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Design & Engineering Services

COMMERCIAL TUBULAR DAYLIGHTING SYSTEM

ET11SCE1050 Report

Prepared by:

Design & Engineering Services

Customer Service Business Unit

Southern California Edison

August 2012

Commercial Tubular Daylighting System ET11SCE1050

Southern California Edison

Design & Engineering Services August 2012

Acknowledgements

Southern California Edison’s (SCE’s) Design & Engineering Services (DES) group is

responsible for this project in collaboration with the Tariff Program & Services (TP&S) group.

It was developed as part of SCE’s Demand Response, Emerging Markets and Technology

program under internal project number ET11SCE1050. DES project manager Doug Avery

conducted this project with overall guidance and management from Paul Delaney, Emerging

Technology Program Manager. For more information on this project, contact

[email protected].

Disclaimer

This report was prepared by Southern California Edison (SCE) and funded by California

utility customers under the auspices of the California Public Utilities Commission.

Reproduction or distribution of the whole or any part of the contents of this document

without the express written permission of SCE is prohibited. This work was performed with

reasonable care and in accordance with professional standards. However, neither SCE nor

any entity performing the work pursuant to SCE’s authority make any warranty or

representation, expressed or implied, with regard to this report, the merchantability or

fitness for a particular purpose of the results of the work, or any analyses, or conclusions

contained in this report. The results reflected in the work are generally representative of

operating conditions; however, the results in any other situation may vary depending upon

particular operating conditions.


Southern California Edison Page i Design & Engineering Services August 2012

EXECUTIVE SUMMARY This report evaluates the daylighting design and implementation at the Trane Southern

California headquarters located in City of Industry, California. The study is managed by

Southern California Edison’s (SCE) Design and Engineering Group.

The primary goals of this project are the following: 1) determine the baseline lighting loads

in the selected areas, 2) determine the post retrofit lighting load profiles, and 3) determine

how much lighting energy and demand savings can be achieved by the new daylighting and

control system.

The project site is a warehouse office building with individual offices, open office space, a

retail area, and warehouse. The demonstration area consists of six individual office spaces

and common office areas at Trane’s headquarters. The pilot area of the building covers

1,780 square feet (sf) and has a 10-foot drop ceiling.

The project design replaced standard T8 fluorescent lighting with a new lighting system that

included Light Emitting Diode (LED) fixtures, high output T5 fluorescent fixtures, and

daylighting through Solatubes®. Advanced lighting controls were installed to operate the

new lighting system. The new lighting control system also used occupancy sensors for

on/off control and incorporated daylight sensors for dimming control of the new lighting

Lighting circuits were monitored before and after the installation of the lighting solution.

Lighting power was recorded for three baseline months and seven months after completion

to capture the seasonal effects of daylighting contributions.

The rated lighting power density (LPD) for the demonstration area was reduced from 1.40 to

1.10 Watts/square foot (W/sf), which results in a LPD design savings of 0.30 W/sf, or 22%.

The average operating LPD during SCE’s peak period (noon to 6:00 p.m.) was reduced from

0.83 to 0.13 W/sf, which results in an average peak period demand savings of 0.71 W/sf, or

85%. This is a significant reduction in demand. Table 1 presents the average peak period

demand and savings in kilowatts (kW), and normalizes to square footage, W/sf. The

estimated average demand savings attributed to the daylighting controls is 0.49 W/sf, or

59%. The monitored lighting energy projected to annual use was reduced from 5,490 to

1,800 kWh per year. The estimated energy savings attributed to the daylighting system is

2,260 kWh/yr, which is a savings of 56%, and the combined total energy savings for the

project is 3,680 kWh/yr, which is 67%.

TABLE 1. PEAK DEMAND USE AND SAVINGS BY PERIOD TYPE AND PER SQUARE FOOT

NOON TO 6 PM PEAK PERIOD AVERAGE DEMAND

PERIOD AND SAVINGS TYPE KW W/SF

Pre Retrofit 1.48 0.83

Post Retrofit 0.22 0.13

Daylight Savings 0.87 0.49

Total Savings 1.26 0.71

Error! Reference source not found. illustrates the lighting demand for pre and post retrofit

conditions and the savings attributed to the daylighting controls and the total retrofit. Two

vertical axis are provided to show kWh/yr and kWh/sf/yr values.


Southern California Edison Page ii Design & Engineering Services August 2012

FIGURE 1. AVERAGE LIGHTING DEMAND IN DEMONSTRATION AREA: PRE, POST, DAYLIGHT SAVINGS, AND TOTAL SAVINGS

The total material and labor costs for the test site was $91,040. The cost may be lower if

utility program incentives are received. A simple payback period calculation used an average

electric rate of $0.15/kWh. Payback period for the site is 165 years without utility

incentives. The calculated Return on Investments is 0.1 based on life expectancies of the

products.

The results of this field evaluation show that significant lighting energy savings are possible

with commercial tubular daylighting and lighting control system technologies. These

technologies can be adapted to other business types beyond the office tested in this study.

Further study of daylighting with dimming controls could be considered for facilities that do

not have existing occupancy controls. Additional savings may be documented with such a

study. Any additional studies should monitor the post-installation period for at least a winter

and summer period.

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Southern California Edison Page iii Design & Engineering Services August 2012

ABBREVIATIONS AND ACRONYMS

ALCS Advanced Lighting Controls Systems

fc Foot-candles

GWh Gigawatt-hours

kW Kilowatt

kWh Kilowatt-hours

LED Light Emitting Diode

LPD Lighting Power Density

M&V Measurement and Verification

ROI Return on Investment

SCE Southern California Edison

sf Square Feet

W Watts

W/sf Watts per Square Foot


Southern California Edison Page iv


CONTENTS

EXECUTIVE SUMMARY ________________________________________________ I

INTRODUCTION ____________________________________________________ 1

Background ............................................................................ 1

Goal of the Pilot Project ........................................................... 1

Potential Market Impact ........................................................... 2

DEMONSTRATION PROJECT DESCRIPTION ________________________________ 3

Site Description ...................................................................... 3

Existing Lighting ..................................................................... 3

LIGHTING SOLUTION ________________________________________________ 4

Tubular Daylighting ................................................................. 4

Lighting Fixtures ..................................................................... 5

Lighting Controls ..................................................................... 7

TECHNICAL APPROACH/TEST METHODOLOGY ____________________________ 9

Metering Equipment and Data Acquisition ................................... 9

DATA ANALYSIS AND RESULTS ________________________________________ 10

Data Analysis ........................................................................ 10

Results ................................................................................ 13

Light Levels .......................................................................... 14

Economics ............................................................................ 15

Discussions .......................................................................... 15

CONCLUSION ____________________________________________________ 17

RECOMMENDATIONS ______________________________________________ 18

REFERENCES _____________________________________________________ 19

APPENDIX A _____________________________________________________ 20


Southern California Edison Page v


FIGURES Figure 1. Average Lighting Demand in Demonstration Area: Pre,

Post, Daylight Savings, and Total Savings ....................... ii

Figure 2. Demonstration Area Post Retrofit Lighting Layout ............. 3

Figure 3. Solatube® 750DS Dome ................................................ 4

Figure 4. Solatube in Attic on Right Side of Picture ......................... 4

Figure 5. View of OptiView® Diffuser from Directly Below and

Looking Up .................................................................. 4

Figure 6. 2’ x 2’ Diffusers Providing Daylighting in Break Room. ...... 5

Figure 7. Recessed Can Fixture with LED Lamp Next to 2x2

Daylighting Diffuser ...................................................... 6

Figure 8. Fluorescent 1x4 Fixture Next to 2x2 Daylighting Diffuser ... 6

Figure 9. Fluorescent 1x4 Fixture Above Cabinets .......................... 6

Figure 10. Fluorescent 1x4 Fixture Above Cabinets .......................... 6

Figure 11. Exergy Controls and Laptop Used for Controlling LED

and Fluorescent Lights .................................................. 7

Figure 12. An Occupancy Sensor (Top) and Daylight Sensor

(Bottom Center) ........................................................... 7

Figure 13. Power Recorder in Lower Right Corner of Picture

Mounted Near Lighting Panel ......................................... 9

Figure 14. Average Weekday Lighting Profiles for Pre retrofit and

Average Annual Post Retrofit Periods and Estimated

Post Retrofit with Only Occupancy Control ..................... 10

Figure 15. Average Weekend day and Holiday Lighting Profiles for

Pre retrofit and Average Annual Post Retrofit Periods

and Estimated Post Retrofit Weekends with Only

Occupancy Controls .................................................... 11

Figure 16. Post Retrofit Lighting Load Profiles for Two Months in

Opposite Seasons and the Annual Average Profile .......... 12

Figure 17. Monthly and Average Daily Lighting Energy Use from

January to June for the Daylight Controlled Period. ......... 12

Figure 18. Annual Lighting Retrofit & Occupancy Control Energy

Use and Savings Estimate for Daylighting ...................... 14

Figure 19. Lighting Demand and Estimated Summer Demand

Savings Due to Daylighting.......................................... 14

Figure 20. Annual Lighting Energy Use and Total Savings ............... 14

Figure 21. Lighting Demand and Estimated Total Summer

Demand Savings ........................................................ 14


Southern California Edison Page vi Design & Engineering Services August 2012

TABLES Table 1. Peak Demand Use and Savings by Period Type and per

Square Foot .................................................................. i

Table 2. Summary of Post Retrofit Lighting Fixtures and

Locations .................................................................... 6

Table 3. Energy and Peak Demand Use and Savings by Period

Type Annually and per Square Foot .............................. 13

Table 4. Post Retrofit Light Level Measurement Summary ............ 15


Southern California Edison Page 1


INTRODUCTION This study evaluates commercial tubular daylighting and integration with an Advanced

Lighting Control System (ALCS) developed by Exergy Solutions. This ALCS was installed in

office areas of the single-story Trane Southern California headquarters building in Industry,

California. This real-world pilot study permitted analysis of data collected on the operation

of the lighting system.

Southern California Edison (SCE) is studying such concepts to advance the implementation

of energy saving technologies and is considering providing incentives for installation of

similar equipment.

BACKGROUND Lighting in commercial buildings represents approximately 29% of the electrical

energy use by this sector.1 Some of this energy use can be substituted by using

daylight. Schools and office buildings with windows and warehouses with skylights

provide the opportunity to reduce the lighting load during daylight hours. Single-

story buildings can be modified by piping daylight from rooftop collectors to interior

zones without natural daylight. This approach provides light to building areas not

accessible by conventional skylights or windows.

The substitution of daylight for artificial light reduces energy use and demand. The

amount of energy or demand that can be saved is dependent on the time of year,

latitude, and availability of sunlight (prevailing weather).

Some studies have shown that schoolchildren learn better in natural daylighting than

from artificial light.2

This technology requires minimal maintenance provided there are no leaks in the

roof penetrations.

GOAL OF THE PILOT PROJECT SCE is testing the implementation of daylighting in a single-story warehouse office

building, representing 1,780 square feet (sf) of office space. The ALCS controls the

level of light output based on daylight sensors installed as part of this project.

1 Itron, 2010, California End Use Survey Results March 2006 prepared for the California Energy Commission retrieved 7/10/12 at http://capabilities.itron.com/CeusWeb/Chart.aspx.

2 Heschong Mahone Group, October 2003, Technical Report for the California Energy Commission, “Windows and Classrooms: A Study of Student Performance and the Indoor Environment”, Publication # P500-03-082-A-07.




The primary goals of this project are to determine:

1) what are the baseline lighting loads in the selected areas,

2) what are the post retrofit lighting load profiles in the selected areas,

3) does the new daylighting control system perform as expected, and

4) how much lighting energy and demand savings can be achieved by the new

daylighting control system?

POTENTIAL MARKET IMPACT According to the California Commercial Energy Use Survey (CEUS), commercial

interior lighting space covers 4,915 million sf in California. In the SCE service

territory, commercial space covers 2,142 million sf and has an interior lighting connected load of 1.06 W/sf.3 It follows that the connected interior lighting load is

2,270 megawatts (MW). If 5% of the lighting was supplemented with daylighting,

and achieved an 80% demand reduction in the summer, it could reduce the peak

loads by approximately 90MW.

The annual commercial interior lighting energy use in SCE service territory is 8,504

Gigawatts per hour (GWh). If 5% of the lighting was supplemented with daylighting,

and achieved a 56% annual energy reduction, it could reduce the energy use by

approximately 238 GWh.

The market impact of daylighting improvements in existing buildings is a discrete

analysis and not a part of this study.

3 Itron, 2010, California End Use Survey Results March 2006 prepared for the California Energy Commission retrieved 3/5/10 at http://capabilities.itron.com/CeusWeb/Chart.aspx.

http://capabilities.itron.com/CeusWeb/Chart.aspx




DEMONSTRATION PROJECT DESCRIPTION The ALCS was installed in a single story warehouse office building used as the Southern

California headquarters of the Trane Corporation. A lighting system was designed for this

demonstration that reduces energy use and demand by using daylight and a multifunction

lighting control system. The light fixtures are dimmed according to available daylight and

turned on/off based on occupancy. Lighting use was monitored to quantify the energy and

demand savings. The project is representative of retrofit projects in typical single story

commercial office space.

SITE DESCRIPTION This project consists of six individual offices, a common copy room, and break room.

They are built inside a warehouse style building with drop ceilings and a tall attic

space. The roof has built-in skylights but they only illuminate the attic space above

the drop ceiling. The ceilings in the demonstration area are 10 feet tall. There are no

wall switches for lighting in the demonstration area, only occupancy sensors. The

demonstration area is 1,780 sf. The layout of the test areas displays in Figure 2.

FIGURE 2. DEMONSTRATION AREA POST RETROFIT LIGHTING LAYOUT

EXISTING LIGHTING The existing lighting system used 4-foot T8 fluorescent lamps rated at 32W. They

were operated in standard recessed three-lamp fixtures. Five of the offices had two

fixtures each, one office had four fixtures, and the copy room and break room each

had six fixtures. There were no wall switches in any of the rooms, but they all had

occupancy sensors to turn lights on/off. The existing occupancy sensors for the

lighting system will provide a conservative baseline of energy use for the analysis

when projecting typical energy savings.

NSky Light TubeLED Can LightsT5 1x4' Lights

Office A Office B Office C Copy Room

Office D Office E Office F

Break RoomLegend




LIGHTING SOLUTION

TUBULAR DAYLIGHTING Natural daylighting was provided to the spaces using commercial Solatubes®. Twenty

Solatubes were installed as diagramed in Figure 2. SolaMaster® series Solatube®

750DS domes (see Figure 3) were installed on the roof. The 750DS uses a Fresnel

lens technology, grooves molded into the dome, which collects all angles of the sun

as it rises over the horizon but deflects the high heat and glare of noonday. It

provides a solar heat gain coefficient of 0.21 and lumen output of 7500. Eight-inch

self-mounted flashings were used to seal the domes to the roof. The 21” diameter

domes channel sunlight into 21” diameter interior reflecting tubes (see Figure 4) that

connect to the drop ceiling. The reflecting tubes connected to 2’ x 2’ optical diffuser

for light dispersion into the rooms. The OptiView® diffuser (see Figure 5) delivers

natural daylight through a matrix of individual Fresnel lenses that offer a unique view

of the sky above.

FIGURE 3. SOLATUBE®

750DS DOME

FIGURE 4. SOLATUBE IN ATTIC ON RIGHT SIDE OF PICTURE

FIGURE 5. VIEW OF OPTIVIEW®

DIFFUSER FROM DIRECTLY BELOW AND LOOKING UP




The picture in Figure 6 shows daylight coming through 2’ x 2’ diffusers that nicely

replace ceiling tiles.

FIGURE 6. 2’ X 2’ DIFFUSERS PROVIDING DAYLIGHTING IN BREAK ROOM.

LIGHTING FIXTURES There are three types of fixtures installed as part of this Emerging Technology

demonstration. They are each discussed in the following paragraphs.

Eleven ceiling-mounted 6-inch diameter recessed downlight fixtures with Light

Emitting Diodes lamps (LED) were installed in three rooms. A side view of one of the

fixtures is shown in Figure 7. The 6VLED1100 series fixture is manufactured by

Pathway Lighting Products. They are compatible with 0-10 Volt (V) dimming controls

and have a rated output of 1,100 lumens, 3,000K color temperature, and 50,000

hours. A Philips Advanced Xitanium 0-10V LED electronic dimming driver is used to

power the LED lamps.

Thirty ceiling-mounted wall-washing fluorescent fixtures with specialty reflectors

were installed throughout all eight rooms. A side view of the fixture is shown in

Figure 8. These are Style 210 fixtures manufactured by Elliptipar. The fixtures use a

single 4-foot T5 fluorescent 3,000K 54W high output lamp. The ballasts are

compatible with 0-10V dimming controls.

Three cabinet-top-mounted ceiling-washing fluorescent fixtures with specialty

reflectors were installed in the lunchroom. A view of the wall washing and the

fixtures can be seen in Figure 9 and Figure 10, respectively. These are Style 305

fixtures manufactured by Elliptipar. The fixtures use a single 4-foot T5 fluorescent

4,100K 50W high output lamp. The ballasts are compatible with 0-10V dimming

controls.




FIGURE 7. RECESSED CAN FIXTURE WITH LED LAMP

NEXT TO 2X2 DAYLIGHTING DIFFUSER

FIGURE 8. FLUORESCENT 1X4 FIXTURE NEXT TO 2X2

DAYLIGHTING DIFFUSER

FIGURE 9. FLUORESCENT 1X4 FIXTURE ABOVE

CABINETS

FIGURE 10. FLUORESCENT 1X4 FIXTURE ABOVE CABINETS

Table 2 provides a summary of the post retrofit lighting fixtures.

TABLE 2. SUMMARY OF POST RETROFIT LIGHTING FIXTURES AND LOCATIONS

LOCATION NUMBER OF

FIXTURES

RATED WATTAGE

(W/FIXTURE)

FIXTURE TYPE

6 Offices 12 0 Solatube®

6 Offices 24 54 T5, elliptipar 210

1 Office 2 17 LED, Pathway

Copy Room 4 0 Solatube®

Copy Room 6 54 T5, elliptipar 210

Copy Room 3 17 LED, Pathway

Break Room 4 0 Solatube®

Break Room 3 50 T5, elliptipar 210

Break Room 6 17 LED, Pathway




LIGHTING CONTROLS A new lighting control system was installed. An Exergy Controls (Figure 11) system

uses wireless signals to provided dimming control of the LED and fluorescent lamps.

Dimming control is based on the amount of available daylight as measured by

ceiling-mounted sensors in each room (see Figure 12). Occupancy sensors (see

Figure 12) turn lighting fixtures on/off based on occupancy in the room.

FIGURE 11. EXERGY CONTROLS AND LAPTOP USED FOR

CONTROLLING LED AND FLUORESCENT LIGHTS

FIGURE 12. AN OCCUPANCY SENSOR (TOP)

AND DAYLIGHT SENSOR (BOTTOM

CENTER)

An illumination system was developed by the lighting designer (in conjunction with

Trane and SCE) to deliver task-appropriate light levels using state-of-the-art

fluorescent and LED lighting instruments. The system’s cumulative energy

consumption (at full light output) was below Title 24 guidelines. The digital lighting

control system was commissioned to provide illumination only when a space was

occupied (using digitally enhanced occupancy sensors), and when in use, to maintain

35 footcandles (fc) at task surfaces using sophisticated digital daylight-harvesting

sensors. As natural daylight increased (from Solatube skylights installed in each test

space), each fixture’s lamp output was reduced (dimmed) to maintain target light

levels while minimizing power consumption.

As spaces become populated in the morning, lights are brought on and managed to

meet the established lighting requirements. As daylight through the Solatube

skylights is introduced into each space, fixture output is reduced accordingly. When

natural light levels meet or exceed the target illumination levels, light fixtures are

turned off. Toward the end of the day, as natural daylight wanes, fixtures are turned

on and lamp light levels automatically adjust to maintain the required work surface

illumination. Each area is independently managed by the digital lighting control

system to constantly monitor occupancy. When it is determined that a space

becomes unoccupied, its lights are extinguished.




A maximum set point was established to prevent any fixture’s output (measured as a

percentage of light output, not power consumption) from exceeding 85% of its

illumination capacity; this only occurs when natural daylight from skylights is not

present. In operation, the spaces operated well below this maximum trim level:

Private offices typically operated at a maximum of 60% light output

Copy and break rooms operated at a maximum of 80% light output

This project is an excellent opportunity to demonstrate state-of-the-art daylighting

control practices in a normal, functional, office building.




TECHNICAL APPROACH/TEST METHODOLOGY In order to characterize the energy and demand reductions resulting from this pilot project,

ADM Associates, Inc. devised a Measurement and Verification (M&V) protocol adapted to

this facility.

Power to all lighting fixtures in the study area were monitored. All lighting circuits were

traced to identify the circuits that exclusively serve the study area. Several breaker panel

circuits were identified to exclusively serve the study area while others also served areas

outside the study area. For those circuits that branched in the false ceiling area, current

transformers were placed in junction boxes above the false ceiling to capture the lighting

load exclusively for the study area. One branch circuit was monitored that served a fixture

outside the study area and was subtracted from the primary breaker circuit in the analysis.

The meter recorder was installed in the electrical room to monitor the lighting circuits.

METERING EQUIPMENT AND DATA ACQUISITION ADM installed an Enernet K-20 meter recorder (see Figure 13) to monitor the power

use of the lighting. Seven circuits were monitored using appropriately-sized 5 Amp

current transducers. Averaged data were recorded at 5-minute intervals. The K-20

was programmed to record kW and kilo Volt Amps. One-time power measurements

were made using an AEMC 3910 true RMS power meter to provide field calibration of

the installation. Power data were recorded from May 26, 2011 to June 30, 2012.

ADM’s monitoring equipment was manually downloaded for several months before

the post retrofit period was extended, at which time a telephone line was installed to

collect data remotely via the modem onboard the recorder. The logger was

synchronized to the NIST clock on Pacific Time, as obtained from the following web

link: http://nist.time.gov/timezone.cgi?Pacific/d/-8/java.

FIGURE 13. POWER RECORDER IN LOWER RIGHT CORNER OF PICTURE MOUNTED NEAR LIGHTING PANEL

For the post retrofit period, light levels were measured at various locations in the

test area using an Extech 407026 Light meter.

http://nist.time.gov/timezone.cgi?Pacific/d/-8/java




DATA ANALYSIS AND RESULTS This section presents and discusses the data collected from monitoring of the lighting in the

study area. Charts and tables displaying the data are presented in this chapter.

DATA ANALYSIS Pre retrofit baseline data collected from May 26 to September 30, 2011 were

averaged together to develop weekday, weekend, and holiday profiles for the

existing lighting loads. The retrofits occurred over a two-week period; however, the

commissioning process was very prolonged. The analysis used data from January 1

to June 30, 2012 for the post retrofit period. Post retrofit data collection was

extended longer than most pilot studies in order to capture the seasonal impact on

the daylight controls. Figure 14 shows the average weekday profiles for pre and post

periods and the estimated profile for the post period with only occupancy controls.

The post retrofit period is the average annual profile generated from the six months

of January through June data. The post profile shows a dip during the middle of the

day that is characteristic of savings contributed by daylighting controls. The peak in

the evening is from the cleaning crew after dark. There was not a designated period

after the retrofits when daylighting controls were not active to determine retrofit-

only profiles. An estimated profile for the retrofit and occupancy control-only

scenario was generated using the pre retrofit profile and a ratio of the January after

dark work hours to pre retrofit period for the same hours.

FIGURE 14. AVERAGE WEEKDAY LIGHTING PROFILES FOR PRE RETROFIT AND AVERAGE ANNUAL POST RETROFIT

PERIODS AND ESTIMATED POST RETROFIT WITH ONLY OCCUPANCY CONTROL

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Figure 15 shows the average weekend day and holiday profiles for pre and post

periods. In addition, the chart shows the estimated profile for the post weekend

period with only occupancy control. This chart is plotted on the same scale as the

weekday chart to show the relative impact weekend lighting has on lighting energy

use.

FIGURE 15. AVERAGE WEEKEND DAY AND HOLIDAY LIGHTING PROFILES FOR PRE RETROFIT AND AVERAGE ANNUAL

POST RETROFIT PERIODS AND ESTIMATED POST RETROFIT WEEKENDS WITH ONLY OCCUPANCY CONTROLS

Figure 16 shows the influence of daylight availability. The variability between winter

and summer is most evident in the late afternoon hours. These are also hours when

peak demand reduction is important. The hours of operation of a business can

influence the savings potential.

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FIGURE 16. POST RETROFIT LIGHTING LOAD PROFILES FOR TWO MONTHS IN OPPOSITE SEASONS AND THE ANNUAL

AVERAGE PROFILE

The monthly progression of lighting energy use for the post retrofit period was

tabulated and then plotted in Figure 17. Both total monthly and average daily energy

use are shown in the chart. There is a very distinct reduction in energy use between

winter and summer. The lighting energy use in June is 38% lower than in January

due to the longer daylight hours. There is approximately a linear relationship in

lighting energy use between the winter and summer months.

FIGURE 17. MONTHLY AND AVERAGE DAILY LIGHTING ENERGY USE FROM JANUARY TO JUNE FOR THE DAYLIGHT

CONTROLLED PERIOD.

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RESULTS Annual energy use was projected based on available pre and post data. Eight

holidays were incorporated into the annual calculation. Energy and demand were

also calculated per square foot for the study area. Average lighting demand during

the 12 Noon to 6:00 PM peak demand period was calculated. The energy use and

demand of the retrofit and occupancy-controls-only period was estimated as

described earlier. These estimates enable savings to be provided by the daylighting

controls. Demand for the post retrofit period with daylighting (and occupancy)

controls was calculated as the average for May and June to represent typical summer

period daylight hours. The results of these calculations are presented in Error!

Reference source not found..

TABLE 3. ENERGY AND PEAK DEMAND USE AND SAVINGS BY PERIOD TYPE ANNUALLY AND PER SQUARE FOOT

ANNUAL ENERGY

NOON TO 6 PM PEAK

PERIOD AVERAGE DEMAND

PERIOD AND SAVINGS TYPE KWH/YR KWH/SF/YR KW W/SF

Pre Retrofit 5,490 3.09 1.48 0.83

Post Retrofit with Occupancy Controls 4,060 2.28 1.10 0.62

Post Retrofit Occupancy & Daylighting 1,800 1.01 0.22 0.13

Retrofit & Occupancy Savings 1,430 0.80 0.39 0.22

Daylight Savings 2,260 1.27 0.87 0.49

Total Savings 3,680 2.07 1.26 0.71

The estimated energy savings attributed to the daylighting system is the difference

between the post retrofit with occupancy controls and post retrofit with occupancy

and daylight controls. The daylighting system energy savings is 2,260 kWh/yr, which

is a savings of 56%. The combined total energy savings for the project are 3,680

kWh/yr, which is 67%. The estimated average demand savings attributed to the

daylighting components during the summer peak period is 0.87 kW, or 80%. The

combined total demand savings is 1.26 kW, or 85%.

Figure 18 and Figure 19 are bar charts respectively showing the energy and demand

use and savings for the daylighting system and controls. Figure 19 specifically

represents the average summer demand savings from daylighting.




FIGURE 18. ANNUAL LIGHTING RETROFIT &

OCCUPANCY CONTROL ENERGY USE AND

SAVINGS ESTIMATE FOR DAYLIGHTING

FIGURE 19. LIGHTING DEMAND AND ESTIMATED SUMMER

DEMAND SAVINGS DUE TO DAYLIGHTING

Figure 20 and Figure 21 are bar charts respectively showing the energy and demand

use and savings for all retrofits and controls. Figure 21 specifically represents the

average total summer demand savings.

FIGURE 20. ANNUAL LIGHTING ENERGY USE AND

TOTAL SAVINGS

FIGURE 21. LIGHTING DEMAND AND ESTIMATED TOTAL

SUMMER DEMAND SAVINGS

LIGHT LEVELS Illumination measurements were made during three sets of conditions for the post

retrofit period. The first was a winter day (noon on January 25, 2012; a clear sunny

day). The second was after dark (6 PM on February 1, 2012). The third was a

summer day (noon on August 6, 2012; a clear sunny day). All measurements were

made at desktop height. Light levels in fc were recorded at four locations in each

room: 1) directly below a Solatube diffuser, 2) directly below a ceiling light fixture,

3) halfway between two ceiling light fixtures, and 4) halfway between a Solatube

0.0

0.5

1.0

1.5

2.0

2.5

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

Lighting in Test Area

kWh

/sf/

Year

kWh

/Ye

ar

Post Retrofit with Occupancy ControlsPost Retrofit Occupancy & DaylightingDaylight Savings

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Average Peak Period (Noon - 6:00 PM) Demand

De

man

d, W

/sf

De

man

d, k

W

Post Retrofit with Occupancy ControlsPost Retrofit Occupancy & DaylightingAverage Daylight Savings

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Lighting in Test Area

kWh

/sf/

Year

kWh

/Ye

ar

Pre RetrofitPost Retrofit Occupancy & DaylightingTotal Savings

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Average Peak Period (Noon - 6:00 PM) DemandD

em

and

, W/s

f

De

man

d, k

W

Pre RetrofitPost Retrofit Occupancy & DaylightingAverage Total Savings




diffuser and a ceiling light fixture. This selection of points provides minimum,

maximum, and additional light level measurements within each room. A summary of

the light level measurements are provided in Table 4. The presented values for each

day type for the six offices is across 24 measurements. The presented values for

each day type for the common areas is across eight measurements. The average

office light level is 57 fc during a clear summer day, 46 fc during a clear winter day,

and 28 fc at night. This compares to the 35 fc target the control system was

intended to maintain. Note that during sunny days the lights are generally off.

TABLE 4. POST RETROFIT LIGHT LEVEL MEASUREMENT SUMMARY

CONDITIONS SIX OFFICES

(FC)

COMMON ROOMS

(FC)

Minimum – Mid Summer Day 45.2 36.7

Maximum – Mid Summer Day 70.2 72.8

Average – Mid Summer Day 57.6 62.3

Minimum – Mid Winter Day 30.9 35.0

Maximum – Mid Winter Day 58.2 55.1

Average – Mid Winter Day 46.0 48.7

Minimum – After Dark 18.6 16.0

Maximum – After Dark 36.3 32.3

Average – After Dark 28.1 23.1

ECONOMICS The material and labor costs for the test site daylight tubes was $35,850. The

material and labor costs for the test site lighting retrofit and controls was $55,190.

The total project cost was $91,040. The cost may be lower if utility program

incentives are received. The simple payback period was calculated based on an

average electric rate of $0.15/kWh. Payback period for the site was 165 years

without utility incentives.

Return on Investment (ROI) was calculated for the expected life of each product. The

expected life is approximately 20 years. The calculated ROI is 0.1.

DISCUSSIONS This project implemented new technology to provide energy and demand reductions.

Installation of tubular daylight in buildings by itself does not provide savings. Savings

are achieved by dimming or turning lights off. Predictable savings only occur if the

controls are automated and use daylight sensors. Savings from manual controls can

occur but are not reliable.

This test case achieved lower total savings than a typical building since the baseline

lighting already used occupancy sensors and controls. Daylighting control savings

can occur whether the retrofit lighting is LED, fluorescent, or other dimmable

lighting. Daylighting can provide sufficient illumination to completely turn off lights

during clear sunny days.




Total daylight savings is maximized by businesses that operate during all available

daylight hours. Percent savings will be maximized by businesses that operate only

during hours with available daylight.

Secondary impacts on HVAC systems are not considered during the savings analysis

presented in this report.




CONCLUSION The main objectives of the project were to answer the following questions:

1. What are the baseline lighting loads in the selected areas? The baseline annual lighting

energy use in the test area was 5,490 kWh, which translates to 3.09 kWh/sf/yr. The

baseline peak period lighting demand was 1.48 kW for the test area.

2. What are the post retrofit lighting load profiles in the selected areas? The retrofit annual

lighting energy use in the test area is 1,800 kWh, which translates to 1.01 kWh/sf/yr.

The post retrofit peak period lighting demand during the summer is 0.22 kW for the test

area.

3. Does the new daylighting control system perform as expected? The lighting profiles

during the daylight hours are significantly reduced with the new daylighting and

controls. The system is performing as expected.

4. How much lighting energy and demand savings can be achieved by the new daylighting

control system? The estimated energy savings attributed to the daylighting system is

2,260 kWh/yr, which is a savings of 56%. The combined total energy savings for the

project are 3,680 kWh/yr, which is 67%. The estimated average demand savings

attributed to the daylighting components during the summer peak period is 0.87 kW, or

80%. The combined total demand savings is 1.26 kW, or 85%.

Since this was a case study, savings for other sites may be higher if lights are generally on

during business hours and there are no existing occupancy controls.

This report can provide measured and technical data to SCE’s emerging technology

evaluation process. The results of this study illustrate the effectiveness of tubular

daylighting systems and controls.




RECOMMENDATIONS The results of this demonstration project show that significant energy savings are possible

with commercial tubular daylighting and lighting control systems technologies. These

technologies can be adapted to other business types beyond the office tested in this study.

As more of these daylighting solutions are installed, installers should learn how to properly

install and commission them in order to provide an effective product to the customer.

Based on this study, tubular daylighting in combination with daylight controls is not cost

effective. If it is to be considered for adoption into a portfolio of energy efficiency incentive

programs, cost analysis should be conducted to determine whether the total resource cost

(TRC) testing result justifies its inclusion. For a marginal additional cost the lighting and

controls could be designed to also provide demand reduction that may help justify costs.

Further study of daylighting with dimming controls could be considered for facilities that do

not have existing occupancy controls; additional savings may be documented with such a

study. Any additional studies should monitor the post installation period for at least a winter

and summer period.




REFERENCES [CEUS] Itron, 2010, California End Use Survey Results, March 2006, prepared for the

California Energy Commission retrieved 3/5/10 at

http://capabilities.itron.com/CeusWeb/Chart.aspx.

[DEER] Database for Energy Efficient Resources, 2004-2005 version 2.01, California Utilities

Commission at http://www.deeresources.com/

Heschong Mahone Group, October 2003, Technical Report for the California Energy

Commission, “Windows and Classrooms: A Study of Student Performance and the Indoor

Environment”, Publication # P500-03-082-A-07.

http://capabilities.itron.com/CeusWeb/Chart.aspx

http://www.deeresources.com/




APPENDIX A Raw and processed data collected for the evaluation of this project can be found in the

embedded Excel file. In addition, information on equipment calibration is provided in one of

the worksheets in the same file.

Appendix A Trane Data 8-8.xlsx

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