In 1948, scientist Mária Telkes—fondly nicknamed “The Sun Queen”—designed a groundbreaking house in Massachusetts that stayed warm throughout freezing winters using only sunlight and salt, without relying on gas or electricity.

In collaboration with architect Eleanor Raymond, she created the Dover Sun House. The secret lay in the use of Glauber’s salt (sodium sulfate), a phase-change material, to store solar energy and release it gradually as heat. This material absorbs heat when it melts and releases it as it solidifies, allowing the house to function efficiently even on cloudy days. It became one of the world’s first passive solar-heated homes.

But Telkes’s work was about more than just technology—it was deeply rooted in liberation. She firmly believed that energy innovation should serve everyday people, especially women who struggled with smoke-filled kitchens and inadequate heating. Over her career, she developed solar ovens, desalination systems, and off-grid technologies that empowered communities across the globe.

With more than 20 patents and a lasting impact on sustainable energy, Mária Telkes proved that clean energy isn’t just a future ideal—it has been a practical possibility for generations.