RT info:eu-repo/semantics/doctoralThesis T1 Analysing and modelling the variability of renewable energy sources in the energy transition A1 Parrado Hernando, Gonzalo A2 Universidad de Valladolid. Escuela de Doctorado K1 Energías renovables K1 Renewable energy sources K1 Energías renovables K1 Power system K1 Sistemas eléctricos K1 Spain K1 España K1 IAM K1 MEI K1 5312.05 Energía AB The use of energy has played a fundamental role in social development since the beginning of humanity, allowing the expansion of its ecological niche through the utilization of the physical potentials available in nature. However, today we face the great challenge of reducing greenhouse gas emissions to mitigate climate change, which is the result of the massive use of fossil resources. The threat is enormous, the extinction of life forms and entire ecosystems that allow human beings to perpetuate themselves as a species. To mitigate this situation and sustain the level of social complexity achieved as civilization, part of the academia advocates for transitioning towards 100% renewable energy systems.Photovoltaic solar energy, onshore and offshore wind energy, and hydropower are the most mature technologies that support these decarbonization projections while electrifying the economy. However, an emerging discussion puts certain limits on their practicability and effectiveness through modelling and analysis. The stochastic and intermittent nature of renewable generation fluctuates the power output according to the instant resource available in the parks, variations that dramatically affect the traditional stability of the fossil-based electrical system. Despite the existence of numerous options to manage these fluctuations, there is not a single energy planning approach to meet the objectives.To assist in policy selection, Integrated Assessment Models (IAMs) have traditionally focused on global representations, resulting in limited temporal resolution that does not yield satisfactory results for energy analysis. These leave the responsibility to more technical models, specifically focused on renewable variability management. This problem is the main motivation of this doctoral thesis. Increasing the temporal resolution in IAMs has required experimentation in the fields of statistics, mathematics, and systems dynamics, among others.The results obtained in this thesis have revealed significant findings. First, emerging research lines have been identified from biophysics in the discussion on 100% renewable energy systems, recognizing technical, natural, and social barriers in a heterogeneous landscape where computational tools are still under intense development. Second, the statistical analysis on the case of Spain has identified differences in renewable generation and electricity consumption patterns, both on a seasonal and daily/hourly basis. Furthermore, future projections have shown the magnitude of storage and interstate transmission needs until 2050 derived from the massive "green" commitment, reaching maximum efficiency of the electrical system ideally by 2035, and dramatically declining from 2040 onwards. Third, a configuration of a 100% renewable energy system for Spain in 2050 is proposed based on official energy balances, detailing each policy applied by sector and energy type. This reveals the fundamental role that coupling technologies between the electrical and heat systems, the emerging hydrogen sector, and the profound transformation of transportation will play. These energy conversion technologies ("power-to-X" technologies) are explained throughout the document and gradually quantified in the conceptualized energy transition for the Spanish state. The fourth and final point refers to the two methods reproduced in IAMs to integrate renewable variability and its derived effects, accompanied by results and limitations to overcome.This thesis has been carried out as a compilation of articles. Three documents contribute to the discussion on a deep integration of variable renewable sources in IAMs, with Spain as the case study. YR 2024 FD 2024 LK https://uvadoc.uva.es/handle/10324/67155 UL https://uvadoc.uva.es/handle/10324/67155 LA eng NO Escuela de Doctorado DS UVaDOC RD 17-jul-2024