Automatic Dimming or Daylighting Controls
Lighting Systems: Daylighting Controls vs. Manual or Scheduled Controls
A lighting control that will either continuously dim, turn off, or bi-level step operate electric lighting in response to daylight entering the space.
Item ID: 144
Lighting--Sensors & Controls
Technical Advisory Group: 2009 Lighting TAG (#1)
Daylight harvesting (DH) is useful in places that get plenty of daylight and have dimming, bi-level or multi-level lighting. The sensor can be mounted in the ceiling or installed in the fixture and has automatic and continuous calibration. Setpoints are easily adjustable by the occupant. Ideally, an occupancy sensor is part of the system or the lights are otherwise prevented from being on when no one is present. Dual loop technology is used to sense both daylight and electric light to adjust the electric light to the appropriate level. Though dimming might not be necessary in consistently bright climates, in the maritime Pacific Northwest, dimming to balance the fluctuating daylight is likely to provide the best occupant satisfaction and lighting quality. Daylight and occupancy sensors together may save 30-60% of lighting energy, depending on climate, work schedules, and occupant behavior.
The simplified controls are self-commissioning and are expected to eliminate many of the problems familiar to those who use systems that require specialized technicians to do the commissioning, namely expense, delay, and possible malfunctioning equipment. The self-calibrating feature compensates for lumen depreciation as well as changes in furnishing reflectances. California Lighting Technology Center (CLTC) Associate Director Konstantinos Papamichael emphasizes the importance of this technological advance, commenting, “Automatic, continuous calibration is key to successful photosensor-based daylight harvesting controls, which are most important to reducing energy requirements and peak electricity demand." http://cltc.ucdavis.edu/images/_projects/research/simplified_daylight_harvesting/wattstopper_legrand_press_release_ls102.pdf
Baseline Description: Retail Office Space with Code Allowable Lighting
Baseline Energy Use: 2.7 kWh per year per square foot
The 2009 WA State Energy Code allows a lighting power density of 0.91 W/sf in office space. Assuming 3,000 hours per year of operation indicates an annual energy use of 2.73 kWh/sf. This annual energy use assumes constant operation with no use of bi-level controls or of occupancy sensors.
Manufacturer's Energy Savings Claims:
Savings Range: From 30% to 60%
Best Estimate of Energy Savings:
"Typical" Savings: 33%
Low and High Energy Savings: 33% to 50%
Very dependant on amount of daylight available at the work surface, orientation of windows, climate conditions and location of photosensors. Potential energy savings vary dependant on amount of daylight available at the work surface, orientation of windows, climate conditions and location of photosensors.
Daylighting works best when a building is designed with features that admit sunlight, such as skylights, redirecting window films, and full-height windows on building facades. SMUD's Customer Service Center utilizes a daylight-linked dimming control system to reduce power consumption from the installed load of 0.87 W/sf to only 0.58 W/sf. Costco uses diffusing skylights and a dimming lighting controls to produce lighting energy savings of about 50% (Lighting Research Center, 2011).
Energy Use of Emerging Technology:
1.8 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
Building codes have been moving towards requiring daylight or occupancy sensing automatic controls in areas with overhead glazing or vertical glazing. The 2009 "Commercial Building Stock Assessment" indicates that 4% of indoor lighting is controlled by daylighting controls or dimmer switches. The remainder is manually controlled or controlled by time clocks, energy management systems, or occupancy sensors (Figure #20). It will be assumed that Office Space, Health Facilities, and Schools represent the most likely candidates for installation of daylighting systems. The Navigant 2014 "Northwest Commercial Building Stock Assessment" prepared for NEEA indicates that the Northwest region now contains 555 million sf of office space, 121 million sf of health, and 259 million sf of school floor area (Figure A.1.1) (Navigant Consulting, 2014). Total potential area is thus 96% x 935 million sf = 897.6 million sf.
Regional Technical Potential:
0.80 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $0.15
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.30
Baseline Technology Unit Cost (Equipment Only): $0.00
Simple daylighting controls that can control up to 600 Watts of electric lighting cost $60 to $100 per control. It is anticipated these prices can be reduced as sales volume increases. Add about $200 each for installation, for a total of about $300 per control. Given a lighting office area power density of 0.91 W/sf, 600 Watts would be used in an area of 659 sf. Total installed cost is thus about $300/659 sf = $0.45/sf ($0.15/sf for equipment and $0.30/sf for installation).
Simple payback, new construction (years): 1.9
Simple payback, retrofit (years): 5.6
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
The proposed technology is a lighting control that will either dim, turn off, or step dim appropriate electric lighting in response to daylight entering the space. A simple daylight harvesting (SDH) control, the device must be easy to install, calibrate, and maintain and also be relatively inexpensive to purchase compared with its energy-saving potential for both new construction and retrofit markets. If possible, it should include a self-calibration function.
“The SDH consists of a photosensor to measure light levels, relays to switch the states of the electric lights, a controller that determines when to change lighting states, and an optional occupancy sensor. The SDH system can be installed by original equipment manufacturers as part of a new fixture or provided as a retrofit kit for an existing fixture. The fixtures can be used in any daylit spaces in commercial buildings.” http://cltc.ucdavis.edu/images/documents/case_studies_spec_sheets/20100728_Simple_Daylight_Harvesting_techbrief.pdf
Current daylighting controls require considerable effort to properly calibrate the devices after installation. The installation of these controls makes them particularly difficult to use in retrofit applications.
Some lighting control manufacturers (such as WattStopper) have commercialized simple on/off daylighting controls that include self-calibration. A device developed and successfully field tested by the Lighting Research Center called the DaySwitch is a simple on/off controller, is self calibrating and has proven to be cost effective even in retrofit situations. The LRC is actively seeking a manufacturing partner.
End User Drawbacks:
Selecting the right location to install simplified daylighting controls is critical. Plenty of daylight must be present on the work surface in the controlled zone. The space must be occupied for a sufficient amount of time to achieve reasonable energy savings.
Operations and Maintenance Costs:
No information available.
We estimate that the proposed technology will have a useful lifespan of approximately 15 years. However, additional study is needed to pinpoint this value.
Standard daylighting controls both on/off and dimming.
Reference and Citations:
Daylight Harvesting Made Simple
Public Interest Energy Research Program
Cost Effective Simplified Controls for Daylight Harvesting
California Lighting Technology Center
The Potential of Simplified Concepts for Daylight Harvesting
Lighting Research and Technology
Field Test DELTA: DaySwitch
Lighting Research Center
ADM Associates, Inc,
Fluorescent dimming Ballast study Report
Sacramento Municipal Utility District
2014 Northwest Commercial Building Stock Assessment
Northwest Energy Efficiency Alliance
Lighting Research Center,
Rensselaer Polytechnic Institute