Solar Engine: Wallace Minto's Newest Invention

Enlarge Image Image Gallery Wallace Minto demonstrates how his solar engine works.  Read on for specifics on this new device. PHOTO: MOTHER EARTH NEWS STAFF

Hold on to your hat! Because if Wallace Minto has done what we think he's done — the backyard solar engine that can make everyone as energy self-sufficient as he or she wants to be has just been invented!

And it's so simple! Minto's new engine is nothing but a big vertical wheel with a rim made of a series of sealed "drums". Sealed, that is, except for a connecting pipe that runs from each separate container to its diametrically opposed partner on the opposite side of the wheel. One of the barrels in each set is filled with propane, Freon, or any other liquid that has a very low boiling point. And the whole wheel is then positioned so that its bottom edge can be heated a few degrees warmer than its top two-thirds or three-quarters. In essence, that's it!

And here's how the Minto Wheel operates: As the Freon or propane in the drum on the bottom of the rim is warmed, it begins to vaporize and push against the surface of the remaining liquid in the container. This push forces most of the fluid up the connecting tube until it cascades into the barrel on the top of the wheel's rim. As a result, of course, the bottom drum becomes increasingly lighter as the top one becomes increasingly heavy and gravity then causes the whole assembly to revolve around its horizontal axis. And — son of a gun! — when that filled drum from the top reaches the bottom and is warmed a few degrees — danged if the entire action isn't repeated all over again.

What we have here, you see, is a waterwheel that doesn't need to be pushed by a mountain stream. Just fill it once with a low-boiling-point liquid, and forget it. As long as you can then maintain a temperature difference between the top and the bottom of the wheel (with, as explained, the bottom being kept warmer than the top), your "engine" — with a little shot of grease now and then — should run dang near indefinitely.

Yes, but will that engine do useful work? Minto says it will. "Take a wheel that's 40 feet in diameter. Put 14 pairs of containers, each of which has a volume of 3.415 cubic feet, around its rim. Fill the cylinders with propane and hold the cool drum in each set at 100 degrees Fahrenheit while the warmer barrel is heated to 103.5 degrees. At 1 rpm, the engine will produce 3.19 horsepower. Furthermore, if you use Freon R-12 instead of propane and increase your temperature gradient to 12 degrees, the output will go up to 8.69 hp."