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Alegría Cía, Patricia

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https://academica-e.unavarra.es/handle/2454/48483

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Alegría Cía

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Patricia

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Ingeniería

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ISC. Institute of Smart Cities

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0000-0003-1174-2037

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811965

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2020 - 20233
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Subject: Phase change ×

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Now showing 1 - 3 of 3
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    PublicationOpen Access
    Thermoelectric generator for high temperature geothermal anomalies: experimental development and field operation
    (Elsevier, 2023) Alegría Cía, Patricia; Catalán Ros, Leyre; Araiz Vega, Miguel; Casi Satrústegui, Álvaro; Astrain Ulibarrena, David; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    In the current climate and energy context, it is important to develop technologies that permit increase the use of renewable sources such as geothermal energy. Enhancing the use of this renewable source is particularly important in some places, due to its availability and the enormous dependence on fossil fuels, as is the case of the Canary Islands. This work proposes the use of thermoelectric generators with heat exchangers working by phase change to transform the heat from the shallow high temperature geothermal anomalies on the island of Lanzarote directly into electricity, since the use of conventional geothermal power plants would not be possible because they would damage the protected environment. To bring this proposal to reality, this work has succeeded in developing and field-installing a geothermal thermoelectric generator that operates without moving parts thanks to its phase-change heat exchangers. This robust generator do not require maintenance nor auxiliary consumption, and produces a minimal environmental impact, it is noiseless, and the use of water as working fluid makes it completely harmless. The developed device consists of a thermosyphon as hot side heat exchanger, thermoelectric modules and cold side heat exchangers also based in phase change. Tests were carried out in the laboratory at various heat source temperatures and varying the number of thermoelectric modules. It was determined that installing more modules decreases the efficiency per module (from 4.83% with 4 modules to 4.59% with 8 modules at a temperature difference between sources of 235 °C), but for the number of modules tested the total power increases, so the field installation was carried out with 8 modules. After the good results in the laboratory, it was satisfactorily installed at Timanfaya National Park (Lanzarote, Spain) in a borehole with gases at 465 °C. This generator presents a maximum output power of 36 W (4.5 W per module), and is generating 286.94 kWh per year, demonstrating the great potential of the developed thermoelectric generators to build a larger-scale renewable installation.
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    PublicationEmbargo
    Diseño, análisis y optimización de un generador termoeléctrico mediante calor geotérmico de origen volcánico
    (2020) Alegría Cía, Patricia; Astrain Ulibarrena, David; Araiz Vega, Miguel; Escuela Técnica Superior de Ingeniería Industrial, Informática y de Telecomunicación; Industria, Informatika eta Telekomunikazio Ingeniaritzako Goi Mailako Eskola Teknikoa
    Frente al actual problema energético al que nos enfrentamos, la termoelectricidad aplicada a la energía geotérmica tiene un gran potencial de futuro. Esta tecnología conlleva grandes ventajas como, entre otras, su robustez, fiabilidad, no necesita mantenimiento ya que es una tecnología sin partes móviles, ausencia de ruidos, y es una energía totalmente renovable y limpia. Sin embargo, la eficiencia de un generador termoeléctrico depende en gran medida de los intercambiadores de calor. Por ello es de gran importancia que estos sean lo más eficientes posible. El objetivo de este proyecto es diseñar y estudiar un prototipo de generador termoeléctrico que sea capaz de transformar en electricidad un gradiente de temperaturas entre el ambiente y el calor del suelo del Parque Nacional de Timanfaya. Para ello, se han diseñado y construido intercambiadores de calor específicamente para esta aplicación. La función de estos intercambiadores será transportar el calor con la máxima eficiencia posible desde el interior del sondeo (foco caliente) hasta los módulos termoeléctricos, utilizando una parte de este calor para generar electricidad y otra parte para disiparlo al medio ambiente a través de intercambiadores en el lado frío. El principio de funcionamiento de todos estos intercambiadores será el intercambio de calor por termosifón y cambio de fase. Para lograr el diseño completo, se propusieron y valoraron diferentes soluciones para las diferentes partes que componen el prototipo. Finalmente, se realizó un estudio económico.
  • Thumbnail Image
    PublicationOpen Access
    Field test of a geothermal thermoelectric generator without moving parts on the Hot Dry Rock field of Timanfaya National Park
    (Elsevier, 2023) Catalán Ros, Leyre; Alegría Cía, Patricia; Araiz Vega, Miguel; Astrain Ulibarrena, David; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    Although in the last years thermoelectric generators have arisen as a solution to boost geothermal power generation, tests on field are still scarce. The vast majority of the available studies focus on computational simulations or laboratory experiments, mainly with active heat exchangers that require pumps or fans, and, consequently, present moving parts and auxiliary consumption. The present paper demonstrates for the first time the suitability of a geothermal thermoelectric generator (GTEG) with passive phase change heat exchangers, and therefore, without moving parts nor auxiliary consumption, on the shallow Hot Dry Rock (HDR) field of Timanfaya National Park (Canary Islands, Spain), where 173 °C air anomalies can be found. The device has been in operation without maintenance for 2 years now, producing more than 520 kWh of energy. In terms of power generation, since the installed device is in turn composed of two prototypes with 10 and 6 thermoelectric modules, it has been confirmed that installing more modules leads to a lower generation per module, although total generation can be higher. In fact, the prototype with 10 thermoelectric modules generated a maximum of 20.9 W (2.09 W per module) with a temperature difference between sources of 158 °C, while the prototype with 6 thermoelectric modules obtained 16.67 W (2.78 W per module) under the same conditions. These results open the door for a large-scale exploitation thanks to the intrinsic advantages of modularity, reliability, robustness, and minimal environmental impact of the developed device.