Mother's Super-simple Solar Tracker

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Each container of working fluid is shaded an equal amount so that when the sun moves across the sky the shadow from the shades will fall on one reservoir more than the other. This causes the tank with greater solar exposure to collect more heat and boil an increased amount of its working fluid. The difference between the higher pressure that this action creates in the warmed reservoir and the lower pressure maintained in the unwarmed reservoir works through the still-liquid freon to either extend or retract the piston in the hydraulic cylinder. As a result, the movement of the piston (which is connected to the pivoted collector through an eccentric arm) either pushes or pulls the solar absorption panel into alignment with the sun.

Freon 12 was chosen as the mechanism's working fluid because it [1] provides, at typical operating temperatures, enough pressure to operate the system in a very positive manner ... but not enough to burst any of the tracker's components, [2] is compatible with all other materials used in the assembly, [3] is non-explosive and relatively non-toxic, [4] has a moderate price tag, and [5] is available almost anywhere in the world from any refrigeration service shop.

Burkholder constructed the two freon tanks mounted on MOTHER's tracking collector from nine feet (4-1/2 feet each) of one-inch "M"-type (thin wall) hard copper tubing. He did this by soldering a sweat-weld sealing cap on each end of each tube. He also soldered a Schroder valve (a metal valve similar to the valve stem found on an automobile or bicycle tire, which may be purchased at most refrigeration and air conditioning repair shops) into each pipe near one end.

It was then a simple matter to connect a vacuum pump to the Schroder valve, evacuate the air from a tube, and charge it half full with the oiled freon. (Note: The oil in the "oiled freon" is important. Unoiled freon will quickly dry out the neoprene "0" rings inside the hydraulic cylinder and cause its piston to bind up and stop working.) The charged tubes were finished by giving them a coat of flat black Rustoleum.

The shades used on MOTHER's rig were constructed from .032" scrap aluminum sheet ... but painted Masonite, plywood, or any other stiff weather-resistant material would have worked as well. The important thing to remember here is that your tracking mechanism will become increasingly sensitive as you make your shades taller and taller.

Two 36"-long refrigerant transfer hoses (available from air conditioning and refrigerator supply outlets and most auto supply stores) were used to connect the two freon reservoirs to the double-acting power cylinder. They were attached to the tanks with fittings that automatically depressed the cores and opened them as they were screwed onto the Schroder valves.

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