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A Smarter Way to Use Sunlight: Array Pushes Solar Deep into Buildings

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A pair of University of Cincinnati researchers want you to see the light — even if you're in an unlit, interior, windowless room.

The new technology, called SmartLight, involves a narrow grid of tiny, electrofluidic cells self-powered by embedded photovoltaics and applied near the top of a window. These open-air "ducts" help sunlight to illuminate windowless work spaces deep inside office buildings. The grid can be applied to any building — big or small, old or new, residential or commercial — and the excess energy can be harnessed, stored and directed to other applications.

This rendering depicts how an office might appear with the University of Cincinnati's SmartLight off (top) and on (bottom). Sunlight is directed to different spaces, including to a "SmartTrackLight" in the outer hallway. Renderings courtesy of Timothy Zarki.

SmartLight is the result of an interdisciplinary collaboration between Anton Harfmann, an associate professor in UC's School of Architecture and Interior Design, and Jason Heikenfeld, a professor of electrical engineering and computer systems. Their research paper, "Smart Light - Enhancing Fenestration to Improve Solar Distribution in Buildings," was presented recently at Italy's CasaClima international energy forum.

"The SmartLight technology would be groundbreaking. It would be game-changing," Harfmann said. "This would change the equation for energy. It would change the way buildings are designed and renovated. It would change the way we would use energy and deal with the reality of the sun. It has all sorts of benefits and implications that I don't think we've even begun to touch."

Existing solar technologies, such as photovoltaic cells, aren't very efficient. A typical PV array loses most of the energy it has gathered as it converts that energy into electricity. But with SmartLight, Harfmann said the sunlight channeled through the system stays, and is used, in its original form. This method is far more efficient than converting light into electricity, then back into light, and would be far more sustainable than generating electric light by burning fossil fuels or releasing nuclear energy, he said.

Diagram showing how the University of Cincinnati's SmartLight can direct sunlight from the outside of a building (far right) to the inner part of a building and to a centralized harvesting- and energy-storage hub (far left). Courtesy of Anton Harfmann, University of Cincinnati.

Each tiny cell in the SmartLight grid contains fluid with optical properties as good or better than glass. The surface tension of the fluid can be rapidly manipulated into shapes such as lenses or prisms through minimal electrical stimulation - about 10,000 to 100,000 times less power than what is needed to light a traditional incandescent bulb. This allows sunlight passing through the cell to be controlled and possibly stored for use on cloudy days or at night.

The grid might direct some light to reflect off the ceiling to provide ambient room lighting. Other light might get focused toward special fixtures for task lighting. Yet another portion might be transmitted across the empty, uppermost spaces in a room to an existing or newly installed transom window fitted with its own electrofluidic grid. From there, the process could be repeated to enable sunlight to reach the deepest, most "light locked" areas of any building. And it's all done without needing to install new wiring, ducts, tubes or cables, they say.

"You're using space that's entirely available already. Even if I want to retrofit to existing architecture, I've got the space and the ability to do so," said Heikenfeld, creator of the SmartLight's electrofluidic cells. "And you don't need something mechanical and bulky, like a motor whirring in the corner of your office steering the light. It just looks like a piece of glass that all of a sudden switches."

A user could control SmartLight through a mobile app, as depicted in this rendering. Courtesy of Anton Harfmann.

Harfmann believes that SmartLight will have the greatest impact on "the major energy hog" — large commercial buildings. Energy needed to occupy buildings accounts for close to 50 percent of total energy consumption, he said.

Plans call for SmartLight to be controlled wirelessly via a mobile software application. It could even use geolocation data from the app to respond when a user enters/leaves a room or changes seats within the room, by manipulating Wi-Fi-enabled light fixtures, the researchers say.

"SmartLight would be controlled wirelessly. There would be no wires to run. You wouldn't have light switches in the room. You wouldn't have electricity routed in the walls," Harfmann said. "You would walk into a room and lights would switch on because your smartphone knows where you are and is communicating with the SmartLight system."

Much of the science and technology required to make SmartLight commercially viable already exist, Heikenfeld said. He and Harfmann have begun evaluating materials and advanced manufacturing methods, but need sufficient funding to create a large-scale prototype to attract government or industry partners.

"We're going to look for some substantial funds to really put a meaningful program together," Heikenfeld said. "We've already done a lot of the seed work. We're at the point where it would be a big, commercially driven type of effort. The next step is the tough part. How do you translate that into commercial products?"

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Photonics Spectra
Jan 2014
AmericasAnton HarfmannCasaClimaelectrofluidicenergyenergy conservationenergy conversiongreen photonicsGreenLightJason HeikenfeldMaterials & Chemicalsmobile appphotovoltaicsResearch & TechnologySensors & DetectorsSmartLightsmartphonesolar efficiencyUniversity of Cincinnatiwindowless work spaces

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