Q: I want to do an inexpensive weekend project with my children to show them how to save money by conserving resources. What is the simplest and cheapest solar water heater I can build myself from scratch?
A: The simplest and cheapest solar water heater is a "breadbox" design. Using common materials, lumber, insulation and an old, discarded water heater tank from a plumber, it should not cost more than $80 to build. A simple, do-it-yourself, breadbox solar water heater can reduce annual water heating costs by 20
percent. For a typical family with an electric water heater, this can pay back the material costs in the first year. Thereafter, the solar hot water is free.
A breadbox water heater is called a batch-type solar heater. It is basically a black water tank inside a box with a clear top and front. As the sun shines on the tank inside the box, it heats the "batch" of water inside it.
This heated tank of water is used as a preheater for your regular water heater. Cold incoming water first flows through the breadbox heater before it goes to your existing gas or electric water heater.
On a sunny day, water in the breadbox heater can get hot enough so that your existing water heater won't have to come on at all. On cloudy or very chilly days, close hinged insulated covers so it does not lose heat.
The total cost can be greatly reduced by getting a discarded water heater tank from a plumber. Electric water heater tanks are the easiest to strip and use because there is no flue up the center.
Pull off the outside shell and remove the insulation. Clean the tank and inspect it for leaks. If you suspect a leak, car radiator shops can pressure test it for you. Paint the cleaned tank flat black.
Make a simple wooden box, leaving the top and front open. Line the inside with foil-faced rigid insulation. Mount the water tank inside and cover the top and front with old storm doors or windows or clear acrylic plastic.
On the top and front, attach hinged insulated covers with reflective foil facing the inside. When open, these covers reflect more of the sun's rays through the clear top and front to the water tank.
There are new low-cost solar kits available. These are designed for do-it-yourself installation. Some use a simple, three-way fitting to attach the solar system to your existing water heater through the tank drain valve.
Write for Update Bulletin No. 676 showing detailed instructions, diagrams and materials list for making a breadbox solar water heater, a plumbing schematic and a list of 20 kit manufacturers. Please include $2 and a business-size SASE. James Dulley, The Sun, 6906 Royalgreen Drive, Cincinnati, Ohio 45244