Colt's Facade Shading with Passive Control

By Mark Piepkorn

Buildings with large expanses of glazing can suffer dramatic cooling energy requirements and create glare problems for occupants. Facade shading systems can make significant contributions toward correcting these difficulties in new construction or retrofits. Colt International’s Solarfin line of controllable shading louvers for exterior facades is available in over 20 standard profiles with a range of polyester-powder color finishes. The system of typically hollow, elliptical, single-piece, extruded aluminum fins can be up to 15 inches deep, or clipped together up to 41 inches, and installed horizontally or vertically. Unsupported spans of almost 20 feet—or, with bracing, spans of over 32 feet—are possible. The fins, when linked to a control system, can pivot up to 120 degrees to follow the sun’s path, optimizing daylighting and minimizing heat gain. If desired, the fins can be installed at fixed angles. The system’s fittings are stainless steel.

While a number of automated controls for the Solarfin line are offered, a simple, nonelectric alternative is the Girasol passive thermo-hydraulic drive. Girasol, Italian for “sunflower,” was developed by Colt’s research partner, the Center for Solar Energy and Hydrogen Research. Using differential temperatures based on solar exposure, the Girasol system consists of two mirrored evaporator tubes attached to the top and bottom of a single louver fin, which then acts as a drive unit for multiple fins.

Each evaporator tube, nearly 10 feet long, is filled with a proprietary, CFC-free thermo-hydraulic fluid. This fluid expands or contracts in the tube, depending on whether it is in shade or sun. An actuator connected to the tubes responds to the unequal pressures by slowly rotating the assembly to achieve balanced pressure; as a consequence, appropriate shading based on current solar conditions is also achieved. The slow movement of the unit prevents optical irritation from rapidly changing light levels. When the façade isn’t in the sun, the fins revert to a predefined setting—generally, fully open.

For building-integrated photovoltaic (PV) applications, a counter-tracking system that rotates alternating louvers in opposite directions can be employed: optimal shading for the façade is preserved even as every other louver—loaded with PV cells—receives full sun. According to the company, solar power yields are increased by 20 to 25 percent.

Designed to install easily on any external controllable solar shading system, the noiseless Girasol drive is made with surface-treated aluminum, stainless steel, and a UV-stabilized, fiber-reinforced polymer. One Girasol drive can control over 500 square feet of shading louvers. Operating temperatures range from –22°F to 140°F.

For more information:

Colt has a number of U.S. distributors; call or visit its website to find the nearest one.

Colt International, Ltd.
Hampshire, United Kingdom
+44 (0) 2392-451111
www.coltgroup.com

This article was produced by BuildingGreen, Inc.- www.buildinggreen.com