Novel method and instruments for the optimal techno-economic sizing of borehole heat exchangers

El test de respuesta térmica (TRT) es ampliamente utilizado como método estándar para caracterizar las propiedades térmicas del terreno adyacente a un intercambiador de calor enterrado (BHE). Los métodos tradicionales para interpretar los resultados aplican soluciones analíticas o numéricas asumiendo que el terreno es infinito, homogéneo e isotrópico. Sin embargo, en realidad el subsuelo presenta generalmente una estructura estratificada y heterogénea, y por lo tanto las propiedades térmicas pueden variar sustancialmente con la profundidad. En este sentido y con la intención de resolver las limitaciones del TRT estándar, la presente tesis doctoral se centra en el desarrollo de métodos e instrumentos para cuantificar las propiedades de transferencia de calor de las capas geológicas alrededor de un BHE. Información que resulta imprescindible para alcanzar la máxima eficiencia energética y el dimensionado técnico-económico óptimo de un BHE. En particular, se propone un nuevo método de TRT, llamado observer pipe TRT (OP-TRT), basado en una medición de temperatura adicional a lo largo de una tubería auxiliar. En las últimas décadas, varios investigadores han desarrollado TRT distribuidos (DTRT) en los cuales se realizan mediciones de temperatura a lo largo del tubo-U en el que se inyecta calor. No obstante, a partir de las investigaciones llevadas a cabo en esta tesis, el tubo observador ha demostrado amplificar los efectos térmicos producidos debido a capas geológicas con propiedades termo-físicas diferentes, requiriéndose así sensores menos precisos para obtener resultados más detallados. En base a este logro, se ha desarrollado un modelo numérico de simulación inversa para parametrizar la conductividad térmica de las capas geológicas a partir de las mediciones a lo largo del tubo observador. Básicamente, el modelo ajusta la conductividad térmica de las capas geológicas hasta que los resultados de la simulación coinciden con el perfil de temperatura experimental a lo largo del tubo observador. El modelo ha sido desarrollado con un algoritmo de estimación de parámetros para un ajuste automático y obtención de resultados más precisos. Otra ventaja es que este método solo requiere dos perfiles de temperatura: (1) subsuelo en reposo (antes del TRT) y (2) al final del TRT (antes de detener la inyección de calor). Con la intención de continuar investigando el método propuesto a partir de datos de mayor calidad, se ha desarrollado un instrumento específico (Geowire) para medir de forma automática y con mayor precisión los perfiles de profundidad-temperatura requeridos. El diseño del Geowire también ha sido orientado para cubrir otros requisitos, como compatibilidad con equipos de TRT y operación intuitiva. Además, se ha desarrollado una versión mejorada de una sonda de temperatura (Geoball) que es arrastrada por el fluido que circula en las tuberías a la vez que calcula su posición, con la ventaja de que puede ser utilizada en tuberías con disposición vertical y horizontal. Después de las pruebas de validación en el laboratorio, las características fundamentales de ambos instrumentos han sido evaluadas en comparación con otros instrumentos novedosos y estándar para mediciones de temperatura distribuidas durante un experimento en un BHE de pruebas. La ventaja principal de los instrumentos propuestos sobre la popular fibra óptica es que miden la temperatura instantáneamente (para intervalos temporales precisos). Asimismo, no necesitan de una calibración dinámica para obtener resultados precisos mientras que proporcionan una mayor resolución espacial y de temperatura: Geowire (0.5 mm, 0.06 K) y Geoball (10 mm, 0.05 K). Además, son más fáciles de integrar en pozos existentes y son una solución potencialmente más rentable para medir la temperatura distribuida. Finalmente, se demuestran los beneficios del método e instrumentos propuestos durante un DTRT en comparación con la fibra óptica y con un programa basado en el modelo de línea infinita para estimar la conductividad térmica distribuida. Los resultados del modelo propuesto revelaron una zona altamente conductiva al usar los datos del Geowire, mientras que esta zona no fue detectada al procesar los datos de fibra óptica.The thermal response test (TRT) is widely used as a standard test to characterize the thermal properties of the ground near a borehole heat exchanger (BHE). Typical methods to interpret the results apply analytical or numerical solutions which assume that the ground is infinite, homogeneous and isotropic. However, in reality the underground is commonly stratified and heterogeneous, and therefore thermal properties may significantly vary with depth. In this sense and with the intention to overcome standard TRT limitations, this Ph.D. study is focused on developing methods and instruments for the evaluation of the heat transfer behavior of the geological layers surrounding a BHE. This information is key for the optimal energy efficiency and techno-economic sizing of BHE. In particular, a novel TRT method, called observer pipe TRT (OP-TRT), is proposed based on an additional temperature measurement along an auxiliary pipe. In the last decades, some researchers developed the so-called distributed TRT (DTRT) by measuring the temperature along the length of the heated U-pipe. However, from the studies carried out in this Ph.D. work, the observer pipe demonstrated to amplify the thermal effects produced due to geological layers with different thermo-physical properties, hence requiring less accurate sensors for obtaining more detailed results. Based on this achievement, an inverse numerical solution was developed to parametrize thermal conductivity of geological layers from the measurements along the observer pipe. Basically, the model adjusts thermal conductivity of the geological layers until simulation results fit experimental temperature profile along the observer pipe. The model was developed with a parameter estimation solver for an automatic fitting and more accurate results. Another advantage is that this method only requires two temperature profiles: (1) undisturbed ground (before the TRT) and (2) at the end of the TRT (before stopping the heat injection). In order to further investigate the proposed method by using higher quality data, a specific instrument (Geowire) was developed to automatically measure the required depth-temperature profiles with high accuracy. The design of the Geowire also coveredother features, such as compatibility with TRT equipment and intuitive operation. In addition, an enhanced version of a flowing probe (Geoball) was developed, suitable for both vertical and horizontal pipe arrangements. After laboratory validation tests, the key features of both instruments were evaluated in comparison with new and standard in-borehole instruments for temperature measurements in a test BHE. The main advantage of the proposed instruments over the widespread fiber optics is that they measure the temperature instantaneously (for precise time instants). Moreover, they do not require a dynamic calibration for accurate results while providing higher spatial and temperature resolutions: Geowire (0.5 mm, 0.06 K) and Geoball (10 mm, 0.05 K). Also, they are easier to integrate in existing boreholes and are a potentially more cost-effective solution to measure the distribute temperature. Finally, the benefits of the proposed method and instruments are demonstrated throughout a DTRT in comparison with fiber optics and with a computer program based on the infinite line source model to estimate the distributed thermal conductivity. The results from the proposed model revealed a highly conductive zone when using data from the Geowire, whereas this was not the case when data from fiber optics were processed

Design of Digital Advanced Systems Based on Programmable System on Chip

This chapter fills up an advanced analysis of the state-of-the-art design in programmable SoC systems, giving a critical overall vision for every designer to implement real time operating systems and concurrent processing. The content of the chapter is divided in the next four main sections. First the evolution timeline of FPGA based systems is covered from its beginning until the last AP SoC chips. They are complex devices and it is necessary to have a well-known understanding to utilise them in the more efficient form possible. The more important advance digital systems structures and architectures are described. The embedded AP SoCs are analysed and main design methodologies are covered, focusing in hardware and co-design strategies. In this section is described the development of a real open source application that covers the fundamental parts in the design of a SoC system, ranging from the hardware development until the software design involving the embedded operating system and the user interface application. Finally, the system described in the last section is tested in a real scientific experiment and the results are evaluated

Extraction of thermal characteristics of surrounding geological layers of a geothermal heat exchanger by 3D numerical simulations

Ground thermal conductivity and borehole thermal resistance are key parameters for the design of closed Ground-Source Heat Pump (GSHP) systems. The standard method to determine these parameters is the Thermal Response Test (TRT). This test analyses the ground thermal response to a constant heat power injection or extraction by measuring inlet and outlet temperatures of the fluid at the top of the borehole heat exchanger. These data are commonly evaluated by models considering the ground being homogeneous and isotropic. This approach estimates an effective ground thermal conductivity representing an average of the thermal conductivity of the different layers crossed by perforation. In order to obtain a thermal conductivity profile of the ground as a function of depth, two additional inputs are needed; first, a measurement of the borehole temperature profile and, second, an analysis procedure taking into account ground is not homogeneous. This work presents an analysis procedure, complementing the standard TRT analysis, estimating the thermal conductivity profile from a temperature profile along the borehole during the test. The analysis procedure is implemented by a 3D Finite Element Model (FEM) in which depth depending thermal conductivity of the subsoil is estimated by fitting simulation results with experimental data. The methodology is evaluated by the recorded temperature profiles throughout a TRT in a BHE (Borehole Heat Exchanger) monitored facility, which allowed the detection of a highly conductive layer at 25 meters depth. © 2015 Elsevier Ltd. All rights reserved.This work has been supported by the EIT Climate-KIC, a body of the European Union inside the PhD Programme of TBE Platform.Aranzabal, N.; Martos, J.; Montero Reguera, ÁE.; Monreal Mengual, L.; Soret, J.; Torres, J.; García Olcina, R. (2016). Extraction of thermal characteristics of surrounding geological layers of a geothermal heat exchanger by 3D numerical simulations. Applied Thermal Engineering. 99:92-102. doi:10.1016/j.applthermaleng.2015.12.109921029

ATLAS LAr Calorimeter Commissioning for LHC Run-3

Liquid argon (LAr) sampling calorimeters are employed by ATLAS experiment at the Large Hadron Collider (LHC) for all electromagnetic calorimetry in the pseudo-rapidity region $\left|\eta\right|$ < 3.2, and for hadronic and forward calorimetry in the region from $\left|\eta\right|$ = 1.5 to $\left|\eta\right|$ = 4.9. After detector consolidation during a long shutdown, the LHC Run-2 started in 2015 and about 150 fb-1 of data at a center-of-mass energy of 13 TeV was recorded. With the end of Run-2 in 2019, a long period of shutdown began for the Phase-I detector upgrades. As part of the Phase-I upgrade, new trigger readout electronics of the ATLAS LAr calorimeter have been developed. Installation began at the start of the LHC shutdown in 2019 and is now completed, while a commissioning campaign is still underway to fully validate and improve stability of the new, higher granularity and precision Level-1 trigger system. This contribution gives an overview of the new trigger readout installation and commissioning, as well as the preparations for Run-3 detector operation and changes in the monitoring and data quality procedures to cope with the increased luminosity and pile-up

ATLAS Liquid Argon Calorimeter Commissioning for LHC Run-3

Liquid argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region |η| < 3.2, and for hadronic and forward calorimetry in the region from |η| = 1.5 to |η| = 4.9. In the first LHC run a total luminosity of 27 fb−1 has been collected at center-of-mass energies of 7-8 TeV. After detector consolidation during a long shutdown, Run-2 started in 2015 and about 150fb-1 of data at a center-of-mass energy of 13 TeV was recorded. With the end of Run-2 in 2018 a multi-year shutdown for the Phase-I detector upgrades was begun. As part of the Phase-I upgrade, new trigger readout electronics of the ATLAS Liquid-Argon Calorimeter have been developed. Installation began at the start of the LHC shut down in 2019 and is expected to be completed in 2020. A commissioning campaign is underway in order to realize the capabilities of the new, higher granularity and higher precision level-1 trigger hardware in Run-3 data taking, as well as the recommissioning of the main readout and the legacy analog level-1 trigger electronics which had to be dismounted for the installation of the new components. This contribution will give an overview of the new trigger readout commissioning, as well as the preparations for Run-3 detector operation and changes in the monitoring and data quality procedures to cope with the increased pileup

ATLAS LAr Calorimeter Commissioning for LHC Run-3

Liquid argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region |η| < 3.2, and for hadronic and forward calorimetry in the region from |η| = 1.5 to |η| = 4.9. In the first Large Hadron Collider (LHC) run a total luminosity of 27 fb−1 was collected at center-of-mass energies of 7-8 TeV. After detector consolidation during a long shutdown, Run-2 started in 2015 and about 150 fb-1 of data at a center-of-mass energy of 13 TeV was recorded. With the end of Run-2 in 2019, a long period of shutdown began for the Phase-I detector upgrades. As part of the Phase-I upgrade, new trigger readout electronics of the ATLAS LAr calorimeter have been developed. Installation began at the start of the LHC shutdown in 2019 and is now completed, while a commissioning campaign is still underway to fully validate and improve stability of the new, higher granularity and precision Level-1 trigger system. This contribution gives an overview of the new trigger readout installation and commissioning, as well as the preparations for Run-3 detector operation and changes in the monitoring and data quality procedures to cope with the increased luminosity and pile-up

ATLAS LAr Calorimeter Commissioning for LHC Run-3

The Liquid Argon Calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region |η| < 3.2, and for hadronic and forward calorimetry in the region from |η| = 1.5 to |η| = 4.9. It also provides inputs to the first level of the ATLAS trigger. After successful period of data taking during the LHC Run-2 between 2015 and 2018 the ATLAS detector entered into the a long period of shutdown. In 2022 the LHC should restart and the Run-3 period should see an increase of luminosity and pile-up up to 80 interaction per bunch crossing. To cope with this harsher conditions, a new trigger readout path have been installed on the during the long shutdown. This new path should improve significantly the triggering performances on electromagnetic objects. This will be achieved by increasing by a factor of ten, the number of available units of readout at the trigger level. The installation of this new trigger readout chain required the update of the legacy system to cope with the new components. It is more than 1500 boards of the precision readout that have been extracted from the ATLAS pit, refurbished and re-installed. The legacy analogic trigger readout that will remain during the LHC Run-3 as a backup of the new digital trigger system has also been updated. For the new system it is 124 new on-detector boards that have been added. Those boards are able to digitize the calorimeter signal for every collisions i.e. at 40 MHz and in radiative environment. The digital signal is then processed online to provide the measured energy value for each unit of readout an for each bunch crossing. In total this is up to 31 Tbps that are analyzed by the processing system and more than 62 Tbps that are generated for downstream reconstruction. To minimize the triggering latency the processing system had to be installed underground. There the limited space available imposed the needs of a very compact hardware structure. To achieve a good enough compacity larges FPGAs with high throughput have been mounted on ATCA mezzanines cards. In total, 3 ATCA shelves are used to process the signal of approximately 40 k channels. Given that modern technologies have been used compared to the previous system, all the monitoring and control infrastructure had to be adapted and commissioned as well. This contribution presents the challenges of such installation, what have been achieved so far and what are the milestones still to be done toward the full operation of both the legacy and the new readout paths for the LHC Run-3