Publication: ESTUDIO TÉCNICO DE UTILIZACIÓN DE LA RADIACIÓN NOCTURNA PARA FUENTE FRÍA DE PLANTA TERMO-SOLAR DE 50 MWE
Date
2016
Authors
MUÑOZ SEPÚLVEDA, FELIPE EMILIO
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Abstract
Es el norte de nuestro país la zona geográfica ideal para las tecnologías solares, dado sus amplios espacios disponibles y sus altos niveles de radiación. Pese a esto las tecnologías solares de generación eléctrica no han podido surgir, esto dado, principalmente, a la alta escases hídrica de la zona, lo que impide el uso de los métodos usuales de condensación: las torres húmedas y secas.Dado las condiciones mencionadas es que en este trabajo se estudiará la radiación nocturna como medio de rechazo de calor. Para esto se modela una planta termoeléctrica de tecnología cilindro parabólico de 50 MWe de generación bruta, la que posee un sistema de almacenamiento de calor de 9 horas. Luego se diseña el sistema de disipación de calor apto para zonas áridas, el aerocondensador. Dicho sistema de condensación tiene una limitante no menor: no es capaz de disipar el total de la energía cuando la temperatura ambiente supera a la nominal de diseño (de 20°C para el caso estudiado), además de que provoca un alto consumo energético.Primeramente, se modelará el intercambio térmico de un radiador nocturno, equipo adaptado a partir de un colector solar plano y por el cual circulará una mezcla de etilenglicol, obteniendo una disipación energética máxima de, prácticamente, 250 [kWh], para el solsticio de verano, alcanzando una temperatura de salida de 14,8 °C.Dentro del laboratorio de Energías Renovables de la Universidad se experimentó con un dispositivo similar al aquí estudiado, donde se registraron los valores de temperatura y humedad durante la noche. Estos datos fueron ocupados para validar el modelo desarrollado, llegando a valores muy similares.La planta térmica, en su operación dentro del solsticio de verano (día crítico), debe bajar su producción eléctrica, por lo que se analiza la radiación nocturna como método de energía de resguardo (a ocuparse cada vez que los aerocondensadores se vean superados). Además, se estudia su aplicación en la disminución de los consumos propios de la planta, y en el reemplazo de los aerocondensadores como método de rechazo de energía.Para el condensador se estudian 2 casos, un intercambiador de calor de tubos y carcasa, y uno de tubos concéntricos (pensado como adaptación al aerocondensador). Dado el alto flujo másico, y la baja potencia térmica extra que puede disipar, es que la segunda opción se descarta. Por su parte el condensador de tubos y carcasas presenta resultados aplicables en la industria.Finalmente se procede a dimensionar el layout del campo de radiadores nocturnos. Donde el área que estos ocupan varía de las 16 a las 50 hectáreas para las opciones de respaldo y reemplazo, respectivamente, las cuales necesitan, además, grandes volúmenes de almacenamiento térmico. Son estas dos últimas variables las que se prevé limitarán el uso de la radiación nocturna en la condensación de plantas termoeléctricas.Las alternativas presentadas generan ganancias económicas para la generadora, las cuales, según el precio de venta de la energía, pudiesen estar cerca de los USD 1,9 millones anuales, para la opción de respaldo, a los USD 2,9 millones para la opción de reemplazo, aumentando, aproximadamente, en USD 13.000 por cada ventilador reemplazado. Esto considerando un precio de venta de 61 [USD/MWh].
The north of Chile is the ideal location for solar technology given its availability of space and high levels of radiation. However, solar technology for electricity generation has not been able to continue developing given the lack of water in the region hindering the use of common methods for condensation: wet and dry cooling towers.This study is aimed at assessing night radiation as a means of heat rejection in desert-like conditions. Thus, a thermoelectric plant with 50 MWe brute generation parabolic trough technology and a 9-hour heat storing system is modelled. An air cooled condenser (ACC) is designed which is a heat sink system suitable for dry areas. However, this condenser has a limitation: it is not capable of dissipating the total amount of energy when the ambient temperature surpasses the nominal design temperature, 20°C in this case, causing high energy consumption.The temperature exchange during the day and night is modelled using a night radiator which has been adapted from a flat solar collector and through which an Ethylene glycol mix runs, producing an energy dissipation of approximately 2 [kW] for the summer solstice and a maximum dissipation of 41 [W] within the assessed times (every 10 minutes).At the Renewable Energy Laboratory belonging to UTFSM, a similar device was used to obtain and record temperature and humidity values during the night. The data obtained at the laboratory were very similar to those obtained previously thus validating the model.The thermoelectric plant during the summer solstice (critical day) must reduce its production. Night radiation is analysed as back-up energy method to be used when the ACC is not able to dissipate all the energy. In addition, this system is assessed in order to consider its application in reducing the plant consumption and in replacing the ACC as an energy rejection method.Two cases are studied for the ACC: a shell and tube heat exchanger and a concentric tube heat exchanger (considering its adaptation to the ACC). The second option is ruled out, given the high mass flow and the low extra temperature power which it can dissipate. The first option presented results that were applicable to the case.The alternatives here presented could generate, according to the market price, a financial profit to the power plant of approximately USD 1,9 for the back-up option and USD 2,9 million for the replacement option, with an increase of USD 13.000 for each replaced fan. These estimates are calculated with the market price of 61 [USD/MWh].
The north of Chile is the ideal location for solar technology given its availability of space and high levels of radiation. However, solar technology for electricity generation has not been able to continue developing given the lack of water in the region hindering the use of common methods for condensation: wet and dry cooling towers.This study is aimed at assessing night radiation as a means of heat rejection in desert-like conditions. Thus, a thermoelectric plant with 50 MWe brute generation parabolic trough technology and a 9-hour heat storing system is modelled. An air cooled condenser (ACC) is designed which is a heat sink system suitable for dry areas. However, this condenser has a limitation: it is not capable of dissipating the total amount of energy when the ambient temperature surpasses the nominal design temperature, 20°C in this case, causing high energy consumption.The temperature exchange during the day and night is modelled using a night radiator which has been adapted from a flat solar collector and through which an Ethylene glycol mix runs, producing an energy dissipation of approximately 2 [kW] for the summer solstice and a maximum dissipation of 41 [W] within the assessed times (every 10 minutes).At the Renewable Energy Laboratory belonging to UTFSM, a similar device was used to obtain and record temperature and humidity values during the night. The data obtained at the laboratory were very similar to those obtained previously thus validating the model.The thermoelectric plant during the summer solstice (critical day) must reduce its production. Night radiation is analysed as back-up energy method to be used when the ACC is not able to dissipate all the energy. In addition, this system is assessed in order to consider its application in reducing the plant consumption and in replacing the ACC as an energy rejection method.Two cases are studied for the ACC: a shell and tube heat exchanger and a concentric tube heat exchanger (considering its adaptation to the ACC). The second option is ruled out, given the high mass flow and the low extra temperature power which it can dissipate. The first option presented results that were applicable to the case.The alternatives here presented could generate, according to the market price, a financial profit to the power plant of approximately USD 1,9 for the back-up option and USD 2,9 million for the replacement option, with an increase of USD 13.000 for each replaced fan. These estimates are calculated with the market price of 61 [USD/MWh].
Description
Catalogado desde la version PDF de la tesis.
Keywords
AEROCONDENSADOR , PLANTA TERMOSOLAR , RADIACION NOCTURNA