New device can capture, store energy from the sun

By Brooks Hays
Engineers combined a pair of thermal energy harvesting and storage technologies to create a more efficient hybrid device. Photo by University of Houston
Engineers combined a pair of thermal energy harvesting and storage technologies to create a more efficient hybrid device. Photo by University of Houston

Nov. 20 (UPI) -- Engineers at the University of Houston have developed a new hybrid device capable of capturing and storing the sun's energy. The device, described Wednesday in the journal Joule, could be used for a variety of purposes, including power generation, distillation and desalination.

Unlike, photovoltaic technology, which converts sunlight into electricity, the new hybrid device captures and stores the sun's thermal energy.


Though photovoltaic solar panels have become increasingly economical, they can only provide power when the sun is out. Even in places where clouds are few, photovoltaic technology can't produce electricity at night.

Around the clock reliability is one of solar power's major pitfalls, and a major concern as the solar power industry scales up production. The latest device could allow power producers to provide sun-derived electricity around-the-clock.

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Researchers describe their invention as a hybrid device because it combines two technologies: molecular energy storage and latent heat storage.

Current thermal energy harvesting technologies mostly rely on optical concentration systems, which are expensive and aren't very efficient. Thermal energy storage devices are more efficient, but they can't effectively store energy for very long.

"We combine the physics of molecular energy and latent heat storage to introduce an integrated, simultaneous harvesting and storage hybrid paradigm for potential 24/7 energy delivery," researchers wrote in their paper.


When engineers tested their hybrid technology on a small scale, they achieved 73 percent efficiency during the day. At larger scales, the device achieved efficiencies as great as 90 percent. At night, the stored energy was recovered at an 80 percent efficiency.

The device works by harvesting energy from the full spectrum of light, harvesting as much as possible for immediate usage and storing the excess thermal energy in a unique molecular storage material called norbornadiene-quadricyclane.

The synthetic material is not only very good at efficiently absorbing and storing thermal, but is also -- just as importantly -- efficient at releasing heat. The material doesn't actually store the sun's thermal energy as heat, but instead stores it in molecular form, which reduces the thermal losses that plague current commercial devices.

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"During the day, the solar thermal energy can be harvested at temperatures as high as 120 degrees centigrade, about 248 Fahrenheit," study co-author T. Randall Lee, professor of chemistry at the University of Houston, said in a news release. "At night, when there is low or no solar irradiation, the stored energy is harvested by the molecular storage material, which can convert it from a lower energy molecule to a higher energy molecule."


The technology allows the energy to be recovered at a higher temperature at night than during the day, boosting the device's efficiency.

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