Trombe wall

A Trombe wall is a passive solar building design where a wall is built on the winter sun side of a building with a glass external layer and a high heat capacity internal layer separated by a layer of air. Light close to UV in the electromagnetic spectrum passes through the glass almost unhindered then is absorbed by the wall that then re-radiates in the far infrared spectrum which does not pass back through the glass easily, hence heating the inside of the building. Trombe walls are commonly used to absorb heat during sunlit hours of winter then slowly release the heat over night. The essential idea was first explored by Edward S. Morse and patented by him in 1881. In the 1960s it was fully developed as an architectural element by French engineer Félix Trombe and architect Jacques Michel.

Trombe walls work on the basic greenhouse principle that heat from the sun in the form of near-visible shorter-wavelength higher-energy ultraviolet radiation passes through glass largely unimpeded.

When this radiation strikes objects the energy is absorbed and then re-emitted in the form of longer-wavelength infra-red radiation that does not pass through glass as readily. Hence heat becomes trapped and builds up in an enclosed structure with high internal heat capacity and glass surfaces that face the sun

How effectively objects absorb and shed radiant heat depends on a number of factors; how dark they are in colour, how directly the surface of the object is opposed to the angle of the radiation striking it, how matte or reflective its surface is, the heat capacity of the object, and the surface conductivity of the object. For Trombe walls to work effectively they are made from high heat capacity materials such as concrete or water, whose surface is dark and matte in colour and placed in direct opposition to the sun striking them.

The clearer the glass in front of a Trombe wall appears in the UV spectrum the more short wave radiation will penetrate and the more reflective or non transparent the glass appears in the infra-red spectrum the less re-emitted heat will be escape.

Trombe walls may be constructed with or without internal vents. 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 passively circulate room air past the heated side of the wall for more immediate heating. Vented Trombe walls may use passively or actively controllable flaps to prevent convection in the undesired direction, as when the wall cools at night in winter or heats during the day in summer. In climates that have higher summer temperatures Trombe walls may also be designed with external vents to improve the shedding of heat at night.

...
Wikipedia