in hybrid electric vehicles (PHEVs). Here’s how:
Impact of Grid Emissions Intensity on PHEV Efficiency
- Tailpipe vs. Upstream Emissions: PHEVs emit zero tailpipe emissions when running on electricity. However, the overall emissions depend on how clean the electricity grid is, because electricity generation from power plants can produce CO2 and other pollutants.
- Cleaner Grid = Greater Emissions Benefit: The lower the emissions intensity of the grid (meaning cleaner electricity generation from renewables or low-carbon sources), the more PHEVs reduce greenhouse gas emissions compared to conventional vehicles. As grid emissions decrease, the relative carbon footprint of a PHEV using grid electricity drops accordingly.
- Flexibility Enhances Grid Efficiency: Studies modeling grid operations (such as on the Texas grid) show that PHEVs can improve overall power system efficiency by shifting charging times to when cleaner or more efficient generation is available. This flexibility can reduce net emissions of CO2, NOx, and SO2 by optimizing generator dispatch.
- PHEVs vs. Battery Electric Vehicles (BEVs): PHEVs often have smaller batteries, so their manufacturing emissions are lower. Because they use less grid electricity overall (some miles are powered by gasoline), they sometimes outperform BEVs on lifecycle emissions across different grid emissions intensities—especially where grids still rely heavily on fossil fuels.
- Emission Reduction Quantification: Real-world data indicate that increasing the electric drive capability (e.g., by increasing PHEV system power) reduces fuel consumption and CO2 emissions by a few percentage points per 10 kW added, implying that grid electricity’s cleanliness directly influences these efficiency gains.
Summary
The overall efficiency of PHEVs is closely linked to the carbon intensity of the electric power grid. As grid emissions intensity decreases, the environmental advantage of PHEVs grows, making them more efficient and cleaner. Additionally, the ability of PHEVs to charge flexibly enhances grid efficiency and reduces emissions further. Because PHEVs combine grid electricity use with gasoline for some miles, they tend to provide significant emissions reductions even on grids that are not yet fully clean, often outperforming pure BEVs in many real-world scenarios where grid emissions are still high.
Thus, the grid’s emissions intensity directly affects the total emissions and efficiency gains PHEVs can deliver in practice.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-emissions-intensity-of-the-grid-impact-the-overall-efficiency-of-phevs/
