Public Defense of Doctoral Thesis of the ETSi

 

Date: Friday, July 7, 2023.

Time: 10:00 AM

Location: Professor Juan Larrañeta Room, Higher Technical School of Engineering of the University of Seville.

Doctoral candidate Andrés Carro Paulete will publicly defend his doctoral thesis entitled "Damage and failure mechanisms under fatigue in long fiber composites with ultra-thin plies," which has been supervised by Professors Ricardo Chacartegui Ramírez  of the Department of Energy Engineering at the Higher Technical School of Engineering of the University of Seville and Carlos Ortiz Domínguez of the Department of Engineering at Loyola University

We are currently in the midst of a global energy system transition, seeking to replace conventional energy sources (gas, oil, coal) with 100% renewable generation. Supported by the reduction of greenhouse gas emissions to mitigate the effects of climate change, the predominant use of renewables is emerging as a key factor in terms of market development, energy independence, and sustainability. Renewable resources have a stochastic and intermittent nature, which can negatively impact energy quality and grid stability. Energy storage, which allows us to overcome both the daily and seasonal lag between the availability of renewable resources and energy demand, is essential for improving the flexibility of energy systems based on 100% renewable generation. The development of new, highly efficient, low-cost, large-scale energy storage systems that utilize inexpensive materials with minimal environmental impact is necessary to fully utilize renewable resources.

This thesis addresses the study of different large-scale thermal energy storage technologies with the potential for impact at various temperature and development levels. Its objective is to contribute to the advancement of new, highly efficient, and environmentally friendly energy storage solutions that can be integrated into large power plants, facilitating the integration of renewable energy sources. The study covers the entire process, from the initial concept formulation to the development of the concept at the model level, with experimental support. The research focuses on three promising thermal energy storage technologies, categorized by temperature level. The contribution to the research is divided into three chapters, each dedicated to a specific temperature level.

The electrothermal energy storage system using transcritical carbon dioxide (CO2) cycles as a low-temperature thermal energy storage technology, within the broader field of thermal energy systems, is in an early stage of technological development. Techno-economic validation of the low-temperature energy storage system is being developed, and a novel study on its integration with geological CO2 storage is being incorporated. The CO2 captured at a power plant or industrial facility is used as the working fluid in the proposed thermodynamic cycle to store electrical energy from renewable sources in the form of thermal energy and CO2 in underground formations. This process takes advantage of the high pressures used in the transcritical CO2 cycle, achieving a round-trip efficiency of 40-50%, depending on operating conditions.

The thermochemical energy storage system based on calcium hydroxide as a medium-temperature thermal energy storage technology is currently in the laboratory stage of technological development. This thermochemical energy storage system is based on the reversible dehydration/hydration reaction of calcium hydroxide. A detailed techno-economic validation of the medium-temperature energy storage system is being developed. A novel aspect is the discussion of the system's technological challenges, highlighting the importance of recovering the latent heat of condensation from the steam generated in the dehydration reaction, which represents 38% of the solar thermal energy reaching the reactor. Extreme cases are analyzed, both those in which all the latent heat is recovered and those in which it is released to the environment. Different recovery mechanisms are proposed, such as an ammonia Rankine cycle or pressurized steam storage, while maintaining the independence of the loading and unloading phases.

The thermochemical energy storage system based on calcium looping, as a high-temperature thermal energy storage technology, is the most advanced among thermochemical systems in terms of technological readiness. The techno-economic analysis performed places the technology in a highly competitive position compared to other thermal storage systems, with a thermal-to-electrical conversion efficiency that can reach 48% and a levelized cost of electricity (LCOE) of around 100 MWh. A novel aspect of this work is the presentation of the design, development, and testing of an experimental campaign at a kW-scale pilot plant, the first of its kind for Calcium-Looping technology, in which the author played a leading role. This experimental campaign positions the technology at the demonstration stage of technological development in a relevant environment, carrying out the calcination and carbonation reactions in just a few seconds in an entrained flow reactor, under the temperature and pressure conditions of the Calcium-Looping storage system. This would allow for the integration of the storage system into large thermal power plants.

The thesis is structured as follows. The first chapter, dedicated to the introduction, presents the background and identified research opportunities, the objectives established in the thesis based on these opportunities, and defines the scope of the study. It also analyzes the state of the art, describes the methodology and research plan according to the established objectives, and presents the results derived from the thesis and the document's structure. Following the introduction, the contributions to the research are presented through the analysis of large-scale energy storage technologies for high, medium, and low temperatures. This section comprises chapters 2 (low-temperature storage based on transcritical CO2 cycles), 3 (medium-temperature storage using calcium hydroxide technology), and 4 (high-temperature storage using calcium looping technology). Finally, a chapter is dedicated to the discussion of the results, future work, and the research conclusions. The appendices contain the publications produced by the author during the development of this doctoral thesis.