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Decades before the term “carbon footprint” came into vogue, MIT held a symposium titled “Space Heating with Solar Energy.”

Scientists at the August 1950 gathering warned of dire situations that have since become all too familiar. Eugene Ayres, a solar expert with the Gulf Research and Development Company, wrote in his paper’s abstract, “We know that time will come when we shall require a consciously engineered plan for solar energy utilization instead of simply burning up everything we can burn as rapidly as we can find and produce it.”

But embedded in this forward-thinking conference was another revolution: the opening of the field to women. Although only three women appeared on the conference’s 98-person registration list, newspapers covering the event focused on two of them, Maria Telkes and Eleanor Raymond. Telkes, an MIT researcher in the Department of Metallurgy, and Raymond, a Boston-based architect, were the talk of the conference for having dreamed up and built the Dover House, a home heated entirely by the sun.

The August 24, 1950, edition of the Transcript crowed, “Woman Scientist Collaborates with Woman Architect to Design Dwelling.” Two days later, another paper parroted the startling news of the participants’ gender: “The house of the day after tomorrow is on the way. In fact one already has been built … and another, much less expensive, is envisaged by a woman scientist and an architect of the same sex.” In the following days, news of the women who “hope to have home heated by sun” appeared in newspapers from Salem, MA, to London, England.

Constructed for about $20,000 in 1948 in Dover, MA, with funding from Boston sculptor Amelia Peabody, the Dover House was the only existing house heated solely with solar energy. The solar house MIT exhibited at the conference used the sun to warm water that circulated in pipes to provide heat, but it relied on auxiliary heat during sunless days. Telkes avoided that need by using a material called Glauber’s salt, the sodium salt of sulfuric acid. A sodium sulfate decahydrate (a solid that contains water), the salt melts at 90 °F and stores heat at seven times the efficiency of water.

The wedge-shaped Dover house looked like a typical home chopped in half, a shape designed to help it collect sufficient light. A bank of 18 windows lined the second story of its south-facing wall, which was a story higher than its north-facing wall. Behind those windows, Telkes installed panels of glass and metal to soak up the sun’s warmth, heating the air that her system blew between the glass and metal layers.

The warmed air traveled through a duct and across enclosed, insulated storage bins built into the walls of the house. The bins were filled with 21 tons of Glauber’s salt. On sunny days, the salt melted and absorbed heat, cooling the air in hot weather. When the temperature fell, the salt cooled and recrystallized, giving off its stored heat.

Telkes’s house effectively solved the storage problem of solar heating. On cloudy days, when no solar energy was entering the system, a fan system blew heat from the cooling, recrystallizing salt throughout the house. Telkes had analyzed data from the National Weather Bureau and found that Boston hadn’t gone more than nine days without sun in 65 years. She calculated that 21 tons of salt would be enough to heat the house through a 10-day sunless period. Despite the Dover House’s success, Telkes was quick to assure symposium attendees that “no one house could be successfully set down in another locality where climate, surroundings, and family demands would be different.”

Still, the sun–no other source of energy–heated the Dover House for two and a half winters before the experiment ended. Sulfuric acid is corrosive; some of Telkes’s bins eroded and leaked. Also, when Glauber’s salt melts, the heavier sodium sulfate sinks to the bottom of its container and the lighter water solution floats on top. If the salt doesn’t mix back together as it cools, it can’t release its stored heat. During the third winter, the salts separated in their containers and couldn’t be remixed, and the heating system failed.

“The problem of the sun-heated house cannot be solved by one or two experimental houses,” Telkes had cautioned at the 1950 symposium. “But each new house is another experimental stepping stone toward the use of the sun as a fuel resource.”

Telkes went on to found a solar-energy lab at New York University, and Raymond designed houses for 50 years. Neither would construct another solar house. But for the days surrounding the 1950 symposium, the Dover House and the two women behind it had their moment in the sun.

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Credit: courtesy of the MIT Museum

Tagged: Computing

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