Public Defense of Doctoral Thesis of the ETSi

 

Date: Friday, July 7, 2023.

Time: 10.00 am

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

The doctoral student 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 directed by professors Ricardo Chacartegui Ramírez  of the Department of Energy Engineering of the Higher Technical School of Engineering from the University of Seville and Carlos Ortiz Domínguez , from the Engineering Department of Loyola University

We are currently in a transition of the global energy system, which seeks to replace conventional production sources (gas, oil, coal) with 100% renewable generation. Supported by the reduction of greenhouse gas emissions with the aim of mitigating 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. The renewable resource has a stochastic and intermittent nature, which can negatively affect the quality of the energy and the stability of the electrical grid. Energy storage, which allows overcoming the daily and seasonal gap that exists between the availability of the renewable resource and the energy demand, is the necessary component to improve the flexibility of the energy system based on 100% renewable generation. The development of new large-scale, high-efficiency, low-cost energy storage systems that use cheap materials with low environmental impact is necessary to take advantage of the renewable resource.

This thesis addresses the study of different large-scale thermal energy storage technologies, with impact capacity, at different levels of temperature and development; with the aim of contributing to the degree of advancement of new high-efficiency energy storage solutions with a low environmental impact, which can be integrated into large power plants, facilitating the integration of renewables; from the phase of proposing the preliminary idea, to the development of the concept at the level of models, and with experimental support. The study focuses on three promising thermal energy storage technologies based on temperature level. The research contribution is divided into three chapters, each dedicated to each temperature level.

The electrothermal energy storage system using transcritical cycles of carbon dioxide (CO2) as a low-temperature thermal energy storage technology, within thermal energy systems, is in an initial stage in the technology development levels. . The techno-economic validation of the low-temperature energy storage system is developed, and as a novelty, a study on the novel integration with the geological storage of CO2 is incorporated. The CO2 captured in a power plant or industrial facility is used as a 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, taking advantage of the high pressures used in the transcritical cycle. of CO2, with a round trip efficiency in a range 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 in the laboratory phase at the technology development levels. It is a thermochemical energy storage system based on the reversible dehydration/hydration reaction of calcium hydroxide. A techno-economic validation of the medium temperature energy storage system is developed in detail. As a novelty, the technological challenges of the system are discussed, highlighting the importance of recovering the latent heat of condensation of the steam generated in the dehydration reaction, which represents 38% of the solar thermal energy that reaches the reactor. Extreme cases are analyzed in which all the latent heat is recovered and in which this heat is released to the environment, and different recovery mechanisms are proposed, such as an ammonia Rankine cycle or the storage of pressurized steam, while maintaining the independent nature of the loading and unloading phases.

The thermochemical energy storage system based on calcium looping as a high-temperature thermal energy storage technology corresponds to the most developed system among thermochemicals at the levels of technological preparation. The techno-economic analysis carried out places the technology in a very competitive position with respect to other thermal storage systems, with a thermal-to-electrical conversion efficiency that can reach 48% and a levelized cost of electricity around 100 MWhe. As a novelty, the design, development and testing of the experimental campaign of a kW-scale pilot plant is presented, the first of this level for Calcium-Looping technology, in which the author was the main actor. The experimental campaign places the technology in the demonstration technological development stage in a relevant environment, developing the calcination and carbonation reactions in a few seconds in an entrained flow reactor, under the temperature and pressure conditions of the storage system based on Calcium-Looping, which would allow the integration of the storage system in large thermal power plants.

The structure of the thesis is as follows. In the first chapter, dedicated to the introduction, the background and research opportunities detected are presented, the objectives established in the thesis based on the opportunities and the scope of the study is delimited, the state of the art is analyzed, and the the methodology and the research plan based on the established objectives, and the results derived from the thesis and the structure that the document follows are shown. After the introduction, the contributions to research are presented, through the analysis of large-scale energy storage technologies, for high, medium and low temperatures. It covers 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 conclusions of the research. Finally, the annexes contain the publications made by the author during the development of this doctoral thesis.