BUSCADOR RECOLECTA

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., The authors would like to thank the Spanish Ministry of
Economy and Competitiveness, and European Regional
Development Fund for providing funding for this work included in the DPI2011-24287 research project.

Esta es la versión no revidada del artículo: Rodríguez, A., Astrain, D., Martínez, A. et al. Experimental Study and Optimization of Thermoelectricity-Driven Autonomous Sensors for the Chimney of a Biomass Power Plant. Journal of Elec Materi 43, 2415–2419 (2014). Se puede consultar la versión publicada en http://doi.org/10.1007/s11664-014-3097-2, 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., The authors are indebted to the Spanish Ministry
of Economy and Competitiveness, and the European
Regional Development Fund for economic support to
this work, included in the DPI2011-24287 research
project.

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., The authors are indebted both to the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund for the economic support to this work, included in the DPI2011-24287 research project.

The final publication is available at Springer via http://dx.doi.org/10.1007/s11664-014-3057-x, 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., The authors are indebted to the Spanish Ministry
of Economy and Competitiveness and the European
Regional Development Fund for economic support of
this work, included in the DPI2011-24287 Research
Project.

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., The authors are indebted to the Spanish Ministry of Economy and Competitiveness, and European Regional
Development Fund for the economic support to this work, included in the DPI2011-24287 research project.

La presente tesis doctoral estudia el aprovechamiento del calor residual mediante generación termoeléctrica para la obtención de potencia eléctrica generada gracias al efecto Seebeck. Dos son las aproximaciones empleadas, la simulación computacional, empleando variables obtenidas experimentalmente y la experimentación de escenarios reales. Ambas dos han obtenido valores muy prometedores para la generación eléctrica a través de los gases residuales.
Con el desarrollo de esta tesis doctoral, se contribuye en gran medida al aumento de la eficiencia energética de los procesos industriales, así como a la reducción de la emisión de gases contaminantes al ambiente, aportando su granito de arena a la sostenibilidad del sistema energético., This doctoral thesis studies the exploitation of the waste heat to obtain electrical power by the Seebeck e˙ect that takes part inside the thermoelectric generators. Two are the approaches used, the computational simulation, through experimentally obtained variables, and the experimentation of real scenarios. Both of them have obtained really promising results in thermoelectric generation obtained from residual flue gases.
To conclude, the development of this doctoral thesis, contributes to a large degree, in the increase of the energetic eÿciency of the industrial processes, as well as reduces the polluting gases emissions to the ambient, helping to achieve a sustainable energetic model., Esta tesis doctoral ha recibido financiamiento del proyecto de investigación DPI2011-24287 "Generación Termoeléctrica con Energía Calorífica Residual (GETER)" perteneciente al Plan Nacional de I+D+I 2008-2011 y del proyecto de investigación DPI2014-53158-R "Sistemas de Generación Eléctrica a partir de calor Residual: aplicación al aprovechamiento de los humos en chimeneas domésticas e industriales (SIGER)", enmarcado dentro del Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, Plan Estatal de I+D+I 2013-2016., Programa de Doctorado en Ciencias y Tecnologías Industriales (RD 99/2011), Industria Zientzietako eta Teknologietako Doktoretza Programa (ED 99/2011)

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., The authors are indebted to the Spanish Ministry of Economy and Competitiveness, and European Regional Development Fund for the economic support to this work, included in the DPI2011-24287 research project.

This work presents the design and development of a thermoelectric generator
intended to harness waste heat in a biomass power plant, and generate electric
power to operate sensors and the required electronics for wireless communication.
The first objective of the work is to design the optimum
thermoelectric generator to harness heat from a hot surface, and generate
electric power to operate a flowmeter and a wireless transmitter. The process
is conducted by using a computational model, presented in previous papers, to
determine the final design that meets the requirements of electric power
consumption and number of transmissions per minute. Finally, the thermoelectric
generator is simulated to evaluate its performance. The final device
transmits information every 5 s. Moreover, it is completely autonomous and
can be easily installed, since no electric wires are required., The authors are indebted to the Spanish Ministry
of Science and Innovation (DPI2011-24287) and
FEDER funds (European Union) for economic support
of this work.