How Do Solar Water Heating Systems Work?

Each morning, you step into the shower and try to wake up under a steaming cascade. When you turn on your dishwasher, you trust that the piping hot water will disinfect your cutting boards and dinner plates. After working in the yard, you throw your dirt-covered clothes into the washing machine and turn up the temperature. You rely on hot water for many of your daily tasks, so investing in a solar water heating system in order to save some money just makes sense. However, before making the change, you may find yourself wondering, “How does a solar water heating system work?” After all, the last thing you want is to invest in an unreliable water heater. Fortunately, many solar water heater types can provide you with a consistent source of hot water for years to come.

How Do Solar Water Heating Systems Work?

A solar water heating system works by using a collector to accumulate solar heat, which is then transferred into the water you use throughout your home. Most solar water heating systems use one of three different types of collectors in order to efficiently perform this task:

Evacuated Tube Solar Collectors

Also known as vacuum tube collectors, this solar water heating system consists of parallel rows of angled, vacuum-sealed glass tubes connected at the top to a pipe that contains heat-absorbing fluid. Each glass tube holds a dark, heat-absorbing plate connected to a small metal cylinder called a “heat pipe.”

When the sunshine warms the plate, it causes fluid in the heat pipe to separate into cold liquid and hot vapor. The hot vapor rises to the top of the heat pipe, where it transfers its warm energy out of the glass tube and into the heat-absorbing fluid running through the upper pipe. This heat-absorbing fluid is then used to warm the water in your home. It’s worth noting that this system works consistently well regardless of the temperature, making it ideal for cooler climates.

Flat-Plate Collectors

This solar water heating system uses flat, rectangular boxes to absorb solar energy and transfer it to your home’s hot water system. Each box consists of glass or polymer cover that surrounds a series of pipes attached to a dark absorber plate. These pipes contain a heat-absorbing fluid.

When working, sunlight passes through the collector’s cover and heats the dark absorber plate underneath. The plate then transfers the warm solar energy into the heat-absorbing fluid running through the pipes. This fluid is carried into your home, where it transfers its solar heat once more into the water in your hot water tank.

Integral Collector-Storage Systems

Similar in structure to flat-plate collectors, integral collector-storage solar water heater systems contain large water storage tubes instead of small heat-absorbing fluid pipes. The storage tubes hold the water that you will use in your home, warming it until it’s needed.

These solar collectors use gravity in order to circulate hot water through your home’s plumbing system. This makes it necessary to install any integral collector-storage systems on a structurally sound part of your roof that receives plenty of consistent sunlight.

Of course, collecting solar energy is only one part of the process when it comes to providing your home with hot water. In order to work, a solar water heating system must effectively transfer that hot energy into your water. Solar water heating systems tend to be classified based on how they perform this energy transfer. Passive solar water heaters, which almost always use integral collector-storage systems, use the sun to directly heat your home’s water. On the other hand, an active solar water heater makes use of an electric pump to circulate heat-transferring fluid from solar collectors to your hot water storage tank and back again.

Which Type of Solar Water Heating System Works Best?

Of the two types of solar water heaters, active systems using flat plate or evacuated tube collectors tend to offer the greatest reliability. A passive solar water heater stores your hot water outdoors inside the solar collector, making it vulnerable to chilling or freezing temperatures. In contrast, the heat-transferring fluid used in most active solar water heating systems is better at retaining heat and possesses a lower freezing point. An active solar water heater works by:

1. Using solar collectors to warm heat-transferring fluid
2. Circulating the warm fluid through pipes to a heat exchanger in your hot water tank
3. Using the heat exchanger to transfer the fluid’s heat to your home’s water
4. Circulating the now-cold fluid back into the solar collectors

Most solar water heating systems are installed alongside a conventional backup water heater. On sunless or below-freezing days, you can manually switch from using the solar water heater to the backup system. At no point does the heat transfer fluid directly enter your home’s water supply, and your water is never directly exposed to the outdoor solar collector. This improves the reliability and efficiency of your solar water heater and ensures that you have access to piping hot water whenever you need it.

Is a Solar Water Heating System Right for You?

The answer to this question depends on how you use hot water in your home. For larger households—where the dishwasher and washing machine are always running and long, steamy showers bookend the days—the right kind of solar water heater can offer unquestionable value and impressive savings. However, even smaller households—where the occasional warm bath serves as the perfect way to unwind—will experience some savings after installing a solar water heating system. Of course, if you live in Florida, you can always ask the area’s leading energy pros for advice. Since 1989, Florida Energy Water & Air has provided homeowners with the energy resources they need to thrive, including a selection of high-performance solar water heating systems. If you’d like to learn more about how you can save, contact us today!