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
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
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
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
Advanced phase-change intermediate heat exchanger development for multistage thermoelectric heat pumps
(Elsevier, 2023) Erro Iturralde, Irantzu; Aranguren Garacochea, Patricia; Alegría Cía, Patricia; Rodríguez García, Antonio; Astrain Ulibarrena, David; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The need to reach a full energy decarbonisation is well known. Heating and cooling consumption is almost half of the global energy end-use. Thus, development of low-carbon and highly efficient power-to-heat technologies must be developed. In this work, the use of thermoelectric technology working as a heat pump is proposed to heat up an airflow of 38 m3/h. Two different prototypes of multistage thermoelectric heat pumps have been developed and compared based on monophasic and phase-change intermediate heat exchangers. The reduced thermal resistance obtained for the novel phase-change heat exchanger increases the heat flux supplied to the airflow and reduces the consumed power of the system, outperforming the operation of the monophasic thermoelectric heat pump between a 30 and a 67 %. The novel multistage phase-change heat pump obtains experimental COP values between 3.25 and 1.26 when the airflow rises its temperature from 3.5 °C to 23.5 °C. Additionally, this experimental study proves a new methodology to calculate the supplied heat flux to the airflow. The validation of this technology proves a discrepancy of ± 9 % when this novel technology is compared to the conventional one based on the airflow temperature rise.