Bi-Level Office Lighting with Occupancy Sensors, Auto-On 50%
Office Lighting: Half On Occupancy Sensors w/Manual Full On Option vs. Full On Occupancy Sensors
Office lighting that turns half the lighting on when occupancy is detected. The other half of the lighting can be brought on manually or turned off as desired for more detailed work, for guests, or other reasons.
Item ID: 222
Lighting--Sensors & Controls
Technical Advisory Group: 2009 Lighting TAG (#1)
Private offices are often used only intermittently, unoccupied for extended periods each day. Yet, the lights are often left on even when no one is home. With the proposed technology, energy savings in the range of 35% to 50% might be expected for lighting systems that come on at 50% of the full light level and turn off when the space is vacant. The actual savings depend on use patterns and occupant switching behavior.
Bi-level wall switches turn lighting on and off based on occupancy, and sometimes also adjust for daylight. This technology provides high/low switching through a bi-level ballast, where the occupant can choose the desired light level: low or high. Studies have shown that most office workers are happy with the half-on option if available. In addition, if the lighting comes on automatically, it is usually not adjusted further by the occupant. Many offices are too bright for occupants who work mostly on their computers, and occupants are more comfortable if the ambient light is lower.
With this technology, occupants also have the option of manually switching the lights off or on. Personal control of light levels is very popular with occupants, and more comfortable light levels may contribute to higher productivity and less absenteeism. Installing bi-level controls is a requirement when applying for the federal Commercial Lighting Tax Deduction.
Baseline Description: Standard office lighting
Baseline Energy Use: 3 kWh per year per square foot
Based on general, nearly code-compliant office general lighting, operating 3000 hours per year.
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 40%
Energy Savings Reliability: 3 - Limited Assessment
Expected savings 35-50%. Savings will vary with the application. 40% is based on only adding control to existing lights with moderate use, and the users choosing to use the 50% setting much of the time. Already in lighting calculator, so rated ESR 6.
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:
Commercial Building Stock Assessment, NEEA, 2009 http://neea.org/resource-center/regional-data-resources/commercial-building-stock-assessment
Regional Technical Potential:
0.72 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
A single-level occupancy sensor switch runs around $60 (Platt Electric 4/11), and a standard ballast for two T8s is $13 while a high performance ballast runs about $21. The bi-level ballast and switch cost about $70 in the WSU study. Codes often require occupancy sensors so the incremental cost is the relevant one.
The WSU study for the retrofit case had installed costs estimated to be approximately $303 for a small office and $698 for a large office. This includes all material and labor costs for installing a bi-level switch and occupancy sensor, and rewiring to bi-level operation (no bi-level ballast). For a new construction case, the installed costs are estimated at approximately $70 for a small office and $200 for a large office. This includes the incremental material costs of a bi-level switch and ballast and occupancy sensor above a standard manual single-level switch. It is assumed that labor costs are the same for wiring a new office in either the baseline or bi-level switch
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
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.
Paybacks for installation in a new facility or major retrofit run from 2 to 9 years, depending on the original equipment, the new equipment used, occupancy rates in the offices, daylight available, and electric rates. Utility incentives can help with the cost because the inclusion of bi-level ballasts pushes the payback toward the longer period, although prices may drop as they become more common.
In offices where T12 technology is still used, a large percentage of savings will be attributed to upgrading to high-performance T8 or T5 technology. When paired with bi-level controls, savings will be dramatic. For facilities already using T8 technology, savings will be less dramatic, even though the percentage of energy saved due to controls might be substantial. Savings will also be more apparent where occupants are frequently away from their desks for longer periods and not in the habit of turning off their lights.
Improved productivity may be a side benefit of improving occupant comfort and satisfaction by allowing personal control of light levels.
This technology is suitable for private offices and conference rooms. The automatic bi-level wall switches turn lighting on and off based on occupancy. These switches contain two relays for controlling two independent lighting loads or circuits. This provides high/low switching where the occupant can choose the desired light level: low or high. After a period of time when no occupancy is detected, lighting automatically switches off. Occupants also have the option of manually switching the lights off or on.
Studies have found that many office occupants make due with whatever the lighting is, whether it is 100% or 50%, unless it is quite inadequate. Starting with 50% light should provide adequate light for most occupants and assure significant savings. It is also important to note that many employees who work on computers most of the time are more comforatable with lower light levels.
Wireless control systems are also available, although a compatible ballast is still required. Sensors for both occupancy and daylight are becoming available, and can be built into the fixtures, saving additional time. Major options for applying this technology are:
1. Install new bi-level ballasts: The bi-level switch can be wired to new bi-level ballasts in each luminaire. Bi-level ballasts are available that operate at 50% and 100% power levels. These ballasts have two line inputs that can be connected to the two relays of the bi-level switch. When one relay is engaged, the lights operate at 50% power. When both relays are engaged, the lamps operate at full power.
2. Rewire existing ballasts, switch alternate luminaires: The bi-level switch can be wired to existing ballasts so that one relay operates half of the luminaires in the office, while the second relay operates the remaining luminaires.
3. Rewire existing ballasts, tandem wiring: The bi-level switch can be wired to existing ballasts so that one relay operates half of the lamps in all of the luminaires in the office, while the second relay operates the remaining lamps in all of the luminaires.
From the D1:
With most office workers now using computers the majority of the time, higher levels of ambient lighting are needed less frequently. This measure brings half the lighting on when occupancy is detected. The other half of the lighting can be brought on manually as needed for more detailed work or for guests. It should be noted that this measure requires that the office be wired for bi-level operation.
The preferred method for a particular installation will depend on a number of factors, including the existing lighting configuration, desired lighting uniformity, and project cost. For instance, installing new bi-level ballasts will provide the same level of lighting uniformity as the existing lighting system, while rewiring the existing ballasts to switch alternate luminaires may result in less uniform lighting. In addition, the cost of each alternative will be different. While the bi-leve
Conventional office lighting is controlled either by manual switching or by 100% auto-on with occupancy control, with no ability to drop lighting to 50%. Some offices with multiple lamp fixtures do have manual bi-level switching capability using separate switches and ballasts to control some of the lamps in each fixture. If there are more than two lamps per fixture, additional light levels may be possible.
Increasingly, building energy codes are requiring at least auto-off controls, so the incremental cost of bi-level controls should not be much of a barrier.
This device is commercially available nationwide from WattStopper, LaMar Lighting, Hubbell, Leviton, Lightolier, Sensor Switch and other manufacturers. The key requirement is a two-pole occupancy sensor that can be switched to turn on 50% or 100% lighting levels as specified by the user.
Note that this bi-level or dimming technology is appropriate for both offices and office campus areas plus other types of commercial and institutional sector buildings including K-12 schools, and even big box stores.
End User Drawbacks:
Utility and government support can provide incentives to overcome first-cost barriers, and education and training will help overcome awareness issues.
This proposed technology uses currently available hardware, so there should be no unusual governmental or institutional risks or environmental regulations.
Proper installation of these components may have a learning curve and installers may be resistant to change. The product’s distributor could train the installation staff to help reduce this curve.
Additional time is needed to commission the sensors and adjust time intervals, motion sensing technologies (fixture level versus zonal control), and select reduced light levels to assure the occupant is happy; if the occupant is not happy with the new system, the building owner runs the risk of having the system disabled. The equipment should be presented to the occupants as a feature that enhances their convenience and comfort. Occupants should be told how their actions may impact its proper operation, such as a blocked view from the sensor to occupant, a moving fan, or other factors.
Operations and Maintenance Costs:
No information available.
The life of this technology should be about equivalent to the life of any other lighting controls, which is approximately ten years.
Competing technologies include:
• Bi-level manual switching and daylight harvesting controls.
• Daylight harvesting controls with auto-on 100%.
• Auto-on 100%.
Rather than provide a 100% light level that is rarely used, it may be more economical to provide lower ambient light and use supplemental, manual on/auto-off task lights at each workstation.
Reference and Citations:
CLTC Study Demonstrates Major Energy Savings for Bilevel Occupancy Sensors
Lighting Controls Association
The Usefulness of Bi-Level Switching
Lawrence Berkeley National Laboratory
Case Study - Bi-level Stairwell Lighting
Public Interest Energy Research Program
New and Underutilized Technology: Bi-level Stairwell lighting
Federal Energy Management Program
Commercial Lighting Tax Deduction
Lighting Controls Retrofit
Bi-Level Office Lighting with Occupancy Sensors
WSU Extension Energy Program
Intel Advanced Lighting Controls Project
Sacramento Municipal Utility District
Studies controls for retrofitting fluorescent and other, non-LED lighting systems for enhanced energy savings.
ADM Associates, Inc,
Fluorescent dimming Ballast study Report
Sacramento Municipal Utility District
Compares popular fluorescent dimming ballast performance of input power, lighting power and energy use. Findings are one-third of popular products on market increase energy use at 70% of full output,a popular setting for energy savings and task tuning, where expectations would be that they drop.
California Lighting Technology Center,
Western Exterior Occupancy Survey for Exterior Adaptive Lighting Applications (Phase 2)
Bonneville Power Administration