Electrified Transportation and Urban Energy Systems for Economic, Efficiency, and Resilience Benefits
Advisor: Professor Eleftheria Kontou
Abstract
Sustainable transportation systems are in the spotlight, promising improved air quality, reduced dependence on fossil fuels, enhanced mobility justice, and driving the adoption of cutting-edge technologies. Electrified transportation emerges as a pivotal decarbonization solution, studied both from industry and academic scholars, who aim to explore the economic and operational complexities, dynamics, and infrastructure imperatives, even as new challenges (e.g., climate change impacts) continue to manifest. With the integration of electric vehicles (EVs) into urban transportation systems, new problems arise while existing ones have intensified. Utilities, management authorities, and EV users are grappling with the need to achieve ubiquitous and affordable charging stations planning and operations while addressing resilience issues to seamlessly integrate EVs into urban energy systems. Without addressing these issues, there could be delays in the transition to electric mobility and detrimental societal impacts and obstacles to realizing sustainable transportation development.
This dissertation investigates the economic, efficiency, and resilience advantages of integrating electrified transportation with urban energy systems. It showcases the following research endeavors: 1) developing a framework and metrics to define and assess transportation energy vulnerability with a US application, 2) quantifying energy use and economic benefits from coupled management of EVs and the workplace buildings, 3) evaluating household energy system resilience with Vehicle-to-Home (V2H)-equipped EVs as backup power sources during outages, and 4) assessing resilience benefits of electric school buses (ESBs) serving as backup power for resilience hubs during power outages.
In response to both budgetary and social implications of facing burdens to meet transportation energy needs, the dissertation introduces a new data-driven framework to quantify transportation energy vulnerability. It measures exposure, sensitivity, and adaptive capacity to energy burdens across U.S. census tracts, revealing spatial patterns of vulnerability. The study examines the sensitivity of vulnerability outcomes to the scoring methodology and the impact of EV adoption on fuel and electricity consumption. It finds that a composite vulnerability score is effective, with an additive index suitable for evaluating adaptive capacity interventions, while a multiplicative index better prioritizes exposure and sensitivity. EV market growth reduces energy vulnerability disparities but shows diminishing returns over time. An analysis of Los Angeles, Chicago, and
New York City demonstrates varying levels of vulnerability, with urban areas in Chicago and New York City presenting lower levels of vulnerability compared to those in Los Angeles.
Significant building energy savings are realized through heating, ventilation, and air conditioning (HVAC) setpoint adjustment and daylighting control. Workplace charging (WPC) enables colocation of EVs with office building loads. The second study in this dissertation proposes managing energy use of workplace EV charging and the office building and determines the average number of EVs that building energy savings can facilitate charging. Building energy savings in typical medium offices in Chicago IL, Baltimore MD, and Houston TX, spanning three U.S. climate regions are simulated. Considering the EV hosting capacity of the saved building energy and travel patterns of roundtrip commuting, an optimization model is formulated to minimize EV charging costs under time-of-use electricity pricing. Managed WPC can significantly reduce charging electricity bills compared to first-come, first-served charging. The ratio of EVs to chargers, the coincident period of commuters' dwell time and lower electricity prices, and the number of EVs in the office impacts the economic benefits achieved through charging management.
The dissertation's third study addresses the exacerbated risks of power outages from climate change and hazardous events, proposing the use of V2H-equipped EVs as backup power sources to mitigate health hazards during outages. We simulate the V2H system in nine U.S. climate regions, over four seasons, and during short-term, long-term, and extremely-severe power outage events. New resilience metrics are proposed to evaluate EV-enabled household energy resilience that measures the duration of time that EVs can serve household energy needs during power outages, and mobility resilience, which represents the remaining driving range of EVs after the outage. The findings indicate that contemporary EV models, even when their state of charge is 50%, can meet residential energy needs during a 12-hour outage in mild seasons (i.e., spring and autumn), except for communities in the Central, West North Central, and East North Central regions (i.e., U.S. Midwest regions) due to lower temperatures and higher household energy needs. The resilience of the household energy system during long-term outages is affected by the start time of the outage, heating and cooling power requirements, and daily travel needs. During extremely severe power outages, EVs can protect residents from cold stress over multiple days. The methods and results inform research and practice on smart management of the integrated residential and EV energy system and propose measures for mitigating the impacts of extreme weather events.
Drawing from the framework developed in the third study, we apply the resilience assessment method to resilience hubs (utilizing a secondary school as a primary example), leveraging the fleet of ESBs as backup power sources during outages. The findings indicate that the existing fleet of ESBs in most of the representative cities across various climate regions in the U.S. falls short in meeting the power demand of a school as a resilience hub or even just its HVAC system. However, we identify the number of ESBs so that their integration can significantly enhance school resilience through Vehicle-to-Building (V2B) technology during power outages. This approach contributes to notable reductions in carbon emissions compared to reliance on backup diesel generators. The positive impact of adjusting HVAC setpoints on enhancing school resilience is limited. Given the ongoing electrification process of school buses, it remains imperative for schools to complement ESBs with stationary batteries and solar or other backup generators to effectively address prolonged outages. Optimizing the deployment of a set of direct current fast charging (DCFC) and Level 2 chargers can reduce infrastructure costs while preserve the resilience benefits of ESBs.
