A trombe wall is a passive heating system that takes advantage of solar radiation by the use of different materials and their conduction and most importantly used heat storage capabilities. The system plays with the air by using its density and how it moves through convection, to re-direct the air masses to one side or the other depending on what its purpose is, either to cool down or warm up. Of course, to make the best use of this technique, we must position this wall in the equatorial direction. To learn more about Trombe wall systems keep reading...
CONTENT
6- Bonus.
From Ancient Times To The Present
Kelbaugh House;
According to data collected the Trombe wall system reduced heating costs by 76% and 84%, respectively in the winter of 1975-1976 and 1976-1977.
The house is located along the northern boundary of the site to maximize shadowless access to available sunlight. The two-story building has a 600 m² thermal storage wall made of concrete and painted with a selective black paint over a wall covering. Although the main heating is provided by radiation and convection from the inside of the wall, both vents in the wall allow daytime heating by natural convection cycle.
What is This Trombe Wall, Detailed Close-up!
A typical Trombe wall consists of a 20-40 cm thick masonry wall which is painted a heat-absorbing color and faced with a single or double layer of glass. The glass is placed between 2 - 15 cm away from the masonry wall to create a small airspace. It could also place a black vinylic sheet on the outside face of the wall to enhance the effect of the solar radiation that hits the wall.
Another critical part of Trombe wall design is choosing the proper thermal mass material and of course the thickness. The optimum thickness of the thermal mass is dependent on the heat capacity and the thermal conductivity of the material used. In addition, It is recommended to use the single glass with a shutter for the evening and night times, to offset its heat losses, the single glass provides the highest solar radiation gain due to its higher solar heat gain efficiency.
How Does The Trombe Wall Works ?
If we go deeper into more technical aspects there is a most important piece of information about the working principle of the Trombe wall; According to Wien's displacement law, whereas direct solar radiation has a shorter wavelength and is therefore easily conducted through glass, the re-emitted heat from the thermal mass takes the form of longer-wavelength radiation, which cannot pass through the glass as easily.
Another phenomenon that plays role in the Trombe wall's operation is the time lag caused by the heat capacity of the materials. Since Trombe walls are quite thick and made of high-heat capacity materials, the heat flow from the warmer outer surface to the inner surface is slower than other materials with less heat capacity. This delayed heat-flow phenomenon is known as time lag and it causes the heat gained during the day to reach the interior surface of the thermal mass later. There is a most important piece of information about the working principle of the Trombe wall; According to Wien's displacement law, whereas direct solar radiation has a shorter wavelength and is therefore easily conducted through glass, the re-emitted heat from the thermal mass takes the form of longer-wavelength radiation, which cannot pass through the glass as easily.
If it has been too technical and we need to summarize simply the heat from sunlight passing through the glass is absorbed by the dark surface, The glass prevents the escape of radiant heat from the warm surface of the storage wall. The heat radiated by the wall is therefore trapped within the air gap, further heating the wall surface. and conducted slowly inward through the masonry. For a 40 cm thick Trombe wall, heat will take about 8 to 10 hours to reach the interior of the building.
Positive And Negative Aspects.
Let's clarify this with the pros and cons chart to make more understandable.
POSITIVE | NEGATIVE |
Trombe wall require little or no effort to operate. | Display a poorer economic performance if solar radiation is low during the heating season. |
Ideal for spaces where silence and privacy are desirable. | Prevent the living spaces behind the Trombe walls from being claustrophobic. |
Materials (masonry, concrete) are relatively inexpensive. | Natural daylight is lost unless the system is combined with a direct-gain system. |
Requires almost no maintenance. | Wall hangings or other type of coverings are not allowed to use with Trombe Wall. |
They provide comfortable heat. | Trombe wall can become a source of heat loss during extended overcast days. |
Perform better at maintaining a steady indoor temperature. | If there is a lower and upper vents, attention should be paid to the reverse siphon effect. |
Among the passive solar heating strategies. | In regions closer to the equator, it my cause overheating during hot season. |
Can reduce a building's energy consumption up to 30%. | It is a very climate-dependent system and external. |
The energy heating savings of 16.36% can be achieved. | Display a poorer economic performance if solar radiation is low during the heating season. |
Glare, ultraviolet degradation, or reduction of night time privacy are not a problem. | The system requires user action to operate movable insulation or shutters, often on a daily basis. |
Energy delivery to a living space is more controllable than for a direct-gain system. | Users should be given guidance either by modeling a prototype or providing a user-friendly operation manual. |
Help greatly to reduce the overall labor and material cost of constructing. | Impact on the overall building design is limited. |
Unlike roof ponds, in multi-storey buildings, the facade of each floor can benefit from the Trombe wall system. | |
Because of the time lag involved in the transfer of energy through the wall into the space not causing potential overheating problem during occupied hours. | |
What Are The Types Of Trombe Wall ?
1-Ventilated trombe wall
This is a step forward variation of the classic Trombe wall. To control the air movement, the upper and lower gaps in the wall and their probability of closing or opening are used.
2-Sunspace
An attached sunspace (conservatories) is essentially a Trombe wall where the air space is so big it is habitable. Sunspace can be heated spaces both through radiation and convection.
3-Solar Chimney
During hot seasons, a Trombe wall with vents are placed at the behind of the glazing. The air from the room will be pulled out by convection in the air gap between the glazing and mass wall.
4-Low-e Glazing
Using low-emissivity glazing to avoid losses can improve trombe wall's performance by reducing the amount of infrared energy radiates towards the glass.
5-Shading Elements
Using overhangs to avoid overheating at hot times of the day or hot seasons of the year to evenly balance solar heat delivery. And ideally, the glazing should have exterior insulating shutters for nighttime use in order to prevent the heat gained from being returned back to the outside.
6-Drum Wall
Which uses water as a thermal mass rather than concrete or stone. Darkened steel containers, like oil drums, are filled with water and stacked behind the glass panel. Because water has a greater heat capacity than masonry, this system theoretically absorbs heat more efficiently than the standard Trombe wall.
Bonus
To minimize the possible drawbacks of the Trombe wall system, there are additional thermal control strategies to employ in the wall design. For instance, the minimum 10cm distance between the glass and the mass allows cleaning the glazing and the insertion of a roll-down radiant barrier as needed.
Another strategy that helps to benefit from the solar collection without some of the drawbacks of the Trombe walls is to use exterior mirror-like reflectors. The additional reflected area helps Trombe walls to benefit more from the sunlight with the flexibility of removing or rotating the reflector device if the solar collection is undesired.
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