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 investigation of the applicability of a thermoelectric generator to recover waste heat from a combustion chamber
(Elsevier, 2015) Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Rodríguez García, Antonio; Martínez Echeverri, Álvaro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
A thermoelectric generator prototype has been built; it produces 21.56 W of net power, the produced thermoelectric power minus the consumption of the auxiliary equipment, using an area of 0.25 m2 (approximately 100 W/m2). The prototype is located at the exhaust of a combustion chamber and it is provided with 48 thermoelectric modules and two different kinds of heat exchangers, finned heat sinks and heat pipes. Globally, the 40 % of the primary energy used is thrown to the ambient as waste heat; one of the many different applications in which thermoelectricity can be applied is to harvest waste heat to produce electrical power. Besides, the influence on the thermoelectric and on the net power generation of key parameters such as the temperature and mass flow of the exhaust gases, the heat dissipation systems in charge of dispatching the heat into the ambient and the consumption of the auxiliary equipment has been studied. In terms of heat dissipation, the heat pipes outperform the finned dissipators, a 43 % more net power is obtained.
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
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
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
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
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.
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
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.