Indirect:
Instead of heating water, the solar collector heats a "heat transfer" fluid, such as antifreeze. The antifreeze then flows into the sealed piping of a heat exchanger, where it is surrounded by water. The water picks up the heat from the antifreeze (but never mixes with it), and is then pumped into a geyser. An alternative to to an indirect system would be Evactuated Tubes.
Direct:
Water moves through the solar collector and into a geyser with the help of electrical pumps and controls, or via a natural thermosiphoning process.
| You may need...
Depending on whether or not you stay in a frost prone area you may need a direct or indirect Solar Water Heater: