The focus of this project is the storage of thermal energy in packed beds for bulk electricity storage applications. Packed beds are composed of pebbles through which a heat transfer fluid passes, and a thermodynamic model of the heat transfer processes within the store is described. The packed beds are investigated using second law analysis which reveals trade-offs between several heat transfer processes and the importance of various design parameters. Parametric studies of the reservoir behaviour informs the design process and leads to a set of design guidelines. Two innovative design features are proposed and investigated. These features are segmented packed beds and radial-flow packed beds respectively. Thermal reservoirs are an integral component in a storage system known as Pumped Thermal Energy Storage (PTES). To charge, PTES uses a heat pump to create a difference in internal energy between two thermal stores; one hot and one cold. The cycle reverses during discharge with PTES operating as a heat engine. The heat pumps/engines require compression and expansion devices, for which simple models are described and are integrated with the packed bed models. The PTES system behaviour is investigated with parametric studies, and alternative design configurations are explored. A multi-objective genetic algorithm is used to undertake thermo-economic optimisations of packed-bed thermal reservoirs and PTES systems. The algorithm generates a set of optimal designs that illustrate the trade-off between capital cost and round-trip efficiency. Segmentation is found to be particularly beneficial in cold stores, and can add up to 1% to the round-trip efficiency of a PTES system. On the basis of the assumptions made, PTES can achieve efficiencies and energy densities comparable with other bulk electricity storage systems. However, the round-trip efficiency is very sensitive to the efficiency of the compression–expansion system. For designs that utilised bespoke reciprocating compressors and expanders, PTES might be expected to achieve electricity-to-electricity efficiencies of 64%. However, using compression and expansion efficiencies typical of off-theshelf devices the round-trip efficiency is around 45%.

As the worldwide energy demand continues to increase, scientists and engineers are faced with the increasingly difficult task of meeting these needs. Currently, the major energy sources, consisting of oil, coal, and natural gas, are non-renewable, contribute to climate change, and are rapidly depleting. Renewable technology research has become a major focus to provide energy alternatives which are environmentally-friendly and economically competitive to sustain the future worldwide needs. Thermal energy storage using adsorption is a promising technology which can provide energy for heating and cooling applications using solar and waste heat sources. The current work aims to improve adsorption systems to provide higher energy outputs and therefore, more economical systems. New adsorbents and operating conditions were tested with the goal of storing the available energy more efficiently. A model was also developed to gain a better understanding of the adsorption system to improve this developing technology.

No description available.

Two aspects of the lead acid battery have been researched in this work. The first investigates some of the complex questions concerning the nature, composition and chemistry of lead sulphate membranes using scanning electron microscopy (SEM), impedance spectroscopy (IS) and inorganic chemistry techniques. A review of the literature on lead sulphate and precipitate impregnated membranes together with their role in the lead acid battery is presented.

This research presents the development of a transmittance- absorptance parameter for a solar pond. Such a parameter represents, directly, the fraction of the incident solar radiation which is absorbed at the bottom of the solar pond. It can be used to represent pond performance through an equation analogous to the Hottel-Whillier-Bliss Equation for a flat-plate solar collector. The above parameter is called the transmittance - absorptance product and is an energy-weighted quantity. Monthly values of the proposed parameter are developed from an hour-by-hour simulation. The simulation utilizes hourly values of spectral solar radiation reaching the earth's surface which are computed from a state-of-the-art algorithm that has been slightly modified to better estimate diffuse spectral radiation at large solar zenith angles; the modification is also presented. Thermal conductive losses through the water layers and the surrounding earth together with evaporative and convective losses are usually the only loss mechanisms considered for a solar pond. Under clear skies and to a lesser extent under cloudy skies, a longwave radiation heat loss also occurs from the pond surface. The estimation of radiative loss from any terrestrial surface requires detailed computations and atmospheric data. The procedure has been greatly simplified through a correlation which yields spectral atmospheric emissivity from the amounts of absorbing gases present in the atmosphere. It is recommended for further study that the performance of a solar pond be estimated using the proposed transmittance-absorptance product to compute the solar energy absorbed in the pond, and that the longwave radiative loss from the pond be included in the analysis. A comparison with data obtained from an existing solar pond is recommended to validate the results obtained in this study. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

On May 11th, 2019, atmospheric CO2 levels reached 415 ppm, a number 40% higher than the maximum level ever reached in the 800 000 years prior to the Industrial Revolution. This rise can be directly attributed to human activity, and has been linked to global temperature increase and climate change. Net CO2 emissions continue to rise as economies grow, and in 2018 global emissions reached 37.1 Gt. In order to reach the climate targets identified in the 2015 Paris Agreement, some scientists estimate that the world will need to attain net-zero anthropogenic greenhouse gas (GHG) emissions by 2050. Achieving this goal will require deployment of multiple technologies across multiple sectors. Of particular importance will be reducing or eliminating emissions associated to energy production via combustion of fossil fuels, which account for over 80% of CO2 emissions in G20 countries. One method of achieving this is to displace fossil fuel electricity generation with renewable source generation. Canada currently has 12 GW of installed wind capacity, and although it is the country’s fastest-growing source of renewable electricity, widespread deployment is inhibited by technical challenges including the time variability and geographic dispersion of sources. A potential solution to overcome the challenges facing integration of renewables is grid-scale energy storage. Many storage technologies currently exist at various levels of maturity. Although currently low on the development scale, thermochemical energy storage (TCES) has gained significant interest due to its potential to offer low-cost, short- or long-term storage of high-temperature heat using non-toxic, abundant materials. Several recent works have focused on the potential to pair the calcium looping (CaL) process, which exploits the reversible calcination of calcium carbonate, with concentrated solar power (CSP). This would enable CSP to provide continuous power to the grid while receiving discontinuous solar input, and recent projects have predicted storage cycle efficiencies in the range of 38-46%. As an extension of the work done to date, this project proposes a novel configuration of the CSP-CaL process which may offer advantages over other proposed configurations, including a reduction in process equipment requirements, elimination of pressure differentials between vessels, and a reduction in compression duty during the energy discharge period. A process simulation of the proposed system shows that it is capable of offering comparable storage cycle efficiencies, with the overall efficiency being strongly dependent on the residual conversion of calcium oxide in the carbonator as well as on the efficiencies of the power cycles employed to discharge the stored energy. In addition to the technical challenges that may come with this type of system, social and economic barriers may arise due to the fact that it will require large-scale storage of CO2, mining of natural limestone, and potentially large and complex facilities. All of these challenges must be considered and addressed in order to achieve deployment of this technology within Canada and around the world.

This dissertation presents the synthesis and characterization of new types of nanostructured materials for use in high-performance aqueous rechargeable batteries and supercapacitors. In the first chapter, nanostructured nickel cobalt sulfide (Ni4.5Co4.5S8) was prepared through pulse-electrodeposition method. In addition, iron oxide nanosheets were prepared from graphite-coated iron carbide/α-Fe in a two-step annealing/electrochemical cycling process. A full-cell battery with supercapacitor-like power behavior was assembled with Ni4.5Co4.5S8 and iron oxide nanosheets as the positive and negative electrodes, respectively. The full-cell device delivers a specific energy of 89 Wh kg−1 at 1.1 kW kg−1 with a rate performance of 61 Wh kg−1 at a very high specific power of 38.5 kW kg−1. In the second chapter, we propose a route towards developing asymmetric supercapacitor devices having high volumetric energy densities though the modification of commercially available current collectors (CCs): nickel foam (NF) and carbon fiber cloth (CFC). A soft templating/solvothermal treatment route was employed to generate NiO/NiOOH nanosheets on NF current collectors (as positive electrode). CFCs were also modified via an electrochemical oxidation/reduction route to generate an exfoliated core-shell structure followed by electropolymerization of pyrrole into the shell structure (as negative electrode). Combining the individual materials resulted in a full-device asymmetric supercapacitor that delivers volumetric energy densities in the range of 1.67-2.65 mWh cm−3 with corresponding power densities in the range of 5.9-273.6 mW cm−3. Such performance is comparable to lithium thin film (0.3-10 mWh cm−3) and better than some commercial supercapacitors (< 1 mWh cm−3). In the third chapter, we established a simple, precise, and reproducible method to construct carbon fiber ultramicroelectrodes (CF-UMEs) with tip radius r < 1 μm. CF-UMEs were successfully used as SECM-tips to examine the “crystal structure orientation-OER electrocatalytic activity” relationship of iridium/iridium oxide catalysts. In addition, CF-UMEs were used as a substrate electrode for the electrodeposition of pH-sensitive iridium oxide. The pH response of these micrometer-sized pH electrodes has a rapid response (< 5 s) over the pH range of 2-12 with a super-Nernstian slope of 65.3 mV/pH. The prepared pH-UMEs were successfully employed as a potentiometric SECM-tip to image the pH changes at different substrates.

In a world that relies heavily on electricity and portable energy, the development of high performing energy storage devices is crucial. The ongoing push for energy storage devices such as batteries and supercapacitors to store more energy and charge/discharge faster has become exponentially stronger over the past decade. In order to meet the high demands, new materials and processing techniques must be developed. A particle extraction through the liquid-liquid interface (PELLI) technique was used with a versatile extracting molecule, Octyl Gallate (OG). It was found that OG was able to extract a variety of materials including oxides, oxyhydroxides, and pure silver. The advantage of PELLI is that it circumvents the drying stage that occurs in many electrode synthesis techniques where metal oxides are synthesized in aqueous then dried and mixed with conductive additives dispersed in organic solvent. This drying stage causes a practically irreversible agglomeration which hinders mixing with conductive additives as well as reduces the surface area of the material, limiting its electrochemical performance. Using hydroxamates such as octanohydroxamic acid and bufexamac, a novel PELLI technique was developed based on the use of OHA as an extracting agent as well as a capping agent. In addition, a preliminary investigation was started on advanced negative electrode material for supercapacitors. FeOOH-based electrodes exhibit high capacitance but low cyclic stability. Zn2+ ions were introduced during synthesis forming a doped Zn/FeOOH electrode which showed a significant increase in cyclic stability. / Thesis / Master of Applied Science (MASc)

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Over the last decade, wind penetration in the Pacific Northwest has increased rapidly. The variable nature of this massive new resource has increased stress on the hydropower resource to the point where system limits are currently being reached. In order to cultivate continued growth of the wind energy industry both in the Pacific Northwest and the rest of the world, something must be added to help mitigate the effects of the variability of wind power. This research aims to show what can be done by adding energy storage to a wind farm. A novel model predictive control structure has been created with the focus of increasing the dispatchability and reliability of wind farm power output along with allowing participation in frequency regulation. First, the effectiveness of the addition of energy storage with simple control is explored. This is followed by a study on the performance of the system when predictive control is added. Finally, a cost analysis is performed to assess the level of savings and potential profitability of the simulated system. Conclusions support the use of an energy storage resource for more reliable wind farm performance. However, storage technologies are still approaching the price point needed to ensure profitability. / Graduation date: 2012