Dear Jim: We have teenage daughters who take long showers. Our water heating costs are sky high. We are on a tight budget, but want to use some solar water heating. Is there a system we can make ourselves? —Tim H.
Dear Tim: For a typical family of four, heating water can account for about 20 percent of its annual utility bills. If you have two daughters taking long showers, yours may be somewhat higher.
Before you consider using solar or any other efficient water heating methods, install low-flow showerheads with shut-off tickle (lathering) valves. Also talk with your family about taking shorter showers. This not only reduces water heating costs, but it also conserves our fresh water supply.
Unless you are an accomplished craftsman, I suggest you make a simple batch solar water heater. This is called a passive system because the water moves through it due to the incoming line pressure or just temperature differences, yet it can be quite efficient and effective.
Trying to build an active system, with collectors on the roof, plumbing and control systems, and storage tanks is beyond the skill level of most homeowners. I am a design engineer and I don’t think I could build a system from scratch.
A batch solar system is used as a preheater for your existing water heater. The incoming cold water flows through the solar preheater before going to your water heater. Every degree the water is warmed in the preheater reduces the amount of electricity or gas used by the water heater.
The simplest batch solar system is called a breadbox design. It utilizes a horizontal metal water tank inside of a box with a clear top. The sun shines in through the clear top to heat the water. Another slightly more efficient option uses a tall box tilted at an angle to face the sun. This allows the warmer water to be drawn first from the top of the tank.
You can buy a stainless steel water tank especially designed for this application with the inlet and outlet water fittings. If you can find an old water heater which is not leaky, strip off the metal skin and insulation to use the inner tank. Paint it flat black to absorb more of the sun’s heat.
It does help to insulate the solid sides and bottom of the box especially if you plan to use it most of the year. Very heavy insulation is not needed because the tank will not get extremely warm, especially if you are using hot water throughout the day. One-inch-thick foil-faced rigid foam sheets should be fine. Attach them inside the box so they reflect the sun’s heat to the tank.
Install water valves and plumbing so the solar tank can be drained and bypassed during cold weather. Install heavy insulation around any exposed pipes and bury as much as possible underground.
The following companies offer solar kits and components: Alternative Energy Store, (877) 878-4060, http://www.altetore.com; Build It Solar, http://www.builditsolar.com; Solar Components, (603) 668-8186, http://www.solar-components.com; and Solar Direct, (800) 333-9276, http://www.solardirect.com.