his futurist invention for sale. Unfortunately, no buyers emerged. Despite the favorable long-term cost analysis, potential customers were suspicious of the machine's durability, deterred by the high ratio of machine size to power output, and fearful of the initial investment cost of Willsie's ingenious solar power plant. His company, like others before it, disintegrated.A Certain Technical Maturity Despite solar power's dismal commercial failures, some proponents continued to believe that if they could only find the right combination of solar technologies, the vision of a free and unlimited power source would come true. Frank Shuman was one who shared that dream. But unlike most dreamers, Shuman did not have his head in the clouds. In fact, his hardheaded approach to business and his persistent search for practical solar power led him and his colleagues to construct the largest and most cost-effective machine prior to the space age.Shuman's first effort in 1906 was similar to Willsie's flat-plate collector design except that it employed ether as a working fluid instead of sulfur dioxide. The machine performed poorly, however, because even at respectable pressures, the steam--or more accurately, the vapor--exerted comparatively little force to drive a motor because of its low specific gravity.Shuman knew he needed more heat to produce steam, but felt that using complicated reflectors and tracking devices would be too costly and prone to mechanical failure. He decided that rather than trying to generate more heat, the answer was to better conserve the heat already being absorbed.In 1910, to improve the collector's insulation properties, Shuman enclosed the absorption plates not with a single sheet of glass but with dual panes separated by a one-inch air space. He also replaced the boiler pipes with a thin, flat metal container similar to Tellier's original greenhouse design. The apparatus could now consistently boil water rather than et...
