A trombe wall is a passive solar building where a wall is built on the wall of a building with a glass external layer and a high heat capacity separated by a layer of air. Light in the electromagnetic spectrum then passes through the glass which is then absorbed by the wall that then re-radiates in the far infrared spectrum which does not pass through the glass easily, hence heating the inside of the building. Trombe walls are commonly used in the heat of the night. The essential idea was first explored by Edward S. Morse and patented by him in 1881. [1]In the 1960s it was fully developed as an architectural element by French engineer Felix Trombe and architect Jacques Michel. [2] [3]
Ultraviolet radiation passes through glass largely unimpeded.
When this radiation strikes the energy is absorbed and then re-emitted in the form of longer-wavelength infrared radiation that does not pass through glass as easily. The heat becomes trapped and builds up in an enclosed structure with high internal heat capacity and glass surfaces that face the sun [4]
How to effectively absorb and shed radiant heat depends on a number of factors; how dark they are in color, how directly the surface of the object is opposed to the angle of the radiation striking, how is the surface reflective of its surface, the heat capacity of the object, and the surface conductivity of the object. For trombe walls to work they are made of high heat capacity such as concrete or water, whose surface is dark and matte in color and placed in direct opposition to the sun.
The clearer the glass in front of a trombone wall will appear in the UV spectrum and the more reflective or not transparent the glass appears in the infra-red spectrum, the less re-emitted heat will escape. [5]
Basic design
Trombe walls can be constructed with or without internal winds. Non-vented walls rely on conduction through the wall to heat the space behind the wall, while vented walls allow the user to actively or indirectly. Vented Trombe Walls can be used as a backdrop to prevent convection in the direction of the sun. Trombe walls can also be designed to improve the heat of the night. [6]
Vented walls are more likely to be used during the day when they are more commonly required. Views differ among the passive solar community. [7]
A simplistic rule of thumb that is often used when designing dense masonry walls that will be absorbed and lost by two hours per inch. [ quote needed ]
Common variations
Common modifications to the Trombe wall include: [ citation needed ]
- Exhaust vent the top of the summer. Such venting makes the Trombe wall act as a chimney pumping fresh air through the house during the day, even if there is no breeze.
- Windows in the Trombe wall. This lowers the efficiency but can be done for natural lighting or aesthetic reasons. If the outer glazing has high ultraviolet transmittance , and the window in the Trombe wall is normal glass, this allows efficient use of the ultraviolet light for heating. At the same time, it protects against ultraviolet radiation and causes high ultraviolet transmittance.
- Electric blowers controlled by thermostats, to improve air and heat flow.
- Fixed or movable shades, which can reduce night-time heat losses.
- Trellis to shade the solar collector during summer months.
- Insulating covering used at night on the glazing surface.
- Tubes or water tanks as part of a solar hot water system.
- Fish tanks added heat capacity.
- Using a selective surface to increase the absorption of solar radiation by the wall.
Half-height Trombe walls
There is a misconception [ citation needed ] that must be removed from the living room and completely absorbed into the living room. In reality Trombe walls can be built to whatever height suits the needs of the homeowner, their reduced height is simply reducing the solar absorption area and increasing direct light and heat gain area. Half-height Trombe walls are a relatively simple solution that can greatly enhance the solar storage capacity of a passive solar home, while still allowing for views to the sun’s winter direction.
Half-height Trombe walls function in the same way as a full height wall. They are commonly constructed around 4-6 inches (100-150 mm) from the inner window surface, allowing a gap large enough for curtains or blinds to reduce heat loss on winter nights and heat gain on summer days.
Application in developing regions
In Ladakh , India , the Ladakh Project is designing Ladakh’s traditional Ladaki homes. This has shown Ladhakis a clean, reliable alternative to fire as a source of heat. The traditional fuel, dung , burns poorly and offers poor relief from the bitter winter temperatures. The smoldering dung produces significant amounts of smoke. Trombe walls offer relief from both the cold and the smoke. Ladakh receives about 320 days of sun annually, and the traditional building materials – stone and mud brick – provide the heat capacity needed for heat storage in Trombe wall. [8]
The Druk White Lotus School in Ladakh uses Trombe walls [9] and as part of “a model of appropriate design and development”. [10]
See also
- List of pioneering solar buildings
- Solar power in India
References
- Jump up^ Old Solar: 1881
- Jump up^ Mazria, Edward (1979). The Passive Solar Energy Book . Emmaus, PA: Rodale Press. ISBN 0-87857-237-6 .
- Jump up^ Denzer, Anthony (2013). The Solar House: Sustainable Design Pioneering . Rizzoli. ISBN 978-0847840052 .
- Jump up^ http://www.yourhome.gov.au/technical/fs45.html
- Jump up^ Infrared # Different regions in the infrared- Near-infrared exhibits low losses in SiO2glass
- Jump up^ http://nmsea.org/lib/ThermalStorageWallDesignManual.pdf
- Jump up^ Passive Solar Design Guidelines for Northern New MexicoGain (Trombe Wall) Guidelines
- Jump up^ Hales, Carolyn (1986). The Ladakh Project. Cultural Survival, 10.3 (Fall 1986) Mountain Peoples. Retrieved fromhttp://www.culturalsurvival.org/publications/cultural-survival-quarterly/hales/ladakh-project.
- Jump up^ Drukpa Trust (2008). Sustainable Design Examples page. Retrieved fromhttp://www.dwls.org/Sustainable-Design-Examples.html.
- Jump up^ Drukpa Trust (2008). Overview of Awards page. Retrieved fromhttp://www.dwls.org/Overview-Of-Awards.html.
