FIG. 4: The collector has been facing west (left). As the sun appears on the eastern horizon (to the right), however, the freon in its unshaded tank has begun to warm and expand. This is pushing the piston down in the hydraulic cylinder and, as the contracting piston pulls on the eccentric arm fastened to the pivoted flat-plate collector, the solar collector is pulled over to face the fresh morning sun.
FIG. 3-A: The sun's rays warm right tank but not the left one. FIG. 3-B: As pressure builds in right tank, liquid freon is forced into left one and collector tilts in that direction. FIG. 3-C: As the collector turns more and more directly toward the sun, its left tank also begins to heat. As pressure builds in that container, it begins to accept less and less liquid freon from the right tank. Equilibrium Is achieved when the two containers are equally exposed to the sun. The system, in short, wants to automatically "lock onto" the sun and track it all day long.
Illustration by the MOTHER EARTH NEWS staff