The first solar water heater was patented in 1891 by Clarence Kemp in a commercial purpose. It works in accordance with a principle known for a long time: exposing metal components to the sun enables to collect and store heat. Water is contained in several iron tubes with an elliptical cross-section, in order to maximize the surface exposed to the sun.
The tubes are wired in parallel and connected by small pipes. Water enters cold from one side, and comes out warmed up from the other side. The multiplicity of the tubes aims at speeding up the heating and avoiding for the cold water to come in contact with warm water. The device is covered with a glass patch, in order to keep it from rain water and to improve the heating thanks to the greenhouse effect. Kemp managed to find a lot of clients in California. For instance, a third of the households in Pasadena were in possession of his heater back in 1987.
Kemp named his water heater CLIMAX. Kemp’s advertisements mostly targeted men whose wives were off to summer vacation, leaving them alone with the housework. He praised the simplicity of his new device.
But the Climax had a main issue: it did not resist winter frosts. From the beginning of the XXth century on, several patents were registered as people tried to improve solar water heaters, and the Climax quickly became obsolete, mostly after William J. Baily patented his own water-heater in 1909.
