Open Access
Thermoelectric power generation optimization by thermal design means
(InTechOpen, 2016) Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Mekanika, Energetika eta Materialen Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería Mecánica, Energética y de Materiales
One of the biggest challenges of the twenty‐first century is to satisfy the demand for electrical energy in an environmentally speaking clean way. Thus, it is very important to search for new alternative energy sources along with increasing the efficiency of current processes. Thermoelectric power generation, by means of harvesting waste heat and converting it into electricity, can help to achieve above‐mentioned goal. Nowadays, efficiency of thermoelectric power generators limits them to become key technology in electric power generation, but their performance has potential of being optimized, if thermal design of such generators is optimized. Heat exchangers located on both sides of thermoelectric modules (TEMs), mass flow of refrigerants and occupancy ratio (the area covered by TEMs related to base area), among others, need to be fine‐tuned in order to obtain the maximum net power generation (thermoelectric power generation minus consumption of auxiliary equipment). Finned dissipator, cold plate, heat pipe and thermosiphon are experimentally tested to maximize net thermoelectric generation on real‐working furnace based on computational model. Maximum generation of 137 MWh/year using thermosiphons is achieved with 32% of area covered by TEMs.
Open Access
Study of a complete thermoelectric generator behavior including water-to-ambient heat dissipation on the cold side
(Springer US, 2014) Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The reduction of the thermal resistances of the heat exchangers of a thermoelectric generation system (TEG), leads to a significant increase in the TEG efficiency. For the cold side of a thermoelectric module (TEM), a wide range of heat exchangers has been studied, form simple finned dissipators to more complex water (water-glycol) heat exchangers. As Nusselt numbers are much higher in water heat exchangers than in conventional air finned dissipators, convective thermal resistances are better. However, to conclude which heat exchanger leads to higher efficiencies, it is necessary to include the whole system involved in the heat dissipation, that is, TEM-to-water heat exchanger, water-to-ambient heat exchanger, as well as the required pumps and fans. This paper presents a dynamic computational model able to simulate the complete behavior of a TEG, including both heat exchangers. The model uses the heat transfer and hydraulic equations to compute TEM-to-water and water-to-ambient thermal resistances, along with the resistance of the hot side heat exchanger at different operating conditions. Likewise, the model includes all the thermoelectric effect with temperature-dependent properties. The model calculates the net power generation at different configurations, providing a methodology to design and optimize the heat exchange in order to maximize the net power generation for a whole variety of TEGs.
Open Access
Experimental study of a multistage thermoelectric heat pump using different internal heat exchangers
(2021) Erro Iturralde, Irantzu; Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Ingeniería; Institute of Smart Cities - ISC; Ingeniaritza
The current need to carry out an energy transition towards a 100 % renewable horizon places the energy storage as the key. Thermal energy storage has the potential to be an optimal technology. Nowadays electrical resistors are used to convert electrical energy to termal energy by heating an air flux which is stored afterwards. In this work, it is proposed to use a multistage thermoelectric heat pump (MS-TEHP) to do this energy conversion. It has been experimentally analyzed and compared the performance of two MS-TEHP with different internal heat exchangers. With this preliminary research, it has been demonstrated the feasibility of this novel thermoelectric technology which aim is to improve the energy conversión process for thermal energy storage.
Open Access
Computational and experimental study of a complete heat dissipation system using water as heat carrier placed on a thermoelectric generator
(Elsevier, 2014) Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Pérez Artieda, Miren Gurutze; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The heat dissipation systems which have liquids as heat carriers outperform conventional dissipation systems at thermoelectric generators (TEGs). However, new elements need to be introduced such as pumps, secondary heat exchangers and piping. A predictive computational model of a dissipation system involving refrigerant liquids has been implemented. The accuracy of the model is 93 % for all its outputs: the total thermal resistance, the hydraulic losses and the auxiliary power consumption. The validation of the model has been done with a prototype mainly composed by a multi-channel heat exchanger, a fan-coil, a pump and several sensors: temperature, pressure and flow meters. A study on the influence of the water and the air mass flow over the total thermal resistance has been conducted. The total resistance dependence on the air mass flow shows the importance of including the secondary heat exchanger into the thermal and hydraulic calculations. The smallest resistance does not always obtain the highest net power generation, the high demanding power of the auxiliary equipment needed to obtain this resistance influences negatively on the net power generation. Among the experimental points, the optimum scenario obtains a 40 % additional power generation with respect to the smallest resistance point.
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.