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
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
Effect of thermoelectric subcooling on COP and energy consumption of a propane heat pump
(Elsevier, 2024-12-01) Aranguren Garacochea, Patricia; Sánchez, Daniel; Haida, Michal; Smolka, Jacek; Cabello, Ramón; Rodríguez García, Antonio; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The building sector has an important impact on the environment, being responsible for 30 % of the total greenhouse gas emissions. Knowing that the energy consumption devoted to HVAC systems accounts for 50 % of the total energy consumption of buildings, it is paramount to develop environmentally friendly technologies able to provide green space heating to the building sector. To that purpose, this manuscript presents a computational study on propane vapor compression heat pumps which include thermoelectric subcooling to boost their operation. The combination of these technologies has been proven in the past to be very beneficial for refrigeration systems and this study concludes for the first time that propane heat pumps can highly benefit from thermoelectric subcooling. The widely conducted research includes the following parameters: ambient temperatures from -20 to 15 °C, voltage supplies to the thermoelectric modules from 0.5 to 10 VDC, number of thermoelectric subcooling blocks from 1 to 8 and two water inlet temperatures, 40 and 55 °C to study their influence on heating capacity, compressor and thermoelectric power consumptions, subcooling degree, propane mass flow, compressor capacity, COP, energy consumption and SCOP of the combined heat pump. The obtained results are very conclusive, COP enhancements up to 12.29 % are achieved when a thermoelectric subcooler with 16 modules is included in a propane heat pump already provided with an internal heat exchanger for an ambient temperature of -20 °C and a water inlet temperature of 55 °C. Additionally, improvements in Seasonal COP up to 9.98 % are achieved if the above-mentioned technologies integration between a vapor compression heat pump and a thermoelectric subcooler substitutes a conventional propane heat pump with an internal heat exchanger for space heating a single-story two-family house.
Open Access
Net thermoelectric power generation improvement through heat transfer optimization
(Elsevier, 2017) Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Rodríguez García, Antonio; Martínez Echeverri, Álvaro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
Thermoelectric generation contributes to obtain a more sustainable energetic system giving its potential to harvest waste heat and convert it into electric power. In the present study a computational optimal net generation of 108.05 MWh/year was produced out of the flue gases of a real tile furnace located in Spain (the equivalent to supply the energy to 31 Spanish dwellings). This maximum generation has been obtained through the optimization of the hot and cold heat exchangers, the number of thermoelectric modules (TEMs) installed and the mass flows of the refrigerants, including the temperature loss of the flue gases and the influence of the heat power to dissipate over the heat dissipators. The results are conclusive, the installation of more TEMs does not always imply higher thermoelectric generation, so the occupancy ratio (δ) has to be optimized. The optimal generation has been achieved covering the 42 % of the surface of the chimney of the tile furnace with TEMs and using heat pipes on the cold side, which present smaller thermal resistances than the finned dissipators for similar consumptions of their fans. Moreover, the high influence of the consumption of the auxiliary equipment shows the importance of considering it to obtain realistic usable electric energy from real applications.
Open Access
Development and experimental validation of a thermoelectric test bench for laboratory lessons
(OmniaScience, 2013) Rodríguez García, Antonio; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Aranguren Garacochea, Patricia; Pérez Artieda, Miren Gurutze; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The refrigeration process reduces the temperature of a space or a given volume while the power generation process employs a source of thermal energy to generate electrical power. Because of the importance of these two processes, training of engineers in this area is of great interest. In engineering courses it is normally studied the vapor compression and absorption refrigeration, and power generation systems such as gas turbine and steam turbine. Another type of cooling and generation less studied within the engineering curriculum, having a great interest, it is cooling and thermal generation based on Peltier and Seebeck effects. The theoretical concepts are useful, but students have difculties understanding the physical meaning of their possible applications. Providing students with tools to test and apply the theory in real applications, will lead to a better understanding of the subject. Engineers must have strong theoretical, computational and also experimental skills. A prototype test bench has been built and experimentally validated to perform practical lessons of thermoelectric generation and refrigeration. Using this prototype students learn the most effective way of cooling systems and thermal power generation as well as basic concepts associated with thermoelectricity. It has been proven that students learn the process of data acquisition, and the technology used in thermoelectric devices. These practical lessons are implemented for a 60 people group of students in the development of subject of Thermodynamic including in the Degree in Engineering in Industrial Technologies of Public University of Navarra.
Open Access
Study of thermoelectric systems applied to electric power generation
(Elsevier, 2009) Rodríguez García, Antonio; González Vian, José; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
A computational model has been developed in order to simulate the thermal and electric behaviour of the thermoelectric generators. This model solves the non linear system of equations of the thermoelectric and heat transfer equations. The inputs of the program are the thermoelectric parameters as a function of the temperature and the boundary conditions, (room temperature and residual heat flux). The outputs are the temperature values of all the elements forming the thermoelectric generator, (performance, electric power, voltage and electric current generated). The model solves the equation system using the finite difference method and semi-empiric expressions for the convection coefficients. It has been built a thermoelectric electric power generation test bench in order to validate and determine the accuracy of the computational model, which maximum error is lower than 5%. The objective of this study is to create a design tool that allows us to solve the system of equations involved in the electric generation process without needing to impose boundary conditions that are not known in the design phase, as the temperature of the Peltier modules. With the computational model we study the influence of the heat flux supplied as well as the room temperature in the electric power generated.
Open Access
Development and experimental validation of a computational model in order to simulate ice cube production in a thermoelectric ice maker
(Elsevier, 2009) Rodríguez García, Antonio; González Vian, José; Astrain Ulibarrena, David; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
We have developed a computational model which allows the simulation of a thermoelectric device to make ice cubes in a vapor compression domestic fridge. This model solves both the thermoelectric and heat transfer equations, including the phase change equations in the ice cube production. The inputs of the model are: the thermoelectric parameters as a function of the temperature; dimensions; material properties (thermal resistances and capacities) and the boundary conditions (room temperature and voltage supplied to the Peltier module). The outputs are the values of the temperature for all the elements of the thermoelectric ice-maker and the ice production. In the experimental phase a prototype of a thermoelectric ice maker incorporated in a vapour compression domestic fridge was constructed in order to adjust and validate the computational model, and to optimize the experimental application. This ice-maker has two Peltier modules, some aluminum cylinders, called fingers, where the ice is made, and a component that acts as heat extender and dissipater which connects the hot side of Peltier module with the freezer compartment. The ice formation on the fingers is obtained by the cooling on the Peltier modules. When the ice cubes are formed, the voltage polarity of the thermoelectric modules is switched so the fingers warm up until the ice around the fingers melts. Then the ice cubes are dropped by gravity. This paper studies the production of ice cubes using the computational model and the experiment results and analyzes the most important parameters for the optimisation of the ice-maker (voltage supplied to the Peltier module, thermal resistance of the hot side dissipater and initial water temperature).
Open Access
Computational study on the thermal influence of the components of a thermoelectric ice maker on the ice production
(Springer US, 2012) Rodríguez García, Antonio; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; González Vian, José; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The main objective of this paper is to study the thermal resistances of two components of a thermoelectric ice maker installed in a no-frost refrigerator, in order to optimize the ice production. This study is conducted via a computational model developed by the Thermal and Fluids Research Group from Public University of Navarre, explained and validated in previous papers. Firstly, three dissipaters with different space between fins are simulated using Computational Fluid Dynamics Fluent to study their influence on both the ice production and the performance of the refrigerator. The computational model predicts a maximum production of 2.82 kg/day of ice with less than 7 W of extra electric power consumption, though these values depend to a great extent on the cooling and freezing power of the refrigerator. Secondly, this work focuses on reducing the size of the components in order to save raw material and reduce the cost of the device. The computational model predicts that the last design produces 2.42 kg/day of ice, saves 65 % of raw material and reduces to the half the expenses assigned to the thermoelectric modules.
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
The importance of the assembly in thermoelectric generators
(IntechOpen, 2018) Araiz Vega, Miguel; Catalán Ros, Leyre; Herrero Mola, Óscar; Pérez Artieda, Miren Gurutze; Rodríguez García, Antonio; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
Generally, in the optimization of thermoelectric generators, only the heat exchangers or the thermoelectric modules themselves are taken into account. However, the assembly of the generator as a whole is of vital importance since a bad contact or a thermal bridge can waste the performance of an optimal generator. In this sense, the present chapter analyzes experimentally the use of different interface materials to reduce the thermal contact resistance between the modules and the heat exchangers, the influence of the pressure distribution in the assembly as well as the effect of different insulating materials in order to reduce the thermal bridge between the exchangers. Thus, it has been demonstrated that a good assembly requires the implementation of thermal interface materials to ensure the microscopic contact between the heat exchangers and the modules, besides a uniform clamping pressure. Nevertheless, since this is normally achieved with screws, they represent a source of thermal bridges in conjunction with the small distance between the exchangers. In order to reduce heat losses due to thermal bridges, which can represent up to one-third of the incoming heat, an increment of the distance between the exchangers and the use of an insulator is recommended.