6,000 Years of Solar: From Solar Heated Boxes to Hot Air and Water
“6,000 Years of Solar” is a series about the history of solar energy technology drawn from John Perlin’s new book Let It Shine: The 6,000-Year Story of Solar Energy. The series profiles the fascinating people, from ancient Greece and China to late 19th century New York to today, who have made the present day solar revolution possible.
The French mathematician Joseph Fourier in the early nineteen hundreds modeled global warming with the solar hot box built by Horace de Saussure almost a century earlier. The solar hot box consisted of a well-insulated box with the top covered by layers of glass. When exposed to the sun, Saussure obtained temperatures inside the box exceeding 240 degrees Fahrenheit (116 degrees Celsius).
As Fourier observed, if the atmosphere allowed sunlight to pass through but trapped the consequent solar heat, as did Saussure’s device, “the lower levels of the atmosphere would acquire elevated temperatures.” The analogy of the hot box and global warming rings true today as well. The solar hot box also became the prototype for all relatively low-temperature solar heating devices such as hot air and water collectors.
The first solar steam engine was built and tested by Augustine Mouchot, a French engineer, in 1866. He focused a parabolic mirror onto a one-inch tube in which the water was turned into steam. He went on to use concentrators to produce ice and electricity.
Mouchot’s work ignited a number of inventors to develop solar motors over the latter part of the nineteenth century. One of those pioneers was John Ericsson, who had helped save the Union during the Civil War by designing the first iron-clad battleship. Ericsson devoted the last twenty years of his life to solar engineering, believing that because “a great portion of our planet enjoys perpetual sunshine, the field therefore awaiting the application of the solar engine is almost beyond computation, while the source of its power is boundless.”
By 1914, the first commercial solar plant producing steam went up in Egypt and compared well in cost and production with its coal-fired competition. The developer could now announce, “Sun power is now a fact and no longer [just] a beautiful possibility.” But the great dream disintegrated with outbreak of World War I and the consequent discoveries of cheap oil in the formerly fuel-short but sunny parts of the world.
The first commercial solar water heater consisted of several 25-gallon cylindrical water tanks painted black inside a hot box, which inventor Clarence Kemp began marketing in 1891 as the Climax Solar Water Heater. They became most popular in the area in and around Los Angeles, California, at the turn of the nineteenth century. Improvements made in 1911, including pipes exposed to the sun that heated the water and a remote insulated storage tank to which the solar-heated water entered, enabled people to enjoy sun-heated water day and night.
The new water heaters spread throughout California. But skepticism sometimes remained so the company challenged doubters to hold their hand in water coming out of the solar heater. One guy did, recalled a rancher, “and the poor guy got an awful roasting. He almost lost his skin.”
Although the California market for solar water heaters plummeted due to the discovery of cheap natural gas in the 1920s, they migrated to other parts of the world. China, for example has more than 60 million installed.
Parts of this post were published on September 23, 2013 as part of Seven of the Greatest Solar Stories Over the Millennia, a post on National Geographic’s Energy Blog.
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John Perlin is an analyst in the physics department of the University of California, Santa Barbara and is a former CEC Staffer. He oversees solar installations at the university, and he writes, speaks, and lectures about solar energy.