Passive solar energy capture box.
After several experiments with simple technology to capture solar energy, including the use of matt black painted domestic heating radiators, it was decided that a black painted wooden case with a K glass double glazed unit fixed to the front would be the most cost effective solution.
The wooded case was divided into two sections a large lower section backed with plywood and insulated from the wall behind it with aluminium foil and an upper section which contained a finned radiator – the sort commonly used for heating on small river boats.
The case was mounted on the wall of the house inside the existing outhouse, meaning sunlight had to travel through one layer of glass before it reached the case. It was necessary to locate the case in this position as water heated in the finned radiator was transferred to a tank located in a utility room on the other side of the wall.
Pump and fan
Heated air was circulated from the lower section of the case through the upper section containing the radiator by means of a 12volt fan of the sort used to cool electrical equipment. The air returned to the large section of the case through a second hole (100mm diameter) cut through the dividing panel within the case.
Water was circulated through the finned radiator and into a tank by means of a 12 volt water pump – an Audi automobile spare part. Both the pump and the fan were powered via direct connection to a Sensei solar panel - marketed as a battery charger. The advantage of using the solar panel was that the pump only ran when the sun shone and pumped water at a rate proportional to the power of the sun.
Water tanks inside house
Water was fed through a pipe into a tank inside a utility room. While both of these vessels were original expansion tanks the lower one had the diaphragm removed so that water would flow through it. The upper tank was still used as an expansion tank to reduce the pressure in the system.
Air temperature reached 68˚C and water temperature reached 50˚C – however this was in early Autumn not in the winter.