Potential Effects of Climate Change on the Plug-in Electric Vehicle Energy Load and Greenhouse Gas Emissions in Los Angeles

This study examines the relationship between climate change and plug-in electric vehicles (PEVs) in terms of the potential energy load and greenhouse gas (GHG) emissions. In the first part of the study, we create an integrated model to estimate PEV-related energy load and greenhouse gas emissions for the City of Los Angeles. A number of scenarios are created based on projected changes in electricity grid mix, level of adoption, and charging patterns. Using the results, we then pose a simple question: assuming that the region’s climate change projections hold true, what are the potential impacts on PEV charging, demand on the energy grid, and emission profiles? The results show a rather nuanced yet important relationship between climate change and PEVs that require deep understanding in order to maximize the technology’s GHG emissions mitigation potential.   

Modeling Emissions from PEV Adoption

Previous studies have shown that the use of PEVs can significantly reduce GHG emissions. However, the extent of PEVs as a means of mitigating emissions is dependent on major factors such as the type and scale of electricity generation sources, electric battery technology, and consumer behavior in terms of adoption and charging patterns.

Grid Energy

The change in grid energy mix plays a significant role because of the type and scale of the energy input source to the generating facility. This in turn dictates the emissions rate of the power supplied to the consumer. The emission profile of LA’s grid energy is modeled by integrating the region’s current short-term and long-term generation sources and capacities with the available data on lifecycle emissions of various power generation sources. Despite California’s reputation as the leader in renewable energy, the power generation sources for LA are significantly different from those of the rest of the state. Unlike the rest of California, the Los Angeles Department of Water and Power (LADWP) currently relies heavily on coal-fired plants that emit high concentrations of greenhouse gas (GHG) and toxic air pollutants. However, LADWP is aggressively shifting a significant portion of its generation capacity from nonrenewable to renewable sources such as wind and solar. Therefore, this study models the changes in LADWP’s marginal emission rate or “grid carbon intensity” from power generation as the agency phases out its coal generation sources.

Consumer Adoption and Charging Pattern

Consumer behavior plays a significant role for PEV emissions in terms of adoption and charging patters. The consumer adoption rate of PEVs determines how quickly the emissions mitigation potential on a per-vehicle basis is actualized over time. Although previous studies have predicted modest PEV sales, LA’s rate of adoption of PEVs has been disproportionately higher relative to the rest of the U.S. With improving battery technology and declining costs, the adoption rate is likely to accelerate and perhaps present us with a paradigm shift in the region’s transportation system. We use the adoption pattern based on the Bass technology diffusion model. The overall impact of PEV adoption in LA’s vehicle population is modeled by using the projected working age population as a surrogate to estimate the region’s fleet size and assigning a survival rate for PEVs based on vehicle age. With growing adoption, PEV charging demands also increase. Therefore, consumer decisions on charging also play a critical role in energy load and emissions. Charging PEVs during “peak” hours results in the use of marginal generation resources to supply the additional demand often resulting in higher emissions. For LADWP, the primary peak power source is its set of hydro power plants near the Sierra Nevada, which is unlike the rest of California that depends on primarily on natural gas peaker plants. This study creates different charging scenarios based on travel behavior data to assess the impacts on the energy load and emissions.

Climate Change Implications on PEVs

Numerous studies have shown that the LA region is already significantly affected by climate change. The region’s average temperatures have been rising at unprecedented levels with higher frequencies of extreme weather conditions each year. As average seasonal temperatures continue to rise for the foreseeable future, the region’s daily energy load profile changes because of greater pressure from cooling (i.e., AC) requirements. Consequently, the peak energy demand increases, which changes the marginal generation sources for PEV charging. That is, the generation resources required as a result of PEV charging demands may have significantly different carbon intensities. Climate change impacts on snowfall also play a role in PEV-related emissions. The snowpack in the Sierra Nevada that supplies most of LA’s fresh water throughout the year is quickly receding. The result is a decrease in the availability of not only fresh water for human consumption but also for electricity generation. Therefore, as PEV charging demand increases, the high variability in hydro resources may shift the marginal generation capacity to other generation sources that potentially have significantly higher carbon intensities (e.g., natural gas). In this study, we explicitly model the climate change effects on the energy load and marginal electricity generation from PEV charging. Preliminary results show that the variability in hydro resources as a result of climate change may significantly increase GHG emissions from PEV charging. Based on these findings, further analysis is required to understand the complex relationship between climate change and PEV charging in order to achieve the best GHG emissions mitigation scenario. The analysis should reveal critical insights on maximizing emission reductions from a large-scale PEV adoption for LA’s transportation and electrical infrastructure over the next decades.