UC’s SmartLight More Than a Bright Idea, It’s a Revolution in Interior Lighting Ready to Shine

The innovative solar technology “would change the equation for energy,” according to UC researchers.

A pair of University of Cincinnati researchers has seen the light – a bright, powerful light – and it just might change the future of how building interiors are brightened.

In fact, that light comes directly from the sun. And with the help of tiny, electrofluidic cells and a series of open-air “ducts,” sunlight can naturally illuminate windowless work spaces deep inside office buildings and excess energy can be harnessed, stored and directed to other applications.

This new technology is called SmartLight, and it’s the result of an interdisciplinary research collaboration between UC’s Anton Harfmann and Jason Heikenfeld. Their research paper “Smart Light – Enhancing Fenestration to Improve Solar Distribution in Buildings” was recently presented at Italy’s CasaClimainternational energy forum.

The SmartLight technology would be groundbreaking. It would be game changing,” says Harfmann, an associate professor in UC’s School of Architecture and Interior Design. “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.”

MAJOR IMPROVEMENT THROUGH MINIMAL ADJUSTMENTS

There’s a simple question SmartLight addresses: Is there a smarter way to use sunlight? Every day the sun’s rays hit Earth with more than enough energy to meet many of society’s energy demands, but existing technologies designed to harness that energy, such as photovoltaic cells, aren’t very efficient. A typical photovoltaic array loses most of the sun’s energy when it gets converted into electricity. But with SmartLight, Harfmann says 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.

The technology could be applied to any building – big or small, old or new, residential or commercial. But Harfmann and Heikenfeld believe it will have the greatest impact on large commercial buildings. The U.S. Department of Energy’s Energy Information Administration shows that 21 percent of commercial sector electricity consumption went toward lighting in 2011. Harfmann calls the energy demand for lighting in big, commercial buildings “the major energy hog,” and he says energy needed to occupy buildings accounts for close to 50 percent of the total energy consumed by humans.

 

Diagram of SmartLight on interior of building
This diagram shows how SmartLight can direct sunlight from the outside of a building (far right) …

 

Diagram of SmartLight on exterior of building
… to the inner part of a building and to a centralized harvesting- and energy-storage hub (far left).

SmartLight could help shift that energy imbalance. It works like this: A narrow grid of electrofluidic cells which is self-powered by embedded photovoltaics is applied near the top of a window. Each tiny cell ¬– only a few millimeters wide – 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’s needed to light a traditional incandescent bulb. In this way, sunlight passing through the cell can be controlled.

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 of light 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.

“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,” says Heikenfeld, professor of electrical engineering and computer systems and creator of the Smart Light’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.”

SMART APPROACH ALLOWS DYNAMIC RESPONSE

As for switching, Harfmann envisions a workplace where physical light switches join other anachronistic office equipment like mouse pads or bulky CRT monitors. Plans call for SmartLight to be controlled wirelessly via a mobile software application. So instead of manually flipping a switch on a wall, a user would indicate their lighting preferences through an app on their mobile device, and SmartLight would regulate the room’s brightness accordingly. SmartLight could even use geolocation data from the app to respond when a user enters or leaves a room or when they change seats within the room by manipulating Wi-Fi-enabled light fixtures.

SmartLight controls on a smartphone
A user could control SmartLight through a mobile app, as depicted in this rendering.

“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 says. “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.”

But what happens at night or on cloudy days? That’s where SmartLight’s energy storage ability comes in. On a typical sunny day, sunlight strikes a facade at a rate that’s often hundreds of times greater than what is needed to light the entire building. SmartLight can funnel surplus light into a centralized harvesting- and energy-storing hub within the building. The stored energy could then be used to beam electrical lighting back through the building when natural light levels are low. The SmartLight’s grid is so responsive – each cell can switch by the second – it can react dynamically to varying light levels throughout the day, meaning office lighting levels would remain constant during bright mornings spent catching up on email, stormy lunch hours spent eating at your desk, and late nights spent reviewing the budget.

With such potential for energy storage, a building’s electrical network also could tap into the centralized hub and use the stockpiled energy to power other needs, such as heating and cooling. And if centralized collection of surplus sunlight isn’t possible inside some existing structures, the light could even be sent straight through a building to a neighboring collection facility.

PARTNERING FOR A BRIGHTER FUTURE

Heikenfeld says much of the science and technology required to make the Smart Light commercially viable already exists. He and Harfmann have begun evaluating materials and advanced manufacturing methods. The only thing missing at this point is enough funding to create a large-scale prototype which could call the attention of government or industry partners interested in bringing SmartLight to market.

“We’re going to look for some substantial funds to really put a meaningful program together,” Heikenfeld says. “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?”

Harfmann and Heikenfeld originally began developing the idea for the Smart Light years ago. Harfmann was one of the leaders on UC’s team in the 2007 Solar Decathlon, a global competition to build the planet’s best solar house. Harfmann, an associate dean in UC’s College of Design, Architecture, Art, and Planning, collaborated with faculty from other disciplines, including the College of Engineering & Applied Science. That led to his relationship with Heikenfeld and eventually the first discussions of the SmartLight concept.

The cross-college efforts of Harfmann and Heikenfeld align with the university’s UC2019 Academic Master Plan goal of expanding collaborative engagement to advance the common good. Additionally, the SmartLight project exemplifies the UC2019 vision by transforming the world through research and creating a deliberate and responsible approach to our environment, resources and operations.

The innovation that results from similar collaborations taking place everywhere at UC, Heikenfeld says, is part of what helps make the university a leader in so many fields.

“A step beyond just working with someone in a multidisciplinary fashion, and where a lot of these partnerships go well, is when you take the time to learn enough about someone else’s discipline that you can then begin to inject innovation into it, but not independently,” Heikenfeld says. “It’s more than just bringing multidisciplinary folks together. You have to stretch yourself to the point where you begin to understand the drivers and some of the fundamentals of the other disciplines as well. One of UC’s greatest strengths is our diversity, this is in the classic sense of the term, but also in terms of academic thinking and expertise, which is a great melting pot for big, new ideas.

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Scientists develop heat-resistant materials that could vastly improve solar cell efficiency

Scientists have created a heat-resistant thermal emitter that could significantly improve the efficiency of solar cells. The novel component is designed to convert heat from the sun into infrared light, which can than be absorbed by solar cells to make electricity – a technology known as thermophotovoltaics. Unlike earlier prototypes that fell apart at temperatures below 2200 degrees Fahrenheit (1200 degrees Celsius), the new thermal emitter remains stable at temperatures as high as 2500 F (1400 C).

“This is a record performance in terms of thermal stability and a major advance for the field of thermophotovoltaics,” said Shanhui Fan, a professor of electrical engineering at Stanford University. Fan and his colleagues at the University of Illinois-Urbana Champaign (Illinois) and North Carolina State University collaborated on the project. Their results are published in the October 16 edition of the journal Nature Communications.

A typical solar cell has a silicon semiconductor that absorbs sunlight directly and converts it into electrical energy. But silicon semiconductors only respond to infrared light. Higher-energy light waves, including most of the visible light spectrum, are wasted as heat, while lower-energy waves simply pass through the solar panel.

“In theory, conventional single-junction solar cells can only achieve an efficiency level of about 34 percent, but in practice they don’t achieve that,” said study co-author Paul Braun, a professor of materials science at Illinois. “That’s because they throw away the majority of the sun’s energy.”

Thermophotovoltaic devices are designed to overcome that limitation. Instead of sending sunlight directly to the solar cell, thermophotovoltaic systems have an intermediate component that consists of two parts: an absorber that heats up when exposed to sunlight, and an emitter that converts the heat to infrared light, which is then beamed to the solar cell.

“Essentially, we tailor the light to shorter wavelengths that are ideal for driving a solar cell,” Fan said. “That raises the theoretical efficiency of the cell to 80 percent, which is quite remarkable.”

So far, thermophotovoltaic systems have only achieved an efficiency level of about 8 percent, Braun noted. The poor performance is largely due to problems with the intermediate component, which is typically made of tungsten – an abundant material also used in conventional light bulbs.

“Our thermal emitters have a complex, three-dimensional nanostructure that has to withstand temperatures above 1800 F (1000 C) to be practical,” Braun explained. “In fact, the hotter the better.”

In previous experiments, however, the 3D structure of the emitter was destroyed at temperatures of around 1800 F (1000 C). To address the problem, Braun and his Illinois colleagues coated tungsten emitters in a nanolayer of a ceramic material called hafnium dioxide.

The results were dramatic. When subjected to temperatures of 1800 F (1000 C), the ceramic-coated emitters retained their structural integrity for more than 12 hours. When heated to 2500 F (1400 C), the samples remained thermally stable for at least an hour.

The ceramic-coated emitters were sent to Fan and his colleagues at Stanford, who confirmed that devices were still capable of producing infrared light waves that are ideal for running solar cells.

“These results are unprecedented,” said former Illinois graduate student Kevin Arpin, lead author of the study. “We demonstrated for the first time that ceramics could help advance thermophotovoltaics as well other areas of research, including energy harvesting from waste heat, high-temperature catalysis and electrochemical energy storage.”

Braun and Fan plan to test other ceramic-type materials and determine if the experimental thermal emitters can deliver infrared light to a working solar cell.

“We’ve demonstrated that the tailoring of optical properties at high temperatures is possible,” Braun said. “Hafnium and tungsten are abundant, low-cost materials, and the process used to make these heat-resistant emitters is well established. Hopefully these results will motivate the thermophotovoltaics community to take another look at ceramics and other classes of materials that haven’t been considered.”

**

Other authors of the study are Nicholas Sergeant, Linxiao Zhu and Zongfu Yu of Stanford; Andrew Cloud, Hailong Ning, Justin Mallek, Berç Kalanyan, Gregory Girolami and John Abelson of Illinois; and Mark Losego and Gregory Parsons of North Carolina State University.

This article was written by Mark Shwartz, Precourt Institute for Energy at Stanford University.

Related information:

Fan Research Group http://www.stanford.edu/group/fan/

Braun Research Group http://braungroup.beckman.illinois.edu/

Global Climate and Energy Project http://gcep.stanford.edu/

 

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Innovative cell structure converts a record 44.7% of sunlight into electricity

A new world record of 44.7% of sunlight was converted into electricity by a photovoltaic panel using a new solar cell structure with four solar subcells last month, says German research organisation Fraunhofer Institute for Solar Energy Systems department head and development project leader Dr Frank Dimroth. Semiconductor and solar company Soitec, French Alternative Energies and Atomic Energy Commission nanotechnology and photonics research and technology institute Leti and German materials and energy company Helmholtz Centre Berlin jointly participated in the project.
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New research suggests perovskite as cheaper replacement for silicon-based solar panels

(Phys.org) —Researchers at Oxford Photovoltaics and other companies investigating the use of perovskite—a crystalline organometal—as a replacement for silicon in photovoltaic cells have created prototypes that are approximately 15 percent efficient. But this is apparently just the beginning. Kevin Bullis suggests in an article published this week in MIT Technology Review, that researchers are predicting efficiencies as high as 25 percent very soon, putting the material on a par with silicon.
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Antifreeze, cheap materials may lead to low-cost solar energy

CORVALLIS, Ore. – A process combining some comparatively cheap materials and the same antifreeze that keeps an automobile radiator from freezing in cold weather may be the key to making solar cells that cost less and avoid toxic compounds, while further expanding the use of solar energy.

And when perfected, this approach might also cook up the solar cells in a microwave oven similar to the one in most kitchens.

Engineers at Oregon State University have determined that ethylene glycol, commonly used in antifreeze products, can be a low-cost solvent that functions well in a “continuous flow” reactor – an approach to making thin-film solar cells that is easily scaled up for mass production at industrial levels.

The research, just published in Material Letters, a professional journal, also concluded this approach will work with CZTS, or copper zinc tin sulfide, a compound of significant interest for solar cells due to its excellent optical properties and the fact these materials are cheap and environmentally benign.

“The global use of solar energy may be held back if the materials we use to produce solar cells are too expensive or require the use of toxic chemicals in production,” said Greg Herman, an associate professor in the OSU School of Chemical, Biological and Environmental Engineering. “We need technologies that use abundant, inexpensive materials, preferably ones that can be mined in the U.S. This process offers that.”

By contrast, many solar cells today are made with CIGS, or copper indium gallium diselenide. Indium is comparatively rare and costly, and mostly produced in China. Last year, the prices of indium and gallium used in CIGS solar cells were about 275 times higher than the zinc used in CZTS cells.

The technology being developed at OSU uses ethylene glycol in meso-fluidic reactors that can offer precise control of temperature, reaction time, and mass transport to yield better crystalline quality and high uniformity of the nanoparticles that comprise the solar cell – all factors which improve quality control and performance.

This approach is also faster – many companies still use “batch mode” synthesis to produce CIGS nanoparticles, a process that can ultimately take up to a full day, compared to about half an hour with a continuous flow reactor. The additional speed of such reactors will further reduce final costs.

“For large-scale industrial production, all of these factors – cost of materials, speed, quality control – can translate into money,” Herman said. “The approach we’re using should provide high-quality solar cells at a lower cost.”

The performance of CZTS cells right now is lower than that of CIGS, researchers say, but with further research on the use of dopants and additional optimization it should be possible to create solar cell efficiency that is comparable.

This project is one result of work through the Center for Sustainable Materials Chemistry, a collaborative effort of OSU and five other academic institutions, supported by the National Science Foundation. Funding was provided by Sharp Laboratories of America. The goal is to develop materials and products that are safe, affordable and avoid the use of toxic chemicals or expensive compounds.

The study this story is based on is available in ScholarsArchive@OSU; http://bit.ly/10Zj0SK

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