The Mother Earth News Solar "Heat Grabber"
(Page 2 of 4)
September/October 1977
By the Mother Earth News editors
(Miami, for instance, is located about 25° north, which means that collectors there should be angled up at 35° to the horizon, which, in turn, means that the 67.5° cuts specified in the following plans should be 72.5° for Miami. Likewise, the cuts should be 65.75° for Washington, D.C; 61.5° for Seattle; and 54.5° for Anchorage. You can calculate the specific angle for your own location [subtract your latitude plus 10 from 180 and divide by two] or just average it out from the figures given here. The angle is critical, but not that critical.)
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Remember that all the dimensions given in the plans are for a collector specifically tailored to fit the windows in one particular house. If your windows are wider or not as wide, feel free to build your Heat Grabber(s) accordingly. And don't get unnecessarily hung up on trying to keep the upper and lower air chambers in the collector exactly as deep as shown here either. A half-inch or more variation is fine. As a matter of fact, it's awfully hard to keep this little Btu-grabber from working, as long as its passages are deep enough for air to circulate through them at all.
One final caution: Although the single-strength glass used to cover the prototype Heat Grabber is no more nor less safe than the single-strength glass currently in use in millions of storm doors and windows throughout the continent. It can break and possibly cut you or a child if, for any reason, either of you falls into it. Take whatever measures you deem necessary so that such an accident never happens.
How It Works
The Heat Grabber is nothing but a weathertight box that's insulated on the bottom and sides and topped with glass. An insulated divider is positioned inside this box and brought out its top to form an open "lip" at the box's upper end. This lip is designed to hook over a windowsill so that the window itself can be pulled down snugly onto the glass which covers the top of the Heat Grabber, leaving the main body of the solar collector "leaning against" the south side of the house at a 45°-or-better angle. (See illustration in the Image Gallery — How it Works.)
The operation of the unit is just as simple. When the sun shines, its rays pass through the glass on top of the Heat Grabber, strike the upper surface of the divider (which is painted black), and warm the aluminum foil covering on that divider. As the foil heats up it, in turn, warms the air next to it. And that air, as might be expected, rises up the face of the divider and begins to pour out the opening at the Heat Grabber's top.
