Morgan, PeterAlnakhli, Mustafa2026-03-042025https://hdl.handle.net/20.500.14154/78386This study addresses the challenge of renewable energy variability, where solar and wind output is clean but unpredictable. Batteries dominate storage today but face high costs, material shortages, and environmental issues. As a result, the dissertation explores three non-battery storage options: supercapacitors, Phase Change Material (PCM) - based thermal storage, and liquid air energy storage (LAES). The overall aim is to assess how suitable these technologies are for domestic, industrial, and grid applications, and the objectives are to review existing literature, compare their performance, evaluate scalability and limitations, and propose future recommendations. Supercapacitors stand out for their ability to deliver power almost instantly, with very high cycle life and relatively low environmental impact. They are already used in homes, industries, and transport for short-burst applications such as stabilizing solar output, supporting elevators, and enabling regenerative braking. However, their low energy density and high self-discharge prevent them from serving as long-duration storage, limiting their role to rapid response and short-duration needs within broader energy systems. PCMs offer a very different pathway, storing energy as heat rather than electricity. They are compact, able to maintain near-constant temperatures during melting and solidification, and already applied in buildings, solar systems, and waste-heat recovery. Though practical deployment at larger scales still faces challenges of thermal conductivity, durability, and cost, PCMs are well suited to thermal management in homes and industries but are not designed to replace long- duration electrical storage. Finally, LAES provides medium- to long-duration storage by liquefying air, storing it in cryogenic tanks, and re-gasifying it through a turbine when power is needed. With integrated thermal storage, efficiency improves and sites can also supply useful heating or cooling, making LAES well-suited to grid and industrial hubs because it is modular, location-flexible, and long-lived. Early projects (e.g., UK 50 MW LAES) show scalability, though high upfront cost and the need for more full-scale operating data remain the main constraints. To carry out this study, a structured literature review and comparative framework were applied to evaluate performance, scalability, and environmental aspects. The findings show that supercapacitors excel in fast, short-burst uses, PCMs in cost-effective thermal management, and LAES in long-duration, grid-scale services. Overall, LAES emerges as the most suitable option for future large-scale energy systems due to its flexibility and sustainability, though high upfront costs and limited operating experience remain important challenges that require further research, supportive policy, and investment.67enRenewable Energy Integration Energy Storage Systems Supercapacitors Phase Change Materials (PCM) Liquid Air Energy Storage (LAES) Long-Duration Energy Storage Grid-Scale Applications Energy System Flexibility SustainabilityThesis