Sol-Air Blog

The Water Heater: Your First Solar Step

Posted on 8/9/18 9:58 AM

Looking to reduce those utility bills by harnessing the power of solar energy, but not sure you can afford it? There’s a way! A solar water heater is the first step toward embracing solar, without completely changing your home’s relationship to the power grid.

Evacuated-tube solar collectors - TEXT-1The addition of a solar water heating system allows homeowners to pilot the process of putting the sun’s  energy to work using rooftop solar panels, without the commitment and expense of a full-scale installation. This type of system doesn’t use your average photovoltaic solar panels that convert solar photon into electricity, rather flat plate or evacuated tube collectors that store the sun’s thermal energy to directly heat up cold water.

The specifics of how solar water heaters work are more complex than your average water heater, depending on the kind of system installed. There are two types of systems: active and passive. Active systems prevent water from freezing by using pumps and controls to circulate water, while passive systems do not.

Active systems offer direct circulation for homes in warmer climates, where water is pumped through the solar collectors and into the home. In colder climates, an active system with indirect circulation is recommended. Instead of water, a non-freezing, heat transfer fluid flows through the solar collectors to heat the water before it’s used in the home.

There are also two types of passive systems that perform better depending on the climate. An integrated collector storage (ICS) system consists of a solar collector and tank combined into a single unit. Therefore, pumps and controls are not needed. This type of system could freeze up, thus, it should only be used in warmer climates.

With an ICS system, cold water flows through the solar collector to preheat, then gets stored in the tank. When needed, the solar heated water flows out of the tank, is replaced with cold water, then goes into the conventional water heater inside the home.

Thermosyphon system - TextThermosyphon systems work passively as well, but with this method the tank and collector are separated. With the tank located above the solar collector, warmer water rises in the tank and the cold water sinks. From there, the cold water can be heated directly through the solar collector and back into the tank, or indirectly by using a non-freezing, heat transfer fluid that transfers the heat back to the tank.

Just how much you’ll save with a solar water heater depends on where you live, the cost of conventional fuels and how much hot water you use. According to energy.gov, if you install a solar water heater your water heating bills should drop 50% - 80%. If you’re interested in transitioning your household toward energy savings, reduced emissions and increased independence, a solar water heater is the perfect place to start!

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