Grades 3–5 · Systems
How can a roof collector warm water for a home?
A solar water heater catches sunlight to warm water. Its roof collector is different from a solar panel that makes electricity. Inside the collector, a dark surface absorbs light and transfers energy to fluid moving through nearby tubes.
A clear cover lets sunlight reach the surface while helping reduce heat loss. Insulation behind the collector also slows energy escaping. When the collector becomes warmer than the storage tank, a pump can circulate fluid through it. The fluid picks up energy on the roof and carries that energy toward the tank.
In the system pictured, collector fluid flows through a metal coil inside the tank. Heat passes through the coil wall into the household water surrounding it. The two liquids stay separate. The cooled collector fluid returns to the roof to be warmed again, completing a loop.
Trace the orange fluid from the collector into the coil, then the blue return route back to the roof.
The insulated tank holds warm water until someone needs it. Cloudy weather, a long night or a large demand can leave too little solar heat, so many systems include a backup heater. A controller prevents the pump from carrying useful tank warmth back to a cold collector. The useful result depends on the whole route: collect energy, transfer it into water, then slow its escape until that water is needed.
About this explanation
This is one indirect pumped design; other solar water heaters circulate household water directly or rely on natural circulation.
Starting knowledge: Follow a sequence of material transfers and distinguish a part from a larger system.
Sources
- U.S. Department of Energy — Water Heaters Solar