http://hdl.handle.net/10174/995 2026-04-04T10:49:44Z http://hdl.handle.net/10174/39957 Title: NONCONVENTIONAL METHODS USED TO STUDY EARTH'S THERMAL PROPERTIES INCLUDING GEOTHERMAL HEAT FLOW Authors: Duque, Maria Rosa Abstract: Nonconventional methods have been used to obtain geothermal density data in regions without adequate holes need to make measurements or where detailed distribution values of this parameter are required. The method used in the present work uses data obtained from seismic tomography, velocity distribution of P waves and VP/VS ratio values, to define “warm” and “cold” regions in the crust.The distribution and intensity of radioactive heat sources near the surface is obtained using radiometric data from rocks. The heat flow at the surface of the Earth is obtained by addition of the heat generated by the sources studied with the heat flowing from deeper regions. With the method presented it is possible to obtain detailed maps of geothermal heat flow density at the Earth’s surface. It is also possible to obtain the depth location of “warm” layers with fluids that can be used in several applications. Physical properties including radioactivity, thermal conductivity and heat expansion coefficient may be used to explain some earthquakes located near the contact zone of different geological materials. 2025-01-01T00:00:00Z http://hdl.handle.net/10174/39892 Title: Geothermal Heat Flow by Conduction in Mainland Portugal Authors: Duque, Maria Rosa Abstract: Heat flow density measurements in Portugal were made in boreholes used for mining prospecting. Heat flow density values in the sedimentary basins of the western and southern margins of the country were obtained using data from oil or gas prospecting works. Due to the scarcity of data in the central and northern regions of the country, numerical models based on some characteristics of the region were used to obtain more heat flow values. The total of heat flow values used in this work is 69, with 17 values obtained using numerical models, 36 obtained in boreholes and 16 obtained from oil/gas prospecting wells data. The analysis and location of these data allows to define different regions in the territory and characterize them using average values of heat flow density, temperature gradient and thermal conductivity. Statistical values with all the data in the territory are also presented. 2024-01-01T00:00:00Z http://hdl.handle.net/10174/38899 Title: Thermal performance of a hybrid steel-concrete tank section for thermal energy storage in concentrated solar power plants Authors: Guerreiro, Luis; Lucio, Tamara; Alonso, Maria; Villardón, Rafael; Lopez, Javier; Martin, Mariano Editors: F. Cabeza, Luisa Abstract: Several studies of thermocline molten salt tanks have proven to be suitable for thermal energy storage systems. However, there is a lack of experimental investigations performed. The building of a hybrid section and its assessment operating as a thermocline tank are the main objectives of this research work. The novelty is to prove the performance of the hybrid tank concept made of a thick concrete layer and a thin steel liner. The tank section studied comprises the following layers of materials: a steel liner, an air gap interface, a high thermal concrete layer and insulating materials. The thermal response was monitored using thermocouples located between the layers, at different heights and widths of the whole tank section length. The performance during the commissioning (first heat) and the operation (3 heat/cool cycles between 200/500 °C) of the tank section is analysed. The thermal appropriateness of using concrete as part of the thermocline tank has demonstrated the suitability and good thermal response up to 425 °C showing isolating and thermal inertia. The presence of the air gap interface between the steel liner and the concrete generates a heat convection current with local energy gradients along the section height. 2023-03-31T23:00:00Z http://hdl.handle.net/10174/38898 Title: Design and optical optimization of a 45 kW beam-down solar-thermal concentrator Authors: Guerreiro, Luis; Nadal, Ramon; Cardona, Gabriel Editors: González-Gómez, David Abstract: Concentrated Solar Power (CSP) technologies offer significant potential as renewable energy sources, particularly when integrated with storage systems. To address the challenges of energy transport and re-radiation losses, beam-down configurations combined with paraboloid-type dish concentrators provide a compact and efficient solution. In this study, we perform an optical analysis of a Cassegrain concentrator using the open-source software OTSunWebApp, a ray-tracing program that allows for the spectral optical analysis of solar collectors. The analysis accounts for specular scattering of the reflectors, the spectral behavior of the materials, and the angular size of the sun. The geometric design is parametrized with six degrees of freedom, while some other parameters, such as the number of mirrors and the aperture area, have been previously chosen. The resulting aperture area is 67.52 m2. We optimize the optical efficiency for operation at 600 C∘, identifying the key parameters that influence performance. The system achieves a power output greater than 45 kW under direct radiation of 900 W/m2. Additionally, maintaining optical efficiency above 74% requires a tracking error below 0.2∘, with peak radiation values at the receiver reaching 26 kW/m2. These results underscore the potential of Cassegrain concentrator designs to advance CSP technology, suggesting that they could significantly enhance this field. 2024-10-30T00:00:00Z