fluential and controversial U.S. engineers of the nineteenth century. While he spent his most productive years designing machines of war--his most celebrated accomplishment was the Civil War battleship the Monitor--he dedicated the last 20 years of his life largely to more peaceful pursuits such as solar power. This work was inspired by a fear shared by virtually all of his fellow solar inventors that coal supplies would someday end. In 1868 he wrote, "A couple of thousand years dropped in the ocean of time will completely exhaust the coal fields of Europe, unless, in the meantime, the heat of the sun be employed."Thus by 1870 Ericsson had developed what he claimed to be the first solar-powered steam engine, dismissing Mouchout's machine as "a mere toy." In truth, Ericsson's first designs greatly resembled Mouchout's devices, employing a conical, dish-shaped reflector that concentrated solar radiation onto a boiler and a tracking mechanism that kept the reflector directed toward the sun.Though unjustified in claiming his design original, Ericsson soon did invent a novel method for collecting solar rays--the parabolic trough. Unlike a true parabola, which focuses solar radiation onto a single, relatively small area, or focal point, like a satellite television dish, a parabolic trough is more akin to an oil drum cut in half lengthwise that focuses solar rays in a line across the open side of the reflector. This type of reflector offered many advantages over its circular (dish-shaped) counterparts: it was comparatively simple, less expensive to construct, and, unlike a circular reflector, had only to track the sun in a single direction (up and down, if lying horizontal, or east to west if standing on end), thus eliminating the need for complex tracking machinery. The downside was that the device's temperatures and efficiencies were not as high as with a dish-shaped reflector, since the configuration spread radiation over a wider area--a li...
