Mary Matteson Bryan, P.E.

415.305.5445

Bi-Level Office Lighting with Occupancy Sensors

E3T Field Assessment

Mary Matteson Bryan, P.E.

January 14, 2011

2

Background Concepts – Heat MgmtBi-level Office Lighting with Occupancy Sensors

Courtesy CLTC

CLTC Study - with the option of bi-level switching, occupants often choose to use a lower light level

Up to 50% savings

3

Background Concepts – Heat MgmtField Assessment Goals

Validate and add to CLTC findings for NW applications Quantify energy savings Develop economic analysis (customer simple payback) Provide energy savings data to support incentives Document occupant acceptance Develop case study Develop specifications Provide NW test installation

4

Background Concepts – Heat MgmtBaseline and Proposed Measures

Worked with BPA program staff to define baseline and proposed measures

Define baseline per BPA lighting calculator Calculator assumes single-level (100%) manual switching

Define proposed measures Rewire to bi-level switching with occupancy sensor For this assessment, also included ballast change to provide uniform

illumination at 50%

5

Background Concepts – Heat MgmtHost Site: Pierce County

High level of interest in energy efficiency, sustainability Individual offices, both perimeter with daylighting and interior Monitoring 30 offices Existing control: manual single level switching (all lights on or

off)

County-City Building

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Background Concepts – Heat MgmtExperimental Design and Procedure

Monitor each of three operational scenarios. Auto On at 50%/Auto Off: Lights are switched on automatically at the low level

(50%) upon occupancy, the remaining lights can be switched on manually. Auto On at 100%, Auto Off: Lights are switched on automatically at the high

level (100%) upon occupancy, lights can be switched to a lower light level (50%) manually.

Manual On/Auto Off: Lights can be switched on and off manually at 50% or 100%.

In all cases, lights can be switched off manually, and lights are turned off automatically after the office is unoccupied for a period of time.

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Background Concepts – Heat MgmtProject Results

Lighting Operation Significant operation at the low light level setting with bi-level

switching as compared to the baseline manual, single level. Maximum operation at low (66% of lit hours) using the auto-on at

50% setting.

Bi-level Lighting Operation

66%

10%27%

100%

34%

90%73%

0%

20%

40%

60%

80%

100%

120%

Baseline Auto on 50% Auto on100%

Manual on

Percent of Lit HoursOn @ 100%

Percent of Lit HoursOn @ 50%

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Background Concepts – Heat MgmtProject Results

Energy Savings Greatest energy savings achieved with the Auto-on at 50% setting.

Percent Energy Savings as Compared to Baseline

37%

12%

26%

0%

5%

10%

15%

20%

25%

30%

35%

40%

Auto on 50% Auto on 100% Manual on

Percent Energy Savings as Compared to Baseline

33%

5%

13%

0%

5%

10%

15%

20%

25%

30%

35%

Auto on 50% Auto on 100% Manual on

Note that savings are different for the retrofit and new construction cases because of the different baseline lighting hours of operation.

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Background Concepts – Heat MgmtProject Results

Occupant Satisfaction Occupants had very favorable reactions to the bi-level switches and

occupancy sensors. Most occupants (64%) preferred the Auto-on at 50% setting.

Satisfaction with New Switches as Compared to Original

7.1%

14.3% 14.3%

28.6%

35.7%

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

Very Dissatisfied Somewhat DissatisfiedSatsified Somewhat Satisfied Very Satisfied

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Project Results

Economic Performance Economic estimates are sensitive to site-specific variables such as

lighting hours of operation, installation labor costs, utility incentives, and energy costs.

Economic calculations presented here are based on variables specific to this field assessment.

Energy Savings (kWh/yr)

Energy Cost Savings ($/yr)

Installed Cost ($)

Payback (yrs)

Small Office, New Construction 64 $5.62 $50 9

Large Office, New Construction 194 $17.04 $110 6

Small Office, Retrofit 85 $7.47 $360 48

Large Office, Retrofit 254 $22.31 $870 39

Assessment Site Specific Analysis

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Project Results

Economic Performance - Impact of Lighting Hours of Operation and Installation Labor Costs

Simple Payback vs Baseline Lighting Operation

0

10

20

30

40

50

60

1900 2900 3900

Lighting Operation (hrs/yr)

Simple Payback Period (yrs)

Small Office - Retrofit Large Office - Retrofit

Small Office - New Large Office - New

Simple Payback vs Installed Cost

0

5

10

15

20

25

30

$0 $50 $100 $150

Installed Cost ($/office)

Simple Payback Period (yrs)

Small Office - Retrofit Large Office - Retrofit

Small Office - New Construction Large Office - New Construction

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Project Results

Economic Performance As a point of reference, economic performance was calculated for a

hypothetical situation with more favorable, put reasonable, assumptions for baseline lighting hours and installed cost than those found for this assessment.

Energy Savings (kWh/yr)

Energy Cost Savings ($/yr)

Installed Cost ($)

Payback (yrs)

Small Office, New Construction 354 $10.26 $22 2

Large Office, New Construction 1062 $30.78 $24 1

Small Office, Retrofit 131 $11.51 $268 23

Large Office, Retrofit 393 $34.52 $638 18

Favorable Assumptions Analysis

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Conclusions

Bi-level switching in individual offices can deliver significant savings as compared to single level switching.

Energy savings are maximized when the switches are set to automatically turn on at the low light level setting.

Bi-level switching provides high occupant satisfaction with the lighting system, possibly delivering non-energy benefits.

The economic performance of bi-level switching is most favorable in a new construction/major remodel situation.

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Background Concepts – Heat MgmtThank You

Mary Matteson Bryan, P.E.

415.305.5445

marymattesonbryan@pacbell.net