The Skylight’s the Limit: How Two Innovations Combined to Revolutionize an Industry


Every person, business and industry that receives power from solar energy should make a pilgrimage to the University of California Merced, find a professor named Roland Winston, shake his hand and say “thank you”.

It was Professor Winston who, in the late 1970s, discovered the mathematics that outlined a framework for the most thermodynamically efficient concentrator that can possibly be made.

The Holy Grail of Curved Mirrors

The shape resulting from Professor Winston’s calculations reverberate throughout the solar industry. He effectively etched the holy grail of thermodynamically efficient concentrators.

Mirror manufacturers like Replex have benefitted immensely. We have been able to use Professor Winston’s concepts to build and test experimental 7x concentrators using Winston’s compound parabolic concentrators.

The Ah-Ha! Moment: The Greatest Skylight Ever Made

Where we decided to apply Professor Winston’s discovery a little differently was in the skylight industry.

We found that if curved mirrors were made much larger, turned around, and flipped upside down, they could become the most optically efficient light harvesting skylights.

With the right curvatures, a skylight could fully capture light from the moment the sun began to rise in the East. It would continue to efficiently bounce light down into the building as the sun rose much higher in the sky, but then have the advantage of retaining effectiveness until the moment the sun crept below the western horizon. What is more, such a skylight design turns out to be surprisingly effective on cloudy days since it efficiently harvests light from all directions simultaneously.

From architectural codes to manufacturing processes, the learning curve was steep. It was with the fourth incarnation that we came away with a 4’x4’ (1.2 m x 1.2 m) skylight that captured sunlight extraordinarily well from sunrise to sunset, with no moving parts

How It Works: Harnessing the Perfection of Natural Sunlight

There is a diffuser at the discharge end of the skylight. This means that when a person inside the building looks up, it appears that they’re looking at a light fixture. But instead of light bulbs gobbling up electricity, it’s natural sunlight being reflected through a deconcentrator of the exact dimensions calculated by Roland Winston nearly 40 years ago — only backwards and upside down.

It is remarkable how well human beings respond to the full spectrum present in natural light. Even the highest quality artificial light cannot compete with the level to which sunlight gels with the structure of the human eye, how we interpret color and the influence on how much we simply like or don’t like a given space because of lighting.

The new skylight, therefore, improves every aspect of human functionality inside a building’s architecture — all while reducing energy use to zero from sunrise to sunset, with no moving parts.

Unlike most cheaper skylights that begin to dull, yellow, or fade in as little as five years, Replex’s patented skylight is built to last 100 years. Thanks, Professor Winston, for your incredible discovery.

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