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Solar water heater easy to build
March 2, 2008
Q: I want to become more green and my children are all for it.
From what I have read, using a solar water heater makes the most sense.
I don't have much money for one. How can we build a simple one ourselves?
Pat F.
A: Solar water heating makes the most economic sense for almost every region of our country because hot water is used year-round. This is in contrast to solar space heating which is used for only about six months each year and its maximum output is needed when the daylight is shortest.
Since your budget is very limited and your children want to help, building a simple batch-type solar water heater is your best option. It is not as effective as an elaborate active solar system, but it does not cost thousands of dollars either. Depending on the scrap materials you can find, you should be able to build a batch system for less than $200 and the savings will payback its cost in a couple of years.
The hot water heating energy savings you can expect to realize depend upon the specific design and your climate. During the summer, 50 percent savings is reasonable, as is 25 percent savings during fall and spring. In many areas of the country, it is best to bypass the solar heater during winter to avoid freezing and possible damage to the heater or plumbing.
A batch solar water heater is used as a preheater for the incoming cold water before it reaches your standard water heater. If the water is warmer, it takes less gas or electricity to heat the water to the regular hot water temperature (120 degrees is best). On a hot sunny summer afternoon, the solar heater can warm water enough that the water heater stays off all day.
The most common design of batch solar water heater uses a water tank inside of an insulated box with a clear top. Special solar water heating tanks can be purchased, but first contact plumbers to find one or two old discarded water heater which do not leak. Strip off the sheet metal skin and insulation to expose the steel tank. It will already have the plumbing fittings.
The water heater tank should be painted flat black. Special solar paints, which are formulated to absorb more solar heat, are also available at a reasonable cost. Use an old glass storm door or buy a sheet of clear acrylic plastic for the top. For the greatest year-round solar gain, slope the clear top at an angle equal to your latitude angle.
Run the hot water outlet pipe from the tank through the back or side of the box and then down near the ground into your house to the water heater. Run another incoming cold water pipe from the water heater to the solar heater. Insulate them very well. Install a crossover pipe and two valves to bypass the solar water heater during winter.
The following companies offer solar kits and components: AAA Solar Supply, 800-245-0311, http://www.aaasolar.com ; Alternative Energy Store, 877-878-4060, http://www.altenergystore.com ; Build It Solar, http://www.builditsolar.com ; FLS Energy, 877-862-5050, http://www.easysolarkits.com ; and Solar Components, 603-668-8186, http://www.solar-components.com .