El termosifón , también conocido como termosifón , se considera una tecnología apropiada . Este proceso utiliza recursos naturales renovables y las leyes básicas de la termodinámica para crear el movimiento de un suministro calentado de aire o agua. La fuente de energía para este proceso es la radiación solar (o cualquier otra fuente de calor). La energía del sol se captura en un dispositivo de recolección solar y se transfiere al aire o al agua por conducción. Todo el proceso puede explicarse por el efecto termosifón : cuando se calienta el aire o el agua, gana cinéticaenergía de la fuente de calor y se excita. Como resultado, el agua se vuelve menos densa, se expande y, por lo tanto, asciende. Por el contrario, cuando se enfría el agua o el aire, se extrae energía de las moléculas y el agua se vuelve menos activa, más densa y tiende a "hundirse". El termosifón aprovecha las diferencias de densidad natural entre los fluidos fríos y calientes, y los controla en un sistema que produce un movimiento de fluido natural. Varios sistemas basados en esta tecnología están actualmente disponibles, y se pueden leer con mayor detalle en el siguiente texto.
El principio del sistema de termosifón es que el agua fría tiene una gravedad específica (densidad) más alta que el agua caliente, por lo que, al ser más pesada, se hundirá. Por lo tanto, el colector siempre se monta debajo del tanque de almacenamiento de agua, de modo que el agua fría del tanque llegue al colector a través de una tubería de agua descendente. Si el colector calienta el agua, el agua vuelve a subir y llega al tanque a través de una tubería de agua ascendente en el extremo superior del colector. El ciclo de tanque → tubería de agua → colector asegura que el agua se caliente hasta que alcance una temperatura de equilibrio. El consumidor puede hacer uso del agua caliente de la parte superior del tanque, y el agua utilizada se reemplaza por agua fría en la parte inferior. El colector vuelve a calentar el agua fría. Debido a las mayores diferencias de temperatura a mayores irradiaciones solares, el agua caliente sube más rápido que con irradiancias más bajas. Por lo tanto, la circulación del agua se adapta casi perfectamente al nivel de radiación solar. El tanque de almacenamiento de un sistema de termosifón debe colocarse muy por encima del colector, de lo contrario, el ciclo puede retroceder durante la noche y toda el agua se enfriará. Además, la bicicleta no funciona correctamente con diferencias de altura muy pequeñas. En regiones con alta irradiación solar y arquitectura de techo plano, los tanques de almacenamiento generalmente se instalan en el techo. la bicicleta no funciona correctamente con diferencias de altura muy pequeñas. En regiones con alta irradiación solar y arquitectura de techo plano, los tanques de almacenamiento generalmente se instalan en el techo. la bicicleta no funciona correctamente con diferencias de altura muy pequeñas. En regiones con alta irradiación solar y arquitectura de techo plano, los tanques de almacenamiento generalmente se instalan en el techo.
Thermosyphon systems operate very economically as domestic water heating systems. The principle is simple, needing neither a pump nor a control. However, thermosyphon systems are usually not suitable for large systems, that is, those with more than 10 m² of collector surface. Furthermore, it is difficult to place the tank above the collector in buildings with sloping roofs, and single-circuit thermosyphon systems are only suitable for frost-free regions.
Contents
Underlying physics
Thermodynamics is the study of energy.
- First law of thermodynamics - States that energy may be changed from one form to another, but cannot be created or destroyed. Energy is always conserved.
This law may be applied to the movement of water in thermosiphoning system: Energy from the sun is directed and transferred (via conduction and convection) to either water, air, or another medium of choice. This natural process of heating eliminates the need for external energy sources such as fossil fuels or electricity.
- Second law of thermodynamics - States that in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state. The net return of a system is always less than that of which was initially put in.
Energy is always conserved, however energy (or heat in this case) may often be lost in a given system (thermosiphoning) as heat. Adding insulation with appropriate R values to the system and its plumbing may greatly reduce heat loss, and thus increase efficiency.
- Planck's Law - The wavelength of radiation emitted from a surface is proportional to the temperature of the surface. Energy transferred as a result of temperature differences between two objects. Dark objects absorb heat, while light objects reflect.
Darkly colored collection plates within the solar collector will aid in increasing solar absorption, thus increasing the amount of heat available to heat water or air in thermosiphoning. In contrast, reflective or lightly colored piping and storage tanks should be utilized as the light colors will help to reduce heat radiation out of the system.
Passive water heating
The passive thermosiphoning of water is the process of heating and moving water within a system without the need or use of electricity. This process functions by utilizing natual phenomena such as solar energy, gravity, and an available water source. A solar collector, piping, and a water tank are materials required for the heating process. The flow of water is distributed into, within, and out of the solar collector. Cool water enters the bottom of the solar collector where it is then heated via convection by solar radiation. When water is heated it becomes less dense than cooler water, expands, and then rises (flows) through the piping. The heated water exits the top of the solar collector naturally. The cooler and more dense water sinks and remains within the solar collector until it is heated. As the cool water is heated, it expands, rises, is pushed out of the top of solar collector, allowing cool water to flow into the solar collector. This process continues naturally until the temperature of the water reaches an equilibrium with solar radiation input.
Two types of thermosiphon water exchange systems are currently available: the close-coupled system, and the gravity-feed system.
Close-coupled system
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Close-coupled systems function on the same principles of passive thermosiphoning mentioned above. The storage tank of these systems must be placed above the solar collector to utilize the water circulation driven by the passive thermosiphoning process.
Materials
- Solar Energy
- Solar Collector
- Piping
- Insulation
- Water
- Storage Tank
- Strong roof or other support system
Cost
- 2007 research suggests that passive thermosiphon water heaters may range from $500 to $6,500. Pricing may vary due to tank size, solar exposure, and geographical location
- Many countries, states, and utility services provide incentives for renewable energy participation
Pros
- Non-polluting
- Energy Savings - No electricity needed for passive thermosiphoning
- Cost Effective
- Space saving - (i.e. indoors)
Cons
- Tank exposure to external environmental condition may reduce efficiency, depending on geographical location
- Aesthetics - May be considered visually unpleasing
- Strong support structure needed (i.e. roof)
- Not suitable for extremely cold climates
- Location - must be positioned in an area with suitable solar exposure (i.e. south side of desired area)
Gravity-feed system
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Gravity-feed systems utilize the same principals of passive thermosiphoning as does the close-coupled system, however placement of the tank differs. Tanks are installed horizontally into a roof, which is often located directly above the solar collector. Once needed, the heated water within the storage tank takes the path of least resistance and moves via gravity down into the desired location. Gravity-feed systems require more piping/plumbing to distribute the heated water, and this factor should be taken into consideration when installing or purchasing a thermosiphoning system.
Materials
- Solar Energy
- Solar Collector
- Piping
- Insulation
- Water
- Storage Tank
- Strong roof or other support system
Cost
- Gravity-feed systems are typically the least expensive passive thermosiphoning water heaters
- 2007 research suggests that the cost may range from $400 to $5,500 (not including the cost -if applicable- of installation). Pricing may vary due to tank size, solar exposure, and geographical location
- Many countries, states, and utility services provide incentives for renewable energy participation
Pros
- Non-polluting
- Energy Savings - No electricity needed for passive thermosiphoning
- Cost Effective
- Space savings - (i.e. indoors)
- Aesthetics - (Horizontal tank placement)
Cons
- Plumbing and piping add additional costs to the system
- Aesthetics - May be considered visually unpleasing
- Strong support structure needed (i.e. roof)
- Not suitable for extremely cold climates
- Location - must be positioned in an area with suitable solar exposure (i.e. south side of desired area)
Active water heating
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Active solar heating systems, also known as pump systems or split systems, function on the same basis of the thermosiphoning effect, however active systems utilize an energy source other than solar energy to help drive the process. This system installs only the solar collector on the roof, while the storage tank is installed on the ground or anywhere else below. These active water heating units require some external form of energy to pump the water throughout the system. By utilizing additional energy, these active systems are less cost efficient than passive systems.
Materials
- Solar Energy
- Solar Collector
- Electrical energy
- Electrical pump
- Additional piping
- Insulation
- Water
- Storage Tank
Cost
- 2007 research suggests that active thermosiphon water heaters may range from $1,200 to $10,500. Pricing may vary due to tank size, internal piping requirements, solar exposure, and geographical location
- Many countries, states, and utility services provide incentives for renewable energy participation
Pros
- Money Savings
- Cost Effective
- Aesthetics - Storage tank not placed on the roof
- Greenhouse gas reduction - If insulated properly, it has the potential of polluting as little as passive systems.
Cons
- Uses more energy than a passive system
- Requires more maintenance than a passive system
- Heat loss - during the transfer from the solar collector to the storage tank below
- Pollutes some - from the electrical usage
- Location - must be positioned in an area with suitable solar exposure (i.e. south side of desired area)
Passive air exchange
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An example of a passive solar thermal heating system method is Thermosiphon Heat Exchange. It is based on the principle of natural convection, in which air or water is circulated in a vertical closed-looped circuit without using a pump. Cool air indoors travels through a vent and is directed into an opening in the bottom of a solar collector. The air contained within the solar collector is then heated by the sun via solar radiation. Cool air is dense and will sink, while warm air is less dense and will rise. As the air heats up within the solar collector, it becomes less dense than the cooler air and rises. The warm air rises out of a vent in the top opening of the solar collector, moves into the desired area (i.e. indoors), and is replaced by cooler air. This air exchange process will continue until the indoor air temperature reaches an equilibrium with the temperature outdoors.
Materials
- Solar collector - The bigger the solar collector, the better.
- Frame
- 6 vertical 2-by-6-inch boards - Sideboards
- 2-by-6, and a 2-by-8 boards - Top sill
- Lag screws - Recommended, but not necessary for attachment
- Glaze
- Corrugated polycarbonate panels
- 10 panels - 26 in wide by 8 ft high
- Pares de paneles superpuestos sobre tiras de madera verticales de 1 por 1 pulgada: hace paneles de 4 pies de ancho para cada bahía
- Recubrimiento resistente a los rayos ultravioleta: aplíquelo en el lado que mira hacia el sol para prolongar la longevidad
- Placa de absorción solar
- Pantalla de ventana de metal negro de 2 capas: fijada en la parte superior e inferior de las bahías
- Respiraderos
- Agujeros cortados a través del revestimiento del edificio: las aletas de plástico evitarán el reflujo de aire a través de las rejillas de ventilación superiores durante la noche.
Costo
- La investigación de 2007 sugiere que los intercambiadores de calor pasivos pueden oscilar entre $ 55,00 y $ 400. El precio puede variar según el tamaño de los colectores, el aislamiento del área a calentar, la exposición solar y la ubicación geográfica.
- Muchos países, estados y servicios públicos brindan incentivos para la participación en energías renovables
ventajas
- Bajo costo
- Ahorrador de energía
- Reducción de la contaminación
- Se puede usar para enfriar dispositivos electrónicos.
Contras
- Mayor mantenimiento - (es decir, cobertura durante épocas de baja radiación solar)
- La ubicación geográfica puede alterar la eficacia
- Requiere el cierre manual de las compuertas traseras durante la noche
- Se prefieren las cuotas orientadas al sur
Proyectos relacionados
Referencias
- Laboratorio Nacional de Energía Renovable (NREL) Mapas dinámicos, datos GIS y herramientas de análisis - Mapas solares (2007) Disponible: http://www.nrel.gov/gis/solar.html
- Citarella, Joe. "Termosifones: ¿un mejor enfoque para la refrigeración de la CPU?" Overclockers. 5 de agosto de 2005. http://web.archive.org/web/20080421004505/http://www.overclockers.com:80/articles1246/
- Reysa, Gary. "Construir un calentador solar simple" Mother Earth News. Enero de 2006 http://www.motherearthnews.com/Alternative-Energy/2006-12-01/Build-a-Simple-Solar-Heater.aspx
- "Parte 2: Un recorrido por las aplicaciones de energía renovable". http://web.archive.org/web/20060513045333/http://www.unepti.e.org/pc/tourism/documents/energy/11-26.pdf
- Mirmov, NI, Belyakova, IG "Liberación de calor durante la condensación de vapor en un termosifón". Diario de Ingeniería Física 43(3), pp.970-974, 1982.
- Diseño y Funcionamiento de un Termosifón Compacto. Aniruddha, P., Yogendra, J., Beitelmal, M, Patel, C., Wenger, T. Woodruff Escuela de Ingeniería Mecánica. 2002. http://www.hpl.hp.com/research/papers/2002/thermosyphon.pdf