Panels collect thermal energy, not electricity.
Q: I’ve been hearing a lot about solar water heating lately. Is it something worth pursuing for my home?
A: To get some answers, we talked to Amy Leedom, the director of marketing for Dwell Development, an award-winning sustainable homebuilder in Seattle.
Let’s start with the basics. What is solar water heating?
Using solar thermal technology, we harness the sun’s energy to generate thermal energy, which is then used to heat the water in your home. It’s a low-cost and environmentally friendly alternative to fossil fuels.
How does it work?
Solar thermal collectors (or solar tubes) sit on your roof and collect solar energy, which is circulated via water or solar fluid within the tubes to the hot water tank in your house. So when you turn on your shower, you get hot water heated naturally by the sun.
Solar water heaters are a cost-effective (sunshine is always free!) and energy-efficient way (all natural!) to generate hot water for your home.
How do I know what type of system is right for my home?
There are two types of solar water heating systems: active and passive.
There are two types of active solar water heating systems that circulate water or fluid:
• Direct circulation systems: These systems circulate water from the home into the solar collectors to heat up and then back into the water tank for everyday use.
• Indirect circulation systems: These systems circulate a non-freezing fluid through the collectors and into a heat exchanger that is used to heat the water in your home.
Direct circulation systems are better for more temperate climates like the California coast, whereas in Seattle, we typically want to use the indirect system in case we have an unexpectedly cold and snowy winter. When using water, instead of the antifreeze fluid, there is always a risk of freezing. Solar water heating technology has been around for many years, but before the non-freezing fluid was introduced, solar water heating wasn’t usable in colder climates and therefore took a bit longer to make its way to homes across the country.
There are two types of passive solar water heating systems:
• Integral collector-storage passive systems: In these systems, the solar collectors and tank are combined into one entity that houses all your household hot water. These systems look very similar to standard rooftop solar systems you see around town.
• Thermosyphon systems: In this case, the solar-heated hot water is siphoned through the collector and into your home. The name says it all: The sun heats the water in the collector, causing the water to expand and rise while simultaneously pushing the remaining cold water down. That hot water is then ready for use in the home.
Can I use the solar panels on my roof to heat my water?
Rooftop solar produces electricity, not heat. So in this instance, you would need a thermal system to heat water.
It’s cloudy nine months out of the year in Seattle. Is there enough sun to heat my water?
Yes. The solar tubes are collection energy from the sun even on cloudy Seattle days. Production may go down, but you will still get plenty of hot water for a family.
What happens when the tank runs out of hot water?
Typically, homeowners have a backup boiler or water heater that kicks into gear when the tank runs out of solar-heated water.
How much do solar water heating systems cost?
The cost is typically more than gas or electric heaters but they will save you money in the long run. And solar heating systems have the added benefit of being energy efficient and the most environmentally friendly way to heat water in your home.
HomeWork is written by Cameron Poague and contributing member professionals of the Master Builders Association (MBA) of King and Snohomish Counties. If you have a home improvement, remodeling or residential homebuilding question you’d like answered by one of the MBA’s more than 2,800 members, write to firstname.lastname@example.org.