Daylight Harvesting: The Oldest Trick in the Lighting Control Book
Daylight harvesting combines integrated lighting control systems with the oldest energy source around – the sun.
By Aaron Stern

Imagine your standard office building, erected in the 1980s – adequately average in every way. Its summer, and this building has one side that faces east, another that faces west. In the morning, sunlight beams in through the windows on the east side of the building, washing out computer screens and making employees squint – as if the glaring fluorescent lights overhead weren’t enough – but only one or two employees have the corporate courage to draw a blind.

Need to Know:

Daylighting and daylight harvesting are two related, but very different concepts that are often misused interchangeably: Daylight harvesting is the use of lighting and HVAC control systems to minimize electrical output based on the varying amount of natural light entering a building throughout the day. Daylighting refers to the controlled admission of natural light into a building through the use of skylights and windows and reflective surfaces; daylight harvesting systems usee daylighting to reduce the use of electrical lighting.

By midday the sun rises high overhead and as it beats down on this facility the HVAC kicks into high gear, doing its best to keep everybody cool. As the afternoon wanes, workers on the west side of the building are facing the same predicament their counterparts on the east side faced that morning – glare, heat and general annoyance.

Now imagine something better: As sunlight shines through windows, blinds automatically lower, overhead lights dim to complement the natural light that penetrates the interior space. With so much sunlight reflected back by shades, the HVAC unit doesn’t have to work as hard, doesn’t spend as much energy. Workers on the east and west sides of the building continue to work, unhindered by the sun’s glare…

Statistics abound to measure the increasing global demand for energy, but a simple observation of a city’s downtown skyline at night, office buildings ablaze with light, is all it takes to see how inefficiently much of that power is used.

“If you fly into any city at night you can just look around and see the wasted energy,” says Brennen Matthews, the North American specifications sales manager for Lutron Electronics, the industry leader in lighting control.

It’s Matthews’ job to change that, and it’s not always an easy job to explain. When people who are unfamiliar with the concepts of daylighting and daylight harvesting ask him what he does, he keeps the explanation simple.

“I balance natural and electric light,” he tells them. “That’s my job.”

In his position with Lutron, Matthews helps to design daylight harvesting systems for facilities

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