Browsing by Subject "Electric vehicles"
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Item An assessment of the system costs and operational benefits of vehicle-to-grid schemes(2013-12) Harris, Chioke Bem; Webber, Michael E., 1971-With the emerging nationwide availability of plug-in electric vehicles (PEVs) at prices attainable for many consumers, electric utilities, system operators, and researchers have been investigating the impact of this new source of electricity demand. The presence of PEVs on the electric grid might offer benefits equivalent to dedicated utility-scale energy storage systems by leveraging vehicles' grid-connected energy storage through vehicle-to-grid (V2G) enabled infrastructure. Existing research, however, has not effectively examined the interactions between PEVs and the electric grid in a V2G system. To address these shortcomings in the literature, longitudinal vehicle travel data are first used to identify patterns in vehicle use. This analysis showed that vehicle use patterns are distinctly different between weekends and weekdays, seasonal interactions between vehicle charging, electric load, and wind generation might be important, and that vehicle charging might increase already high peak summer electric load in Texas. Subsequent simulations of PEV charging were performed, which revealed that unscheduled charging would increase summer peak load in Texas by approximately 1\%, and that uncertainty that arises from unscheduled charging would require only limited increases in frequency regulation procurements. To assess the market potential for the implementation of a V2G system that provides frequency regulation ancillary services, and might be able to provide financial incentives to participating PEV owners, a two-stage stochastic programming formulation of a V2G system operator was created. In addition to assessing the market potential for a V2G system, the model was also designed to determine the effect of the market power of the V2G system operator on prices for frequency regulation, the effect of uncertainty in real-time vehicle availability and state-of-charge on the aggregator's ability to provide regulation services, and the effect of different vehicle characteristics on revenues. Results from this model showed that the V2G system operator could generate revenue from participation in the frequency regulation market in Texas, even when subject to the uncertainty in real-time vehicle use. The model also showed that the V2G system operator would have a significant impact on prices, and thus as the number of PEVs participating in a V2G program in a given region increased, per-vehicle revenues, and thus compensation provided to vehicle owners, would decline dramatically. From these estimated payments to PEV owners, the decision to participate in a V2G program was analyzed. The balance between the estimated payments to PEV owners for participating in a V2G program and the increased probability of being left with a depleted battery as a result of V2G operations indicate that an owner of a range-limited battery electric vehicle (BEV) would probably not be a viable candidate for joining a V2G program, while a plug-in hybrid electric vehicle (PHEV) owner might find a V2G program worthwhile. Even for a PHEV owner, however, compensation for participating in a V2G program will provide limited incentive to join.Item Batteries half full? : an analysis of electric vehicles and a proposal for charging stations at the University of Virginia(2012-05) Laycock, John Patrick; Paterson, Robert G.; Wagner, WendyElectric Vehicles (EVs) have been hailed by some as a revolutionary new technology whose adoption will clean our air, reduce our dependence on foreign oil, and change the way we drive. A key step to achieving this vision is the installation of charging stations, which EVs require if they run out of energy if not plugged in at special charging stations. Most charging will take place at home, but public charging stations are necessary to prevent EV drivers from getting stranded with no energy. Many universities across the country have installed charging stations on their campus, while enthusiastically embracing the above vision. This report examines the promise of EVs and makes is a proposal for the University of Virginia to also install charging stations. However, it finds that EVs present a much more complicated picture: there are as many downsides as upsides, and the weaknesses in demand call into question the actual need for charging stations. The report finds that a cost-benefit analysis is difficult, if not impossible. That said, the rest of the report looks at case studies from other universities to determine good practices for installing charging stations. Building from this analysis, the report offers five sample proposals, ranging in involvement from none to "aggressive" are proposed with the conclusion that a moderate amount of involvement is the recommended course. In the end, it seems wiser to err on the side of a sustainable future than to reject EVs before their full potential is known.Item Constrained traffic equilibrium : impact of electric vehicles(2012-08) Jiang, Nan, Ph. D.; Waller, S. Travis; Boyles, Stephen; Damnjanovic, Ivan; Lasdon, Leon; Machemehl, Randy; Zhang, ZhanminIn many countries across the world, fossil fuels, especially petroleum, are the largest energy source for powering the socio-economic system and the transportation sector dominates the consumption of petroleum in these societies. As the petroleum price continuously climbs and the threat of global climate changes becomes more evident, the world is now facing critical challenges in reducing petroleum consumption and exploiting alternative energy sources. A massive adoption of plug-in electric vehicles (PEVs), especially battery electric vehicles (BEVs), offers a very promising approach to change the current energy consumption structure and diminish greenhouse gas emissions and other pollutants. Understanding how individual electric vehicle drivers behave subject to the technological restrictions and infrastructure availability and estimating the resulting aggregate supply-demand effects on urban transportation systems is not only critical to transportation infrastructure development, but also has determinant implications in environment and energy policy enactment. Driving PEVs inevitably changes individual’s travel and activity behaviors and calls for fundamental changes to the existing transportation network and travel demand modeling paradigms to accommodate changing cost structures, technological restrictions, and supply infrastructures. A prominent phenomenon is that all PEV drivers face a distance constraint on their driving range, given the unsatisfactory battery-charging efficiency and scarce battery-charging infrastructures in a long period of the foreseeable future. Incorporating this distance constraint and the resulting behavioral changes into transportation network equilibrium and travel demand models (static and/or dynamic) raises a series of important research questions. This dissertation focuses on analyzing the impact of a massive adoption of BEVs on urban transportation network flows. BEVs are entirely dependent on electricity and cannot go further once the battery is depleted. As a modeling requirement in its simplest form, a distance constraint should be imposed when analyzing and modeling individual behaviors and network congestions. With adding this simple constraint, this research work conceptualizes, formulates and solves mathematical programming models for a set of new BEV-based network routing and equilibrium problems. It is anticipated that the developed models and methods can be extensively used in a systematic way to analyze and evaluate a variety of system planning and policy scenarios in decision-making circumstances of BEV-related technology adoption and infrastructure development.Item Design : a tool for transformation(2009) Ferguson, Beth Jean; Catterall, KateMy graduate research has been focused on testing how visual communication in the form of three-dimensional polemic works can become a tool for effecting social change. The change I am interested in relates to the global energy crisis, and resolving imminent transportation and associated ecological problems by promoting the use of electric vehicles. The main focus of my work has been the use of a strategy that is best described as the transformation of old and iconic artifacts in order to communicate complex new ideas. The main project that I will use to discuss this strategy uses the form and implications of a 1950’s gas pump emblematic of the golden era of petroleum production and the heyday of the automobile as the lynchpin for a conversation with my audience. By tweaking the original meaning of the pump and by juxtaposing an image of gas guzzling vehicles with a proposal for sustainable electric powered vehicles I have created a public dialogue about the current energy crisis and a compelling argument to support the move towards alternate fuels. This 3-D design intervention in public space has proven to be an effective way to, convey a socio-political message, more effective than any poster because it is a functional element which is both warmly received because it hits home an idea in a positive, even humorous way and elicits an emotional response from the viewer. The station not only charges electric vehicles and encourages the public to test ride them, it allows people to re-envision mobility through experience, become involved and take action.Item Electric vehicles and public charging infrastructure : impediments and opportunities for success in the United States(2012-05) Borden, Eric Joshua; Boske, Leigh B.; Duncan, RogerToday’s debate regarding the United States (U.S.) transportation sector has never been more important. As similar discussions embroil electricity generation, one can see the powerful forces of the status-quo pitted against growing momentum behind alternatives. The electric vehicle (EV) finds itself somewhere in the middle of the debate, as a possible alternative to the conventional vehicle (CV). As demonstrated in this report, electric vehicles are neither new nor technologically infeasible. Current circumstances have initiated what appears to be a revival of the EV – this includes years of high oil prices, geopolitical instability, and growing awareness of environmental concerns resulting from CV usage. Nevertheless, impediments remain. One of the most important is the prospect of building public charging infrastructure to allow drivers to use an EV like their conventional vehicle, for both long and short distances. Public charging infrastructure, however, cannot be built without some critical mass of EV’s on the road to use them – otherwise they are not economically feasible. This report analyzes various facets of both EV’s and public charging infrastructure to give the reader a clear understanding of the complex criteria that must be understood to assess EV’s in the United States. Texas is given special consideration as a case study in this report, particularly the Austin area where public charging infrastructure for EV’s is currently being implemented. Through a detailed analysis of electric vehicles and charging infrastructure, as well as the United States transportation system, this report seeks to reach conclusions over the role EV’s and public charging infrastructure should play in the future U.S. transportation system.Item Estimating emissions impacts to the bulk power system of increased electric vehicle and renewable energy usage(2013-12) Meehan, Colin Markey; Webber, Michael E., 1971-; Baldick, RossThe research presented in this thesis examines the use of electric vehicles and renewable energy to reduce emissions of CO₂, SO₂ and NO[subscript x], and within the state of Texas. The analysis examines the impact of increased renewable energy output and electric vehicle charging on the emissions of fossil fuel electric generators used to serve the bulk power system within Texas. The analysis then compares those impacts to alternative scenarios in which fossil fuel generation replaces some renewable energy generation, and Internal Combustion Engine (ICE) vehicles of varying efficiency are used instead of electric vehicles. This research uses temporally-resolved regression analysis combined with a unit commitment and dispatch model that incorporates several different scenarios for EV charging and fuel mixes to evaluate emissions outcomes based on a variety of conditions. Hourly historical generation and emission data for each fossil fuel generator, combined with hourly output data for non-fossil fuel units aggregated by fuel type (i.e. nuclear, wind, hydro-electric) within the Electric Reliability Council of Texas (ERCOT) footprint is regressed to assess the impact of wind generation output on fossil-fuel generation emissions. The regression analysis is used to assess potential increases in emissions resulting from the ramping of fossil-fuel Electric Generation Units (EGUs) to compensate for variability in wind generation output due to changing weather conditions. The unit commitment dispatch model is used to evaluate the impact of changes in customer demand due to increased usage and charging of electric vehicles on the ERCOT system and any resulting increase in emissions from generation used to meet this new demand. The model uses detailed cost, performance and emissions data for EGUs in the ERCOT footprint to simulate the impact of a variety of charging scenarios and fuel mixes on EGU dispatch patterns and any resulting change in system-wide emissions. The results of this model are combined with the results of the regression analysis to present a more complete analysis of the combined impacts of increase EV and renewable energy usage on the emissions of CO₂, SO₂ and NO[subscript x] within the ERCOT footprint. Based on these analyses the increases in renewable energy generation demonstrate clear benefits in terms of emission reductions when the impacts of increased emissions due to more frequent ramping of fossil-fuel units are taken into account. This analysis also finds that EV charging generally has emissions benefits across a range of charging patterns and bulk power system fuel mixes, although in certain circumstances EV charging might result in higher emissions than the use of ICE vehicles. This research finds when future ICE vehicles with reduced emissions are taken into account, approximately half of the modeled scenarios show net emissions benefits from EV charging, while half show net emissions costs when emissions impacts across pollutants are taken into account.Item Estimating the impact on fuel tax revenues from a changing light vehicle fleet with increased advanced internal combustion engine vehicles and electric vehicles(2012-12) Hall, Andrea Lynn; Walton, C. Michael; Jin, Peter JAdvanced fuel economies in both traditional internal combustion engine vehicles (ICEs) and electric vehicles (EVs) have a strong influence on transportation revenue by reducing fuel consumption per vehicle and ultimately drawing down the amount of fuel tax revenue received. It is expected that more ICE vehicle with advanced fuel economies and electric vehicles, especially gasoline hybrid electric vehicles, will enter the roadway in coming years, and fuel tax revenues and the Highway Trust Fund will increasingly become more affected. This study estimates the impact that increased sales of advanced ICEs and EVs will have on future fuel tax revenues by drawing on industry estimates of future EV and ICE market shares and anticipates future fleet mix and fuel economy for both vehicle technologies. An estimation process overview is provided and assumptions are described. Fuel tax revenue amounts that would be expected from future light vehicle fleets with increased shares of EVs are compared to equally sized fleets comprised of all ICEs, and future fleet mixes are estimated. Results show that as more electric vehicles enter the light vehicle fleet, greater revenue losses are expected, and total losses from years 2011 through 2050 depend on fleet composition and fuel economy of both vehicle types. Finally, it is found that the amount of fuel taxes paid by ICE drivers each year remain greater than fuel taxes paid by EV drivers even with advances in the average ICE vehicle fuel economy.Item Impact of electric vehicle loads on utility distribution network voltages(2012-08) Dubey, Anamika; Santoso, SuryaThis work evaluates the impact of electric vehicle loads (EVs) on utility distribution secondary networks and determines the factors affecting the network voltage quality. The study is conducted using two actual distribution circuits, residential and mix residential and industrial circuits. The study reveals the following. A distant secondary network experiences a greater steady-state voltage drop than a nearby secondary network. Location of EV loads relative to the service transformer affects the secondary voltage more significantly. An EV load installed on a distant load node from a service transformer causes comparatively higher undervoltage condition (about 1.5%) than an EV on a nearby load node from the service transformer (about 0.75%). Increasing the size of EV charger increases the severity of an undervoltage condition. A 240V/30A EV charging station causes undervoltage condition to double compared to that of a 240V/16A EV charger. Also installing an EV load adjacent to the existing EV load customer approximately doubles the undervoltage condition at the EV load nodes.Item Integrated network-based models for evaluating and optimizing the impact of electric vehicles on the transportation system(2012-08) Zhang, Ti; Waller, S. Travis; Boyles, Stephen D.; Machemehl, Randy B.; Zhang, Zhanmin; Kendrick, David A.; Hasenbein, JohnThe adoption of plug-in electric vehicles (PEV) requires research for models and algorithms tracing the vehicle assignment incorporating PEVs in the transportation network so that the traffic pattern can be more precisely and accurately predicted. To attain this goal, this dissertation is concerned with developing new formulations for modeling travelling behavior of electric vehicle drivers in a mixed flow traffic network environment. Much of the work in this dissertation is motivated by the special features of PEVs (such as range limitation, requirement of long electricity-recharging time, etc.), and the lack of tools of understanding PEV drivers traveling behavior and learning the impacts of charging infrastructure supply and policy on the network traffic pattern. The essential issues addressed in this dissertation are: (1) modeling the spatial choice behavior of electric vehicle drivers and analyzing the impacts from electricity-charging speed and price; (2) modeling the temporal and spatial choices behavior of electric vehicle drivers and analyzing the impacts of electric vehicle range and penetration rate; (3) and designing the optimal charging infrastructure investments and policy in the perspective of revenue management. Stochastic traffic assignment that can take into account for charging cost and charging time is first examined. Further, a quasi-dynamic stochastic user equilibrium model for combined choices of departure time, duration of stay and route, which integrates the nested-Logit discrete choice model, is formulated as a variational inequality problem. An extension from this equilibrium model is the network design model to determine an optimal charging infrastructure capacity and pricing. The objective is to maximize revenue subject to equilibrium constraints that explicitly consider the electric vehicle drivers’ combined choices behavior. The proposed models and algorithms are tested on small to middle size transportation networks. Extensive numerical experiments are conducted to assess the performance of the models. The research results contain the author’s initiative insights of network equilibrium models accounting for PEVs impacted by different scenarios of charging infrastructure supply, electric vehicles characteristics and penetration rates. The analytical tools developed in this dissertation, and the resulting insights obtained should offer an important first step to areas of travel demand modeling and policy making incorporating PEVs.Item Management of a shared, autonomous, electric vehicle fleet : vehicle choice, charging infrastructure & pricing strategies(2015-08) Chen, Tong Donna; Kockelman, Kara; Machemehl, Randy; Boyles, Stephen; Stone, Peter; Baldick, RossThere are natural synergies between shared autonomous vehicle (AV) fleets and electric vehicle (EV) technology, since fleets of AVs resolve the practical limitations of today's non-autonomous EVs, including traveler range anxiety, access to charging infrastructure, and charging time management. Fleet-managed AVs relieve such concerns, managing range and charging activities based on real-time trip demand and established charging-station locations, as demonstrated in this paper. This work explores the management of a fleet of shared autonomous (battery-only) electric vehicles (SAEVs) in a regional (100-mile by 100-mile) discrete-time, agent-based model. The dissertation examines the operation of SAEVs under various vehicle range and charging infrastructure scenarios in a gridded city modeled roughly after the densities of Austin, Texas. Results indicate that fleet size is sensitive to battery recharge time and vehicle range, with each 80-mile range SAEV replacing 3.7 privately owned vehicles and each 200-mile range SAEV replacing 5.5 privately owned vehicles, under Level II (240-volt AC) charging. With Level III 480-volt DC fast-charging infrastructure in place, these ratios rise to 5.4 vehicles for the 80-mile range SAEV and 6.8 vehicles for the 200-mile range SAEV. However, due to the need to travel while "empty" for charging and passenger pickup, SAEV fleets are predicted to generate an additional 7.1 to 14.0% of travel miles. Financial analysis suggests that the combined cost of charging infrastructure, vehicle capital and maintenance, electricity, insurance, and registration for a fleet of SAEVs ranges from $0.42 to $0.49 per occupied mile traveled, which implies SAEV service can be offered at the equivalent per-mile cost of private vehicle ownership for low-mileage households, and thus be competitive with current manually-driven carsharing services and significantly less expensive than on-demand driver-operated transportation services. The mode share of SAEVs in the simulated mid-sized city is predicted to be between 14 and 39%, when competing against privately-owned, manually-driven vehicles and city bus service. This assumes SAEVs are priced between $0.75 and $1.00 per mile, which delivers significant net revenues to the fleet owner-operator, under all modeled scenarios, assuming 80-mile-range EVs and remote/cordless Level II charging infrastructure and $10,000-per-vehicle automation costs.Item Modeling of hybrid electric vehicle batteries(Texas Tech University, 2003-05) Maddala, RamachandraBattery models are essential in estimating the performance, life and operating characteristics, which are required for hybrid electric vehicle analysis. The battery discharge and charge models are developed and explained in detail. The two models are directly based on the empirical data from literature and manufacturers data sheet. Detail analysis in the development of empirical equations using interpolation and curve fitting methods is provided. Datafit 8.0.32 and TableCurve2D are used to fit the data and Simulink is used in developing the model. Gassing which affects the performance characteristics of batteries is included in the charge model. The overall battery model is assumed to be in a vehicle and tested for a driving cycle to observe the simulation results.Item On-board hydrogen production for fuel cell vehicles via a membrane separator and an externally-fired methanol reformer(Texas Tech University, 2004-05) Mathakari, Sushil PrakashMany options exist for on-board hydrogen production from liquid fuels for fuel cell powered vehicles. This paper reports on design and construction of an on-board system for hydrogen production from methanol. Methanol reforming is accomplished using an externally fired catalytic reactor. Carbon monoxide, separated from the reactor effluent by a membrane separator, is consumed with the reactor fuel. The reactor is operated at 1950 kPa to supply gas to the membrane separator at its maximum design pressure, and at a temperature of 500°C, to minimize the amount of methanol remaining the reactor product. The design methanol feed rate of 0.32 1/min used for the prototype should be sufficient to supply a 10 kW fuel cell package, but the design can easily be expanded to larger sizes. The membrane separator is an off-the-shelf, polymer-based model, and it is not expected to reduce the carbon monoxide to below 10 ppm, required by proton exchange membrane fuel cells, being considered for vehicular power. For this reason it is necessary to include a selective oxidation reactor to remove the carbon monoxide as a contaminant. An adiabatic energy balance indicates that 30% excess energy is available from combustion of the separated carbon monoxide when used as fuel to the reformer. The thesis includes the design of methanol reformer system, calculation of heat transfer coefficients and heat transfer areas required for the heat exchange of the exhaust gases and the reaction mixture. It also includes the simulation of the entire process using ChemCAD as a chemical process simulator.