Passive solar heating of buildings using a transwall structure

Abstract

Passive solar heating systems can utilize a number of design approaches, but the most prominent ones are those employing “direct gain” or a “Trombe thermal storage wall”. In this work we propose a new passive system employing a “transwall”, which is a partially transparent thermal storage wall placed adjacent to a window admitting solar energy. Part of the solar energy is absorbed within the transwall, and the remaining part is transmitted to the interior of the room. The transwall is architecturally more attractive than the completely absorbing Trombe wall, since it admits light to the room and allows the occupants to see out through the window without glare and overheating problems of direct gain systems. Calculations using thermal network models and based on reasonable assumptions for relative comparisons have been used to compare thermal performance of transwall, Trombe wall, and direct gain systems. The analysis shows that the transwall system can be expected to have thermal performance very close to or exceeding the other systems, depending on how effectively convective heat transfer is quenched in the thermal storage medium. The important question of visual clarity for the transwall system has been evaluated for a prototype by photographing a scene with and without optical transmission through the structure. Optical distortion is minimal in the transwall transmission photograph.