Solar Heat Storage
There are two aspects to the Storage process. The first involves the actual storage of the excess heat recovered by the system; the second involves how this heat is managed. Both are covered in this section.
SOLAR STORAGE - Once the heat is obtained by the collector array, a means is needed to save it for later use. Note also the amount of heat recovered at noon on a sunny day would quickly cause the house to become extremely hot if no means were provided to absorb the excess. The storage assembly, located in the basement of the house, performs this function.
The assembly is basically an insulated room with a volume of about 800 cubic feet. The room is filled with a large thermal mass to absorb heat from the collectors. The first storage unit used a rock bed to absorb the heat. Early research discovered a problem with the rocks in that they encouraged the formation of mildew in the summer when the system was not storing heat. The porous nature of the rock contributed to this problem. As a result, the rock was eliminated and shelves were installed. (See Fig. 1) Only three shelves are shown in the drawing, the actual system uses 6.
About 3000 glass jars are filled with water and sealed. They are placed on the shelves and arranged so the air flow is around and between them. The jars at the top of the pile are heated first, and are hotter than those near the bottom. As the heat recovery continues, the heat is driven deeper down the pile to increase the heat reserves. The glass surface of the jars has solved the mildew problem. Currently, as a result of ongoing testing, the size and capacity of the storage unit may be increased. This will provide a greater reserve capacity and improved buffering effect on the temperature thereby improving the system performance.
Storage Unit under construction.
This shows about 1/3 of the jars as they were being placed.
There are two motorized dampers, A1 and A2, shown in Figure 1. These are placed in the supply and return trunks to the collector array. They prevent heat loss back to the collectors when the system is not in the heat recovery mode. If the storage temperature is greater than the collector temperature, these dampers will be closed.
AIR HANDLER - The Air Handler is a motorized damper assembly, B1 and B2, located between the storage unit and the furnace return air duct. (Refer to figure 1 above) Its purpose is to allow the return air to the furnace to either go through the storage unit or to bypass it. The bypass occurs if the system is in the air conditioning mode or if no solar heat is available from storage or the collectors. Note that heat may be pulled directly from the collectors since the storage output duct is located directly beside the collector hot air trunk. Operation of the dampers is determined by the Digital Control system.