A solar water heater is extremely simple. On a typical single-family residence, there will typically be one, two or three solar collector panels on the roof. The panels resemble skylights, and will be about 4 feet wide and 6 to 10 feet long. Depending on the type of system, there will be a storage tank inside or above the collectors on the roof or in a separate location. If it is an "active" solar heater, there will be a pump and automatic control located on the separate storage tank or near it.
The cold water supply is connected to the solar storage tank. Water to be heated circulates between the storage tank and the solar collectors. The output from the solar storage tank becomes the cold water connection to the conventional gas, electric or oil water heater. When a hot tap is opened, preheated water is drawn from storage into the conventional ("auxiliary") water heater. The burner or electric element turns on only if the temperature cannot be maintained by the solar heater. Most properly-designed solar water heaters will supply 70 per cent or more of all the energy needed for water heating.
The facing direction ("orientation") may be any direction within 90 degrees of due south (in the northern hemisphere), but you will need more solar collectors as the angle from due south increases to near 90 degrees. If you cannot use an orientation within these limits, the solar heater will be useless. Solar panels need to face north in the southern hemisphere. Also, be sure that the collectors will not be shaded.
The collector area required will depend on the daily amount of hot water use, the type of collectors used, the orientation of the collectors and your geographic location. If you consider a standard "package", you should be sure it is sized appropriately for your specific installation.
If you choose a "Passive" solar water heater, the storage tank(s) will be on the roof. In this event, simple structural bracing may be required. Active solar systems do not normally require structural calculations or roof bracing, because the weight of the collectors is well within normal roof load limits.
An "Active" solar water heater uses a small pump for solar collector circulation, and does not require a tank on the roof. A "Passive" solar heater depends on thermosyphon action, so does not use a pump, but tanks(s) must be on the roof.
Many systems are capable of furnishing all the hot water for six months or more, and have manual bypass valves that permit you to shut down your auxiliary water heater during those "100% solar" months. Re- setting the bypass valves twice yearly, and shutting down or restarting the auxiliary water heater are the only items requiring regular attention on most solar water heaters.
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