Placing a TV or PC (LED Display) in an outdoor location subject to direct sunlight presents technical challenges.
The TV typically must be placed in a protective enclosure that will prevent ingress of dust, dirt, and water (see
NEMA 4). Placing a TV inside an enclosure that utilizes a transparent window for viewing can cause
significant heat-management problems when the window is exposed to direct sunlight.
When sunlight (radiation) passes through the window of a TV enclosure, the interior heats in the same fashion as a
greenhouse. Sunlight passes through the window and is then absorbed onto internal surfaces and converted into
infrared energy (heat). Infrared energy has a longer wavelength than visible light and cannot easily pass back out of
the window, therefore “trapping” heat inside. This is a familiar phenomenon in closed cars in the summer. This
experimenter showed how to bake cookies on the dashboard of his car —
Scott Sutherland, Science Writer.
At PC Enclosures, we experimented with an enclosure designed to house a 55″ TV. On a sunny spring day, we placed the
enclosure on the ground with the window facing up toward the sun. We placed thermometers inside and outside of the
enclosure and timed the internal heating. The outside temperature was measured at 73°F. When the window was uncovered
and exposed to sunlight, the internal temperature rose to 128°F (a 55°F rise) in 30 minutes. In mid-summer this can
lead to internal temperatures over 170°F.
Regular TVs typically have a maximum operating temperature of about 104°F. Above that, the screen will begin to “black
out.” Blacked-out LED TV screens will recover once they cool, but repeated blackouts can damage the screen.
Polycarbonate windows can warp in direct sunlight at internal temperatures above 125°F. While they can normally
withstand up to 150°F, operating at that level is risky. Above 150°F, some TV electronics may suffer permanent damage.
Some outdoor-rated TVs can handle temperatures of 125°F to 130°F before they black out.
Cooling calculations for a windowed enclosure are complex. For a detailed discussion see
Thermal Management of Displays/Signage in Outdoor Enclosures
. For direct sunlight applications, two methods of cooling are typically used: air curtain and air conditioning.
Air Curtain
An air curtain design can be employed to sweep heat from a gap between the TV screen and the viewing window. Fresh
air is drawn from outside the enclosure and blown by fans across the front of the TV screen. The air is heated by
sunlight, but is continually exchanged with fresh, cooler air from outside. Once the air passes across the screen, it
is then expelled by additional fans. In this method, the higher the airflow, the lower the temperature rise inside the
enclosure. Typical air curtain designs aim to keep the internal temperature about 10°F above the outside ambient
temperature. Note that an air curtain cannot cool the enclosure below the outside ambient temperature.
Air Conditioning
A TV or PC enclosure can be fitted with an air-conditioning system to cool the enclosure as needed. This is a relatively
expensive solution but provides robust operation in hot, sunny climates. Companies such as
Ice Qube offer enclosure-specific air conditioners that can be sized to the
application and are rated for NEMA 12, 4, 4X, and IP 66.
Conclusion
Care should be employed when considering an outdoor TV enclosure exposed to direct sunlight. Without a heat-management
solution such as an air curtain or air conditioning, damage to the TV and polycarbonate window is likely.
