Person:
Araiz Vega, Miguel

person.page.identifierURI

https://academica-e.unavarra.es/handle/2454/48554

Last Name

Araiz Vega

First Name

Miguel

person.page.departamento

Ingeniería

person.page.instituteName

ISC. Institute of Smart Cities

ORCID

0000-0002-7674-0078

person.page.upna

811140

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Now showing 1 - 10 of 30

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 Unibertsita
To 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.
Open Access
Thermoelectric generators for waste heat harvesting: a computational and experimental approach
(Elsevier, 2017) Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
Waste heat generation has a widespread presence into daily applications, however, due to the low-temperature grade which presents, its exploitation with the most common technologies is complicated. Thermoelectricity presents the possibility of harvesting any temperature grade heat; besides it also includes many other advantages which make thermoelectric generators perfect for generating electric power from waste heat. A prototype divided into two levels along the chimney which uses the waste heat of a combustion has been built. The experimentation has been used to determine the parameters that influence the generation and to validate a generic computational model able to predict the thermoelectric generation of any application, but specially applications where waste heat is harvested. The temperature and mass flow of the flue gases and the load resistance determine the generation, and consequently, these parameters have been included into the model, among many others. This computational model incorporates all the elements included into the generators (heat exchangers, ceramics, unions) and all the thermoelectric phenomena and moreover, it takes into account the temperature loss of the flue gases while circulating along the thermoelectric generator. The built prototype presents a 65 % reduction in the generation of the two levels of the thermoelectric generator due to the temperature loss of the flue gases. The general computational model predicts the thermoelectric generation with an accuracy of the ±12 %.
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.
Embargo
New opportunities for electricity generation in shallow hot dry rock fields: a study of thermoelectric generators with different heat exchangers
(Elsevier, 2019) Catalán Ros, Leyre; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Pérez Artieda, Miren Gurutze; Astrain Ulibarrena, David; Institute of Smart Cities - ISC
Despite being one of the largest renewable sources, geothermal energy is not widely utilized for electricity generation. In order to leverage shallow hot dry rock (HDR) fields, the present paper proposes an alternative to enhanced geothermal systems (EGS): thermoelectric generators. Based on the conditions of Timanfaya National Park, a prototype has been built to experimentally analyze the feasibility of the proposed solution. The prototype is composed by a two phase closed thermosyphon (TPCT) as hot side heat exchanger, two thermoelectric modules, and it considers different cold side heat exchangers: fin dissipators assisted by a fan and loop thermosyphons, both with various geometries. Experiments have demonstrated that loop thermosyphons represent the best alternative due to their low thermal resistance and, especially, due to their lack of auxiliary consumption, leading to a maximum net power generation of 3.29 W per module with a temperature difference of 180 °C (200 °C in the hot side and 20 °C as ambient temperature), 54% more than with fin dissipators. Hence, there exists a new opportunity for electricity generation in shallow hot dry rock fields: thermoelectric generators with biphasic thermosyphons as heat exchangers, a patented and robust solution.
Open Access
Prospects of autonomous volcanic monitoring stations: experimental investigation on thermoelectric generation from fumaroles
(MDPI, 2020) Catalán Ros, Leyre; Araiz Vega, Miguel; Padilla, Germán D.; Hernández, Pedro A.; Pérez, Nemesio M.; García de la Noceda, Celestino; Albert, José F.; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
Fumaroles represent evidence of volcanic activity, emitting steam and volcanic gases at temperatures between 70 and 100 °C. Due to the well-known advantages of thermoelectricity, such as reliability, reduced maintenance and scalability, the present paper studies the possibilities of thermoelectric generators, devices based on solid-state physics, to directly convert fumaroles heat into electricity due to the Seebeck effect. For this purpose, a thermoelectric generator composed of two bismuth-telluride thermoelectric modules and heat pipes as heat exchangers was installed, for the first time, at Teide volcano (Canary Islands, Spain), where fumaroles arise in the surface at 82 °C. The installed thermoelectric generator has demonstrated the feasibility of the proposed solution, leading to a compact generator with no moving parts that produces a net generation between 0.32 and 0.33 W per module given a temperature difference between the heat reservoirs encompassed in the 69–86 °C range. These results become interesting due to the possibilities of supplying power to the volcanic monitoring stations that measure the precursors of volcanic eruptions, making them completely autonomous. Nonetheless, in order to achieve this objective, corrosion prevention measures must be taken because the hydrogen sulfide contained in the fumaroles reacts with steam, forming sulfuric acid.
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, 0011-1365-2018-000101
Thermoelectricity, 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.
Open Access
Heat pipes thermal performance for a reversible thermoelectric cooler-heat pump for a nZEB
(Elsevier, 2019) Aranguren Garacochea, Patricia; Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Araiz Vega, Miguel; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
The nZEB standards reduce the energy demand of these buildings to a minimum, obtaining this little energy from renewable resources. Taking these aspect into consideration, a thermoelectric cooler-heat pump is proposed to achieve the comfort temperature along the whole year. The same device can provide heat in winter and it can cool down the buildings in summer just by switching the voltage supply polarity. Heat pipes are studied to work on both sides of the thermoelectric modules in order to optimize the heat transfer as these devices present really good thermal resistances and they can work in any position. However, they present pretty different thermal resistances if they work on the cold or on the hot side of the modules. A methodology to thermally characterize these heat exchangers working in both orientations is proposed and a validated computational model is developed to optimize the thermoelectric cooler-heat pump for a nZEB application. The number of thermoelectric modules, the position of the device, the ambient temperature and the air mass flow determine the operation and consequently they need to be studied in order to optimize the application.
Open Access
Thermoelectric generator with passive biphasic thermosyphon heat exchanger for waste heat recovery: design and experimentation
(MDPI, 2021) Araiz Vega, Miguel; Casi Satrústegui, Álvaro; Catalán Ros, Leyre; Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua
One of the measures to fight against the current energy situation and reduce the energy consumption at an industrial process is to recover waste heat and transform it into electric power. Thermoelectric generators can be used for that purpose but there is a lack of experimental studies that can bring this technology closer to reality. This work presents the design, optimizations and development of two devices that are experimented and compared under the same working conditions. The hot side heat exchanger of both generators has been designed using a computational fluid dynamics software and for the cold side of the generators two technologies have been analysed: a finned dissipater that uses a fan and free convection biphasic thermosyphon. The results obtained show a maximum net generation of 6.9 W in the thermoelectric generator with the finned dissipater; and 10.6 W of power output in the generator with the biphasic thermosyphon. These results remark the importance of a proper design of the heat exchangers, trying to get low thermal resistances at both sides of the thermoelectric modules, as well as, the necessity of considering the auxiliary consumption of the equipment employed.
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.
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.