How it Works
A solar water heater combines solar energy with electricity,
gas or oil to heat water for cooking, cleaning, bathing and heating. The unit
consists of a storage tank and a solar collector which collects solar heat
while sitting on the roof.
Solar hot water systems can be either “active” or “passive”.
Active models use pumps to circulate water to and from the heated solar
collector. Passive models use heat-driven convection or heat pipes to circulate
the water. When solar power is not enough to keep water above the desired
temperature, the second energy source (electricity, gas or oil) kicks in. In
colder climates, some solar heaters use a mixture of water and glycol. The
glycol keeps the water from freezing and prevents corrosion.
What Can Go Wrong?
If hot water is not used for an extended period of time, the
tank water can get extremely hot. Any glycol in the system can become acidic at
high temperatures and may begin to eat away at the system’s collectors, pipes
and pump. This will lead to failure of the system.
Even though a secondary energy source is often
used - especially when there’s no sun - a solar hot water system is far more energy
efficiency than a conventional hot water heater. Your solar water heater can
reduce electricity consumption by 1,500 kilowatt hours annually, which can save
you hundreds of dollars. It can also reduce carbon dioxide emission by 2,300