Indirect Gain Systems

These are passive thermal systems that collect and store the sun's energy. The storage is directly linked to the comfort of the interior space. In winter, energy is collected and stored to be released later in the day. This allows better control of indoor temperatures and heat distribution. In summer, the systems reverse their operation preventing overheating.

A building component can be heated by absorbing heat radiated from warmer components (walls, floors) or by convection from the surrounding air. The storage is influenced by the component temperature difference, location and emissivity. Indirect gain systems may be characterized by the placing of a sheet of glass in front of, and quite close to, a solid masonry wall or other building element that has a high thermal storage capacity. These systems are designed to capture and store a large fraction of the indirect radiation for subsequent release into the adjoining occupied space. When a wall is used for thermal energy storage in an indirect gain system it is called a Solar Wall or a Mass Wall.

A Mass Wall relies on conduction to transfer heat. For better thermal efficiency mass storage elements are located within a building, taking up some space that could be used for other things. Commonly a large wall is constructed on the sun-orientated face of the building. The sun warms up the mass of the wall during the day. After sunset, the stored heat is emitted for a period of time that depends on the thickness of the wall and its thermal characteristics. The glazing on the external face reduces heat loss to the outside. After sunset, the stored heat is emitted for a period of time that depends on the thickness of the wall and its thermal characteristics. The glazing on the external face reduces heat loss to the outside. There are several variations of the mass wall principle, as follows.

The Trombe-Michel wall

The Trombe-Michel wall (also known simply as the Trombe wall) is a variation of the mass wall principle. Here the mass wall has controllable vents at high and low levels to allow convective heat transfer. Solar radiation heats the wall. The inclusion of vent holes through the heated wall permits some convection to take place, as a means of circulating heat to the building during the day.

The water wall

The water wall is a variation of the mass wall where water replaces the solid wall. This is attractive in situations where a low-mass wall is required. Water-filled containers take the place of a masonry wall. Tall fibreglass tubes are often used. Water has a greater unit heat capacity than brick or cement so, for a given volume, a water wall works more efficiently than a solid wall.

The Barra-Constantini wall

The Barra-Constantini system uses lightweight glazed collectors mounted on a wall. The glazed wall panel acts as a heat collector. Ducts in the building circulate the warm air by natural convection. The heated air warms heavyweight ceilings, walls and floor.

ROOF STORAGE SYSTEMS

Roof storage systems are a variation of the storage wall principle for indirect heat gain. Moveable insulating decks can be situated over the roof (storage medium). These are used to cover the roof during winter nights and summer days.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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