Light at the End of the Tunnel

Revolutionary solar pipe captures sunlight outside and channels it inside buildings to light the darkest spaces.


Liliana Beltrán, associate professor in the College of Architecture, along with an interdisciplinary team of students at the Digital Fabrication Facility at TAMU’s Riverside Campus, designed and built the solar pipe.  Photograph by Jean WulfsonEven the darkest rooms of any building may soon receive sunlight thanks to a new device under development in Texas A&M’s College of Architecture.

The solar pipe—an apparatus that gathers sunlight and uses highly reflective materials to channel it through a long, clear tube—has the potential to revolutionize architectural lighting, according to Environmental Protection Agency (EPA) experts.

The design earned top honors (including $75,000 in developmental funding) at the EPA’s 2010 People, Prosperity and the Planet competition held last spring on the National Mall in Washington, D.C. The contest challenged college students to create sustainable solutions for worldwide environmental problems through technological innovation.

“Application of the invention is far-reaching, potentially changing certain aspects of architecture,” notes one sustainability expert who reviewed the entry at the recent EPA competition.

“This was an excellent project presented in a first-rate manner by students.” Liliana Beltrán, associate professor of architecture, along with an interdisciplinary team of students at the College of Architecture’s Digital Fabrication Facility at Texas A&M’s Riverside Campus, designed and built the solar pipe.

The prototype they created now channels sunlight into a simulated office space built in an old railcar container.

“Light coming through the pipe looks magical,” says Beltrán. “It’s a high-intensity, full-spectrum light with no buzzing, flickering or heat. This quality and intensity of light cannot be achieved with today’s electric light sources.”

For the next phase, the team will install the pipe in a simulated office space suspended in water. This approach will allow the researchers to rotate the floating structure to simulate sunlight angles at locations around the world.

The team will also work on making the device easier to install.

“The system can deliver light to the interior of any type of building, such as an office, hospital, school, library or a basement,” says Beltrán. “It could be used in multistory buildings where standard skylights aren’t an option.”

The process begins with the light guide, which captures sunlight through a small piece of glass resembling a window, about 52 inches wide by 11 inches deep. The glass sits on a box.

“The sunlight collection is maximized with very complex ray-tracing computer programs, where we trace 10,000 rays or more and observe how each ray of the sun will be entering the tube,” Beltrán says. “All the light guide’s surfaces, especially on the front part, have a series of angles with reflectors, all shooting sunlight through the shaft.”

After the light travels through the tube’s highly reflective surface, made of a polymeric film with 99.3 percent reflectivity, it is spread into the simulated office space through a new daylight diffusing film that 3M developed. Special patterns are embedded in the film to spread the light at a wide angle.

The prototype delivers 2,000 to 2,500 luxes (a lux is a unit of illumination) to the windowless office space, says Beltrán, far exceeding the 300-lux standard that the Illuminating Engineering Society established for office lighting.

Health care facility architects interested in the device’s potential for lighting spaces such as nurses’ stations deep inside hospitals have approached Beltrán since she developed the prototype.

During the EPA competition, a group from Louisiana also approached Beltrán, interested in the potential energy savings that the solar pipe could provide for large exposition spaces and rodeo arenas.

“Their electric bills are so high, it’s unbelievable,” she says.

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