On the Front Lines of a Sustainable Transportation Fleet: Applications of Vehicle-to-Grid Technology
By Tolga Ercan
The electricity generation/supply and transportation sectors are the two largest contributors to greenhouse gas (GHG) emissions in the U.S., and vehicle-to-grid (V2G) technology is a rapidly emerging solution to reduce these emissions with the adoption of battery-electric (BE) vehicles. Deployments of BE transit and school buses are expected to have larger battery capacities than passenger vehicles, making them more feasible candidates for V2G service. Five electricity generation regions are considered for cash flow analysis of BE and diesel transit and school buses over their entire respective lifetimes with the allowance of V2G services’ net revenue. Besides, the environmental benefits of using the V2G system are studied in place of combustion power generation plants for the regulation services of each study region. Air emission externalities are another crucial issue for bus operations because buses are operated near highly populated areas, so these externalities are also studied in this research with the benefits of a V2G emission reduction potential taken into account. The analysis concluded that BE transit and school buses with V2G application have potential to reduce electricity generation related greenhouse-gas emissions by 1067 and 1420 tons of CO2 equivalence (average), and eliminate $13,000 and $18,300 air pollution externalities (average), respectively.
The air emission externalities for BE and diesel transit and school buses are presented in Figure 2. It is important to note that tailpipe emissions contribute the most to these externalities, as the tailpipe emissions for transit and school buses are assumed to occur primarily in and near highly populated areas. Due to high annual mileage values, transit buses cause significantly higher air emission externalities than school buses. Figure 2 presents that the V2G system can provide enough electricity back to the grid to reduce the mean air externality value of transit BE buses by $13,000, which reduce it to almost the maximum air externality rate of diesel school buses (please see red-dotted lines on Figure 2 for V2G related reduction). More interestingly, V2G services provided from BE school buses effectively eliminated their mean externality value, and even provided a net benefit due to less electricity generation and emissions from power plants. However, it should be noted that negative externality values do not necessarily mean that BE school bus operations can provide negative emissions, but it does mean that V2G systems can neutralize all of the emission impacts of electricity consumption from BE school bus operations. Hence, Figure 2 clearly highlights the potential benefits of V2G technology in terms of public health cost reductions.