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Basic components
Collectors absorb sunlight and transform it into heat. Their mounting should be in an optimal location for receiving sunlight. The flow system guides the heated water to its destinations. A controller decides when to allow water or heat exchange fluids to move. In active systems, you have electrically controlled pumps.
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Collectors
Probably the most important decision you will make is what kind of collector you will use in your water heating system. There are a number of designs and mechanisms appropriate for differing conditions and budgets. Some are basic, like the ICS collectors, some are more complex like evacuated tube collectors.
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Flat-plate collectors
The most commonly used collectors because of their efficiency and low maintenance needs. An enclosed, thin rectangular box has a glazed window on one side. This allows the sunlight to pass through to hit rows of circulation tubes. To maximize efficiency, the tubes sit on an absorber plate insulated from the housing of the collector.
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ICS collectors
Integrated collector storage are direct collectors often used in swimming pools and less economically developed countries due to their low cost, ease of installation and relatively good efficiency. The water to be heated is simply placed in the collector and the sun does the rest. Add a pump and you’re good to go.
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Evacuated tube collectors
Copper rods run through a vacuum tube, the sun heats the copper which is an excellent conductor of heat, and this travels to a large copper pipe with the water inside. Although expensive, these are reliable and freeze-free collectors.
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Complete systems
These are the entire collections of components and associated equipment connected together to collect solar energy to convert it into heat for your needs. There are many different types of systems but the most basic categories include passive, active, direct and indirect.
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Passive systems
Passive systems require little input other than the sun and a means of pumping the water around (as long as the pump is not contained within the solar heating system itself, it’s passive). A passive system contains no moving parts.
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Active systems
These are able to produce more output energy for your use, and they can also work in a wider variety of designs and climates. As the name implies, they are categorised by having a powered appliance and a controller within the system, forcing circulation at prescribed times.
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Direct systems
Direct systems have the water sitting inside the collector, heated directly by the sun. Open-loop systems are an example of this. Once the water is heated, it is taken out of the loop and fresh water is drawn in to wait for its turn for heating.
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Indirect systems
Indirect systems use a secondary fluid to collect heat which is then transferred to the water via a heat exchanger. These systems are more common in colder climates prone to freezing. Closed-loop systems are an example of this. The fluid is constantly circulating, hence it is also an active system because it needs a pump.
