Typically, a flat-plate collector is used with a number of types of hot water storage systems. Generally though, there are three main kinds of tank/panel arrangements used in domestic dwellings. They are:
Pumped or split system
A mains pressure tank is located at ground level and the solar collectors are mounted on the roof. With this system, when the water in the collectors is hot enough, the circulating pump is activated and water is pumped through the collectors’ water tubes where it absorbs the sun’s heat.
Advantages: The tank can be located (either internally or externally) at ground level and the panels can be above the tank. Good for roofs that do not have the strength for a close coupled system.
Disadvantages: Needs electricity to run the circulating pump and can’t be connected to a wood stove.
Close coupled system
Both the solar panels and tank are mounted on the roof. The panels are located just below the storage cylinder and water rises into the tank through a principle known as ‘natural thermosiphon’.
Advantages: Usually the most cost-effective system to install. Provides water at mains pressure or low pressure. Has no moving parts and has the highest efficiency. Can also be used as a waterproofed gravity -feed tank for wood heater backup in winter. A good option if a position for a ground mounted tank cannot be found.
Disadvantages: Roof needs to be designed to withstand the combined weight of tank and water. May not be aesthetically pleasing to some.
Gravity or low pressure system
The tank is located in a roof cavity or if waterproofed, on the roof itself, with the solar panels installed on a north facing roof. The panels must be below the tank to allow for natural thermosiphon of water from tank down to panels and returned in an upwards flow to the tank.
Advantages: Usually the most cost-effective system to purchase. May be directly connected to a wet-back in a woodstove or heater. The tanks lasts a very long time, as they’re made of copper and it sit at gravity pressure.
Disadvantages: The house must be plumbed for gravity pressure requiring larger pipe diameters. The flow rate from the taps may not be to the liking of some.