Open Access
Annual energy performance of a thermoelectric heat pump combined with a heat recovery unit to HVAC one passive house dwelling
(Elsevier, 2022) Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper proposes a HVAC system that integrates a thermoelectric heat pump with a double flux ventilation system and a sensible heat recovery unit able to provide heating, cooling and ventilation to a 74.3 m2 Passive House certified dwelling in Pamplona (Spain). This study computationally investigates the energy performance of the system and the comfort conditions of the dwelling for one year long. The thermoelectric HVAC system maintains adequate comfort conditions with an indoor temperature between 20–23 °C in wintertime and 23–25 °C during summer, thanks to the precise control of the voltage supplied to the thermoelectric heat pump that can regulate the heating/cooling capacity from 5 to 100 %. The system consumes 1143.3 kWh/y (15.3 kWh/m2y) of electric energy, that can be provided by 4 photovoltaic panels of 250 Wp each. This system is then compared with a vapor compression heat pump with a COP of 4.5. The vapor compression system reduces the electric energy consumption by 36.1 % with respect to the thermoelectric system, which allows saving only 270 Wp (1–2 PV panels). This demonstrates the promising application of thermoelectricity for HVAC in passive houses.
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
Improvement of a thermoelectric and vapour compression hybrid refrigerator
(Elsevier, 2012) Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Rodríguez García, Antonio; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
This paper presents the improvement in the performance of a domestic hybrid refrigerator that combines vapour compression technology for the cooler and freezer compartments, and thermoelectric technology for a new compartment. The heat emitted by the Peltier modules is discharged into the freezer compartment, forming a cascade refrigeration system. This configuration leads to a significant improvement in the coefficient of operation. Thus, the electric power consumption of the modules and the refrigerator decrease by 95 % and 20 % respectively, with respect to those attained with a cascade refrigeration system connected with the cooler compartment. The optimization process is based on a computational model that simulates the behaviour of the whole refrigerator. Two prototypes have been built and tested. Experimental results indicate that the temperature of the new compartment is easily set up at any value between 0 and -4 ºC, the oscillation of this temperature is always lower than 0.4 ºC, and the electric power consumption is low enough to include this hybrid refrigerator into energy efficiency class A, according European rules and regulations.
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
Zero-power-consumption thermoelectric system to prevent overheating in solar collectors
(Elsevier, 2014) Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Rodríguez García, Antonio; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
Highly promoted by the European Union Climate and Energy Package for 2020, solar collectors stand out as the most promising alternative to meet water heating demands. One of the most limiting problems in these systems involves the overheating of the working fluid, resulting in rapid fluid degradation, scaling and premature component failure. This paper presents the computational design of a zero-power-consumption system that combines thermoelectric-self-cooling technology and thermosyphon effect to dissipate the excess heat from a real solar-collector installation. Thermoelectric self-cooling is a novel thermoelectric application proven to enhance the heat dissipation of any hot spot without electricity consumption. The simplest design outperforms currently-used static and dynamic dissipaters for overheating protection in solar collectors, since it increases the global heat transfer coefficient of a static dissipater by 75 % and requires no electricity. Likewise, the final design presents a global heat transfer coefficient of 15.23 W/(m2K), 155 % higher than that provided by static dissipaters, forming a reliable, robust and autonomous system that stands out as a promising alternative to prevent the overheating of solar collectors.
Open Access
Experimental study and optimization of thermoelectric-driven autonomous sensors for the chimney of a biomass power plant
(2014) Rodríguez García, Antonio; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Aranguren Garacochea, Patricia; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
In the work discussed in this paper a thermoelectric generator was developed to harness waste heat from the exhaust gas of a boiler in a biomass power plant and thus generate electric power to operate a flowmeter installed in the chimney, to make it autonomous. The main objective was to conduct an experimental study to optimize a previous design obtained after computational work based on a simulation model for thermoelectric generators. First, several places inside and outside the chimney were considered as sites for the thermoelectricity-driven autonomous sensor. Second, the thermoelectric generator was built and tested to assess the effect of the cold-side heat exchanger on the electric power, power consumption by the flowmeter, and transmission frequency. These tests provided the best configuration for the heat exchanger, which met the transmission requirements for different working conditions. The final design is able to transmit every second and requires neither batteries nor electric wires. It is a promising application in the field of thermoelectric generation.
Open Access
Influence of temperature and aging on the thermal contact resistance in thermoelectric devices
(Springer, 2020) Rodríguez García, Antonio; Pérez Artieda, Miren Gurutze; Beisti Antoñanzas, Irene; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
During thermal design in the first phases development, thermoelectric systems, such as thermoelectric generators, the most important parameter affecting the performance is thermal resistance of the components. This paper focusses on the thermal contact resistance (TCR), analyzing the influence of aging and temperature on different thermal interface materials (TIMs), i.e., thermal paste, graphite and indium. In previous papers, TCR has been studied depending on parameters such as surface roughness, bonding pressure, thermal conductivity and surface hardness. However, in thermoelectric applications, a relevant aspect to consider when choosing a TIM is aging due to thermal stress. The exposure of this type of material to high temperatures for long periods of time leads to deterioration, which causes an increase in the TCR impairing the conduction of the heat flow. Therefore, there is a need to study the behavior of TIMs exposed to temperatures typical in thermoelectric generators to make a correct selection of the TIM. It has been observed that exposure to temperatures of around 180°C induces a significant increase in the thermal impedance of the three TIMs under study, although this effect is much more relevant for thermal paste. The contact, comprising steel, thermal paste and ceramic, presents a 300% increase in the thermal impedance after 70 days of aging, whereas that exceeds 185% for the contact of aluminum, thermal paste and ceramic. In the tests with exposure temperature of 60°C, there is no observed decrease in the thermal impedance.
Open Access
Design and analysis of a two-stage cascade system for heating and hot water production in nearly zero-energy buildings using thermoelectric technology
(MDPI, 2024-12-16) Ordóñez, Javier ; Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Algarra Pérez, Fernando; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
This paper proposes an innovative system that integrates two thermoelectric heat pumps (one air–water and the other water–water) with two thermal storage tanks at different temperatures to provide heating and domestic hot water to a 73.3 m2 passive-house-certified dwelling in Pamplona (Spain). The air–water thermoelectric heat pump extracts heat from the ambient air and provides heat to a tank at intermediate temperature, which supplies water to a radiant floor. The water–water heat pump takes heat from this tank and provides heat to the other tank, at higher temperature, which supplies domestic hot water. The system performance and comfort conditions are computationally analyzed during the month of January under the climate of Pamplona and under different European climates. The COP of the system lays between 1.3 and 1.7, depending on the climate, because of the low COP of the air–water thermoelectric heat pump. However, it is able to provide water for the radiant floor and to maintain the temperature of the dwelling above 20 °C 99.8% of the time. Moreover, it provides domestic hot water at a temperature above 43 °C 99.9% of the time. Noteworthy is the fact that the water–water heat pump presents a COP close to 4, which opens up the possibilities of working in combination with more efficient heat pumps for the first stage.
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
Experimental and computational investigation of passive heat exchangers to enhance the performance of a geothermal thermoelectric generator
(Elsevier, 2024) Pascual Lezaun, Nerea; Alegría Cía, Patricia; Araiz Vega, Miguel; Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
Thermoelectric devices hold significant promise for generating electricity from geothermal heat, enabling the powering of measuring equipment in remote locations without the need for moving parts. Nevertheless, most developed geothermal thermoelectric generators employ fans and pumps to enhance heat transfer, thereby compromising the robustness and reliability inherent to thermoelectricity. Furthermore, there is a lack of research on passive heat exchangers for geothermal thermoelectric generators, particularly in studying their operation under a wide range of meteorological conditions. Therefore, this paper conducts a comprehensive analysis of passive heat exchangers for the cold side of the generators. Phase-change-based heat exchangers differing in their length and fluid are studied experimentally, along with a fin dissipator. Additionally, the influence of wind velocity on heat transfer and mechanical requirements is further explored through a Computational Fluid Dynamics model. The most significant outcome is quantifying the impact of the design parameters and operational variables on the electrical production of the thermoelectric generator. Accordingly, this research aims to broaden the application of these generators to extreme environments, such as Deception Island in Antarctica. Under average operational conditions, generators incorporating 400 mm water heat pipes generate 0.95 W per thermoelectric module, while those incorporating heat pipes with methanol achieve an average of 0.70 W. Moreover, water and methanol-based systems produce 120% and 60% more power than generators using a fin dissipator. Nonetheless, for temperatures beyond -6.5 °C, water might freeze and the methanol-based heat exchangers become more suitable.