Person: Casi Satrústegui, Álvaro
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Casi Satrústegui
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Álvaro
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Ingeniería
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ISC. Institute of Smart Cities
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0000-0001-5459-7613
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811627
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Publication Open Access Impact of a thermoelectric subcooler heat exchanger on a carbon dioxide transcritical refrigeration facility(Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Alegría Cía, Patricia; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako UnibertsitaTo improve the performance of vapour compression refrigeration cycles, the inclusion of a thermoelectric subcooler for low-medium power units has been the focus of recent studies due to its robustness, compactness and simplicity of operation. In thermoelectric systems, it has been demonstrated that the heat exchangers used in the hot and cold side of the thermoelectric modules have a critical impact in the performance of the system. This influence has not yet been studied for thermoelectric subcooling systems in vapour compression cycles. This work, for the first time, evaluates the impact that the heat exchangers of a thermoelectric subcooler, included in a transcritical carbon dioxide refrigeration cycle, have, in the performance of the refrigeration cycle. The influence is quantified in terms of: optimum working conditions, coefficient of performance and cooling capacity. The results show that, through an optimization of the heat exchangers of the thermoelectric subcooler, the performance improvements on the coefficient of performance using this technology are boosted from 11.96 to 14.75 % and the upgrade in the cooling capacity of the system rises from 21.4 to 26.3 %. Moreover, the optimum gas-cooler working pressure of the system is reduced and the optimum voltage supplied to the thermoelectric modules increases.Publication Open Access The promising combination of thermoelectric generators with IoT technologies for autonomous monitoring systems(2019) Garacochea Sáenz, Amaia; Catalán Ros, Leyre; Casi Satrústegui, Álvaro; Gubía Villabona, Eugenio; Astrain Ulibarrena, David; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería; Ingeniería Eléctrica, Electrónica y de ComunicaciónMonitoring stations becomes essential in any volcanic system in the world but, because of their remote location, both the electricity supply and the communications represent a technological challenge. The present work studies the feasibility of an autonomous volcanic monitoring system powered by thermoelectric generators for one of the monitoring stations of the Teide National Park (Canary Island), where temperatures of 80°C at few centimeters from the surface are found. The stable generation and robustness of thermoelectricity in combination with a new communication system based on LoRa (a low power wireless technology) make this solution a good alternative.Publication Open Access Producción de energía eléctrica mediante efecto Seebeck gracias al aprovechamiento de calor residual en una industria productora de lana de roca(2019) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola TeknikoaEn la actualidad, más de la mitad de la energía consumida es disipada en forma de energía calorífica con el ambiente. Esta energía, que se denomina calor residual, presenta un alto potencial de aprovechamiento. Los generadores termoeléctricos son capaces de transformar esta energía calorífica en electricidad. Dichos generadores están formados por dos elementos principales: módulos termoeléctricos, donde se genera la electricidad basándose en efecto Seebeck e intercambiadores de calor, los cuales condicionan el funcionamiento del generador termoeléctrico y por tanto la electricidad producida. El objetivo de este proyecto consiste en la instalación de generadores te rmoeléctricos para el aprovechamiento del calor residual en una industria productora de lana de roca, en la cual, debido a su proceso productivo, se obtienen humos de desecho a altas temperaturas. Para alcanzar este objetivo es necesario realizar un proceso previo de diseño de los intercambiadores de calor, la construcción y experimentación de prototipos de generación en las instalaciones de la Universidad Pública de Navarra y la puesta a punto de dichos prototipos.Publication Open Access Experimental evaluation of a transcritical CO2 refrigeration facility working with an internal heat exchanger and a thermoelectric subcooler: performance assessment and comparative(Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThe use of carbon dioxide in transcritical state has become one of the most used solutions to comply with the F-Gas directive and reduce greenhouse gases emissions from refrigeration systems at high ambient temperatures. For low-medium power units, the commonly used solutions to improve the efficiency such as the ejector, multiple compressor arrangements, mechanical subcooler, etc., add complexity and increase the cost of the refrigeration facility, which is not ideal for small units. In this low-medium power range, two technologies stand out to increase the performance of a carbon dioxide transcritical cycle: the internal heat exchanger and the thermoelectric subcooler. This study brings a complete research in which both solutions have been tested in the same experimental transcritical carbon dioxide refrigeration facility under the same working conditions. It focuses on the real performance of both systems and discusses the strengths and weaknesses of using an internal heat exchanger or a thermoelectric subcooler. The results show that the thermoelectric subcooler outperforms the internal heat exchanger in both the coefficient of performance and the cooling capacity while also being a more controllable and flexible solution.Publication Open Access Experimental evidence of the viability of thermoelectric generators to power volcanic monitoring stations(MDPI, 2020) Catalán Ros, Leyre; Garacochea Sáenz, Amaia; Casi Satrústegui, Álvaro; Araiz Vega, Miguel; Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; IngenieríaAlthough there is an important lack of commercial thermoelectric applications mainly due to their low efficiency, there exist some cases in which thermoelectric generators are the best option thanks to their well-known advantages, such as reliability, lack of maintenance and scalability. In this sense, the present paper develops a novel thermoelectric application in order to supply power to volcanic monitoring stations, making them completely autonomous. These stations become indispensable in any volcano since they are able to predict eruptions. Nevertheless, they present energy supply difficulties due to the absence of power grid, the remote access, and the climatology. As a solution, this work has designed a new integral system composed of thermoelectric generators with high efficiency heat exchangers, and its associated electronics, developed thanks to Internet of Things (IoT) technologies. Thus, the heat emitted from volcanic fumaroles is transformed directly into electricity with thermoelectric generators with passive heat exchangers based on phase change, leading to a continuous generation without moving parts that powers different sensors, the information of which is emitted via LoRa. The viability of the solution has been demonstrated both at the laboratory and at a real volcano, Teide (Canary Islands, Spain), where a compact prototype has been installed in an 82 C fumarole. The results obtained during more than eight months of operation prove the robustness and durability of the developed generator, which has been in operation without maintenance and under several kinds of meteorological conditions, leading to an average generation of 0.49W and a continuous emission over more than 14 km.Publication Open Access Computer simulations of silicide-tetrahedrite thermoelectric generators(MDPI, 2022) Coelho, Rodrigo; Casi Satrústegui, Álvaro; Araiz Vega, Miguel; Astrain Ulibarrena, David; Branco Lopes, Elsa; Brito, Francisco P.; Gonçalves, Antonio P.; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISCWith global warming and rising energy demands, it is important now than ever to transit to renewable energy systems. Thermoelectric (TE) devices can present a feasible alternative to generate clean energy from waste heat. However, to become attractive for large-scale applications, such devices must be cheap, efficient, and based on ecofriendly materials. In this study, the potential of novel silicide-tetrahedrite modules for energy generation was examined. Computer simulations based on the finite element method (FEM) and implicit finite difference method (IFDM) were performed. The developed computational models were validated against data measured on a customized system working with commercial TE devices. The models were capable of predicting the TEGs’ behavior with low deviations (≤10%). IFDM was used to study the power produced by the silicide-tetrahedrite TEGs for different ∆T between the sinks, whereas FEM was used to study the temperature distributions across the testing system in detail. To complement these results, the influence of the electrical and thermal contact resistances was evaluated. High thermal resistances were found to affect the devices ∆T up to ~15%, whereas high electrical contact resistances reduced the power output of the silicide-tetrahedrite TEGs by more than ~85%.Publication Open Access Performance assessment of an experimental CO2 transcritical refrigeration plant working with a thermoelectric subcooler in combination with an internal heat exchanger(Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaRegulations in the refrigeration sector are forcing the transition to low global warming potential fluids such as carbon dioxide in order to decrease direct greenhouse gases emissions. Several technologies have arisen over the past years to compensate the low performance of the transcritical carbon dioxide vapour compression cycle at high ambient temperatures. For low-medium power units, the inclusion of a thermoelectric subcooler or an internal heat exchanger have been proven as effective solutions for enhancing the coefficient of performance. However, the combination of a thermoelectric subcooler and an internal heat exchanger working simultaneously is yet to be explored theoretically or experimentally. This work presents, for the first time, an experimental transcritical carbon dioxide refrigeration facility that works simultaneously with a thermoelectric subcooler and with an internal heat exchanger in order to boost the cooling capacity and coefficient of performance of the refrigeration system. The experimental tests report improvements at optimum working conditions of 22.4 % in the coefficient of performance and an enhancement in the cooling capacity of 22.5 %. The 22.4 % increase in coefficient of performance would result in a decrease of energy consumption along a reduction of the greenhouse gases emissions. The proposed combination of a thermoelectric subcooler and an internal heat exchanger outperforms each of the technologies on their own and presents itself as a great controllable solution to boost the performance and reduce the greenhouse gasses emissions of transcritical carbon dioxide refrigeration cycles.Publication Open Access Thermoelectric heat recovery in a real industry: from laboratory optimization to reality(Elsevier, 2021) Casi Satrústegui, Álvaro; Araiz Vega, Miguel; Catalán Ros, Leyre; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako Gobernua, 0011-1365-2018-000101Thermoelectricity, in the form of thermoelectric generators, holds a great potential in waste heat recovery, this potential has been studied and proved in several laboratory and theoretical works. By the means of a thermoelectric generator, part of the energy that normally is wasted in a manufacturing process, can be transformed into electricity, however, implementing this technology in real industries still remains a challenge and on-site tests need to be performed in order to prove the real capabilities of this technology. In this work, a computational model to simulate the behaviour of a thermoelectric generator that harvest waste heat from hot fumes is developed. Using the computational model an optimal configuration for a thermoelectric generator is obtained, also an experimental study of the performance of different heat pipes working as cold side heat exchangers is carried out in order to optimize the performance of the whole thermoelectric generator, thermal resistances of under 0,25 K/W are obtained. The optimized configuration of the thermoelectric generator has been built, installed and tested under real conditions at a rockwool manufacturing plant and experimental data has been obtained during the 30 days field test period. Results show that 4.6 W of average electrical power are produced during the testing period with an efficiency of 2.38%. Moreover, the computational model is validated using this experimental data. Furthermore, the full harvesting potential of an optimized designed that takes advantage of the whole pipe is calculated using the validated computational model, resulting in 30.8 MWh of energy harvested during a sample year which could meet the demand of 8.34 Spanish average households.Publication Open Access Thermoelectrics working in favour of the natural heat flow to actively control the heat dissipation(Elsevier, 2024) Alzuguren Larraza, Iñaki; Aranguren Garacochea, Patricia; Casi Satrústegui, Álvaro; Erro Iturralde, Irantzu; Rodríguez García, Antonio; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaIn sectors such as electronics, photonics and HVAC and refrigeration, heat dissipation has a major impact in their performance. However, there is generally not much control over this effect. Thus, one way of making these units more controllable would be to include thermoelectric technology in the heat dissipation systems. Therefore, in this work, a computational model based on the resistance-capacitance model to solve a thermoelectrically aided heat dissipation system is proposed, considering all the thermoelectric effects, temperature dependent thermoelectric properties and four temperature levels. Besides, an experimental prototype has been built to assess the real performance of thermoelectric modules (TEM) working under different operating conditions. Additionally, these results have been used to validate the computational model, obtaining maximum errors of ±6% in the main parameters. Moreover, the computational model has been used to simulate the effect of modifying the temperature difference between the hot and cold sources and the thermal resistances of the heatsinks located on both sides of the TEMs. The results show that the thermoelectrically aided dissipation system would be beneficial when working with low temperature differences and low thermal resistance values of the heatsinks, especially on the heatsink located on the hot side of the TEMs.Publication Embargo Improvements on the effiency of an autonomous commercial refrigeration system that uses low GWP fluids by the development of a thermoelectric subcooling system(2022) Casi Satrústegui, Álvaro; Astrain Ulibarrena, David; Araiz Vega, Miguel; Ingeniería; IngeniaritzaLa producción de frío de manera artificial es considerada una de las contribuciones más relevantes de la historia, jugando un papel clave en el desarrollo de la sociedad humana, gracias a su contribución en la conservación de productos perecederos y como herramienta para conseguir confort térmico tanto en edificios como vehículos. Debido a su importancia, el sector de la refrigeración cuenta con un gran volumen y se encuentra ampliamente extendido tanto en el ámbito industrial como doméstico. Como consecuencia de su gran volumen, el sector viene ligado de un considerable impacto sobre el medioambiente debido al consumo eléctrico de las instalaciones y a los refrigerantes utilizados. Además, la demanda de refrigeración se espera que siga creciendo durante las próximas décadas y las estimaciones más recientes predicen que llegará a duplicarse para el año 2050. Estos hechos, junto con la actual problemática medioambiental, ponen de manifiesto la importancia de disminuir el impacto medioambiental del sector de la refrigeración. El impacto medioambiental de los equipos frigoríficos se debe a la emisión de gases de efecto invernadero a la atmósfera los cuales contribuyen al calentamiento global del planeta. Estas emisiones se deben por un lado al consumo eléctrico del sistema de refrigeración y por otro lado a la fuga de refrigerantes con alto potencial de calentamiento atmosférico de las instalaciones. Con el objetivo de reducir las emisiones de los equipos frigoríficos existen dos principales vías de acción: el uso de refrigerantes naturales con bajo poder de calentamiento atmosférico, como el dióxido de carbono, y el desarrollo de equipos más eficientes para disminuir el consumo eléctrico de los sistemas de refrigeración. Esta tesis doctoral combina ambas líneas de acción centrándose en el desarrollo de un sistema de subenfriamiento termoeléctrico para la mejora de la eficiencia de un ciclo de refrigeración por compresión de vapor que utiliza dióxido de carbono en estado transcrítico como refrigerante. Esta combinación de tecnologías se presenta como una solución novedosa y prometedora para la reducción de las emisiones de los equipos frigoríficos y es posible gracias a la robustez, escalabilidad,controlabilidad y versatilidad que ofrecen los sistemas termoeléctricos. Para ello, en primer lugar se ha desarrollado un modelo computacional capaz de simular el comportamiento de un ciclo de compresión de vapor de dióxido de carbono en estado transcrítico junto con un sistema de subenfriamiento termoeléctrico. El modelo computacional desarrollado ha sido validado de manera experimental y los resultados muestran que es capaz de predecir el comportamiento real del sistema con desviaciones dentro del +/-7% de error. Una vez desarrollado y validado el modelo computacional, este ha sido utilizado para el estudio y diseño del sistema de subenfriamiento termoeléctrico con el objetivo de optimizar el funcionamiento del sistema global de refrigeración. En el estudio se ha realizado una caracterización térmica de los intercambiadores de calor utilizados en el subenfriador termoeléctrico y mediante la utilización del modelo computacional se ha cuantificado el impacto de los interacambiadores de calor en el sistema global de refrigeración. Los resultados obtenidos muestran que mediante la utilización de intercambiadores optimizados, el aumento en potencia frigorífica con el sistema de subenfriamiento termoeléctrico se incrementa desde un 21.4% a un 26.3%. Asimismo, la mejora obtenida en el coeciente de operación pasa de un 11.96% a un 14.75%. Los resultados obtenidos demuestran el gran impacto que los intercambiadores de calor del subenfriador termoeléctrico tienen en el funcionamiento global del sistema de refrigeración. Gracias a la información obtenida mediante el modelo computacional, se ha sido diseñado, construido e incorporado un sistema de subenfriamiento termoeléctrico en una instalación experimental de compresión de vapor que utiliza dióxido de carbono en estado transcrítico como refrigerante. La planta experimental ha sido ensayada bajo diferentes condiciones climáticas y de operación para comprobar de manera experimental el efecto del subenfriador termoeléctrico en el funcionamiento global del sistema. Además, los resultados obtenidos mediante la incorporación del subenfriador termoeléctrico han sido comparados con la utilización de un intercambiador recalentador subenfriador, una tecnología comúnmente utilizada para mejorar la eficiencia de ciclos de refrigeración por compresión de vapor. Los resultados obtenidos muestran como las mejoras obtenidas mediante el subenfriador termoeléctrico superan las obtenidas mediante el intercambiador recalentador subenfriador tanto en coeficiente de operación como en potencia frigorífica. La inclusión del sistema de subenfriamiento termoeléctrico resulta en un aumento de potencia frigorífica de hasta un 20.8% y una mejora del coeficiente de operación del sistema de hasta el 16.2%. Por último, debido a la versatilidad y controlabilidad del subenfriador termoeléctrico, esta tecnología se ha combinado junto con el intercambiador recalentador subenfriador, con el objetivo de comprobar el funcionamiento del ciclo de compresión de vapor trabajando con ambas tecnologías simultáneamente. La incorporación de un subenfriador termoeléctrico junto con el intercambiador recalentador subenfriador resulta en un aumento de la potencia frigorífica de un 22.5% y en un incremento del coeficiente de operación del 22.4%. Estos resultados muestran que mediante la combinación de estas dos tecnologías se obtienen mejoras superiores a las obtenidas a través de cada una de ellas de manera independiente. Los resultados de esta tesis demuestran que la utilización de un sistema de subenfriamiento termoeléctrico es una solución tecnológicamente viable para la mejora de la eficiencia de sistemas de refrigeración por compresión de vapor con dióxido de carbono en estado transcrítico, disminuyendo así, las emisión de gases de efecto invernadero de los sistemas de refrigeración y contribuyendo a la producción de frio de manera sostenible y respetuosa con el medio ambiente.