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
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
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
Experimental validation and development of an advanced computational model of a transcritical carbon dioxide vapour compression cycle with a thermoelectric subcooling system
(Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Sánchez, Daniel; Araiz Vega, Miguel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
The inclusion of a thermoelectric subcooler as an alternative to increment the performance of a vapour compression cycle has been proved promising when properly designed and operated for low-medium power units. In this work, a computational model that simulates the behaviour of a carbon dioxide transcritical vapour compression cycle in conjunction with a thermoelectric subcooler system is presented. The computational tool is coded in Matlab and uses Refprop V9.1 to calculate the properties of the refrigerant at each point of the refrigeration cycle. Working conditions, effect of the heat exchangers of the subcooling system, temperature dependent thermoelectric properties, thermal contact resistances and the four thermoelectric effects are taken into account to increment its accuracy. The model has been validated using experimental data to prove the reliability and accuracy of the results obtained and shows deviations between the ±7% for the most relevant outputs. Using the validated computational tool a 13.6 % COP improvement is predicted when optimizing the total number of thermoelectric modules of the subcooling system. The computational experimentally validated tool is properly fit to aid in the design and operation of thermoelectric subcooling systems, being able to predict the optimal configuration and operation settings for the whole refrigeration plant.

Casi Satrústegui, Álvaro

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