A Golden Thread

A Golden Thread: 2500 Years of Solar Architecture and Technology

by Ken Butti and John Perlin

Main Points:

• Solar Thermal: In the 18th century Horace de Saussure built the world's first solar collectors called "hot boxes" which were heat trapping glass boxes that would heat water above the point of boiling (108 degrees Celsius). This led to August Mouchet to build solar powered steam engines due to his concerns of coal limitations in the 1860's and 1870's. Due to these two gentleman research into solar thermal devices began, but would soon be cast aside due to the falling prices of coal. It was not until 1968, when Professor Giovanni Francia built the first solar concentrating plant in Genoa, Italy. 
• Solar Water Heating: In the late 1800's, Clarence M. Kemp from Baltimore built the Climax- the nation's first commercial solar water heater. These designs were improved by Frank Walker who put the water tanks in a glass covered box and piped the water through the house. The biggest improvement to these designs arrived in 1909 when William Bailey used the "thermosyphon principle"- that hot water is lighter than cold and can rise naturally, by hooking up a storage tank to the collector of these boxes. Warm water would enter at the top of the tank, pushing cold water back into the solar collector, thus creating warm water through both day and night.
• Solar House Heating: The ancient Greeks were the first to adopt the "solar building principle" that all main rooms of a house led to a south facing porch to maximize solar irradiance. Summer rooms were built to the north side and winter rooms faced south. With the rise of epidemics in the mid-1800's and heavy industrialization, south facing houses were adopted in Great Britain not for heat, but for germ-killing UV rays. Augustin Rey, a French housing official, set the minimum amount of open space between buildings (2.5 times their height) so that shadows cast to do not block adjacent homes. The Germans did not accomplish this in their Zeilenbau plan which created row houses facing east and west, but Holland, Sweden's community of Neubühl created cooperative housing projects that adopted the south facing principles. The famous 1938 M.I.T. Solar House was lead by Professor Hoyt Hottel from the Department of Chemical Engineering. The goal was to build a house exclusively from solar energy. The house used 14 solar collector plates on the roof and pumped water to a storage tank in the basement, cool air from the rooms fell to the basement, and were actively heated by the storage tank, thus rising naturally when re-entering the house. The house remained at a steady 72 degrees Fahrenheit during the winter. However the house was built 7 degrees off true-south orientation, so never received the maximum amount of solar radiance possible. 

For a brief introduction to the history of solar technology, watch this video by the Solar Optimum and the Department of Energy's resources! Or watch a more detailed history by Arno Smets of TU Delft University!