Mountain Scholar :: Browsing by Author "Bradley, Thomas H., advisor"

Browsing by Author "Bradley, Thomas H., advisor"

Now showing 1 - 20 of 30

Open Access
A model of the effects of automatic generation control signal characteristics on energy storage system reliability
(Colorado State University. Libraries, 2012) Campbell, Timothy M., author; Bradley, Thomas H., advisor; Zimmerle, Daniel, committee member; Young, Peter M., committee member
No electrochemical batteries constructed to date have the storage capacities necessary for integration into conventional energy markets; aggregation will be required to meet industry-standard metrics for reliability and availability. This aggregation of individual energy storage devices into a distributed energy storage (DES) system will be useful not only to allow standard connection to the grid, but to provide higher-quality fast-response grid services with low-cost technologies. These smaller installations will have lower capital costs than traditional energy storage facilities. Ancillary services, and more specifically frequency regulation services, are understood to be the most technically viable and economically valuable market available to DES. Accordingly, this study is based on the properties of the frequency regulation market. This study presents a simplified model of a DES resource, its frequency regulation actuation signal, and its mode of market participation. The inputs to the model are scaling parameters of the DES system and of the actuation signal. The outputs from the model are the individual and aggregated reliability of the DES system. An analytical calculation of reliability is performed and analytical results are compared to numerical simulation solutions. Results show that the reliability of the energy storage device can be characterized using a set of non-dimensional parameters. These device-level reliability results are then translated into system-level reliability through several different models of ancillary services contracting and dispatch. Previous studies of DES systems have assumed that the energy storage system has no energy storage limitations and that the actuation signal has no net or instantaneous energy content. This model includes these conditions so as to capture the interaction between the energy content of the Automatic Generation Control (AGC) signal and the device-level and system-level reliability of DES systems. These results are novel in that they can guide the independent system operator/balancing authority in constructing an AGC signal specific to the needs of DES system resources.
Open Access
A real-time building HVAC model implemented as a tool for decision making in early stages of design
(Colorado State University. Libraries, 2015) Syed, Zaker Ali, author; Bradley, Thomas H., advisor; Anderson, Charles, committee member; Sampath, Walajabad, committee member
Construction of buildings is one of the major sources of greenhouse gases (GHGs) and energy consumption. It would therefore be beneficial to improve the design of new buildings so that they consume less energy and reduce GHG emissions over their lifecycle. However, the design of these “green buildings” is challenging because the analyses required to design and optimize these buildings is time intensive and complicated. In response, numerous software applications have been developed over the years by various government agencies, organizations and researchers. But, recent surveys of architects have found that these energy simulation programs are used irregularly and by very few architectural firms. The utility of these programs is limited by three main factors. First, these software applications are complicated, stand-alone programs that require extensive training to be effective. Second, there are a large set of energy simulation programs available, all of which have differing metrics of building performance with differing degrees of accuracy. And lastly, these applications do not fit into the conventional workflow that architects follow for a majority of projects. To address these issues, this thesis focuses on the development of a simplified HVAC model that not only gives sufficiently accurate results but also can be easily integrated into the conventional design workflow. There are some key challenges in developing such a model. • Early in the design process (when many irreversible energy impacting design decisions are made) there is very limited information available about the building materials, heat loads, and more. • The simulation must be integrated into the design software and workflows that are currently being used by architects. This requires a near-instantaneous calculation method that can extract information from the only available data at the initial design (sketching) phase, the computer aided design (CAD) models and the location. To achieve these objectives, the Radiant Time Series (RTS) method was supplemented with real data from National Solar Radiation Database to enable a near-instantaneous annual HVAC load calculation to be integrated into preliminary CAD modelling software. This model was integrated in to the Trimble Sketch-up™ software. The combined software system is demonstrated to enable effective design feedback in early design decisions including building orientation, construction material and design of fenestration.
Open Access
Advancing medium- and heavy-duty electric vehicle adoption models with novel natural language processing metrics
(Colorado State University. Libraries, 2024) Ouren, Fletcher, author; Bradley, Thomas H., advisor; Coburn, Timothy, committee member; Windom, Bret, committee member
The transportation sector must rapidly decarbonize to meet its emissions reduction targets. Medium- and heavy-duty decarbonization is lagging behind the light-duty industry due to technical and operational challenges and the choices made by medium- and heavy-duty fleet operators. Research investigating the procurement considerations of fleets has relied heavily on interviews and surveys, but many of these studies need higher participation rates and are difficult to generalize. To model fleet operators' decision-making priorities, this thesis applies a robust text analysis approach based on latent Dirichlet allocation and Bi-directional Encoder Representations of Transformers to two broad corpora of fleet adoption literature from academia and industry. Based on a newly developed metric, this thesis finds that the academic corpus emphasizes the importance of suitability, familiarity, norms, and brand image. These perception rankings are then passed to an agent-based model to determine how differences in perception affect adoption predictions. The results show a forecast of accelerated medium- and heavy-duty electric vehicle adoption when using the findings from the academic corpus versus the industry corpus.
Open Access
Analysis of life cycle assessment of food/energy/waste systems and development and analysis of microalgae cultivation/wastewater treatment inclusive system
(Colorado State University. Libraries, 2013) Armstrong, Kristina Ochsner, author; Bradley, Thomas H., advisor; De Long, Susan, committee member; Marchese, Anthony, committee member
Across the world, crises in food, energy, land and water resources, as well as waste and greenhouse gas accumulation are inspiring research into the interactions among these environmental pressures. In the food/energy/waste problem set, most of the research is focused on describing the antagonistic relationships between food, energy and waste; these relationships are often analyzed with life cycle assessment (LCA). These analyses often include reporting of metrics of environmental performance with few functional units, often focusing on energy use, productivity and environmental impact while neglecting water use, food nutrition and safety. Additionally, they are often attributional studies with small scope which report location-specific parameters only. This thesis puts forth a series of recommendations to amend the current practice of LCA to combat these limitations and then utilizes these suggestions to analyze a synergistic food/waste/energy system. As an example analysis, this thesis describes the effect of combining wastewater treatment and microalgae cultivation on the productivity and scalability of the synergistic system. To ameliorate the high nutrient and water demands of microalgae cultivation, many studies suggest that microalgae be cultivated in wastewater so as to achieve large scale and low environmental costs. While cultivation studies have found this to be true, none explore the viability of the substitution in terms of productivity and scale-up. The results of this study suggest that while the integrated system may be suitable for low-intensity microalgae cultivation, for freshwater microalgae species or wastewater treatment it is not suitable for high intensity salt water microalgae cultivation. This study shows that the integration could result in reduced lipid content, high wastewater requirements, no greenhouse gas emissions benefit and only a small energy benefit.
Open Access
Assessment, design and control strategy development of a fuel cell hybrid electric vehicle for CSU's ecocar
(Colorado State University. Libraries, 2013) Fox, Matthew D., author; Bradley, Thomas H., advisor; Labadie, John, committee member; Zimmerle, Dan, committee member
Advanced automotive technology assessment and powertrain design are increasingly performed through modeling, simulation, and optimization. But technology assessments usually target many competing criteria making any individual optimization challenging and arbitrary. Further, independent design simulations and optimizations take considerable time to execute, and design constraints and objectives change throughout the design process. Changes in design considerations usually require re-processing of simulations and more time. In this thesis, these challenges are confronted through CSUs participation in the EcoCAR2 hybrid vehicle design competition. The complexity of the competition's design objectives leveraged development of a decision support system tool to aid in multi-criteria decision making across technologies and to perform powertrain optimization. To make the decision support system interactive, and bypass the problem of long simulation times, a new approach was taken. The result of this research is CSU's architecture selection and component sizing, which optimizes a composite objective function representing the competition score. The selected architecture is an electric vehicle with an onboard range extending hydrogen fuel cell system. The vehicle has a 145kW traction motor, 18.9kWh of lithium ion battery, a 15kW fuel cell system, and 5kg of hydrogen storage capacity. Finally, a control strategy was developed that improves the vehicles performance throughout the driving range under variable driving conditions. In conclusion, the design process used in this research is reviewed and evaluated against other common design methodologies. I conclude, through the highlighted case studies, that the approach is more comprehensive than other popular design methodologies and is likely to lead to a higher quality product. The upfront modeling work and decision support system formulation will pay off in superior and timely knowledge transfer and more informed design decisions. The hypothesis is supported by the three case studies examined in this thesis.
Open Access
Battery end-of-life considerations for plug-in hybrid electric vehicles
(Colorado State University. Libraries, 2011) Wood, Eric, author; Bradley, Thomas H., advisor; Marchese, Anthony J., committee member; Young, Peter M., committee member
Plug-in hybrid electric vehicles (PHEVs) represent an advanced vehicle technology with the potential to displace petroleum consumption with energy generated on the US electric grid. While many benefits have been associated with the increased electrification of the US vehicle fleet, concerns over battery lifetime and replacement costs remain an obstacle to widespread PHEV adoption. In order to accurately determine the lifecycle cost of PHEVs, assessment studies must make use of informed assumptions regarding battery degradation and replacement. These assumptions should approach end-of-life (EOL) metrics not only in terms of pack level degradation but also loss of vehicle efficiency and performance in order to accurately represent consumer incentive for battery replacement. Battery degradation calculations should also remain sensitive to the range of ambient conditions and usage scenarios likely to be encountered in the US market. Degradation resulting from a single duty cycle has the potential to misrepresent battery life distributions for the US fleet. In this study, the sensitivity of PHEV lifecycle cost to the battery replacement assumption is explored to underscore the need for an improved understanding of PHEV battery EOL conditions. PHEV specific battery test results are presented to evaluate the ability of industry standard life test procedures to predict battery degradation in PHEVs. These test results are used as inputs to a vehicle simulation program to understand changes in efficiency and performance with respect to battery degradation using a light commercial vehicle simulated as a blended-mode capable, parallel PHEV20. A predictive battery degradation model based on empirical data is used to explore sensitivity of battery wear to various parameters including design variables, ambient conditions, and usage scenarios. A distribution of expected wear rates for a light-duty, midsize passenger vehicle modeled as a series PHEV35 is presented to highlight the uncertainty associated with battery life subject to US ambient conditions and driving distributions. The results of this study show that active management of PHEV battery degradation by the vehicle control system can improve PHEV performance and fuel consumption relative to a more passive baseline. Simulation of the PHEV20 throughout its battery lifetime shows that battery replacement will be neither economically incentivized nor necessary to maintain performance. The spectrum of climate and usage conditions PHEVs are expected to face in the US market suggest that the assumption of a single average ambient condition for battery wear calculations may not be representative of observed behavior in the fleet. These results have important implications for techno-economic evaluations of PHEVs which have treated battery replacement and its costs with inconsistency.
Open Access
Design considerations for an engine-integrated reciprocating natural gas compressor
(Colorado State University. Libraries, 2014) Malakoutirad, Mohammad, author; Bradley, Thomas H., advisor; Young, Peter, committee member; Olsen, Daniel, committee member
This thesis presents the development of an engine retrofit concept to turn a ICE vehicle's engine into a compressor for convenient natural gas refueling, as opposed to building a smaller secondary standalone unit. More specifically, this project seeks to outfit an internal combustion engine (ICE) to serve the dual purposes of providing vehicle propulsion and compression for natural gas refueling with minimal hardware substitution. The principal objective of this thesis is to describe and analyze the dynamic and thermal design considerations for an automotive engine-integrated reciprocating natural gas (NG) compressor. The purpose of this compressor is to pressurize storage tanks in NG vehicles from a low-pressure NG source by using one of the cylinders in an engine as the compressor. The engine-integrated compressor is developed by making minor changes to a 5.9 liter displacement diesel-cycle automotive engine. In this design, a small tank and its requisite valving are added to the engine as an intermediate storage tank to enable a single compressor cylinder to perform two-stage compression. The resulting pressure in the compressor cylinder and storage tank is 25 MPa, equivalent to the storage and delivery pressure of conventional compressed NG delivery systems. The dynamic simulation results show that the high cylinder pressures required for the compression process create reaction torques on the crankshaft, but do not generate abnormal rotational speed oscillations. The thermal simulation results show that the temperature of the storage tank and engine increases over the safety temperature of the NG unless an active thermal management system is developed to cool the NG before it is admitted to the storage tanks. Results are then translated into vehicle-level operating costs and petroleum consumption for a dual-fuel NG-diesel vehicle.
Open Access
Design tradeoffs of a reciprocating auxiliary power unit
(Colorado State University. Libraries, 2013) Renquist, Jacob Vinod, author; Bradley, Thomas H., advisor; Olsen, Daniel, committee member; Young, Peter, committee member
This thesis presents a comparison of reciprocating auxiliary power units to conventional, gas turbine auxiliary power units. A metric of interest is created to represent the specific auxiliary power system weight including the prime mover, generator, gearbox, and fuel consumed. The metric of interest is used to compare the different auxiliary power unit technologies by incorporating detailed engine simulations, auxiliary power unit system weight modeling, and flight path-realized fuel consumption modeling. Results show that reciprocating auxiliary power units can be competitive with gas turbines in near-term, more-electric aircraft applications.
Open Access
Development of predictive energy management strategies for hybrid electric vehicles
(Colorado State University. Libraries, 2017) Baker, David, author; Bradley, Thomas H., advisor; Petro, John, committee member; Young, Peter, committee member
Studies have shown that obtaining and utilizing information about the future state of vehicles can improve vehicle fuel economy (FE). However, there has been a lack of research into the impact of real-world prediction error on FE improvements, and whether near-term technologies can be utilized to improve FE. This study seeks to research the effect of prediction error on FE. First, a speed prediction method is developed, and trained with real-world driving data gathered only from the subject vehicle (a local data collection method). This speed prediction method informs a predictive powertrain controller to determine the optimal engine operation for various prediction durations. The optimal engine operation is input into a high-fidelity model of the FE of a Toyota Prius. A tradeoff analysis between prediction duration and prediction fidelity was completed to determine what duration of prediction resulted in the largest FE improvement. Results demonstrate that 60-90 second predictions resulted in the highest FE improvement over the baseline, achieving up to a 4.8% FE increase. A second speed prediction method utilizing simulated vehicle-to-vehicle (V2V) communication was developed to understand if incorporating near-term technologies could be utilized to further improve prediction fidelity. This prediction method produced lower variation in speed prediction error, and was able to realize a larger FE improvement over the local prediction method for longer prediction durations, achieving up to 6% FE improvement. This study concludes that speed prediction and prediction-informed optimal vehicle energy management can produce FE improvements with real-world prediction error and drive cycle variability, as up to 85% of the FE benefit of perfect speed prediction was achieved with the proposed prediction methods.
Open Access
Dynamic model of a spherical robot from first principles
(Colorado State University. Libraries, 2010) Schroll, Gregory C., author; Alciatore, David G., advisor; Bradley, Thomas H., advisor; Young, Peter M., committee member
A prototype of a pendulum driven spherical robot has been developed during previous research and shown to exhibit unique dynamic behavior. Starting from first principles, a mathematical model for this spherical robot rolling on flat ground was developed in order to determine if this unique behavior was inherent to spherical robots in general or simply peculiar to this prototype. The complete equations of motion were found using Lagrangian methods, and numerically integrated using computer tools. A 3D simulation program was written to animate the results of integrating the equations. The dynamics apparent in the simulations were found to closely match the observed dynamics of the physical prototype.
Open Access
Enabling predictive energy management in vehicles
(Colorado State University. Libraries, 2018) Asher, Zachary D., author; Bradley, Thomas H., advisor; Chong, Edwin, committee member; Young, Peter, committee member; Zhao, Jianguo, committee member
Widespread automobile usage provides economic and societal benefits but combustion engine powered automobiles have significant economic, environmental, and human health costs. Recent research has shown that these costs can be reduced by increasing fuel economy through optimal energy management. A globally optimal energy management strategy requires perfect prediction of an entire drive cycle but can improve fuel economy by up to 30\%. This dissertation focuses on bridging the gap between this important research finding and implementation of predictive energy management in modern vehicles. A primary research focus is to investigate the tradeoffs between information sensing, computation power requirements for prediction, and prediction effort when implementing predictive energy management in vehicles. These tradeoffs are specifically addressed by first exploring the resulting fuel economy from different types of prediction errors, then investigating the level of prediction fidelity, scope, and real-time computation that is required to realize a fuel economy improvement, and lastly investigating a large computational effort scenario using only modern technology to make predictions. All of these studies are implemented in simulation using high fidelity and physically validated vehicle models. Results show that fuel economy improvements using predictive optimal energy management are feasible despite prediction errors, in a low computational cost scenario, and with only modern technology to make predictions. It is anticipated that these research findings can inform new control strategies to improve vehicle fuel economy and alleviate the economic, environmental, and human health costs for the modern vehicle fleet.
Open Access
Evaluation of distributed energy storage for ancillary service provision
(Colorado State University. Libraries, 2011) Quinn, Casey W., author; Bradley, Thomas H., advisor; Zimmerle, Daniel, committee member; Young, Peter M., committee member
Researchers have proposed that distributed energy storage devices could be used to perform ancillary services for the electric grid. This work focuses on vehicle-to-grid and battery-to-grid distributed energy storage devices. In conceptual studies, distributed energy storage devices were shown to be able to accrue revenue for performing these grid stabilization services, and these revenues were used to show that the use of vehicle-to-grid and battery-to-grid can help to offset the initial increased capital cost of electric vehicles. These conceptual studies have assumed a command architecture that allows for a direct and deterministic communication between the grid system operator and the distributed energy storage devices. The first part of this thesis compares this direct, deterministic command architecture to an aggregative command architecture on the basis of the availability, reliability and value of the vehicle-to-grid provided ancillary services. This research incorporates a new level of detail into the modeling of vehicle-to-grid ancillary services by incorporating probabilistic vehicle travel models, time series ancillary services pricing, a consideration of ancillary services reliability. Results show that including an aggregating entity in the command and contracting architecture can improve the scale and reliability of vehicle-to-grid ancillary services, thereby making vehicle-to-grid ancillary services more compatible with the current ancillary services market. However, the aggregative architecture has the deleterious effect of reducing the revenue accrued by plug-in vehicle owners relative to the default architectures. The second part of this work investigates the effects of introducing battery state of charge and time series generation control signals. Results show that in order to integrate a vehicle-to-grid system into the existing markets and power grid the distributed energy storage system will require: 1) an aggregative architecture to meet current industry reliability standards, 2) the construction of low net energy automatic generation control signals, 3) a lower percent call for distributive energy storage systems even if the pool of contracted ancillary service resources gets smaller, 4) a consideration of vehicle performance degradation due to the potential loss of electrically driven miles, and 5) the incorporation of power-to-energy ratios. The third part of this work adapts the vehicle-to-grid model to a battery-to-grid system. Results show that if the automatic generation control signals contain low energy content, battery-to-grid has higher revenue potential than vehicle-to-grid due not having to account for vehicle driving behavior. Additionally, the third portion of this work proposed and performed high level analyses of operational options for battery-to-grid systems receiving automatic generation control signals with high energy content.
Open Access
Evaluation of power-assist hydraulic and electric hybrids for medium- and heavy-duty vehicle applications
(Colorado State University. Libraries, 2014) Wagner, Justin Taylor, author; Bradley, Thomas H., advisor; Bandhauer, Todd M., committee member; Sega, Ronald M., committee member
Under pressure from rising fuel costs, emissions constraints, and new government regulations on medium- and heavy-duty vehicles, hybrid technologies for these classes of vehicles are becoming more prevalent. A variety of technologies have been proposed to meet these requirements including power-assist hybrid electric and hybrid hydraulic systems. Although there has been great discussion about the benefits surrounding each of the technologies individually, no direct comparisons are available on the basis of economics and fuel economy. This study focuses on comparing these power-assist technologies on these bases as well as determines the ability of these technologies to fulfill the newly adopted fuel economy regulations. In order to accomplish this goal, three computational models of vehicle dynamics, thermal behavior and fuel economy were created and validated to simulate the conventional vehicle and hydraulic and electric hybrids. These models were simulated over the Heavy-Duty Urban Dynamometer Driving Schedule, the HTUF Class 4 Parcel Delivery Cycle, and the Orange County Bus cycle. These drive cycles were chosen on their ability to characterize the variety of operating conditions observed in medium- and heavy-duty vehicles. Using these models, cross technology comparisons were constructed comparing commercially available systems, systems with a fixed mass, and systems with a fixed incremental cost. The results of the commercially available systems showed that the Azure Dynamics HEV provided greater fuel economy improvement than the Lightning Hybrids HHV for drive cycle kinetic intensities less than 3.19 miles-1. Although this system showed a cost of fuel savings over the HHV, it was seen that the incremental cost of the HEV exceeded the cost of fuel savings over the HHV. The fixed mass comparison case, which compared vehicles with equal cargo carrying utility, showed similar results to that of the commercially available case. Although the increase in incremental cost for the varying HEV systems designed for the fixed mass case correlated to an improvement in fuel savings, the cost associated with the systems surpassed the savings seen. Lastly, the fixed cost case provided results which were also similar to the commercially available case. Due to the fixed system cost, it was seen that for these systems, the fuel economy benefits and associated cost showed the greatest benefits for the HEV. This study concluded that given the evaluation, the HEV was the only power-assist hybrid technology which could fulfill the regulated fuel economy improvement of 15%. Although the HEV was the only technology which could fulfill the requirements, the HHV showed an improvement upwards of 7% greater than the HEV for the Orange County Bus Drive Cycle.
Open Access
Financial and environmental impacts of new technologies in the energy sector
(Colorado State University. Libraries, 2015) Duthu, Ray C., III, author; Bradley, Thomas H., advisor; Bandhauer, Todd M., committee member; Carlson, Kenneth H., committee member; Suryanarayanan, Siddharth, committee member
Energy industries (generation, transmission and distribution of fuels and electricity) have a long history as the key elements of the US energy economy and have operated within a mostly consistent niche in our society for the past century. However, varieties of interrelated drivers are forcing changes to these industries’ business practices, relationship to their customers, and function in society. In the electric utility industry, the customer is moving towards acting as a fuller partner in the energy economy: buying, selling, and dispatching its demand according to its own incentives. Natural gas exploration and production has long operated out in rural areas farther from public concerns or regulations, but now, due to hydraulic fracturing, new exploration is occurring in more urbanized, developed regions of the country and is creating significant public concern. For these industries, the challenges to their economic development and to improvements to the energy sector are not necessarily technological; but are social, business, and policy problems. This dissertation seeks to understand and design towards these issues by building economic and life cycle assessment models that quantify value, potential monetization, and the potential difference between the monetization and value for two new technologies: customer-owned distributed generation systems and integrated development plans with pipeline water transport in hydraulically fractured oil and gas fields. An inclusive business model of a generic customer in Fort Collins, Co and its surrounding utilities demonstrates that traditional utility rates provide customers with incentives that encourage over-monetization of a customer’s distributed generation resource at the expense of the utilities. Another model which compares customer behavior incented by traditional rates in three New England cities with the behavior incented through a real-time pricing market corroborates this conclusion. Daily customer load peak-shaving is shown to have a negligible and unreliable value in reducing the average cost of electricity and in some cases can increase these costs. These models support the hypothesis that distributed generation systems provide much greater value when operated during a few significant electricity price events than according to a daily cycle. New business practices which foster greater cooperation between customers and utilities, such as a real-time price market with a higher fidelity price signal, reconnect distributed generation’s potential monetization to its value in the marketplace. These new business models are required to ensure that these new technologies are integrated into the electric grid and into the energy market in such a way that all of the market participants are interested and invested stakeholders. The truck transport of water associated with hydraulic fracturing creates significant local costs. A life cycle analysis of a hypothetical oil and gas field generic to the northern Colorado Denver-Julesburg basin quantifies the economic, environmental, and social costs associated with truck transport and compares these results with water pipeline systems. A literature review of incident data demonstrates that pipelines historically have spilled less hazardous material and caused fewer injuries and fatalities than truck transport systems. The life cycle analysis demonstrates that pipeline systems also emit less pollutants and cause less local road damage than comparable trucking systems. Pipeline systems are shown to be superior to trucking systems across all the metrics considered in this project. In each of these domains, this research has developed expanded-scope models of these new technologies and systems to quantify the tradeoffs that are present between monetization, environment, and economic value. The results point towards those business models, policies, and management practices that enable the development of more equitable, efficient, and sustainable energy systems.
Open Access
Implications of temporally and geographically realized energy use for electrified transportation
(Colorado State University. Libraries, 2014) Kambly, Kiran, author; Bradley, Thomas H., advisor; Kirkpatrick, Allan, committee member; Wilson, Bryan, committee member; Young, Peter, committee member
Plug in electric vehicles (PEVs) are vehicles that use energy from the electric grid to provide tractive and accessory power to the vehicle. The nonexistent (electric vehicles) or reduced-sized (plug in hybrid vehicles) engine in these vehicles results in high energy conversion efficiencies, lower GHG emissions, and reduced environmental pollution. Consumer demand for these vehicles is limited by their reduced range relative to conventional vehicles. Range limitations in PEVs are primarily due to the lower onboard energy storage capacity of lithium ion (720kJ/kg) relative to gasoline (47.2MJ/kg), and the range sensitivity of PEVs to accessory loads, primarily cabin conditioning loads, is higher. The factors such as local ambient temperature, local solar radiation, length of the trip and thermal soak have been identified to affect the cabin conditioning power requirements and to therefore affect vehicle range. The steady increase in consumer demand for PEVs has resulted in research initiatives by USDOE, the automotive industry and utility industry to overcome these range limitations. The focus of this research is to develop a detailed systems-level approach to connect HVAC technologies and usage conditions to social, environmental, and consumer-centric metrics of performance. This is accomplished through the development of a toolset that consider transient environmental parameters, real world driver behavior, charging behavior, and regional passenger fleet population for HVAC system operation. The resulting engineering toolset can be used to determine geographical distribution of energy consumption by HVAC systems in electric vehicles, identify regions of US where EVs can elicit positive user response, evaluate the sensitivity of PEV range to the local weather conditions, identify times of use to extract maximum performance from PEVs, establish HVAC component specifications, and optimize vehicle energy management strategies and technologies. A case study with the alternative accessory technology such as a combination of phase change materials to provide for heating and cooling is explored. The results of this research show that PEV HVAC energy consumption is geographically and temporally disparate, that range variability may be more of a driver of consumer dissatisfaction than actual range, and that HVAC energy management and technologies can reduce the variability in PEV range and may thereby improve PEV consumer acceptability.
Open Access
Increased understanding of hybrid vehicle design through modeling, simulation, and optimization
(Colorado State University. Libraries, 2010) Geller, Benjamin M. (Benjamin Michael), author; Bradley, Thomas H., advisor; Kirkpatrick, Allan Thomson, committee member; Keske, Catherine M., committee member
Vehicle design is constantly changing and improving due to the technologically driven nature of the automotive industry, particularly in the hybridization and electrification of vehicle drive trains. Through enhanced design vehicle level design constraints can result in the fulfillment of system level design objectives. These constraints may include improved vehicle fuel economy, all electric range, and component costs which can affect system objectives of increased national energy independence, reduced vehicle and societal emissions, and reduced life-cycle costs. In parallel, as computational power increases the ability to accurately represent systems through analytical models improves. This allows for systems engineering which is commonly quicker and less resource consuming than physical testing. As a systems engineering technique, optimization has shown to obtain superior solutions systematically, in opposition to trial-and-error designs of the past. Through the combination of vehicle models, computer numerical simulation, and optimization, overall vehicle systems design can greatly improve. This study defines a connection between the system level objectives for advanced vehicle design and the component- and vehicle-level design process using a multi-level design and simulation modeling environment. The methods and information pathways for vehicle system models are presented and applied to dynamic simulation. Differing vehicle architecture simulations are subjected to a selection of proven optimization algorithms and design objectives such that the performance of the algorithms and vehicle-specific design information and sensitivity is obtained. The necessity of global search optimization and aggregate objective functions are confirmed through exploration of the complex hybrid vehicle design space. Whether the chosen design space is limited to available components or expanded to academic areas, studies can be performed for numerous design objectives and constraints. The combination of design criteria into quantifiable objective functions allows for direct optimization comparison based on any number of design goals. Integrating well-defined objective functions into high performing global optimization search methods provides increased probability of obtaining solutions which represent the most germane designs. Additionally, key interactions between different components in the vehicular system can easily be identified such that ideal directions for gain relative to minimal cost can be achieved. Often times vehicular design processes require lower order representations or consist of time and resource consuming iterations. Through the formulation presented in this study, more details, objectives, and methods become available for comparing advanced vehicles across architectures. The main techniques used for setting up the models, simulations and optimizations are discussed along with results of test runs based on chosen vehicle objectives. Utility for the vehicular design efforts are presented through comparisons of available simulation and future areas of research are suggested.
Open Access
Investigation of resin infusion consumable effect on fusion bond strength in the manufacture of a thermoplastic vertical axis wind turbine prototype
(Colorado State University. Libraries, 2020) Bair, Jamison, author; Bradley, Thomas H., advisor; Radford, Donald W., committee member; Heyliger, Paul R., committee member
To further research the economic viability, manufacturability, and wider adoption of Vertical Axis Wind Turbines (VAWT), a project team led by Steelhead Composites (SHC), with assistance from Colorado State University (CSU), National Renewable Energy Laboratory (NREL), and Arkema Inc. designed and fabricated VAWT rotor assembly with thermoplastic composite blades using novel fabrication techniques. Thermoplastics present many advantages over traditional thermosets including recyclability as well as the ability to be thermally welded and reformed without machining. Thermal welding, or fusion bonding can eliminate the need for adhesive bonding, a requirement in the manufacture of thermoset and thermoplastic turbine blades, as currently being produced. Colorado State University was tasked with using Elium®, a novel liquid poly methyl-methacrylate (PMMA) thermoplastic manufactured by Arkema to conduct the manufacture of protype vertical axis wind turbine blades. Elium® is a reactive, in-situ polymerizing thermoplastic that is processed using liquid processing techniques and it has mechanical properties comparable to counterpart thermosetting resins. The CSU research team developed a resin infusion molding process with closed two-part molds to create thin, hollow fiber reinforced airfoils. When high quality airfoils were successfully manufactured the team investigated the feasibility of fusion bonding end fittings into the hollow airfoils to reduce part count and mass. It was hypothesized that the consumables that produced a rough, matrix rich texture at the bond interface would lead to higher strength bonded joints. The fusion bonding focus investigated three different infusion consumables: Compoflex® RF3 a combination release film and flow media, G-FLOW™, a structural glass fiber flow media, and Release Ply Super A, a heavy weight nylon release film. The products produced varying surface textures that were measured using a surface profilometer to compare and quantify the roughness and form of the surface, to examine how the induced surface textures impacted the quality of fusion bonded joints. This hypothesis was tested via manufacture of double lap shear strength coupons which were tested via ASTM 3528. Processing parameters of the bulk heating fusion bonding process were varied included temperature, consolidation pressure and time, and cooling method. Strength testing results in addition to failure mode analysis and digital microscopy imaging were used to determine which consumables provided a higher bond strength in both glass fiber and carbon fiber Elium® thermoplastic reinforced specimens. The results of the double lap shear tests showed that with the right combination of surface texture and processing variables, lap shear strengths of over 16 MPa (2300 psi) were achieved with glass fiber reinforcements. Results indicated that more consistent strength values were obtained from infusion consumables that had smaller surface asperities, and that larger asperities often led to the inclusion of air bubbles creating voids thus reducing the strength of the bonded joints. Subsequent testing using carbon fiber as the reinforcement provided satisfactory values for lap shear strength and the team proceeded develop a process to fusion join to end attachment plates used to attach blades to the turbine hub. After successfully fusion bonding the tower to blade attachment plates into 129" long hollow airfoil sections, post-mold reforming was used to thermoform the blades into the desired geometry to complete a three-blade vertical axis wind turbine blade prototype.
Open Access
Life cycle and technoeconomic analysis of microalgae-based biofuels
(Colorado State University. Libraries, 2014) Batan, Liaw Yih Der, author; Bradley, Thomas H., advisor; Willson, Bryan D., advisor; Marchese, Anthony J., committee member; Graff, Gregory D., committee member; Paustian, Keith, committee member
Microalgae are an appealing feedstock for production of biofuels due to their high productivity compared to terrestrial plant-based feedstocks, and their relative tolerance of low quality land and water. Despite these potential benefits, there are technological, environmental and economic challenges that must be overcome to enable commercialization of any microalgae-to-biofuels process. Due to the relative immaturity of the field, assessments of the environmental performance, scalability and economic performance of microalgae-based biofuels are highly uncertain, data poor, and incomparable across technologies. This dissertation seeks to study these aspects of microalgae-based biofuels so as to provide models of increased utility for technical design, investment planning, and achieving policy-level objectives. This work is divided in three primary research efforts. First, this research develops an integrated life cycle assessment of the microalgae to biofuels process using a detailed engineering model derived from a pilot-scale photobioreactor system. The life cycle assessment quantifies and compares energy consumption, greenhouse gas emissions, and scalability of the biofuel life cycle. Second, this work defines the water footprint for a photobioreactor-based biofuel production system with geographical and temporal resolution. The water footprint (WF) of microalgae biofuel is comprehensively assessed using a combined process and economic input-output lifecycle analysis method, using blue, green and lifecycle WF metrics, four different fuel conversion pathways, and 10 continental US locations with high productivity yields. Finally, a technoeconomic analysis of the baseline enclosed photobioreactor microalgae to biofuels system is performed with stochastic economic risk assessment. This section provides a range of probabilities of economic success based on the sensitivity of the microalgae-to-biofuel process to the variable economic variables and scenarios. Based on the results of these integrated assessments of microalgae biofuels, this study communicates an improved understanding of the economic and environmental performance of microalgae biofuels and their characteristics compared to petroleum and biofeedstock-based biofuels.
Open Access
Measurement of direct nitrous oxide emissions from microalgae cultivation under oxic and anoxic conditions
(Colorado State University. Libraries, 2011) Fagerstone, Kelly Dawn, author; Marchese, Anthony John, 1967-, advisor; Bradley, Thomas H., advisor; De Long, Susan K., committee member
Lifecycle assessments (LCA) of microalgae-based biofuels have demonstrated net greenhouse gas (GHG) emissions reductions, but limited data exist on direct emissions of GHG's from microalgae cultivation systems such as open raceway ponds (ORP) or photobioreactors (PBR). For example, nitrous oxide (N2O) is a potent GHG that has been detected from microalgae cultivation. However, N2O emissions have not been experimentally quantified to determine their impact on overall lifecycle assessment of the microalgae-to-biofuels process. Theoretical calculations using the Intergovernmental Panel on Climate Change standards for terrestrial crops (1% of available nitrogen applied as fertilizer is converted to N2O) suggest the potential for significant levels of N2O from microalgae cultivation. In this study, microalgae species Nannochloropsis salina was cultivated with nitrate under conditions representative of PBR and ORP growth conditions with diurnal light-dark cycling. To examine the effect of dissolved oxygen on N2O emissions, experiments were conducted with an air headspace and nitrogen headspace, respectively. During these experiments N2O emissions were quantified utilizing Fourier Transform Infrared spectrometry. Under a nitrogen headspace, N2O emissions were elevated during dark periods and minimal during light periods. Under an air headspace, N2O emissions were negligible for both the light and dark periods. The experimental results show that N2O production was induced by anoxic conditions with nitrate present in the growth media, suggesting that N2O was produced by denitrifying bacteria within the microalgal growth media. The presence of denitrifying bacteria was verified through PCR-based detection of norB genes, which encode bacterial enzymes that produce N2O. Furthermore, antibiotic treatments inhibited N2O emissions. Application of these results to LCA and potential strategies for management of growth systems to reduce N2O emissions are discussed.
Open Access
Methods for advancing automobile research with energy-use simulation
(Colorado State University. Libraries, 2014) Geller, Benjamin M., author; Bradley, Thomas H., advisor; Marchese, Anthony J., committee member; Olsen, Daniel B., committee member; Young, Peter M., committee member
Personal transportation has a large and increasing impact on people, society, and the environment globally. Computational energy-use simulation is becoming a key tool for automotive research and development in designing efficient, sustainable, and consumer acceptable personal transportation systems. Historically, research in personal transportation system design has not been held to the same standards as other scientific fields in that classical experimental design concepts have not been followed in practice. Instead, transportation researchers have built their analyses around available automotive simulation tools, but conventional automotive simulation tools are not well-equipped to answer system-level questions regarding transportation system design, environmental impacts, and policy analysis. The proposed work in this dissertation aims to provide a means for applying more relevant simulation and analysis tools to these system-level research questions. First, I describe the objectives and requirements of vehicle energy-use simulation and design research, and the tools that have been used to execute this research. Next this dissertation develops a toolset for constructing system-level design studies with structured investigations and defensible hypothesis testing. The roles of experimental design, optimization, concept of operations, decision support, and uncertainty are defined for the application of automotive energy simulation and system design studies. The results of this work are a suite of computational design and analysis tools that can serve to hold automotive research to the same standard as other scientific fields while providing the tools necessary to complete defensible and objective design studies.