Harvest Daylight and Reap Rewards

The concept of daylight harvesting (also callednatural light decreases.
daylighting) is simple. During the day when natural light isThe goal for successful daylight harvesting is to adjust
streaming in through windows and skylights, you don'telectric light levels gradually enough that building
need to use as much artificial light. You can eitheroccupants don't notice the change.
adjust lighting levels manually, or you can use anThis means that using stepped dimming, where light
automated system that detects daylight levels (usinglevels typically change from 100% to 50% in a single
photosensors), and automatically dims or brightensstep, is not ideal for buildings such as offices or
electric lights as required.schools where occupants perform stationary tasks.
Making more use of natural light helps you to consumeInstead, you will achieve better results with continuous
less energy, which reduces both your energy costsdimming, where fixture light output can be gradually
and carbon footprint. Lights that are dimmed or turneddimmed over the full range, from 100% to 10% (or
off typically emit less heat, which can help to reduceeven less).
air conditioning costs. Dimming can also extend the lifeStepped dimming is more suitable for areas where
of a lamp, helping to further reduce costs (and landfill).occupants spend less time and do not perform
And numerous studies have shown that people arestationary tasks, such as corridors and parking
happier in an environment that contains more naturalgarages. In these areas, you can combine occupancy
light.sensors and photosensors to achieve greater savings
The cost and energy savings are especially important(dimming lights further when the area is unoccupied).
in commercial buildings, where lighting can account forMany traditional building and lighting control systems are
up to 40% of the total energy spend.fully wired, with all lights, sensors and switches
A number of automated daylight harvesting solutionshard-wired to a central controller (or to a gateway that
are available, consisting of dimmable luminaires (orfacilitates communication between the lighting network
lamps within luminaires), photosensors, and lightingand lighting control software). Because of the cost of
control software.the wiring, and the complexity of covering a large area,
The sensors have a photoelectric "eye" thatthese often operate as a number of self-contained
measures the illumination in a specified zone. Theysystems (for example, one per room or floor).
transmit this information to lighting control software,Newer lighting systems take advantage of wireless
which is programmed with acceptable threshold levels.mesh networking, which allows the lights, sensors,
If the illumination levels fall outside those thresholds, theswitches and the central controller to communicate
software sends commands to dim or brighten thewith each other without the need for wires. Removing
luminaires as required.those wires provides more flexibility in terms of where
It is possible to implement pseudo-daylight harvestingswitches and sensors can be placed, and lower
that uses timers to dim and brighten luminaires at theinstallation costs also make it more affordable to
same time every day, but this is a less satisfactoryinclude additional sensors in your network (allowing you
solution. Timers are not able to take into account thingsto obtain more granular information about occupancy
like whether the sky is clear or overcast, or whetherand illumination levels).
people have closed the window coverings to reduceWireless mesh also supports more flexible and easier
heat and glare, so often result in inappropriate levels ofcontrol of larger systems with more devices. It allows
illumination.you to run your lighting control solution as a single
Daylight harvesting can return maximum benefits insystem that covers an entire building (or multiple
buildings that are occupied primarily during daylightbuildings), as well as room by room (or floor by floor)
hours, such as office buildings, schools and otherdeployments. This approach provides a system-wide
government buildings.view of operations, current power usage, savings, and
Levels of natural light vary throughout a buildingmore.
affected by things like orientation, proximity to windowsCost and energy savings, increased flexibility, and
or skylights, and the colors of walls, ceilings andhigher productivity are major design considerations for
furnishings. To achieve the best results, you need amodern lighting systems. A wireless daylight harvesting
solution that is flexible enough to allow luminaires to beand lighting control solution provides all this and more.
dimmed in different "zones" at different times andRemoving the wires from the lighting controls provides
rates, and to different levels.additional benefits, including greater flexibility in where
For example, you might select to enable daylightcontrols can be placed, significant savings in installation
harvesting only for the first three or four banks of(by avoiding the expense and disruption of wiring), and
ballasts next to windows. The bank immediately nextthe ability to control and monitor large lighting
to the window, which receives the greatest amount ofinstallations as a single system.
natural light, would be dimmed by the greatest amount.Natural daylight is the most affordable, best quality, and
If required, dimming levels could gradually reduce asmost environmentally friendly light that you can provide
you move away from the window and the amount ofto your building occupants. So let the sun shine in!