Solar heating of cold water from the water main enters the system and appears at the valve (1). The cut-off level in the valve is below the maximum level of the hot water storage tank (2).
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The incoming water is fed to the collector’s cold end (bottom) (3).
As the collector heats up from exposure to the sun, the water becomes less dense, rises through the collector, and is fed internally into the top of the storage tank(4).
The water in the storage tank will become hot at the top as the heated water rises above the cooler water in the tank.
Cool water (5) at the bottom of the tank is drawn down to replace the heated water rising from the collector.
As the water in the tank rises above ambient temperature, the water in the bottom of the tank, being mixed with the incoming hot water, is also warming. This has the effect of providing a source of warmed water (6) to the collector, further increasing its outgoing temperature.
As hot water expands, a means of accommodating the expanding water is provided by the open-to-air expansion tube (7) at the top of the tank.
When the faucet (8) is opened, hot water which has collected at the top of the tank is drawn off. This lowers the water level in the hot water storage tankand therefore the water level at the valve allowing the main supply water to enter the system to the same volume as that which has been drawn.
More information on solar hot water systems can be read here
The main supply water enters the bottom of the collector and the collector continues to heat this incoming water which continues to be supplied to the tank. This increases the temperature of the hot water supplied to the tank due to the addition of the solar heating temperature plus the pre-heated water from the bottom of the tank entering the collector.
Please realise that this is the simplest form of solar water heater. The water should be used and not left to stand unused as there is no separation between the incoming water and the heating source.
Expanding The System
The system can be expanded by the addition of extra collectors in series with the original. One collector supplies pre-heated water to the next. The other benefit of a second collector is that one can be installed facing east north-east to get morning sun and a second facing west south-west for afternoon sun, thereby getting maximum solar energy all day.
Expanding The System Warning
A word of warning. Whilst the system can theoretically benefit from an increased number of panels, it should be realised that if the water temperature is increased too much, there is every chance of boiling the water in the storage tank with detrimental effects to the tank and the system. Boiling water will be ejected from the expansion pipe and create a possible dangerous hazard.
The original version of this solar water heater was built for a neighbour in a village in Turkey. A wedge-shaped frame was welded together from 50cm angle iron. The solar collector was to hand having recently had my own replaced with a more modern version.
A large poly barrel was sourced from the local dump, cleaned and fitted horizontally at the top of the wedge with the solar panel attached to the sloping section of the wedge. A further poly one gallon bottle was mounted above the poly barrel by attaching extensions to the top of the wedge frame and fitted with a ball valve inside, to control the water level in the system and add more water as the level dropped in use. All connections and pipes were of the plastic hot water variety and the overall cost came to a modest 10 dollars. The construction was lifted onto the flat roof of the building and our neighbour had hot water on tap for the first time in her life.
