Solar hydronic/thermal technology uses an evacuated tube collector system located on a roof. Sun shining on the solar collectors heats a special fluid within the tubes. The fluid then pumps into heat exchange coils in an insulated storage tank.
The evacuated tubes don’t require direct sunlight, which means they get more heat from the sun for longer periods of the day and makes them ideal for the colder seasons or colder climates.
As the storage tank is insulated this means the water can be stored for several days at the required temperature so you don’t have top worry about not having hot water or heating at night or on cloudy days.