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
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
Development and experimental validation of a computational model in order to simulate ice cube production in a thermoelectric ice maker
(Elsevier, 2009) Rodríguez García, Antonio; González Vian, José; Astrain Ulibarrena, David; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
We have developed a computational model which allows the simulation of a thermoelectric device to make ice cubes in a vapor compression domestic fridge. This model solves both the thermoelectric and heat transfer equations, including the phase change equations in the ice cube production. The inputs of the model are: the thermoelectric parameters as a function of the temperature; dimensions; material properties (thermal resistances and capacities) and the boundary conditions (room temperature and voltage supplied to the Peltier module). The outputs are the values of the temperature for all the elements of the thermoelectric ice-maker and the ice production. In the experimental phase a prototype of a thermoelectric ice maker incorporated in a vapour compression domestic fridge was constructed in order to adjust and validate the computational model, and to optimize the experimental application. This ice-maker has two Peltier modules, some aluminum cylinders, called fingers, where the ice is made, and a component that acts as heat extender and dissipater which connects the hot side of Peltier module with the freezer compartment. The ice formation on the fingers is obtained by the cooling on the Peltier modules. When the ice cubes are formed, the voltage polarity of the thermoelectric modules is switched so the fingers warm up until the ice around the fingers melts. Then the ice cubes are dropped by gravity. This paper studies the production of ice cubes using the computational model and the experiment results and analyzes the most important parameters for the optimisation of the ice-maker (voltage supplied to the Peltier module, thermal resistance of the hot side dissipater and initial water temperature).
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
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
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
Computational study of geothermal thermoelectric generators with phase change heat exchangers
(Elsevier, 2020) Catalán Ros, Leyre; Araiz Vega, Miguel; Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
The use of thermoelectric generators with phase change heat exchangers has demonstrated to be an interesting and environmentally friendly alternative to enhanced geothermal systems (EGS) in shallow hot dry rock fields (HDR), since rock fracture is avoided. The present paper studies the possibilities of the former proposal in a real location: Timanfaya National Park (Canary Islands, Spain), one of the greatest shallow HDR fields in the world, with 5000 m2 of characterized geothermal anomalies presenting temperatures up to 500 °C at only 2 m deep. For this purpose, a computational model based on the thermal-electrical analogy has been developed and validated thanks to a real prototype, leading to a relative error of less than 8%. Based on this model, two prototypes have been designed and studied for two different areas within the park, varying the size of the heat exchangers and the number of thermoelectric modules installed. As a result, the potential of the solution is demonstrated, leading to an annual electricity generation of 681.53 MWh thanks to the scalability of thermoelectric generators. This generation is obtained without moving parts nor auxiliary consumption, thus increasing the robustness of the device and removing maintenance requirements.
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.