Water Heater

• When solar hydronic systems are used to heat water, they are also called solar water heating systems. Water is heated as it flows through solar collectors that harness the sun's energy, and on to a solar storage tank attached to a water supply.
  
  

Heating Buildings

• Solar hydronic systems that are used to heat buildings have two primary components:
  
  1.) Solar collectors, which absorb energy from sunlight. The sunlight heats a transfer fluid (water or an antifreeze).
  
  2.) A radiant heat-delivery system, which uses hot transfer fluid to heat the floor, or via heat exchangers or radiators, the air in a building.
  
  

Passive and Active

• Passive solar technologies do not employ mechanical devices to capture the sun's energy; however, active technologies do. Solar hydronic systems that heat water can be active or passive; but systems that work with a radiant heat-delivery system are active technologies.