In this work I describe various approaches to electrochemical energy storage at the grid-scale. Chapter 1 provides an introduction to energy storage and an overview of the history and development of flow batteries. Chapter 2 describes work on the hydrogen-chlorine regenerative fuel cell, detailing its development and the record-breaking performance of the device. Chapter 3 dives into catalyst materials for such a fuel cell, focusing on ruthenium oxide based alloys to be used as chlorine redox catalysts. Chapter 4 introduces and details the development of a performance model for a hydrogen-bromine cell. Chapter 5 delves into the more recent work I have done, switching to applications of quinone chemistries in flow batteries. It focuses on the pairing of one particular quinone (2,7-anthraquinone disulfonic acid) with bromine, and highlights the promising performance characteristics of a device based on this type of chemistry. / Engineering and Applied Sciences

To combat climate change, governments have pledged to become more dependent on renewable electricity production. However, the intermittency of renewable power generation requires modern grid-scale energy storage systems, which are currently being explored with lithium-ion batteries (LIBs). However, this technology faces significant safety, social, and financial concerns. As an alternative chemistry, aqueous zinc-ion batteries (ZIBs) show much promise for grid-scale energy storage with their safe, inexpensive design. Major bottlenecks of ZIB performance include their limited practical specific capacity, and low capacity retention. Organic cathodes, specifically the use of redox-active quinone molecules, are an upcoming contender for customizable and simple ZIB cathode design that can be optimized for good performance. However, these cathodes are often plagued by capacity fade caused by quinone dissolution and inactivation. Grafting these quinone molecules to the supporting conductive carbon substrate via covalent bonding had been previously explored in LIB and supercapacitor electrode design as an effective way to mitigate capacity fade. In this work, the development of aqueous ZIB cathodes with 9,10-phenanthrenequinone (PQ) molecules grafted to carbon black substrates was done via a facile in-situ generated diazonium salt reaction synthesis technique. Electrochemical and material analysis confirmed the presence of covalent grafting. This grafting modification was compared to the standard cathode design of adsorbing the quinones on carbon substrates like Ketjenblack (KB) and Vulcan Black (VB). Battery cycling tests were performed and the grafted PQ-KB cells achieved a discharge capacity of 99 mAh g-1 after 1000 charge-discharge cycles with accelerated testing at a charge/discharge rate of 200 mA g-1 and 10 mA g-1. These cells maintained 67% of their initial capacity compared to the 55% for the adsorbed PQ on KB cells. This approach highlights the promise of grafting organic material as a technique to support organic cathodes for next-generation ZIB design. / Thesis / Master of Applied Science (MASc) / Renewable electricity production is necessary to mitigate climate change but the production of electricity through many renewables like wind and solar can vary significantly on any given day. Lithium-ion batteries are being explored for storing electricity for use on the grid, but they have many downsides including being flammable and expensive. Zinc-ion batteries are non-flammable and cost-effective alternatives to lithium-ion batteries. They are currently not as widely used as lithium-ion batteries because of their poorer performance. However, for storing electricity for power grids, with the correct selection of materials to make the battery, zinc-ion batteries can perform well enough to compete with lithium-ion batteries. This work investigates a modification of a material used in zinc-ion batteries, that allows the battery to maintain a higher capacity after many charge and discharge cycles.

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Emerging integration of renewable energy has prompted a wide range of research on the use of energy storage to compensate for the added uncertainty that accompanies these resources. In the Electric Reliability Council of Texas (ERCOT), compressed air energy storage (CAES) has drawn particular attention because Texas has suitable geology and also lacks appropriate resources and locations for pumped hydroelectric storage (PHS). While there have been studies on incorporation of renewable energy, utilization of energy storage, and dispatch optimization, this is the first body of work to integrate all these subjects along with the proven ability to recreate historical dispatch and price conditions. To quantify the operational behavior, economic feasibility, and environmental impacts of CAES, this work utilized sophisticated unit commitment and dispatch (UC&D) models that determine the least-cost dispatch for meeting a set of grid and generator constraints. This work first addressed the ability of these models to recreate historical dispatch and price conditions through a calibration analysis that incorporated major model improvements such as capacity availability and sophisticated treatment of combined heat and power (CHP) plants. These additions appreciably improved the consistency of the model results when compared to historical ERCOT conditions. An initial UC&D model was used to investigate the impacts on the dispatch of a future high wind generation scenario with the potential to utilize numerous CAES facilities. For all future natural gas prices considered, the addition of CAES led to reduced use of high marginal cost generator types, increased use of base-load generator types, and average reductions in the total operating costs of 3.7 million dollars per week. Additional analyses demonstrated the importance of allowing CAES to participate in all available energy and ancillary services (AS) markets and that a reduction in future thermal capacity would increase the use of CAES. A second UC&D model, which incorporated advanced features like variable marginal heat rates, was used to analyze the influence of future wind generation variability on the dispatch and resulting environmental impacts. This analysis revealed that higher amounts of wind variability led to an increase in the daily net load ramping requirements which resulted in less use of coal and nuclear generators in favor of faster ramping units along with reductions in emissions and water use. The changes to the net load also resulted in increased volatility of the energy and AS prices between daily minimum and maximum levels. These impacts were also found to increase with compounding intensity as higher levels of wind variability were reached. Lastly, the advanced UC&D model was also used to evaluate the operational behavior and potential economic feasibility of a first entrant conventional or adiabatic CAES system. Both storage systems were found to operate in a single mode that enabled very high utilization of their capacity indicating both systems have highly desirable characteristics. The results suggest that there is a positive case for the investment in a first entrant CAES facility in the ERCOT market. / text

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