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 Teknikoa
En 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.
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 Comunicación
Monitoring 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.
Open Access
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; Ingeniaritza
La 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.
Open Access
Experimental assessment of a thermoelectric subcooler included in a transcritical CO2 refrigeration plant
(Elsevier, 2021-05-25) Aranguren Garacochea, Patricia; Sánchez, Daniel; Casi Satrústegui, Álvaro; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This study brings an experimental research that has tested a real transcritical CO2 vapor compression cycle that includes a thermoelectric subcooler at the exit of the gas-cooler of the refrigeration plant. The aforementioned technology hybridization increases the COP of refrigeration systems as long as the subcooling system is properly designed and operated. The experimental facility studied has been tested under constant ambient conditions (30 °C and relative humidity of 55%) and maintaining the evaporating temperature at -10 °C; while the voltage supplied to the thermoelectric modules and the thermal resistances of the heat exchangers located at the thermoelectric subcooler have been experimentally modified. The voltage supplied to the fans located at these heat exchangers was modified implying thermal performance deviation of the heat exchangers and a variation on the power consumption of the cooling facility. The results show an experimental increase on the COP of 11.3% while the cooling capacity increases a 15.3% when the thermoelectric modules are supplied with 2 V and the fans with 9 V. Moreover, the importance of optimizing the voltage supplied to the thermoelectric modules and to the auxiliary consumption of the thermoelectric subcooler is addressed along this research.
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 Publikoa
In 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.
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 Publikoa
The 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.
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; Ingeniería
Although 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.
Open Access
Thermoelectric generator for high temperature geothermal anomalies: experimental development and field operation
(Elsevier, 2023) Alegría Cía, Patricia; Catalán Ros, Leyre; Araiz Vega, Miguel; Casi Satrústegui, Álvaro; Astrain Ulibarrena, David; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In the current climate and energy context, it is important to develop technologies that permit increase the use of renewable sources such as geothermal energy. Enhancing the use of this renewable source is particularly important in some places, due to its availability and the enormous dependence on fossil fuels, as is the case of the Canary Islands. This work proposes the use of thermoelectric generators with heat exchangers working by phase change to transform the heat from the shallow high temperature geothermal anomalies on the island of Lanzarote directly into electricity, since the use of conventional geothermal power plants would not be possible because they would damage the protected environment. To bring this proposal to reality, this work has succeeded in developing and field-installing a geothermal thermoelectric generator that operates without moving parts thanks to its phase-change heat exchangers. This robust generator do not require maintenance nor auxiliary consumption, and produces a minimal environmental impact, it is noiseless, and the use of water as working fluid makes it completely harmless. The developed device consists of a thermosyphon as hot side heat exchanger, thermoelectric modules and cold side heat exchangers also based in phase change. Tests were carried out in the laboratory at various heat source temperatures and varying the number of thermoelectric modules. It was determined that installing more modules decreases the efficiency per module (from 4.83% with 4 modules to 4.59% with 8 modules at a temperature difference between sources of 235 °C), but for the number of modules tested the total power increases, so the field installation was carried out with 8 modules. After the good results in the laboratory, it was satisfactorily installed at Timanfaya National Park (Lanzarote, Spain) in a borehole with gases at 465 °C. This generator presents a maximum output power of 36 W (4.5 W per module), and is generating 286.94 kWh per year, demonstrating the great potential of the developed thermoelectric generators to build a larger-scale renewable installation.
Open Access
Prospects of waste-heat recovery from a real industry using thermoelectric generators: economic and power output analysis
(Elsevier, 2020) Araiz Vega, Miguel; Casi Satrústegui, Álvaro; Catalán Ros, Leyre; Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako Gobernua, 0011-1365-2018-000101
One of the options to reduce industrial energy costs and the environmental impact is to recover the waste-heat produce in some processes. This paper proposes the use of thermoelectric generators at a stone wool manufacturing plant to transform waste-heat from a hot gas flow into useful electricity. A combination of two computational models, previously developed and validated, has been used to perform the optimization from a double point of view: power output and economic cost. The proposed thermoelectric generator includes fin dissipaters and biphasic thermosyphons as the hot and cold side heat exchangers respectively. The model takes into account the temperature drop along the duct where the gases flow, the electric consumption of the auxiliary equipment, and the configuration and geometry of the heat exchangers. After the simulations a maximum net power production of 45 838 W is achieved considering an occupancy ratio of 0.40 and a fin spacing of 10 mm. The installation cost is minimized to 10.6 €/W with an occupancy ratio of 0.24. Besides, the Levelised Cost of Electricity, LCOE, is estimated for a thermoelectric generator for the first time. It is necessary to use standar methodologies to compare this technology to others. The LCOE estimated for the proposed design is around 15 c€/kWh within the ranges of current energy sources, proving, in this way, the capabilities of waste-heat recovery from industrial processes at reasonable prices with thermoelectric generators.
Open Access
Gamification and a low-cost laboratory equipment aimed to boost vapor compresion refrigeration learning
(OmniaScience, 2022) Aranguren Garacochea, Patricia; Sánchez García-Vacas, Daniel; Casi Satrústegui, Álvaro; Araiz Vega, Miguel; Catalán Ros, Leyre; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The nowadays European educational framework boosts applying the learned theoretical concepts to real situations. Hence, practice sessions are key resources to present students direct applications of the theoretical concepts shown in class. Thus, developing new educational equipment and practice sessions oriented to bringing theoretical knowledge closer to practice should be one of the objectives of teachers. The present work describes a solution proposed by lectures of two Spanish universities looking to increase the knowledge of their engineering students. Along the years, these docents have noticed the lack of connection between the theoretical and practical knowledge among their students, drastically harming their learning procedure. Thus, in order to deepen into practical learning, a teaching methodology involving low-cost prototypes of vapor compression systems and a gamification method to help the students understand the concepts is proposed. The proposed methodology is expected to make a big positive impact on the results obtained by the students, taking into account the preliminary results reached.