Ultra-high temperature thermal energy storage for industrial decarbonisation

Abstract

Sustainable energy solutions are crucial to mitigating global warming. The integration of Ultra-High Temperature Thermal Energy Storage (UHTS) into industrial processes and power generation stands out as a compelling strategy to decarbonise pre-existing infrastructure. This thesis introduces a novel approach to enhancing energy efficiency and reducing carbon emissions within the framework of existing thermal power cycles and industrial operations. Through an extensive review of current energy storage technologies, this study identifies UHTS as a critical technology capable of facilitating the transition to a low-carbon economy.

Employing computational methods, quantitative modelling techniques are used to explore the feasibility of UHTS deployment. The research examines the feasibility of retrofitting Rankine and Brayton cycles, specifically a gas turbine (GT) and a heat recovery steam generator (HRSG), with UHTS, assessing enhancements in operational efficiency and environmental performance.

This research also includes the development of a comprehensive mathematical model to simulate the optimal operational behaviour of a UHTS system integrated into GTs, HRSGs and Industrial Boilers (IBs) under two design conditions - arbitrage profitability and fuel displacement. This model allows for an evaluation of the impact on the cost-effectiveness of a UHTS system, and the resulting carbon footprint reduction across different industrial applications.

This study's findings emphasise the potential of UHTS to improve the flexibility and sustainability of thermal power generation and industrial heat processes. Integration into the combustion chamber of a GT for hybrid burning is shown to offer a fuel displacement of up to 88.9 %, facilitating a reduction in NOx of 93.8 %, CO of 98.6 %, and CO₂ of 86.6 %. Flow augmentation of the inlet of a HRSG is shown to be viable with minimal design alterations, providing additional heat in the manner of supplemental firing, without the use of additional fuel. The feasibility of fully replacing the inlet flow with a UHTS system has also been explored, outlining the requirement for flow stratification measured to make the retrofit route viable. The research also demonstrates that UHTS integration can provide an average monthly arbitrage profitability of up to £2,225,000, and carbon emission reductions of 33,900 tonnes.

The implementation of UHTS can significantly boost the viability of an increasingly renewable grid, by providing the ability to reliably dispatch stored renewable energy, thereby decreasing reliance on fossil fuels and curtailing industrial carbon emissions.

The results and conclusions presented in this thesis outlined a detailed investigation of UHTS technologies, encapsulating their operational, economic, and environmental benefits. The research offers valuable insights for design engineers, policymakers, and industrial investors. It outlines the benefits of further development and implementation of UHTS, based on its ability to drive an increase in the profitability of pre-existing systems, whilst aligning with decarbonisation goals.