Open Access
Study of the degradation of heat exchanger materials in the acidic environment of Teide National Park
(2019) Catalán Ros, Leyre; Pérez Artieda, Miren Gurutze; Berlanga Labari, Carlos; Garacochea Sáenz, Amaia; Rodríguez García, Antonio; Domínguez, Vidal; Montañez, Ana Carolina; Padilla, Germán D.; Pérez, Nemesio M.; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC; Ingeniería
Supplying power to volcanic monitoring stations constitutes a challenge due to both the access difficulties and the acidic environment associated with volcanoes. ELECTROVOLCAN project is developing thermoelectric generators that make use of the temperature of the available fumaroles to directly supply electricity to the stations in a robust, compact and reliable way. The main element of thermoelectric generators are the thermoelectric modules, based on Seebeck effect. Nonetheless, since the efficiency of these modules increases with the temperature difference between their sides, the introduction of heat exchangers becomes essential. The present study analyses the behavior of different materials used in the construction of the heat exchangers in the acidic environment of Teide National Park.
Open Access
Geothermal thermoelectric generator for Timanfaya National Park
(2019) Catalán Ros, Leyre; Astrain Ulibarrena, David; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
Despite being one of the largest renewable sources, geothermal energy is not widely utilized for electricity generation. In the case of shallow Hot Dry Rock (HDR) fields, thermoelectric generators can entail a sustainable alternative to Enhanced Geothermal Systems (EGS). The present work studies two configurations of thermoelectric generators for Timanfaya National Park (Spain), one of the most important Hot Dry Rock fields in the world, with temperatures of 500°C at only 3 meters deep. The first configuration includes biphasic thermosyphons as heat exchangers for both sides, leading to a completely passive thermoelectric generator. The second configuration uses fin dissipators as cold-side heat exchangers.
Open Access
Design and experimental development of thermoelectric generators for shallow geothermal anomalies of volcanic origin
(2020) Catalán Ros, Leyre; Astrain Ulibarrena, David; Aranguren Garacochea, Patricia; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
En el contexto energético actual, caracterizado por un incesante aumento en el consumo de energía y una gran dependencia de los combustibles fósiles, resulta imprescindible apostar por sistemas eficientes y basados en energías renovables que contribuyan a un mejor aprovechamiento de los recursos y sean respetuosos con el medio ambiente. En este sentido, la energía geotérmica destaca entre otras fuentes renovables por su carácter permanente, al no depender de las condiciones meteorológicas. Sin embargo, su contribución al sistema energético mundial es mínimo, sobre todo en generación de electricidad. Como alternativa a los ciclos que tradicionalmente se emplean para la generación eléctrica geotérmica, esta tesis doctoral propone la utilización de generadores termoeléctricos debido a sus numerosas ventajas tales como fiabilidad, durabilidad y escalabilidad. Concretamente, la tesis se centra en anomalías geotérmicas superficiales de origen volcánico para dos aplicaciones distintas: la generación eléctrica de media escala en yacimientos de roca caliente seca y el abastecimiento autónomo de estaciones de vigilancia volcánica. Dada la importancia de los intercambiadores de calor en la eficiencia total del sistema, en ambas aplicaciones se ha realizado un profundo estudio para determinar qué tipo de intercambiadores de calor son los más adecuados. En ambos casos, se ha demostrado experimentalmente que los intercambiadores de calor más propicios son aquellos basados en el cambio de fase, ya que aparte de presentar bajas esistencias térmicas, no tienen partes móviles ni requieren de equipos auxiliares, minimizando así el mantenimiento. Asimismo, también ha resultado de gran importancia el desarrollo de un modelo computacional rápido y fiable que tenga en cuenta los intercambiadores de calor, la fuente de calor y el sumidero, sin despreciar ningún efecto termoeléctrico, y considerando los contactos térmicos y eléctricos y la influencia de la temperatura en las propiedades. Este modelo, programado en base al método de las diferencias finitas, se ha convertido en una verdadera herramienta de diseño y optimización para las dos aplicaciones objeto de estudio en esta tesis doctoral, gracias a su error relativo menor al 8%. Los resultados derivados de esta tesis doctoral demuestran que la termoelectricidad puede solucionar las problemáticas de generación eléctrica en los yacimientos de roca caliente seca y en las estaciones de monitorización volcánica, dos aplicaciones inéditas de generación termoeléctrica que pueden hacer que esta tecnología se convierta por fin en una realidad en el ámbito civil.
Open Access
Experimental development of a novel thermoelectric generator without moving parts to harness shallow hot dry rock fields
(2021) Alegría Cía, Patricia; Rodríguez García, Antonio; Catalán Ros, Leyre; Astrain Ulibarrena, David; Araiz Vega, Miguel; Ingeniería; Institute of Smart Cities - ISC; Ingeniaritza
Nowadays, geothermal energy in shallow hot dry rocks is not exploited enough due to the high economic and environmental impact as well as the lack of scalability of the existing technologies. Here, thermoelectricity has a great future potential due to its robustness, absence of moving parts and modularity. With this research, the feasibility of a novel and robust geothermal thermoelectric generator whose working principle is phase change has been experimentally demonstrated, as well as the importance of compactness to maximize its efficiency and thus, power generation.
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
Enhanced behaviour of a passive thermoelectric generator with phase change heat exchangers and radiative cooling
(Elsevier, 2023) Astrain Ulibarrena, David; Jaramillo-Fernández, Juliana; Araiz Vega, Miguel; Francone, Achille; Catalán Ros, Leyre; Jacobo-Martín, Alejandra; Alegría Cía, Patricia; Sotomayor-Torres, Clivia M.; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Heat exchangers are essential to optimize the efficiency of Thermoelectric Generators (TEGs), and heat pipes without fans have proven to be an advantageous design as it maintains the characteristic robustness of thermoelectricity, low maintenance and lack of moving parts. However, the efficiency of these heat exchangers decreases under natural convection conditions, reducing their heat transfer capacity and thus thermoelectric power production. This work reports on a novel heat exchanger that combines for the first time, phase change and radiative cooling in a thermoelectric generator to improve its efficiency and increase the production of electrical energy, specially under natural convection. For this, two thermoelectric generators with heat-pipes on their cold sides have been tested: one with the radiative coating and the other without it. Their thermal resistances have been determined and the electric power output was compared under different working conditions, namely, natural convection and forced convection indoors and outdoors. The experimental tests show a clear reduction of the heat exchanger thermal resistance thanks to the radiative coating and consequently, an increase of electric production 8.3 % with outdoor wind velocities of 1 m/s, and up to 54.8 % under free convection conditions. The application of the radiative surface treatment is shown to result in a more stable electrical energy production, suppressing the drastic decrease in the generated electric power that occurs in thermoelectric generators when they work under free convection.
Open Access
Simulation of thermoelectric heat pumps in nearly zero energy buildings: why do all models seem to be right?
(Elsevier, 2021) Martínez Echeverri, Álvaro; Díaz de Garayo, Sergio; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Catalán Ros, Leyre; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
The use of thermoelectric heat pumps for heat, ventilation, and air conditioning in nearly-zero-energy buildings is one of the most promising applications of thermoelectrics. However, simulation works in the literature are predominately based on the simple model, which was proven to exhibit significant deviations from experimental results. Nine modelling techniques have been compared in this work, according to statistical methods based on uncertainty analysis, in terms of predicted coefficient of performance and cooling power. These techniques come from the combination of three simulation models for thermoelectric modules (simple model, improved model, electric analogy) and five methods for implementing the thermoelectric properties. The main conclusion is that there is no statistical difference in the mean values of coefficient of performance and cooling power provided by these modelling techniques under all the scenarios, at 95% level of confidence. However, differences appear in the precision of these results in terms of uncertainty of the confidence intervals. Minimum values of uncertainty are obtained when the thermal resistance ratio approaches 0.1, being ±8% when using temperature-dependent expressions for the thermoelectric properties, ±18% when using Lineykin's method, and ± 25% when using Chen's method. The best combination is that composed of the simple model and temperature-dependent expressions for the thermoelectric properties. Additionally, if low values of resistance ratio are anticipated, empirical expressions from the literature can be used for the thermal resistance of the heat exchangers; for high values, though, experimental tests should be deployed, especially for the heat exchanger on the hot side.
Open Access
Improvements in the cooling capacity and the COP of a transcritical CO 2 refrigeration plant operating with a thermoelectric subcooling system
(Elsevier, 2019) Astrain Ulibarrena, David; Merino Vicente, Amaya; Catalán Ros, Leyre; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Llopis, R.; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
Restrictive environmental regulations are driving the use of CO 2 as working fluid in commercial vapour compression plants due to its ultra-low global warming potential (GWP 100 = 1) and its natural condition. However, at high ambient temperatures transcritical operating conditions are commonly achieved causing low energy efficiencies in refrigeration facilities. To solve this issue, several improvements have been implemented, especially in large centralized plants where ejectors, parallel compressors or subcooler systems, among others, are frequently used. Despite their good results, these measures are not suitable for small-capacity systems due mainly to the cost and the complexity of the system. Accordingly, this work presents a new subcooling system equipped with thermoelectric modules (TESC), which thanks to its simplicity, low cost and easy control, results very suitable for medium and small capacity plants. The developed methodology finds the gas-cooler pressure and the electric voltage supplied to the TESC system that maximizes the overall COP of the plant taking into account the ambient temperature, the number of thermoelectric modules used and the thermal resistance of the heat exchangers included in the TESC. The obtained results reveal that, with 20 thermoelectric modules, an improvement of 20% in terms of COP and of 25.6% regarding the cooling capacity can be obtained compared to the base cycle of CO 2 of a small cooling plant refrigerated by air. Compared to a cycle that uses an internal heat exchanger IHX, the improvements reach 12.2% and 19.5% respectively.
Open Access
Women, Science and Technology Chair—Promoting women’s careers in stem fields
(IEEE, 2023) Pérez Artieda, Miren Gurutze; Gómez Fernández, Marisol; Aranguren Garacochea, Patricia; Barrenechea Tartas, Edurne; Catalán Ros, Leyre; Díaz Lucas, Silvia; Jurío Munárriz, Aránzazu; Martínez Ramírez, Alicia; Millor Muruzábal, Nora; Ortiz Nicolás, Amalia; San Martín Biurrun, Idoia; Estadística, Informática y Matemáticas; Ingeniería; Ingeniería Eléctrica, Electrónica y de Comunicación; Estatistika, Informatika eta Matematika; Ingeniaritza; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The Chair of Women, Science and Technology of the Universidad Pública de Navarra (UPNA) aims to increase the participation of women in the fields of science and technology. Scientific culture and dissemination are the main focus of the different actions of the Chair. These activities include: the theatrical performance "Yo quiero ser científica", experimental workshops and conferences and exhibitions for all audiences and ages. More than 6.000 people have seen the play, more than 1.500 secondary school students have participated in the workshops and the audiovisual material has received more than 20.000 visits.
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.