The practical application of solar thermal was first introduced by the Swiss in 1767, but heating water with a patented solar water heating collector did not happen until 1891 in America. The man largely given credit for this countries popular residential application of solar thermal was Clarence Kemp who invented a solar collector and sold it through his Baltimore appliance factory outlet.
Kemp had witnessed earlier solar water heaters put together by farmers metal water tanks painted black acting as collectors and placed directly in the sun out in the fields during the summer. By late afternoon, when farm work had everyone’s skin full of grit, grime, and sweat, and their bodies exhausted, farmhands opened up the spigot on the tank, and filled buckets with water hot enough to soothe their aching muscles and refresh their overheated bodies.
The problem with earlier versions of solar thermal water heating, Kemp observed, was not whether they could produce hot water, but when and for how long. Even on clear, hot days, it usually took from morning to early afternoon for the water to get hot. And as soon as the sun set, the tanks rapidly lost heat because they were uninsulated and unprotected from the cool night air.
Kemp had also read in popular journals how the American astrophysicist Samuel Pierpoint Langley had taken an insulated, glass-covered box and exposed it to the sun on the snow-covered slopes of Mount Whitney. Though outside temperatures had dropped below freezing, the inside of the box heated up above the boiling point of water. Kemp realized that if he placed several tanks painted black inside a glass-covered box, he would have a superior method of heating water with the sun. In 1891, he won a patent for the new heater, and called it the Climax, the world’s first commercial solar thermal water heater.
Kemp advertised his solar heater as “the acme of simplicity” compared with conventional water heaters. Just turn on the faucet and “instantly out comes the hot water,” the sales literature boasted. Thanks to the Climax, according to company brochures, housewives no longer had to fire up the stove in summer, and wealthy gentlemen, who had to stay behind to work while their families and servants left sultry Baltimore to summer in more pleasant climes, could return home at night and instantly draw hot water with no fuss or bother thanks to the thermal power of the sun.
Sales of the Climax thermal hot water heater really took off in California. By 1897, one-third of households in Pasadena relied on the Climax for heating water. More than 1,600 were sold in southern California by 1900. Economics was the prime lure of the Climax. For an investment of $25, the owner saved about $9 a year on coal. As one journalist pointed out, exorbitant fuel prices forced Californians “to take the asset of sunshine into full partnership. In this section of the country where soft coal sells for $13 a ton (and the huge peaches bring only $2 a ton), a builder cannot afford to waste his sun-rays. California is in particular need of its solar water heaters.”
Others, though, saw a more important reason for going solar. Charles Pope, writing in 1903, urged consumers to “consider that wood and oil and coal and gas are steadily consumed by use. Not only will the coming generations be less comfortably supplied a thing most of us care very little about but the drain today may produce distress in our own homes and lay an embargo on our own business tomorrow. Contrast this with the freedom of the people who receive daily gifts of fuel from the Creator, taking all they wish, all they can use, freely.”
Between 1898 and 1909, more than a dozen inventors filed patents for new solar thermal water heater collectors, but everyone merely refined the Climax design. In 1909, William J. Bailey saw the shortcomings of the glass-covered tank solar water heaters collecting and The discovery of cheap local supplies of natural gas concurrent with the development of the hermostatically controlled gas water heater in the early 1920s killed the solar water heater industry in southern California.
The solar water heater business then migrated to southern Florida, where a booming housing market and high energy costs created much demand for Bailey’s invention. By 1941, more than half the households in Miami heated their water with the thermal power of the sun.
But war came, the government froze the use of copper, and the solar thermal water heater industry came to an abrupt halt. Solar water heating took off again after the war, but cheap electric rates, combined with aggressive sales of electric water heaters by the utilities, stymied new growth. The once thriving Floridian solar water heater industry was reduced to a small service business by 1955.
The two oil embargoes of the 1970s encouraged new interest in solar thermal water heating. Subsequent sharp drops in fossil fuel prices, combined with the end of tax credits for purchasing solar water heaters, once again put a damper on the American solar water heater industry. Other parts of the world have enthusiastically embraced Bailey’s invention. Millions of Japanese have purchased solar thermal water heaters. More than ninety percent of Israelis heat their water with the sun. In Europe, so many people use solar thermal water heaters like the Day and Night design that they save the equivalent of the energy produced by five large nuclear power plants. Most never imagined that the technology they use dates back so far and comes from California!
Image Courtesy of: Perlin/Butti Solar Historical Archive Collection. Source Used With Permission Home Power Magazine by John Perlin. This on article on solar thermal hot water was adapted from the book A Golden Thread: 2500 Years of Solar Architecture and Technology, by John Perlin and Ken Butti, Van Vostrand Reinhold Company, 1980. (Out of printing).