Back to Basics with Solar Water Heating

Winter, with fewer hours of sunlight and dropping temperatures, might not seem the most obvious time of year to consider solar power. But you can fight the chill in the air—at least when bathing—with solar water heating.

In general, solar water heating systems can meet more than half of a household’s water heating needs over the course of a year. In addition, the solar panels used for water heating are not “high-tech” like those needed to produce electricity. This makes them more affordable.

Solar water heaters, you see, don’t focus on converting sunlight into electricity. Instead they harness radiant heat energy of the sun to dial up the temperature of your home’s water.

Placement of solar water heating panels matters, though. For best results, they should face south. Be careful when planting trees; the panels should remain unshaded year-round.

There are several types of solar water heating systems, each employing a similar method. All depend on a dark, heat-absorbing material inside a collector—a glazed box or tube. A heat-exchange fluid passes through the collector, gets hot, then runs through a heat exchanger, which transfers the heat to water in a storage tank.

Different Systems for Different Climates
In four-season climates, closed-loop antifreeze systems are the most popular. These use an antifreeze heat transfer fluid in the collector.
Closed-loop drainback systems, on the other hand, use distilled water with a corrosion inhibitor. When operating, the drainback tank is mostly filled with air. But when the heat transfer fluid cools below a useful temperature, it flows into the drainback tank, forcing air into the collector and protecting the system from freezing. Drainback systems are most useful in warmer climates.

Open-loop direct systems heat and circulate household (potable) water directly through collectors. A batch heater, one type of open-loop system, simply consists of a tank filled with water and placed on the roof either in a glazed box or attached to a solar collector panel. Because batch heaters have few parts, they’re highly reliable. However, the tank must be protected from freezing or drained before winter.This design is common for do-it-yourself projects serving summer homes or workshops.

Solar Shopping
Several resources are available to help you choose a solar water heater.Access Energy Cooperative provides information on qualified local dealers at www.accessenergycoop.com. You can also get advice on reputable installers from your state or regional chapter of the Solar Energy Industries Association, www.seia.org, and the American Solar Energy Society, www.findsolar.com.

You should be confident in the equipment as well as the installer. Solar water heating equipment routinely gets tested by the Solar Rating and Certification Corporation at www.solar-rating.org. The U.S. Environmental Protection Agency’s ENERGY STAR® program, www.energystar.gov, certifies solar water heating equipment and other energy efficient water heaters.

Investing in a certified system not only gives you confidence; it helps your bottom line. Federal solar tax credits, available through 2016, can cover 30% of the cost of investing in a qualified solar water heating system. On top of this, consumers in some states may qualify for additional incentives. Check the national database of incentives for renewable energy at www.dsireusa.org for details.

Source: Cooperative Research Network, an arm of Arlington, Va.-based National Rural Electric Cooperative Association