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Engineered cementitious composites (ECCs) are special types of fibre-reinforced cementitious composites (FRCC) with higher strain capacity which can be achieved with low fibre volume as low as 2% and total elimination of coarse aggregates. Due to the outstanding performance of ECCs, they are suitable for various construction and repair applications. However, in order for ECCs to achieve their properties; a high amount of binder which is primarily composed of Portland cement (PC) is used alongside a special type of ultrafine silica sand (USS) which is different from the conventional natural fine aggregates. The production of PC is known to be detrimental to the environment due to its high carbon dioxide emissions coupled with the high consumption of natural resources. Thus, the high use of PC content in ECCs posed a sustainability threat. Similarly, the USS used in ECCs are not readily available everywhere and are expensive. The processing of the USS coupled with its transportation over long distances would also increase the cost and embodied carbon of ECCs. Hence, in order to promote more development and applications of ECCs for various applications; this dissertation aims to provide innovative ways to improve the sustainability of ECCs and their performances. This dissertation offers four solutions to improve the sustainability of ECCs which are (i) use of unconventional industrial by-products as partial replacement of PC (ii) total replacement of PC in ECCs with alternative sustainable binders (iii) replacement of USS in ECCs with recycled materials and (iv) the use of supplementary cementitious materials to replace a high volume of PC. The findings from this study revealed sustainable ECCs with acceptable mechanical and durability performance can be achieved with the use of alternative binders or replacement of the conventional USS used in ECC mixtures. The sustainability and cost assessment of the ECCs indicated that the incorporation of industrial by-products such as blast furnace slag (BFS) especially at higher content is beneficial to reducing the negative environmental impact and economic burden associated with ECCs compared to the conventional ECC. The sustainability index and cost index of the ECCs further showed that the use of BFS is more beneficial when the sustainability and cost of the ECCs are compared with the corresponding performance. Similarly, the use of recycled materials as an alternative to USS was found to result in a significant reduction in the embodied carbon and cost of ECCs. The use of recycled materials such as expanded glass (EG) as aggregates in ECCs was also found to improve the thermal insulation properties of ECCs making such ECC suitable for the production of building envelope elements.

An important limitation of polymer electrolyte fuel cell technology is the low mechanical strength and dimensional instability with changes of water content of proton exchange membranes (PEMs). A range of different approaches to more stable PEMs based on Nafion have been studied of which composite materials of Nafion with mechanically stronger polymers is one of the most promising directions. If successful, they will lead to thinner composite PEMs with enhanced fuel cell performance, life span, and cost-effectiveness. Developed in this thesis are electrospinning conditions for the fabrication of electrospun mats for potential application in PEMs. Polysulfone (PSU), poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride (PVDF) were tested as mechanically stronger but inert (minimal contribution to proton transport) polymers that can tolerate the fuel cell condition. PVDF-HFP generated defect free electrospun mats over a wide range of spinning conditions, while PSU required very specific conditions and no successful conditions were found for PVDF mostly due to over-wetting. These mats might function as mechanical support and could be tested as PEMs when filled with Nafion, but the complete filling of electrospun mats with Nafion has been proven difficult. Instead, the electrospinning of Nafion was tested to explore options of electrospinning mixed mats of two different polymers and co-electrospinning of core-sheath fibers. Two commercial Nafion solutions D520 and D2020 with 5 wt% and 20 wt% content of Nafion were electrospun together with polyethylene oxide of two different molecular weights as a carrier polymer. Mats of sufficient quality for PEM tests were obtained with solutions based on 20 wt% content of Nafion, a low flow rate of 0.2 mL/h, and the lower molecular weight polyethylene oxide as the carrier. Finally, coaxial electrospinning conditions for the formation of core-sheath fibers were developed for Nafion as sheath material and PVDF-HFP or PSU as the core material. Defect-free, core-sheath fibers were generated when the concentration of both solutions was high (20 wt%), the Nafion flow rate was about 0.2 mL/h for the sheath, and the core flow rate was below the flow rate of the sheath (0.1-0.15 mL/h for PVDF-HFP and 0.15 mL/h for PSU). Mats of these core-sheath fibers should provide good mechanical strength combined with much better compatibility with Nafion. A straightforward pore filling with Nafion solutions is expected and their investigation as PEMs in fuel cells is planned as future work.

The deep-sea, defined as the area 200 m below the surface, is facing emerging chemical, physical and biological stressors. Currently, very little is known regarding deep-sea ecosystems both globally and in the Arctic. In this thesis I undertook a literature review on the current understanding of global deep-sea ecosystems through the use of stable isotopes. Specifically, I synthesized the available literature on spatial variation, energy pathways, depth, temporal variation, feeding behaviour, niche, trophic position and body size isotopic trends. This thesis then presents a case study examining the isotopic niche of five teleost and two decapod species within Arctic deep-sea food webs across the localized latitudinal gradient of Baffin Island. Spatial variation in isotopic niche was quantified using 13C and 15N for seven deep-sea species at three locations on Baffin Island, Nunavut to determine whether the “Latitudinal Niche Breadth Hypothesis” which states that niche breadth should increase with latitude holds true in the Arctic. Overall, isotopic patterns in global deep-sea ecosystem are variable; consistent trends are not observed across all taxa and habitats. It was concluded that niche breadth did not consistently increase with latitude in the eastern Canadian Arctic; localized conditions (e.g. sea ice, temperature) and individual condition (e.g. hepatosomatic index) may contribute more to a species’ niche than latitude. Overall, this thesis improves our understanding of deep-sea ecosystems globally, contributes baseline data for future monitoring, and by investigating multiple species and locations it will provide input on how climate change may impact Arctic food web diversity, energy dynamics and ecosystem structure to aid in sustainable fishery development.

Climate change is a growing concern across the globe, and the Provincial Government of Ontario recognizes that climate change impacts need to be considered in all decision-making. In Southern Ontario, a critical and ongoing challenge is balancing the competing water demands under changing climate for various uses to ensure prosperity and sustainability in the future. A better understanding and quantification of impacts of possible climate change on regional hydrology are necessary for sustainable water resources management and maintaining healthy ecosystems in this region. In order to study the impacts of future climate on the regional water resources, a large-scale hydrologic model was developed for Southern Ontario within the Great Lakes basin using the Soil and Water Assessment Tool (SWAT). The study area includes four basins: Eastern Georgian Bay, Eastern Lake Huron, Northern Lake Erie, and Lake Ontario and Niagara Peninsula basins, covering a total area of about 84,650 km2. The hydrologic model was calibrated and validated using monthly observed streamflow data at 40 gauging stations, and spatially validated at another 40 gauging stations across the study area. The developed model was employed to estimate water budget components for a reference period (1971-2000), and to assess climate change impacts on the hydrologic regime during the mid-century (2041-2070) and the end-century (2071-2100). Projected climate data from five GCM-RCMs simulations for RCP4.5 and RCP8.5 scenarios were obtained from the NA-CORDEX archive. After bias correction, climate data sets were used in the SWAT model for the impact assessment. Based on the model calibration and validation results, the overall performance of the model was found to be satisfactory. Its performance was better in the predominantly agricultural Northern Lake Erie and Eastern Lake Huron basins than the other two basins. The average annual precipitation, evapotranspiration (ET), surface runoff and water yields for the study area over the period 1971-2000 were estimated at 979 mm, 540 mm, 183 mm and 410 mm, respectively. The average annual precipitation in the four basins varied from 923 mm to 1049 mm, and water yields were found to vary between 377 mm and 465 mm. The projected increases in mean annual temperature are 3.0oC and 2.4oC by the mid-century, while the increases are 5.2oC and 3.2oC by the end-century for RCP8.5 and RCP4.5 scenarios, respectively. The average annual precipitation of the study area is projected to increase by 8% to 16%, depending on the scenario and time period. The possible increases in precipitation are relatively high for the RCP8.5 scenario and likely to vary between 13% and 18% in the four basins by the end of the 21st century. By the mid-century, the average annual water yields in the four basins are predicted to increase by 7% to 20%, and 5% to 13% under RCP8.5 and RCP4.5 scenarios, respectively. By the end-century, the projected increases in the annual water yields of the basins are 5% to 26% for RCP8.5 scenario and 3% to 11% for RCP4.5 scenario. In general, the average monthly water yield in the study area is likely to increase during December to February, but decrease in the months of March and April. The results are also presented spatially for the subwatersheds across the study area. The study results would help in planning and management of water resources, and in developing climate change adaptation plans and strategies.

There is a significant need to research and develop a compatible controller for the DC–DC converter used in fuel cells electric vehicles (EVs). Research has shown that fuel cells (FC) EVs have the potential of providing a far more promising performance in comparison to conventional combustion engine vehicles. This study aims to present a universal sliding mode control (SMC) technique to control the DC bus voltage under varying load conditions. Additionally, this research will utilize improved DC–DC converter topologies to boost the output voltage of the FCs. A DC–DC converter with a properly incorporated control scheme can be utilized to regulate the DC bus voltage–. A conventional linear controller, like a PID controller, is not suitable to be used as a controller to regulate the output voltage in the proposed application. This is due to the nonlinearity of the converter. Furthermore, this thesis will explore the use of a secondary power source which will be utilized during the start–up and transient condition of the FCEV. However, in this instance, a simple boost converter can be used as a reference to step–up the fuel cell output voltage. In terms of application, an FCEV requires stepping –up of the voltage through the use of a high power DC–DC converter or chopper. A control scheme must be developed to adjust the DC bus or load voltage to meet the vehicle requirements as well as to improve the overall efficiency of the FCEV. A simple SMC structure can be utilized to handle these issues and stabilize the output voltage of the DC–DC converter to maintain and establish a constant DC–link voltage during the load variations. To address the aforementioned issues, this thesis presents a sliding mode control technique to control the DC bus voltage under varying load conditions using improved DC–DC converter topologies to boost and stabilize the output voltage of the FCs.

This thesis investigates the agricultural greenhouse sector in a cold climate, which requires a large amount of natural gas for supplying the substantial heating demands. The heating demand of these structures is calculated, and potential sustainable design methods are implemented to reduce the reliance on carbon-based fuels. Assessment of the environmental impacts of a bell pepper greenhouse in Southwestern Ontario, Canada heated by natural gas was studied. A life cycle assessment (LCA) method is employed to scrutinize the bell pepper greenhouse, pinpointing areas that need improvement. It was concluded that Global Warming (GW) is the significant environmental hazard among other environmental categories (3.87e-2 kg ??2-Eq). It should be noted, the main contributor to global warming is the natural gas being used as the heating resource (3.2e-2 kg ??2-Eq). The analysis is extended to explore the deployment of solar energy as an alternative source for heating. Solar energy is found to be a superior alternative in terms of emissions. Furthermore, in order to integrate solar energy into the energy supplying systems of the greenhouses, a hybrid Solar Thermal/Photovoltaic-Battery Energy Storage (ST/PV-BES) system is modeled. Evaluation of the best configuration of photovoltaic (PV) and solar thermal (ST) modules, and battery energy storage (BES) size to have the minimum Levelized Cost of Energy (LCOE) was conducted. It is proved that the system is economically optimized. Moreover, to improve operational efficiency and reduce the energy demand of commercial greenhouses, parametric optimization of major growing environment variables including cladding material and window to wall ratio as well as the characteristics of the solar thermal model elements such as hot water tank capacity and heat exchanger effectiveness was carried out. It is demonstrated that the best greenhouse configuration which is a system with 80% window area and 20% brick wall area in both lower nodes and upper nodes results in heating and cooling demand energy reduction without significantly compromising the solar energy absorption. This scenario leads to increasing system performance from 36% to 39%. It is also concluded that doubling the tank capacity improves system performance from 36% to 43% and changing the heat exchanger effectiveness has minor impacts on the system performance.