Direct solar collector system (direct system) in the solar collector directly to the water to the user's solar collector system.
General solar water heater engineering modules are direct system. Collector inside the water.
Indirect solar collector system (indirect system) in the solar collector heating liquid heat transfer fluid, and then through the heat exchanger by the heat transfer fluid heating water to the user's solar collector system.
Generally used for alpine and high fever areas, solar water heater project which is taking the medium, do not take the water, the temperature difference will not affect the medium inside.