The following decisions will ensure that energy consumption is minimized by turning lighting OFF or turning it down when it is not needed:
The ASHRAE/IES 90.1-2010 energy standard, which provides code-ready language for jurisdictions seeking to regulate energy-efficient building design, requires the following for exterior lighting in new construction projects:
1. Automatically turn OFF all lighting during daylight hours.
2. Automatically turn OFF all building facade and landscape lighting between midnight or business closing (whichever is later) and 6:00 AM or business opening (whichever is earlier).
3. For all lighting that is not building facade or landscape lighting, reduce lighting power by at least 30% either: 1) between midnight or within one hour of business closing (whichever is later) and 6:00 AM or business opening (whichever is earlier), OR 2) after no activity has been detected (e.g., using an occupancy sensor) for no longer than 15 minutes.
4. Ensure that all time switches are able to retain their time setting and programming during a loss of power of at least 10 hours.
Exemptions to the above: emergency lighting, lighting required by health or safety law or regulation, decorative gas lighting and lighting for covered vehicle entrances/exits where needed for eye adaptation, safety or security.
While automatic shutoff is a longstanding requirement, lighting power reduction for dusk-to-dawn luminaires is a new development, resulting in new products and approaches. This approach has been demonstrated in CLTC and DOE research to generate up to 75% energy savings, although effective commissioning is essential to realizing maximum benefit. It is compatible with fluorescent, HID, LED, induction and plasma sources.
CLTC research, for example, found:
• 40% energy savings with bilevel HID wallpacks compared to uncontrolled HID wallpacks
• Additional 30% energy savings with LED wall packs compared to traditional HID
CLTC also found good energy savings with bollards, post-top luminaires and area lights involving different energy-saving sources.
Achieving lighting power reduction for dusk-to-dawn luminaires involves equipment that can:
1. automatically reduce lighting power at a certain time of night;
2. raise lamp output and power when the area is occupied; and
3. return to the energy-saving dim state when the area becomes unoccupied again.
For #1 above, some type of scheduling capability will be needed, which may be implemented at a central device (e.g., control panel) or at the device level (i.e., within the luminaire). The luminaire will require dual-circuiting allowing bilevel switching or a dimmable ballast or driver to allow continuous or step dimming.
For #2 and #3 above, an occupancy sensor is required.
The occupancy sensor, mounted remotely or within the exterior luminaire, may utilize PIR, microwave or video- (camera-) based detection technology, with PIR being most common. The control system may be centralized (networked to a central control point) or standalone (each luminaire controlled individually or in groups). The coverage pattern may be related to mounting height (8-40 ft. for PIR). The sensor should be rated for use in outdoor environments.
Communication may occur over power lines, low-voltage wiring, digital low-voltage wiring, or radio waves (radio-frequency wireless). Digital and RF wireless networks provide the advantages of being able to zone, program and calibrate controls remotely; rezone, reprogram and recalibrate controls over time to fine tune operation; and, for some systems, monitor the installation.
The sensor bilevel output may be switching or dimming. For exterior lighting control, dimming is often preferable as it ensures uniform light level reduction and enables single-lamp luminaires, such as HID, LED, induction and plasma, to step dim. Step dimming will occur between a designated HIGH setting (typically full light output during normal hours of occupancy) and a LOW setting (typically 30-70% of rated power afterhours). With HID, induction, plasma and fluorescent, the LOW state may be available across a limited range, while with LED, dim levels may be available across a broad range. Some sensor products permit light level to ramp/fade over a period of time to avoid an abrupt change in lighting state. Centrally controlled digital and RF wireless control systems featuring remote programming enable fine tuning of calibration settings.
Lighting power reduction capability offers significant additional energy savings for exterior lighting while posing new requirements. A variety of solutions is now available from manufacturers that can be used to realize this opportunity and satisfy code requirements.
The Department of Energy’s Better Buildings Alliance recently published exterior lighting control guidance, developed with support from the Lighting Controls Association. Click here to download this free guidance.