//* {Light Cannons} ::
*//{2010.04.20 ~ Professional Work; Loisos & Ubbelohde Architecture + Energy}

Clients:: Smith Group Architects, Lawrence Berkeley National Laboratory, University of California Berkeley, Helios Energy Research Center
Light Cannon Design, Optical Design :: Matt Bitterman, George Loisos
Light Pipe Design :: Matt Bitterman, Abe Shameson
Structural Engineering :: Susie Douglas
Mockup Fabrication :: Matt Bitterman, Abe Shameson, David Sheer, Eduardo Pintos, Ibone Santiago
Monitoring Equipment and Data Analysis :: David Sheer, Chris Humann
Materials :: Various weaves/biases S-2 + E-glass Fiberglass/West System Epoxies, PVC 2lb/ft3 Closed-Cell Foam Core, Mild Steel, EMT, Stainless Steel, Aluminum Extrusions, Acrylic, 3m Optical Lighting Films, Reflective Mylar

Light Cannon Design & Performance ::
The Light Cannon project is a mockup for an 85’ {26m} daylighting sculpture proposed for a new building on the University of California, Berkeley’s campus. The conceit is for this sculpture to act as an experiential mechanism for understanding the solar/celestial calender. These cannons concentrate direct solar radiation from the sun through a series of penetrations in the roof, and shoot it down the center of the main circulation stair in this proposed research and laboratory building .

The cannons are designed as passive, non-mechanised reflecting devices, which concentrate the sun’s energy six times and illuminate a fixture inside the building at different set times throughout the solar day and year. For example, this mockup cannon installed at our office in Alameda is calibrated to illuminate for 1.5 hours per day, all year, from 12:45pm - 2:15pm solar time, or at present 1:45-3:15pm daylight savings time. Through the use of advanced optically treated films from 3m, the cannon’s light can brought to great depths inside the building with an evenness comensurate to the sky conditions above.

The optics, while relying on the simple principles of reflection, are a delicate balence of complex solar geometry, radiation in the form of heat, and luminous flux. Two mockups were built to before the final mockup. Controlling the focal points and heat was a critical component of design to avoid materials reaching their flash point and cauing fire, while still ensuring enough luminous flux reaches the fixture below to make a notable impression. Thermocouples were added near the concentration points to monitor the heat while the cannon operates, which reaches 190degress on a daily basis as the sun is focused and passed through.

The challenge of the optics however truely likes in accepting and effectively concentrating such a wide angle of acceptance, as the sun moves 15degrees in asimuth per hour and about 46degrees in altitude around the year. Our solution is a type of asymmetric compound parabolic concentrator sometimes found in solarthermal devices, however finessed for the use of daylight in an application to our knowledge is without precedent. Parametric modeling was a necessity to finess the reflecting surfaces, in addition to various raytracing software used to test performance. The molds for the laminates were all digitally produced and vacuumed bagged for tolerance control, and the final product was within a 32ths of an inch. The cannon is working +- 3minutes from its designed illumination schedule.