How to Build a Passive Solar Hot Water System
A passive solar water heater can save you thousands of dollars over the years if properly installed and maintained. You could always buy solar panels, but simple solar water heaters, often called batch heaters, can be built more cheaply using glass, piping and old storage tanks. When designing your system, consider climate issues in your area to choose the appropriate fittings---you don't want components that will freeze or overheat in extreme temperatures. Does this Spark an idea?
Things You'll Need
- Water tank
- Copper piping
- Two wooden boxes
- Insulation
- Glass
- Reflective material
- Valves
- Plumbing tools
Instructions
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1
To build cheaply, find used materials. An old---but not leaking---water heater tank is ideal for the storage tank, although the insulation and some fixtures will have to be removed and replaced. In addition, you can make the glass cover of your solar hot water system from old windows or sliding glass doors. Make the boxes from salvaged plywood.
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Determine the best placement for the system. The box should be positioned and tilted to best follow the sun's path. The angle will vary, depending on the climate and the latitude of the home.
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Build two wooden boxes large enough to hold your water tank; one box should be slightly larger than the other. Essentially, you're building a box within a box. The inner box will hold the water tank, the outer box a layer of insulation---old styrofoam and packing peanuts, for example. Both boxes should be caulked and tightly sealed to hold in the heat.
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Line the exposed surfaces of the inner box with a reflective material to increase the amount of sunlight and heat focused on the tank. Depending on the sun's path, you may need to rig your reflective material into angled panels (forming a sort of V-shape starting at the boxes' edges and peaking underneath the tank) that can effectively catch the rays.
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Place the water tank inside the inner box, with connections to the incoming cold water supply on one end, and to the home on the other. The home connection should be from the top of the tank, because warm water rises. Make sure the pipe connections are tightly sealed where they enter the wooden boxes.
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Place the glass over the top of the box and seal it as tightly as possible. The sunlight should pass through the glass and heat the water in the tank. The hot water will rise to the top and flow into the home when faucets are opened or showers are turned on.
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Add a store-bought tempering valve, if necessary. The hot water may get too hot in some climates and seasons. If so, a tempering valve will add small amounts of cold water into the system to lower the temperature.
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Tips & Warnings
Paint the water tank black so it will better absorb the sunlight. If possible, use double-paned glass for better insulation.
Plastic or PVC pipe is cheaper, but in the summer or in hot climates, this type of pipe can melt or rupture. Use copper piping if possible. In cold climates, water can freeze inside the pipes. Be careful to insulate all exposed pipes.
