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SWE Magazine Feature: Celebrating the Sun Queen

Mária Theresa Telkes was born Dec. 12, 1900, in Budapest, Hungary, to banker Aladar Telkes and his wife, Mária. Over the course of her long life, she would become a scientist, inventor, author, and advocate of solar energy, fueled by an intellect and vision as bright as the sun that inspired her.
Swe Magazine Feature: Celebrating The Sun Queen

“Celebrating the Sun Queen” was written by Seabright McCabe, SWE Contributor. This article appears in the 2019 Conference issue of SWE Magazine.

Swe Magazine Feature: Celebrating The Sun Queen
Mária Telkes, Ph.D., scientist, inventor, research associate, and author

“My aim was to develop new energy sources, especially the use of solar energy. I have studied with this aim in mind, and nothing could have stopped me from working in this field. If I have succeeded to some extent, I feel that I enjoy my scientific work more than any other activity.”

Mária Telkes, Ph.D., lived by those words. Blessed with parents who encouraged her love of chemistry, she created her own home lab at the age of 10, occasionally causing small explosions. As a first-year student at the University of Budapest, Dr. Telkes read a book by Kornél Zelovich, called Energy Sources of the Future. Decades later, she would say, “This was the deciding moment for me. The book explained that the usual energy sources have geographical limitations, especially in the less developed tropical regions, but the sun is directly overhead and you do not have to explore for it. The book described experiments, mostly conducted in the United States, and therefore this was the place for me.”

She received her B.A. in physical chemistry in 1920 from the University of Budapest and her Ph.D. in physical chemistry four years later. Encouraged by an uncle who worked in the U.S. Diplomatic Corps, Dr. Telkes visited America in 1925, taking up residence in Cleveland after receiving an offer to work as a biophysicist at the Cleveland Clinic. For the next 12 years, she collaborated with clinic co-founder George Crile, M.D., and together they invented a photoelectric device that could record brain waves. She and Dr. Crile also collaborated on a book, The Phenomena of Life, which reported on the device’s findings. During this period, she became nationally prominent, and was named one of America’s 11 most influential women by The New York Times, three years before receiving U.S. citizenship in 1937.


Dr. Telkes was also an early inventor of water desalination technology. During World War II, she was recruited and served as a civilian adviser to the U.S. Office of Scientific Research and Development (OSRD). Previously, Dr. Telkes had read a 1942 newspaper account in which WWI flying ace Eddie Rickenbacker (then an airline president, flying on a mission for the U.S. Air Force) survived for three weeks stranded at sea when his aircraft ditched in the South Pacific. Moved by the suffering of Rickenbacker and his crew, she invented a still that could make fresh water from seawater.

In order to desalinate seawater, it had to be vaporized and distilled, leaving the salts behind. Dr. Telkes improved on that system, creating a portable solar still made of aluminum and plastic film that used the sun’s heat to vaporize seawater and collect it as fresh water. The still was collapsible, lightweight, and small enough to be used on a life raft. Her invention became standard-issue equipment, saving the lives of many stranded sailors and airmen. For her contribution, Dr. Telkes received OSRD’s certificate of merit in 1945. The system was later enlarged and adapted for use in the Virgin Islands, which did not have a reliable supply of potable water at the time.

In 1947, Dr. Telkes invented the first thermoelectric generator that used the sun’s heat to create electricity. In 1948, she moved to Boston, where the world’s first all-solar house would be built in Dover, Massachusetts.


The Dover Sun House was a grand experiment, funded and led entirely by women — certainly an anomaly for the times. The single-family home stood on the estate of sculptor and philanthropist Amelia Peabody, who also contributed the $20,000 construction cost. Designed by architect Eleanor Raymond, its solar heating system was developed and designed by Dr. Telkes, by then a research associate at the Massachusetts Institute of Technology. It was here that Dr. Telkes’ early love of chemistry and solar energy crystallized.

The Dover Sun House, during a cold Massachusetts winter.

Where previous iterations of home solar heating storage systems were dependent on solar-heated rocks or huge tanks of hot water, Dr. Telkes designed a system that used a chemical reaction sparked by sunlight to produce heat: crystallization of sodium sulfate decahydrate. Sunlight streaming through a bank of south-facing windows on the second floor heated the air trapped behind it and between another layer of glass. The hot air was funneled by metal sheets and blowers into storage compartments in the wall; bins filled with sodium sulfate decahydrate, commonly known as Glauber’s salt.

The salts melted at 90 degrees Fahrenheit, and stored heat seven times more efficiently than water. The storage compartments, which together weighed 21 tons, served as the heating elements of the home. As the temperature fell, the salts recrystallized, radiating heat. The house was warm even in the cold, gloomy New England winter, with Dr. Telkes calculating that the “fully charged” system could heat the home for 10 days without sun. As the spring and summer months rolled around, the chemical reaction reversed, causing the salts to melt, drawing heat out of the indoor air and back into the bins, effectively turning the system into an air conditioner.

Confident in the concept, Dr. Telkes moved her recently immigrated second cousin, his wife, and their young son into the wedge-shaped home. The family lived there (with some difficulty) for two years, giving tours and recording data. Thousands flocked to see the house, which struck some as “something dropped by aliens in the middle of a field.” Gradually, the salts degraded, corroding the bins and causing leaks. The salts began to crystallize and mix in layers, causing the system to fail — an inevitable outcome. Dr. Telkes knew the Dover House was only a beginning, and later referred to it as “the Model T of solar-heated houses.” Still, it was widely regarded as a scientific landmark, if a local curiosity, and the house remained standing on Peabody’s Dover estate until 2010.

This would not be the only time Dr. Telkes would work on solar homes. She was just getting warmed up.

Telkes at Solar One house and Solar One brochure
LEFT: Dr. Telkes continued her work on solar thermal storage systems at the University of Delaware’s Solar One house. CREDIT: UNIVERSITY OF DELAWARE SPECIAL COLLECTIONS // RIGHT: More than two decades after the Dover Sun House, Dr. Telkes refined her design for another solar house, built in conjunction with the University of Delaware’s Institute of Energy Conversion. A brochure promoted the design and the use of solar energy for home heating.


In the 1950s, cooking fuels for those without electricity or gas sometimes consisted of coal, wood, and, in some regions of the developing world, dried cow dung. In 1954, Dr. Telkes saw an opportunity to improve quality of life in impoverished regions, saying in her own words, “ by developing practical devices for the basic needs of human existence.” By then a research professor at New York University’s College of Engineering, she received a $45,000 Ford Foundation grant to develop her latest invention: an inexpensive solar oven.

Maria Telkes with solar oven
Dr. Telkes demonstrates her solar oven, 1954.

The Telkes oven was designed for mass production and marketing in arid regions where sun was plentiful but access to power utilities was not. Made of fiberglass-insulated aluminum, the oven captured heat from sunlight, and could reach a temperature of 350 degrees Fahrenheit. It did not char food or need careful supervision — even a child could use it. Cooking temperature was maintained by its heat sink for an hour past sunset, making it convenient for evening meals.

Dr. Telkes’ invention was covered extensively by the press, and she was frequently photographed demonstrating it for the public, roasting chicken, baking cakes and bread, and simmering stews. Where other types of solar ovens required costly and cumbersome parabolic reflectors, the Telkes oven eliminated that need with four polished metal surfaces, angled to concentrate sunlight into a boxlike area where food was placed. Lightweight, portable, and inexpensive at a cost of $5, it was used all over the world. An enlarged version of the same design was developed and used to dry crops. The Telkes oven is still in use today, and its simple construction can be executed by anyone from online instructions.


Every new discovery served as a springboard for Dr. Telkes’ energetic mind. After a brief stint as director of a new solar laboratory at Curtiss-Wright, in 1961 she moved to Cryo-Therm, where she developed materials that would protect temperature-sensitive instruments. These materials went on to be used by NASA’s Apollo missions, and by the Polaris and Minuteman programs.

In the early 1960s, developing solar power for space applications such as satellite communication skyrocketed. There was even research taking place for solar electric power stations to be built on the moon. Dr. Telkes was concerned about these developments and their direction. In a 1964 speech at the International Conference of Women Engineers and Scientists (ICWES), she said, “[…] when I left MIT 10 years ago, solar energy conversion into electrical power was considered ‘too far out’ and of little practical importance. The sudden eruption of solar energy research for outer space has not been paralleled by a similar progress for the peaceful uses of solar energy on earth, at least not yet.”

Dr. Telkes never wavered in her belief in solar energy’s potential to improve the human condition. In 1972, she became an adjunct professor at the University of Delaware’s brand-new Institute of Energy Conversion (IEC). In a letter to SWE Secretary Carolyn Phillips, P.E., informing her of the new appointment, she wrote: “You probably read a number of articles about the impending energy crisis during the 1970s. The aim of our project here is to substitute the clean energy of the sun for at least some of the polluting fuels. We are glad to receive visitors and to show them the possibilities of solar heating for buildings and eventually of complete solar electric systems and general use.”

Dr. Telkes developed another solar home heating system for IEC’s Solar One home, which featured bins of her salts in its basement, storing heat and cooling the house with solar energy collected from its roof. This time, she improved the sodium sulfate decahydrate by mixing it with borax as a nucleating agent and hydrous magnesium aluminum silicate. These additives kept the salts in suspension during repeated heating and cooling cycles, and prevented them from degrading as they had at the Dover Sun House in 1948. Dr. Telkes received patents in the U.S. and abroad for this process and many other solar-related inventions she created at IEC. During this time, she also created new systems for storing cool air during the night and releasing it during the day, with the goal of reducing power consumption during times of peak demand.

Retiring from the University of Delaware in 1978 as a professor emeritus, Dr. Telkes remained a research consultant until her early 90s. And in 1980, she assisted the U.S. Department of Energy in the design of the world’s first home to generate all of its electricity with a photovoltaic rooftop system.

Dr. Telkes was rightfully impatient with some of her employers for their slow adoption of solar energy. To Evelyn Murray, past president of SWE, Dr. Telkes wrote in 1984: “At present I am a ‘consultant’ in the use of solar energy and thermal storage systems, serving the whims and doubts of heads of large Companies, who cannot make up their collective minds to turn to ‘solar’ rather than ‘nuclear.’ So far I had a marvelous life in pursuit of my work, ambition and life-long aim to: ‘reach the sun.’ I hope this will succeed and eliminate possible ‘Nuclear disaster’ and the end of humanity.”

Dr. Telkes never stopped reaching for the sun. She continued to invent new solar thermal storage systems and received her final patent at the age of 90, for “a eutectic composition for coolness storage,” which combined sodium sulfate with sodium tetraborate pentahydrate and a small amount of buffering acid that reduced alkalinity.

Maria Telkes shows off SWE achievement award
Mária Telkes, Ph.D., then research associate of technology, became the first to receive the Society of Women Engineers’ Award for Meritorious Contribution to Engineering (today’s Achievement Award). At SWE’s annual banquet, held in the Statler Hotel of New York, Dr. Telkes proudly shows the award to members of the Society. From left: Dr. Telkes; Katherine Stinson, of Washington; Lillian Murad, SWE vice president; and Beatrice Hicks, SWE president. Dr. Telkes was selected to receive the award for the design of a distilling system using solar heat to convert seawater to drinking water.


Dr. Telkes, a SWE life member, received numerous awards throughout her long career, among them SWE’s inaugural Achievement Award (then called the “Award for Meritorious Contribution to Engineering”) in 1952, and the Charles Greeley Abbot Award from the International Solar Energy Society in 1977. Also in 1977, she received a Lifetime Achievement Award from the National Academy of Sciences Building Research Advisory Board. For her contributions to solar thermal storage systems, she was posthumously inducted into the National Inventors Hall of Fame in 2012.

While visiting her native Hungary for the first time in 70 years, Dr. Telkes passed away in 1995, less than two weeks before her 95th birthday. With more than 20 patents and 100 papers and book chapters authored, her life’s work underscored her words: “Sunlight will be used as a source of energy sooner or later … why wait?”

Swe Magazine Feature: Celebrating The Sun Queen