A joint Fermilab/SLAC publication

CERN spin-off: More efficient solar panels


SRB Energy solar panels in Valencia, Spain. Image: CERN

Nothing exists in a vacuum, except for maybe the physics career of Cristoforo Benvenuti.

While working at CERN, Benvenuti developed equipment to maintain the vacuum in one of the world’s largest particle accelerators. Now he uses that same technology in a spin-off company to produce extremely efficient solar panels.

Geneva International Airport just began installing 300 of Benvenuti’s panels in one of his biggest deals yet. In six months, 1,200 square meters of the main terminal will be covered, which will provide energy to heat and cool the airport’s buildings year-round.

Benvenuti did his first work on solar panels during the petrol crisis of the ‘70s, when CERN management became interested in funding an alternative energy project. Benvenuti and his colleagues built three prototypes, but the crisis passed, and they abandoned the work for physics once again.

However, while researching how to maintain vacuums in his solar panels, Benvenuti realized he’d found a piece of equipment with equally amazing potential for accelerators. Called a ‘getter,’ it is basically a sticky surface that traps any particle that bounces onto it, like molecular flypaper, he said. This keeps the vacuum clean. Not only that, but molecules collected by getters may diffuse out with heating, refreshing the surface and making replacement getters unnecessary.

Getters turned out to be perfect for the Large Electron Positron Collider, the precursor accelerator to the Large Hadron Collider. They were cheaper and easier than any alternatives for maintaining vacuums, and LEP ended up with 14 miles of getter strips. They were even adapted into a coating rather than strips for use in the more space-constrained LHC.

Decades later, Benvenuti returned to his solar panels. “When I did it in the ‘70s I said, ‘If I don’t do it, nobody will.’ And 30 years later when I started, nobody had,” he said. The challenge was in the geometry: No one had ever been able to vacuum-seal 2 square meters of glass to a metal frame. Flat solar panels are much harder to seal than cylindrical ones, but the panel shape is better for collecting sunlight. Thanks in part to their experiences working with accelerators, Benvenuti’s team was able to make it work.

Accelerators require vacuums in their pipes to keep beam particles from losing energy in interactions with random gas molecules. Having vacuum between the glass and the solar absorbers gives the panels incredibly efficient thermal insulations. Without this insulation, gas molecules inside solar panels would lose energy by transferring heat each time they traveled between the hot light absorber and the cold front glass. “We've had temperatures of 80 degrees Celsius [176 degrees Fahrenheit] inside the panel when the panels were covered in snow,” Benvenuti said.

In Geneva, the vacuum-sealed solar panels can supply heat at over 300 degrees Fahrenheit with 50 percent efficiency, meaning each square meter of panel generates a half kilowatt of power. Moreover, unlike other solar panels that use parabolic mirrors, Benvenuti’s do not rely only on direct sunlight. Instead, they capture diffuse light, which makes up more than 50 percent of the light in central European climates like Switzerland.

In 2005, the technologies transfer office at CERN publicized Benvenuti’s patent, which led to him finding an investor and founding his company, SRB Energy. He retired from CERN the same year, though R&D for the panels is still temporarily housed at the laboratory. Unfortunately, he said, without a strong solar market the company hasn’t been able to fund further research projects.

“I hope I get the opportunity to develop my other ideas,” he said. Beyond the panels, Benvenuti dreams of vacuum-insulated windows and walls, heat storage devices and other clandestine-for-now inventions.

Benvenuti’s work on vacuums in solar panels influenced his work on vacuums in accelerators, which came back and influenced his work on vacuums in solar panels. The cycle may continue: CERN is evaluating the possibility of installing Benvenuti’s panels on new buildings, where they will power offices for another set of creative minds.

Watch a video of CERN News: Solar panels with a CERN technology.

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