Energy saving control for street lighting, parking lots, daylit hallways and building facade lights.

Public outdoor lights are on for long periods of time, they cover large areas and are very bright, and thus they often enormous amounts of power. But since they are in the public, they are very visible and noticeable, oftentimes they are already on even when there’s still light, which gives the public the impression that there is no effort to save on energy, and management is ineffective. Hence, this is a focal point for energy management.

Most traditional approaches to energy saving for outdoor lighting is by making use of automatic control to turn the lights on or off, which works in conjunction with light and dark to automatically turn the lights either on or off, but this approach has several shortcomings.

1. The lights should come on when it becomes dark, but it doesn’t mean that the lights should remain on up until it is light before turning off. The best approach is to have a different time schedule for each light post depending on its location to turn the lights on at a designated time and to turn it off early. But if automatic control is dependent entirely on a daylight sensor, then the lights would only turn off when it is light. The correct approach would be to turn on at a certain time depending on the venue, and turn off at a designated time, it should not be that the  lights only turn off when it is light. This is not something that can be easily done using a simple daylight sensor. But if a timer is used, it cannot adjust its time to match seasonal changes, and can either turn the lights on too early or too late.
2. It can often be seen in sidewalks, that even though it is already daylight, the street lights are still on, this is often caused by the daylight sensors when their calibration skews over time. Or it could also be caused by having its receptors obscured by trees, nearby buildings or plant overgrowths, which causes it to malfunction. This results in much wasted energy and also in reducing the lamp lifespan, constantly maintaining the street lights to ensure that they are operating in peak condition is labor intensive and costly for both its labor and materials.
3. The sensitivity of daylight sensors can vary widely, which can be seen in some areas wherein a segment of lights being turned on, while another segment in the same vicinity remaining off. This appears inconsistent and gives a bad impression to the public and reduces the quality of service.
4. Daylight sensors do not gauge dimness in the same manner as people do, which causes the daylight sensors to turn on the lights even though people still think it is still light. This of course results in unnecessarily wasted energy. The administrator is unable to make adjustments to and is entirely at the mercy of the daylight sensor in deciding when to turn on the lights.
5. The location in which to install the daylight sensor is very finicky, if there are objects or structures close by that could potentially block its receptors, then it could cause it to make faulty decisions. If the daylight sensor is in an ideal location, it could be far from the switch that controls the lights, which means that additional wiring need to be laid out from the sensor to the switch, which of course means additional labor and material costs, not to mention the difficulty in the actual construction job.

Improved Approach

1. Make use of the K40 monthly adjustable controller, each month would have its own turn on time, which solves the problem of indeterminate turn on time, and won’t turn on too early nor too late. Since there is no longer the need to install a daylight sensor, it also eliminates the problems associated with the laying of the conduit wiring. Thus, costs are reduced. Turn on times are not determinate and all lights could now be synchronized.
2. Depending on the place and purpose, it is not always necessary to have the lights all turn off at the same time, as for example, the circuit could be arrange so that the light posts alternate, or grouping could be made into primary and secondary circuits, and each group could have their own turn off time. Applications for this such as for billboards, exterior building wall wash lighting, pathways, streetlights, parking lots.
3. Late at night, when few people are about, such as in parking lots, one could make use of the LT3000 with motion sensors, so that instead of leaving the lights on all night, they will only turn on when there are people about. Which also helps to reduce wasted energy.

In Conclusion

Daylight sensors are simple in principle, and they are inexpensive. But the difficulties that they cause results in much energy wasted and also in reduced lamp lifespan. With the use of the K40 and the K90 in combination with push button wall switches can be used to adapt to the routine and also helps to reduce energy use at the same time. In addition, they can be adjusted to the venue and seasonal changes, with the ability to change the turn on and turn off times which allows the administrator to be in control at all times.