Conscious Choice: Solar Water Heaters

June 2001 | Sensible Home

Solar Water Heaters

by James Dulley

Dear Jim: With energy shortages, global warming, and rolling blackouts, I need to do my part and save a few bucks too. I want to make a simple low-cost solar water heater. What is the simplest design to build? — Peg J.

Dear Peg: Heating water with the sun is an efficient and effective use of solar energy for all climates. Unlike solar space heating that is used only in the winter, solar water heating is utilized and saves money year-round.

Water heating typically accounts for about 20 percent of a family’s annual utility bills and a simple solar water heater can contribute up to half of your hot water needs. In addition to saving money and protecting the environment, building a solar water heater sets an excellent example for your children.

There are several designs of effective solar water heaters that an average do-it-yourselfer can easily build out of mostly scrap materials. Among these designs, a batch-type is the simplest. All the materials required to build one should be less than $100 to yield a payback within a year or so.

If you are not a do-it-yourselfer, don’t give up. Ready-to-build solar batch kits, with two thirty-gallon tanks, double-wall glazing, foam insulation, etc., are available and typically come with an instruction manual. You can also buy completely assembled batch units that are easy to hook up yourself.

A solar batch water heater is used as a preheater for your existing water heater and is usually mounted on the ground on the southern side of your house. There are no ugly rooftop collectors and very little maintenance.

The plumbing is very simple. The cold water pipe leading to your water heater is connected to the solar batch unit inlet. Its outlet is connected back to your water heater. Install two low-cost valves at the cold water inlet to your water heater so you can bypass the solar heater anytime you wish.

One or two water tanks in the batch heater are exposed to the sun. This preheats the incoming water. On a sunny day, the outlet water will be warm enough that your existing water heater will not have to come on at all.

A simple bread box design is basically a black water tank, typically thirty to forty gallons, in a plywood box with a clear top. A discarded water heater tank, stripped down and painted black, works great. An old storm window/door or clear acrylic plastic is effective for the clear top cover.

Insulating the sides and back of the box is important to minimize the loss of solar heat. If you are handy with tools, build a hinged insulated cover with reflective foil to direct more of the sun’s rays on the tank. Close the insulated covers at night or just throw an old quilt over the clear top.

Write for (or instantly download) Update Bulletin No. 832, do-it-yourself instructions, diagrams, materials list, plumbing schematic for several designs of batch solar water heaters and a list of ready-to-use batch solar kits. Please include $3.00 and a business-size SASE. James Dulley, Conscious Choice, 6906 Royalgreen Dr., Cincinnati, OH 45244.

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