Selling high-bay lighting control projects on an energy-savings basis has traditionally been difficult to do. One reason is that utility payments and project funding come out of different budgets. Another is that energy savings does not translate into increased output. It does, however, translate into lower per unit cost.
Relamping interval recommendations are typically expressed in hours of operation at full output. After X number of hours of operation, the lamp’s output starts to sharply decline. Replacing lamps at this point will best balance light output against cost.
You can significantly extend the relamping interval through a combination of automatic dimming and on/off operation. Consider a combination of photo sensors, occupancy sensors, and timers. For example:
- In a facility that has windows, open bay doors, and other sources of natural light, install photo sensors to reduce lamp output during peak sunlight period. On most days, this allows such a facility to avoid peak load usage penalties.
- One warehouse holds a specific product that is picked up only twice a day. Occupancy sensors bring the lights from 40% operation to full on. After 30 minutes, timers revert them to 40% operation.
- A painting operation runs only on first shift. Timers prevent wasting electricity and lamplife on the other two shifts. The system does have occupancy sensor override in case someone needs to enter off hours.
As the last two of these examples show, a good control scheme may combine control methods.