Solar Radiation on Digital Signage

I attended an outstanding webinar on digital signage given by Peter Kaszycki of MRI. In the webinar he mentioned that the morning or evening sun in winter can be as bad for an LCD as the noon day sun in summer. I found some interesting data to back that up.

The chart comes from Research Needs: Glass Solar Reflectance and Vinyl Siding by R. Hart, C. Curcija, D. Arasteh, H. Goudey, C. Kohler, S. Selkowitz in the Environmental Energy Technologies Division of Lawrence Berkely Labs. Solar radiation can be a much larger contributor to the display temperature than than the ambient temperature. In fact data from the study shows that for black vinyl siding, solar radiation can raise surface temperatures to 70 degrees F higher than the ambient. Further, if the display is near a window and gets surface reflections from that window, it can get a double dose, or more, of solar radiation.

This picture shows the side of a house on a winter day when the ambient air was 24 degrees. The light on the side of the house is a reflection from the windows of a neighboring house. The issue of solar radiation and reflections has been well studied in the vinyl siding industry as it is a common cause for product replacement. The LCD being new to outdoor environments will experience the same conditions.

An important additional point to consider... because solar radiation is delivered at the speed of light rather than being conveyed by air currents or thermal conduction, the surface of the vinyl siding or the LCD can equilibrate with the current level of solar radiation within 10 minutes. Unlike heat transfer from the ambient, there are no thermal conduction issues or boundary layer effects. So, if some other surface happens to reflect directly on your digital signage installation for only twenty minutes; but the wrong time of day 20 minutes; that can be enough to cook your installation. Further, as contact burns can be almost instantaneous above 145 degrees and everyone assumes that every large LCD within reach is a touch panel, there could be some consumer complaints as well.

"But all we've discovered is that the blaze was started from a great distance through the refraction and convergence of light." from "Limoney Snickets: A Series of Unfortunate Events"


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