OFF-GRID COMMERCIAL DIRECT CURRENT GRID SYSTEM

Design & Engineering Services OFF-GRID COMMERCIAL DIRECT CURRENT GRID SYSTEM Report Prepared by: Design & Engineering Services Customer Service Business Unit Southern California Edison December 2012

Acknowledgements Southern California Edison s Design & Engineering Services (DES) group is responsible for this project. It was developed as part of Southern California Edison s Emerging Technologies Program under internal project number. DES Neha Paul Delaney. For more information on this project, contact Neha.Arora@sce.com. 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

EXECUTIVE SUMMARY Southern California Edison (SCE) conducted this Emerging Technologies (ET) field assessment to evaluate the light performance and energy savings potential of the Direct Current (DC) ceiling grid technology compared to a typical T-bar ceiling grid technology in commercial buildings. This project evaluated DC system and its components to measure its annual energy consumption, average demand, and light output. Within SCEs service territory, a site with a test area of approximately 1,080 square feet with 16 light fixtures was selected. Each fixture contains three 28 or 32 Watt (W) T-8 fluorescent lamps with electronic instant start, non-dimming ballasts. To evaluate this technology, SCE used the following process: Monitored and recorded the demand, energy consumption, and light output of the existing system i.e. Baseline 1. The existing system at the site was a typical T-Bar ceiling with 120/277 Volt (V) three phase wye lighting configuration. Restored the system to like-new condition by adding new 28W T-8 fluorescent lamps with electronic instant start non-dimming ballasts - This system formed Baseline 2. Monitored and recorded the demand profile, energy consumption, and light output of Baseline 2. Installed the DC ceiling grid and Photovoltaic (PV) panels, and then added light fixtures with three 28W T-8 DC lamps and electronic program-start, dimming ballasts. Monitored and recorded the average demand, energy consumption, and light output of DC system. The study recorded the average demand of Baseline 1 at 1.33 kw. DC ceiling s average demand was 1.16kW. The total demand reduction is 170W. The difference between the Baseline 2 demand and the DC system demand is 0.01kW, which falls within the error range and is considered equal. Offsetting the DC demand met by the PV panels, from total demand of the ceiling, increases the AC demand reduction. These results are shown in Table 1. TABLE 1. AVERAGE AC DEMAND REDUCTION OF THE DC SYSTEM COMPARED TO BASELINES Name kw Demand Demand Reduction compared to Measure (kw) Average AC Contribution to Total Demand (kw) Average DC Contribution to Total Demand (kw) Baseline 1 1.33 0.17 1.33 0.73 Baseline 2 1.15 0 1.15 0.55 DC System 1.16 NA 0.60 0.56 NA Demand Reduction (kw) (AC Only) The annual energy savings of the DC system is approximately 378.18 or 12.58% compared to Baseline 1. The test site was 1080 sq. ft.; therefore, the estimated energy saving per square foot for baseline 1 is 0.350 kwh/sq.ft. SCE has 824,000 Southern California Edison Page i

customers in its territory and at an estimated 25% market penetration, the potential annual energy savings can be 77.9 GWh. After compensating for the energy provided by PV panels, the annual AC energy savings between the DC system and Baseline 1 is 1649.45 kwh/yr. or 54%. The annual AC energy savings compared to Baseline 2 is 1233.23 kwh/yr. or 48%. The estimated energy saving per square foot for baseline 1 with DC offset is 1.53 kwh/sq.ft. and for Baseline 2 is 1.14kWh/sq.ft. Therefore, DC system can potentially save 339.78 GWh in comparison to Baseline 1 and 254.04 GWh in comparison to Baseline 2 across SCEs service territory at an estimated 25% market penetration. The light output of the DC system is measured at 56 foot-candle output compared to 41 foot-candle output for Baseline 1, and 54 foot-candle output for Baseline 2. For a room equal to the size of the test area at the test site, the cost of retrofittingthe DC system is approximately $27,348.50 and the cost of retrofitting a typical T-bar ceiling system is approximately $10,248. The cost of installing PV panels for the size similar to test area is $6840. The cost of installing a DC ceiling in a new construction building is $28,815 and for a typical T-bar ceiling is $8898. This price difference can significantly affect market penetration. Overall, the DC system is a very aesthetically pleasing system with the potential to save energy even though the installation cost is high. To encourage facilities to adopt this system, manufacturers need to reduce the costs of the components to achieve a realistic return. SCE tested this technology in climate zone 6 only. Note that the performance of PV panels can change based on the climate. Additionally, SCE only tested the performance of the DC system with PV panels. As a result, the following is recommended: Perform tests at a site with a typical T-bar ceiling and PV panels to assess the energy consumption of such system. Southern California Edison Page ii

ABBREVIATIONS AC Alternating Current DC Direct Current ET Emerging Technologies GWh Giga-Watt Hour HVAC Heating, Ventilation and Air Conditioning kw Kilowatt kwh Kilo-Watt Hour MPPT Maximum Power Point Tracking PSM Power Supply Module PV Photovoltaic SCE Southern California Edison Southern California Edison Page iii

CONTENTS EXECUTIVE SUMMARY I INTRODUCTION 1 Baseline Technology... 1 Emerging Technology/Product... 1 ASSESSMENT OBJECTIVES 6 TECHNOLOGY/PRODUCT EVALUATION 7 TECHNICAL APPROACH/TEST METHODOLOGY 8 Field Testing of Technology... 8 Test Plan... 8 Instrumentation Plan... 10 Error Analysis... 11 RESULTS 12 Average Demand Reduction... 12 Annual Energy Savings... 14 Light Performance... 16 Cost Analysis... 16 Retrofit Cost... 16 New Installation Cost... 17 Economy of Scale for PV Contribution... 18 DISCUSSION 21 CONCLUSION 22 RECOMMENDATIONS 23 APPENDIX A 24 APPENDIX B 26 Southern California Edison Page iv

FIGURES Figure 1. Power Supply Module (PSM)... 2 Figure 2. Maximum Power Point Tracking (MPPT) Unit... 3 Figure 3. Power feed Cable with Bus Bar Connector... 3 Figure 4. Bus Bar Power Feed Cable... 4 Figure 5. DC Fixture... 4 Figure 6. Ceiling Tile... 5 Figure 7. Schematic Diagram for Data Monitoring... 10 Figure 8. Comparison of Demand for Baseline 1, Baseline 2 and New System... 12 Figure 9. Average AC Demand Comparison of Baseline 1, baseline 2 and New System... 13 Figure 10. Typical Daily Demand Profile of New System... 14 Figure 11. Annual Energy Consumption Comparison and PV Contribution... 15 Figure 12. Schematic Diagram of Data Monitoring of the DC Ceiling Grid System.... 24 TABLES Table 1. Average AC Demand Reduction of the DC System Compared to Baselines... i Table 2. Average Demand reduction of New System in comparison to Baseline 1 and Baseline 2... 13 Table 3. Annual Energy Savings (Cumulative)... 15 Table 4. Simple Payback Analysis of New System without PV in Retrofit Application... 17 Table 5. Simple Payback Analysis of New System with PV Panels in Retrofit Application.... 17 Table 6. Table 7. Simple Payback Analysis of New System without PV Panels in New Construction Application.... 17 Simple Payback Analysis of New System with PV Panels in New Construction Application.... 18 Table 8. Economies of Scale of PV Panels for Baseline 1... 19 Table 9. Economies of Scale of PV Panels for Baseline 2... 20 Table 10. List of Equipment Used in this Field Assessment... 25 Southern California Edison Page v

EQUATIONS Equation 1. Calculation of Annual Hours of Operation for Test Area.. 14 Equation 2. Simple Payback Calculation... 16 Equation 3. Error analysis for independent variables... 25 Southern California Edison Page vi

INTRODUCTION Southern California Edison (SCE) conducted this Emerging Technologies (ET) field assessment to evaluate the light performance and potential energy savings of Direct Current (DC) ceiling grid technology compared to T-bar ceiling grid technology in commercial buildings. This project evaluated the DC ceiling and its components for its energy consumption, average demand and light output. BASELINE TECHNOLOGY Most commercial buildings have a secondary ceiling and are commonly called dropped ceiling or a T-bar ceiling. This ceiling consists of a grid work of metal bars that intersect at equally spaced locations; a 2x2 or 2x4 grid is very common. This arrangement creates cells (2x2 or 2x4) in the grid and each cell is filled with light weight ceiling tiles. The area above the grid, usually called plenum space, is used to run conduits, electrical connections and HVAC air supply or return. The grid also contains Heating, Ventilation and Air Conditioning (HVAC) return grills, lighting fixtures, fire alarm system and other electrical connections for safety of the building. EMERGING TECHNOLOGY/PRODUCT A DC ceiling is similar to a typical dropped or T-bar ceiling except that the fixtures in this ceiling are powered by DC current rather than Alternating Current (AC). The ceiling grid layout is similar to a typical 2x2 or 2x4, and its electrical infrastructure contains power cables, bus bar connectors, device connectors, bulk cable, Power Supply Module (PSM), and Maximum Power Point Tracking (MPPT). The DC system grid configuration is as follows: The power to the ceiling is supplied by a PSM, essentially a rectifier, shown in Figure 1, which converts the AC supply from the electric utility company to the DC. The PSM is fed a DC voltage from the MPPT unit shown in Figure 2. The MPPT unit samples the output of the PV panels and applies the appropriate resistance values to obtain maximum power from the PV panels under any environmental conditions. The PSM uses internal logic to balance the AC and DC to provide constant DC power to the ceiling grid. The output of PSM is a 24 Volt DC supply to the grid on 16 channels. Each channel supports a low voltage power feed cable that energizes one T-bar of the DC grid. The power feed cable with bus bar connector is shown in Figure 3. Although the grid is energized, there is no hazard of electrical shock because only the non-energized portion of the beam faces the occupants of the room. Southern California Edison Page 1

To support more than 16 channels of T-bars, additional PSM and related infrastructure can be added to the system. If the T-bar beam is shorter than the room, two DC T-bar beams are mounted sequentially to cover the entire run.the bus bar-to-bus bar cables and connectors energize this extra beam by providing a jump from one beam to another. The bus-bar power feed cable is illustrated in Figure 4. The installation of this system is very similar to a typical ceiling, and electricians should have some knowledge of DC systems. This DC fixture technology gives the room a clean look and provides increased lumen output due to the high reflectivity of the ceiling tiles. The DC fixture and high reflectance tile and is part of DC system. Dc Fixture and high reflectance ceiling tile are shown in Figure 5Error! Reference source not found. and Figure 6. FIGURE 1. POWER SUPPLY MODULE (PSM) Southern California Edison Page 2

FIGURE 2. MAXIMUM POWER POINT TRACKING (MPPT) UNIT FIGURE 3. POWER FEED CABLE WITH BUS BAR CONNECTOR Southern California Edison Page 3

Energized portion of beams Non-Energized portion of beams Two beams: connection point FIGURE 4. BUS BAR POWER FEED CABLE FIGURE 5. DC FIXTURE Southern California Edison Page 4

FIGURE 6. CEILING TILE The advantages of the DC system are as follows: The modular grid allows the flexibility to reconfigure, remodel, or maintain a portion without affecting the operation of the entire ceiling. Changing fixtures and lamps is easier because it is not necessary to deenergize the whole grid. Fixtures can be changed out hot because the system is low voltage. DC-compatible fixtures can be purchased in any local hardware store. The clip-on installation of the fixtures and the power infrastructure make the ceiling more durable, easy to install, and maintenance-free. Aesthetics is another added benefit of this technology. The fixture design lends a pleasing, clean look to the room. Increased lumen output due to high reflectivity of the ceiling tiles is another benefit to this technology. All of the ceiling parts have at least a 10-year warranty and if any one of the fixtures, power cables, or main beam reaches the end of its life, the changeout does not require extensive labor. Southern California Edison Page 5

ASSESSMENT OBJECTIVES The objective of this field assessment is as follows: Determine the potential energy savings and demand reduction of the DC system compared to a typical suspended ceiling. Determine the capability of DC systems to properly light the occupied space. Determine the change in the light level upon installation of the new system. Determine the contribution of PV panels to the total power draw of the DC system and calculate the energy savings. Document the findings and provide recommendations. Southern California Edison Page 6

TECHNOLOGY/PRODUCT EVALUATION This field assessment evaluates the performance of the DC system at the test site. The test site is administrative offices in the Conejo Valley Unified School District in Newbury Park, California. This test site was selected due to its constant lighting load during the day. The existing system is a typical T-Bar ceiling with a 120/277 Volt three phase wye lighting configuration. The tests area is approximately 1080 square feet with 16 light fixtures in the ceiling. Each fixture contains three 28 or 32 Watt T-8 fluorescent lamps with electronic instant start, non-dimming ballasts. A field assessment is required to capture vital data points, such as the cost of installation, the contribution of PV panels to the total demand of the DC system, the change in light output compared to the existing ceiling, and the energy saving potential. To achieve the objectives of this field evaluation SCE performed the following steps: 1. Monitored the existing ceiling to collect data for Baseline 1. 2. Restored the ceiling to new like conditions by replacing the old lamps with 28W T-8 fluorescent lamps with electronic instant start non-dimming ballasts, and then cleaning the fixtures and ceiling to make the ceiling compliant to Title 24 standard. This data is collected for Baseline 2. 3. Replaced the existing ceiling with the DC system, by adding new 28 watt T-8 DC lamps, program-start dimming ballasts, and additional circuitry described in Introduction section. PV panels on the roof and AC power connection is provided to operate the ceiling. Southern California Edison Page 7

TECHNICAL APPROACH/TEST METHODOLOGY FIELD TESTING OF TECHNOLOGY The following steps were taken to compare the baseline and measure results: 1. A single breaker located in the electrical room serves the lighting load for the entire building. Initial monitoring shows that the lighting load of the building remains constant during the hours of operation. This step is important to collect data for Baseline 1 and Baseline 2. 2. The demand, energy consumption, and light output data for Baseline 1 is collected and recorded. During data collection for Baseline 1, the test area is isolated from the building by running isolation tests. During the isolation tests, the lights in the test area are turned on for approximately one hour and the data for that period is used as the average demand profile for Baseline 1. 3. The existing ceiling is refreshed with new lamps, ballasts, and then cleaned to bring the existing ceiling to like-new condition. The demand, energy consumption, and light output data for Baseline 2 is collected and recorded. 4. The existing ceiling is demolished and PV panels are installed for the DC system. 5. A dedicated electrical panel is installed for the DC system. This panel supplies AC power to the DC system and the DC power is supplied directly from the PV panels. To obtain the demand profile of the DC system and the contribution of DC and AC components to the total load, the PV power supply and AC supply are monitored and the data is recorded. The AC supply for the DC ceiling grid is a dedicated panel, so all of the power on the panel breaker is fed to the DC system and no isolation from the building is required. Together the AC and DC power supply provide the aggregate demand of the new ceiling. A schematic diagram of the DC system is provided in Appendix A TEST PLAN The DC system, Baseline 1, and Baseline 2 were monitored for energy consumption, demand, and light output. The appearance of the DC system and the satisfaction of the occupants are also considered when evaluating the overall performance of the new ceiling. The test plan is as follows: The total demand for Baseline 1 is collected at the main breaker panel. The electrical configuration for this lighting system is a 120/277 Volt, 20 Amp, three phase wye circuit. Demand is recorded for approximately 30 days. The light output of Baseline 1 is measured using spot readings across the room. Southern California Edison Page 8

The demand for Baseline 2 is monitored and collected for approximately 30 days. The electrical configuration of Baseline 2 is the same as Baseline 1. The light output for Baseline 2 is measured using spot readings across the room. The DC system power supplied by PV is monitored and recorded at the point where it feeds into the PSM. The AC power supply is monitored and recorded at the electric panel located in electrical room. Power/demand is recorded for approximately 30 days. The light output for the DC ceiling is measured using spot readings across the room. Figure 7 shows a schematic diagram of the data monitoring of the test area as follows: The stars represent the mapping used to record spot light levels for the DC system, Baseline 1 and Baseline 2. The green dots represent the power monitoring location for the DC system. The green dot on the right top corner of the diagram represents the data monitoring location for Baseline1 and Baseline 2 on a different panel in the electrical room. The data is monitored at 256 samples per cycle and recorded every five minutes during the data collection period for Baseline 1, Baseline 2, and the DC system. The data for both baselines and the DC system is downloaded every two or three minutes from a compact flash card to a laptop, and analyzed using data monitoring equipment software. Southern California Edison Page 9

FIGURE 7. SCHEMATIC DIAGRAM FOR DATA MONITORING INSTRUMENTATION PLAN List of equipment, its calibration information and detailed specification is available in Appendix A. Southern California Edison Page 10

ERROR ANALYSIS Equation 1 shows the error analysis for a small number of independent variables. For example, if the kw reading depends on two independent variables, such as voltage (V) and the current (I). The kw error equation is provided in Appendix A. The most inaccurate device drives the error in kw, so in this case, the current probe is the most inaccurate device. Its accuracy level is 2%, which implies that the kw error for AC power is less than ±2.1%. For DC power readings, the maximum error is less than ±1.1%. For light meter readings, the error of the photometric sensor and the light meter are added to calculate the total error. In this assessment, all readings were taken at a room temperature of 75 degrees, so the total absolute error in light readings is less than ±5.4%. Southern California Edison Page 11

RESULTS The results of this assessment are discussed in this section. Detailed calculation worksheets are available in Appendix B. AVERAGE DEMAND REDUCTION Average demand reduction is the difference between the average demand of the baseline system and the DC system. A demand comparison for Baseline 1, Baseline 2, and the DC system is shown in Figure 8. FIGURE 8. COMPARISON OF DEMAND FOR BASELINE 1, BASELINE 2 AND NEW SYSTEM The Figure 8 shows Baseline 1 has an average demand of 1.33 kw. Baseline 2 and the DC system have almost equal demand of 1.15 and 1.16 kw respectively. The demand reduction of DC system compared to Baseline 1 is 170 watts or 12.58%. Baseline 2 and the DC system demand is within the error range of the instrumentation used in this assessment, so the demand of Baseline 2 and DC system is considered equal and no savings calculation are performed. Since the DC system s total demand is the sum of its DC and AC components, offsetting the DC component provides different results for AC demand reduction as shown in Figure 9. Southern California Edison Page 12

FIGURE 9. AVERAGE AC DEMAND COMPARISON OF BASELINE 1, BASELINE 2 AND NEW SYSTEM On average, the PV contributed approximately 50% of the power to the DC system. Error! Reference source not found. Error! Reference source not found. Table 2 summarizes the potential average demand reduction potential of the DC system compared to Baseline 1 and Baseline 2 with and without solar. TABLE 2. AVERAGE DEMAND REDUCTION OF NEW SYSTEM IN COMPARISON TO BASELINE 1 AND BASELINE 2 NAME KW DEMAND DEMAND REDUCTION (KW) AVERAGE AC CONTRIBUTION TO TOTAL DEMAND (KW) AVERAGE DC CONTRIBUTION TO TOTAL DEMAND (KW) Baseline 1 1.33 0.17 1.33 0.73 Baseline 2 1.15 0 1.15 0.55 DC Grid System 1.16 NA 0.60 0.56 NA DEMAND REDUCTION (KW) (AC ONLY) Figure 10 shows a typical daily demand profile of the DC system and how PV picks up most of the load during the day. Between 10 AM and 4 PM, PV panels contribute approximately 70% of the power to the total demand of the DC system, minimizing the AC contribution and enhancing the potential for demand savings and avoided peak demand charges. Southern California Edison Page 13

FIGURE 10. TYPICAL DAILY DEMAND PROFILE OF NEW SYSTEM ANNUAL ENERGY SAVINGS The total energy consumption of the DC system is calculated by multiplying the average kw by the hours of operation of the test area, typically 9 hours. This provides an average energy consumption estimate for one day. To calculate annual average energy consumption, kwh is multiplied by the total annual hours of operation. The total number of hours of operation in a year is calculated by subtracting the holidays, weekends and other non-work days. Summer break is not factored in because even though the school was closed for summer break, the test area is still operational. Equation 1 shows the calculation for the total annual hours of operation. EQUATION 1. CALCULATION OF ANNUAL HOURS OF OPERATION FOR TEST AREA = 251 x 9 = 2259 annual hours The difference in the annual energy consumption of Baseline 1, Baseline 2 and the DC system provides an estimate of the annual energy savings potential compared to Baseline 1 and Baseline 2. Results from the test site show that the DC system saves 378.18 kwh or 12.58 % annually compared to Baseline 1, and consumes a little more than Baseline 2. Since the difference between Baseline 2 and the DC system is within the error range of the instrumentation, the energy consumption is considered equal. Detailed results for energy savings are shown in Table 3. Southern California Edison Page 14

TABLE 3. ANNUAL ENERGY SAVINGS (CUMULATIVE) TECHNOLOGY AVERAGE KWH/DAY NO. OF WORKING DAYS/YEAR ESTIMATED ANNUAL ENERGY CONSUMPTION (KWH) Baseline 1 11.97 251 3005.55 MEASURE ENERGY CONSUMPTION ESTIMATED ANNUAL ENERGY SAVINGS ESTIMATED ANNUAL ENERGY SAVINGS (%) (KWH/YR.) 2627.37 378.18 12.58% Baseline 2 10.32 251 2589.33 2627.37 -- -- The test site was 1080 sq. ft.; therefore, the estimated energy saving per square foot for baseline 1 is 0.350 kwh/sq.ft. There are approximately 824,000 buildings within SCE service territory that use office lighting. At 25% estimated penetration rate, the potential of annual energy savings across SCE service territory is 77.90 GWh. If you subtract the energy supplied by PV panels, the annual energy savings potential of the DC system compared to Baseline 1 increases to 1649.45 kwh/yr. or 54%. Similarly, the energy savings compared to Baseline 2 increases to 1233.23 kwh/yr. or 48%. The DC offset provided by PV panels compared to Baseline 2 shows the potential of grid energy savings and avoided energy costs to the customers. Figure 11 compares the energy savings potential and total contribution of PV panels to the annual energy consumption of the DC system. FIGURE 11. ANNUAL ENERGY CONSUMPTION COMPARISON AND PV CONTRIBUTION Southern California Edison Page 15

The estimated energy saving per square foot for baseline 1 with DC offset is 1.53 kwh/sq.ft. and for baseline 2 is 1.14kWh/sq.ft. With these savings and an estimated market penetration of 25%, the annual energy savings of DC system (AC only) across the SCE service territory can be 339.78 GWh when compared to Baseline 1 and 254.04 GWh when compared to Baseline 2. LIGHT PERFORMANCE SCE recorded the light output of all of the systems using spot measurements. For precision, we used the diagram shown in Figure 8. The light output of Baseline 1 is measured at 41-foot candles. Baseline 2 light output is 54 foot-candles. The DC system performed better than both systems. To readings were taken for the DC system. The first spot measurement at the test area gave a light output of an average 55 foot-candles and second read spot measurement 57 foot-candles. For conservative estimates, an average of 56 foot-candles will be considered for a DC system. Overall, the light performance of the DC system is better than both baseline ceilings. During a follow up interview, the principal of the school told us the ceiling looks much better and has a clean look to it and it s also brighter than the original ceiling COST ANALYSIS This section discusses the cost to retrofit the DC system into an existing ceiling and installing a new DC ceiling in a new building. RETROFIT COST The cost of retrofitting the DC system without any PV into an existing 1080 square foot room is $27,348.50. This cost includes the cost of tearing-down the existing ceiling, and then installing the DC ceiling and 16 fixtures, each containing 3 lamps. By comparison, the cost of retrofitting a typical T-bar ceiling is $10,248 for the same sized room with the same lighting configuration. The simple payback analysis for Baseline 1 shows that with the energy savings of 378.2 kwh/yr. at $0.15 per kwh, it will take over 300 years to recover the cost of installing the DC system. For Baseline 2, no cost analysis is done because there is no energy savings. The simple payback calculation is shown in Equation 2. EQUATION 2. SIMPLE PAYBACK CALCULATION The simple payback calculation for the DC system without PV panels is shown in Table 4. Southern California Edison Page 16

TABLE 4.SIMPLE PAYBACK ANALYSIS OF NEW SYSTEM WITHOUT PV IN RETROFIT APPLICATION COST OF INSTALLATION OF NEW SYSTEM ($) COST OF INSTALLATION OF TYPICAL T-BAR CEILING ($) INCREMENTAL COST ($) ESTIMATED ANNUAL ENERGY SAVINGS (KWH/YR.) AVERAGE ENERGY COST ($/KWH) TOTAL COST SAVINGS ($) 27,348.50 10,248 17,100.50 378.18 0.15 56.73 301.45 SIMPLE PAYBACK (YRS) If the cost of installing a PV in an existing building is added to this equation, the payback is still more than the preferred payback of less than 2 years. The payback analysis for this scenario is shown in Table 5. TECHNOLOGY TABLE 5. SIMPLE PAYBACK ANALYSIS OF NEW SYSTEM WITH PV PANELS IN RETROFIT APPLICATION. Total cost of installation (DC Grid+PV) ($) Cost of installation of typical T- Bar ceiling ($) Increment al cost ($) Annual Energy Savings (kwh/yr.) Energy cost ($/kwh) Annual Cost Savings ($) Simple Payback (Yrs.) Baseline 1 33,828.5 10,248 23,580.5 1,649.45 0.15 247.417 95.30671 Baseline 2 33,828.5 10,248 23,580.5 1,233.23 0.15 184.984 127.4732 NEW INSTALLATION COST The cost of installing a DC system in a 1080 ft. square room in a new building, including 16 fixtures with 3 lamps per fixture is $28,815. This cost is higher than retrofitting the DC system in an existing building because the ceiling suspensions and the support infrastructure in the new building have to be built. By comparison, the cost of installing a typical T-bar ceiling in a new building is $8,898. The incremental cost is $19917 and the annual cost savings for the DC system is $56.72, which is an annual energy savings of 378.18 kwh/yr @ 0.15 $/kwh. The simple payback for this scenario is over 351 years. These calculations are shown in Table 6. The payback is better with PV panels although PV panels add $6840 to the total installation cost in both scenarios. The AC savings are increased substantially because the PV panels offset some of the AC load. The payback for DC system with PV panels is shown in Table 7. TECHNOLOGY TABLE 6.SIMPLE PAYBACK ANALYSIS OF NEW SYSTEM WITHOUT PV PANELS IN NEW CONSTRUCTION APPLICATION. Total cost of installatio n (DC Grid+PV) ($) Cost of installatio n of typical T- Bar ceiling ($) Increment al cost ($) Annual Energy Savings (kwh/yr.) Average Energy cost ($/kwh) Annual Cost Savings ($) Simple Payback (yrs.) Baseline 1 28,815 8,898 19,917 378.18 0.15 56.72 351.10 Southern California Edison Page 17

TECHNOLOGY TABLE 7.SIMPLE PAYBACK ANALYSIS OF NEW SYSTEM WITH PV PANELS IN NEW CONSTRUCTION APPLICATION. Total cost of installation (DC Grid+PV) ($) Cost of installation of typical T-Bar ceiling ($) Increment al cost ($) Annual Energy Savings (kwh/yr.) Energy cost ($/kwh) Annual Cost Savings ($) Baseline 1 35,655.00 8,898.00 26,757.00 1,649.45 0.15 247.42 108.15 Baseline 2 35,655.00 8,898.00 26,757.00 1,233.23 0.15 184.98 144.64 Simple Payback (yrs.) For new construction, the Baseline 2 scenario is more realistic because a new ceiling in a new building is always in compliance with the latest building code. The energy consumption of a regular ceiling with PV is unknown at this point and accurate payback cannot be calculated for a regular ceiling with PV. Note: The cost of PV has not been added to the cost of installation typical ceiling because it was not tested with the PV panels. ECONOMY OF SCALE FOR PV CONTRIBUTION Based on the results of this assessment, SCE performed an interpolation for simple payback to determine the best and worst case scenarios for the number of years it will take to payback the cost of installation. The contribution of DC power from PV panels to the lighting load varies between 10% and 100. The payback is calculated for both baselines in retrofit and new construction application. Table 8 shows that for Baseline 1, the DC system pays for itself in approximately 38 years if all power to the lighting load is supplied by PV and the system is retrofitted to an existing building. During this assessment, approximately 70% of the load was met by the PV panels on some days. In this scenario, it will take approximately more than 54 years for simple payback to recover the investment in the DC system. Southern California Edison Page 18

TABLE 8. ECONOMIES OF SCALE OF PV PANELS FOR BASELINE 1 Est. Annual Energy Consum ption kwh/yr PV Contribution Incremental Cost Retrofit Incremental Cost New Construction (NC) Payback for retrofit (yrs.) Payback for NC (yrs.) Annual Energy Cost % kwh Cost Savings With PV W/O PV With PV W/O PV With PV W/O PV With PV W/O PV 3005.55 10% 300.56 0.15 45.08 17100.50 23580.50 19917.00 26757.00 379.31 523.04 441.78 593.50 3005.55 20% 601.11 0.15 90.17 17100.50 23580.50 19917.00 26757.00 189.65 261.52 220.89 296.75 3005.55 30% 901.67 0.15 135.25 17100.50 23580.50 19917.00 26757.00 126.44 174.35 147.26 197.83 3005.55 40% 1202.22 0.15 180.33 17100.50 23580.50 19917.00 26757.00 94.83 130.76 110.45 148.38 3005.55 50% 1502.78 0.15 225.42 17100.50 23580.50 19917.00 26757.00 75.86 104.61 88.36 118.70 3005.55 60% 1803.33 0.15 270.50 17100.50 23580.50 19917.00 26757.00 63.22 87.17 73.63 98.92 3005.55 70% 2103.89 0.15 315.58 17100.50 23580.50 19917.00 26757.00 54.19 74.72 63.11 84.79 3005.55 80% 2404.44 0.15 360.67 17100.50 23580.50 19917.00 26757.00 47.41 65.38 55.22 74.19 3005.55 90% 2705.00 0.15 405.75 17100.50 23580.50 19917.00 26757.00 42.15 58.12 49.09 65.94 3005.55 100% 3005.55 0.15 450.83 17100.50 23580.50 19917.00 26757.00 37.93 52.30 44.18 59.35 Southern California Edison Page 19

Table 9 shows that it will take 44 years for the system to pay for itself if all of its power is supplied by the PV panels. At 70% power supplied by PV panels, it will take at least 55 years in a retrofit application. TABLE 9. ECONOMIES OF SCALE OF PV PANELS FOR BASELINE 2 Est. Annual Energy Consum ption kwh/yr PV Contribution Incremental Cost Retrofit Incremental Cost New Construction (NC) Payback for retrofit (yrs.) Payback for NC (yrs.) Annual Energy Cost % kwh Cost Savings With PV W/O PV With PV W/O PV With PV W/O PV With PV W/O PV 2589.33 10% 258.93 0.15 38.84 17100.50 23580.50 19917.00 26757.00 440.28 607.12 512.80 688.90 2589.33 20% 517.87 0.15 77.68 17100.50 23580.50 19917.00 26757.00 220.14 303.56 256.40 344.45 2589.33 30% 776.80 0.15 116.52 17100.50 23580.50 19917.00 26757.00 146.76 202.37 170.93 229.63 2589.33 40% 1035.73 0.15 155.36 17100.50 23580.50 19917.00 26757.00 110.07 151.78 128.20 172.23 2589.33 50% 1294.67 0.15 194.20 17100.50 23580.50 19917.00 26757.00 88.06 121.42 102.56 137.78 2589.33 60% 1553.60 0.15 233.04 17100.50 23580.50 19917.00 26757.00 73.38 101.19 85.47 114.82 2589.33 70% 1812.53 0.15 271.88 17100.50 23580.50 19917.00 26757.00 62.90 86.73 73.26 98.41 2589.33 80% 2071.46 0.15 310.72 17100.50 23580.50 19917.00 26757.00 55.04 75.89 64.10 86.11 2589.33 90% 2330.40 0.15 349.56 17100.50 23580.50 19917.00 26757.00 48.92 67.46 56.98 76.54 2589.33 100% 2589.33 0.15 388.40 17100.50 23580.50 19917.00 26757.00 44.03 60.71 51.28 68.89 Based on this information, the manufacturer must reduce the cost of the DC system components to make the payback more realistic and to overcome the financial market barrier. Southern California Edison Page 20

DISCUSSION The DC system saves 12.58% in energy costs when compared to an existing ceiling that has been in operation for many years. When comparing this to the energy consumption of a new, typical T-bar ceiling, the energy consumed by both ceilings is almost identical. However, the DC offset provided by the PV panels can prove beneficial for small commercial as well as other customers who are on time of use rate. The DC power from the PV reduces the AC energy consumption during peak demand period and can result in avoided energy costs and time of use rates if they have a DC system installed at their facilities. If the DC system is installed with PV panels, the energy savings increase because a portion of demand is offset by the DC power supplied by the panels. The total energy savings of the DC system increases to approximately 54.9% compared to an aged T-bar ceiling, and approximately 47% compared to a brand new T-bar ceiling. Although the savings increase because PV panels are used, the cost of installing the ceiling also increases as the cost to install PV is added to the cost of the installation. The payback analysis shows that payback is not within the desired two-year range. At the test site, the light performance for the DC system is superior to the existing ceiling and the staff at the test site is pleased by its look and feel. Modularity is a key feature of DC system because the T-bar is low power DC and the fixtures are clipped to the T-bar. For future expansion, reconfiguration, a, facility maintenance worker can snap-off the fixtures and easily snap-on to a T-bar in a different location because the ceiling is safe to touch. Additionally, to replace an old fixture or to perform fixture maintenance, a live fixture can be removed from the ceiling by snapping off the fixture connector from the T-bar. This is another advantage that a portion of the ceiling can be changed out or serviced while the rest of the ceiling is still ON. This reduces potential maintenance down time at a facility and can save lost man-hours that go wasted while a facility is being serviced. It is important to note that the DC system included program-start dimming ballasts. Although these ballasts are slightly inefficient compared to instant start ballast but are known to be beneficial for the lamp life. This can result in higher cost savings over the life of system due to fewer lamps being replaced and associated labor costs. Other electronic components such as PSM have efficiency factor of less than 95%. Improving the efficiency of these components can also improve the overall functionality and the savings potential of the DC ceiling grid. Although the initial installation costs of the DC system are high, the modularity saves on future maintenance costs, expansion, and reconfiguration. Southern California Edison Page 21

CONCLUSION The DC system shows energy savings of approximately 12.58% compared to an existing ceiling that is fed by AC supply. This results in potential annual energy savings of 77.90 GWh in an SCE service territory at 25% market penetration. Discounting the contribution of power supplied by the PV panels, the energy savings of the DC system increased to 54% and 47% when compared to Baseline 1 and Baseline 2 respectively. This has the potential of annual energy savings of 339.78 GWh compared to Baseline 1, and 254.04 GWh compared to Baseline 2. The cost of installing a DC system is much higher when compared to a typical T-bar ceiling which can significantly impact market penetration. The overall look and feel of the DC system is very clean and sharp. The staff working in the test area is very happy with the results. The light output increased to 56 foot candles for the DC system compared to 41 foot candles for Baseline1, and 54 foot-candles for Baseline 2. Since the test site did not have pre-existing PV panels, the demand of the existing ceiling with PV panels was not recorded during this assessment. In summary, the DC system is a very aesthetically pleasing system with a potential to save energy albeit the cost to install this technology is high. This can discourage the customers to install this technology at their facilities. The manufactures of this technology will need to bring down the prices significantly to make payback of this technology more attractive for the consumers and to overcome the financial market barriers towards adoption of this technology. Southern California Edison Page 22

RECOMMENDATIONS Based on the conclusions of this assessment, the following is recommended: Perform testing at a test site with existing PV panels to obtain the energy consumption data of a typical T-bar ceiling with solar panels. Southern California Edison Page 23

APPENDIX A Figure 12 shows a schematic diagram of the DC system installed at the test site. FIGURE 12. SCHEMATIC DIAGRAM OF DATA MONITORING OF THE DC CEILING GRID SYSTEM. Southern California Edison Page 24

Table 10 lists the instrumentation used during the field assessment of the DC system. TABLE 10. LIST OF EQUIPMENT USED IN THIS FIELD ASSESSMENT NAME MODEL MANUFACTURER RANGE ACCURACY NUMBER Power Meter (power Visa) PVUSFA178, PVUSFA169 Dranetz Differential Inputs : 1-600 Vrms (AC/DC),256 samples/cycle Current Input: 0.1-3000 Arms (AC/DC), 256 samples/cycle Differential Inputs: 0.1% rdg +0.05% FS, 256 samples/cycle, 16bit ADC Frequency range, 10mHx resolution, 45-65 Hz Current Input:- 0.1% rdg + CTs, 16 bit ADC *Vrms: Root mean Square Voltage *Root mean square Current Current Transformer (CT for AC measurements) TR2510A Dranetz 1-10 Amps (rms) Amplitude accuracy: ±1.2%-2% Phase Accuracy: ±1-1.5 Current Transformer (CT for DC measurements) PR150 Dranetz 15Amp-150Amps Amplitude accuracy: ±1% Phase Accuracy: ±3 Light Meter LI-COR LI- 250A LI-Cor Operating range: 0 to 55 C, 0 to 95% RH (noncondensing Storage Conditions: -55 to 60 C, 0 to 95% RH (non-condensing) Accuracy: 25 C: Typically ± 0.4% of reading [± 3 counts on the least significant digit displayed (all ranges)]. Linearity: ± 0.05% Photometric Sensor LI-COR LI- 210SA LI-Cor Typically 30 μa per 100 klux Absolute Calibration: ±5% traceable to NIST Linearity: Maximum deviation of 1% up to 100 klux Stability: < ± 2% change over a 1 year period The error analysis equation for kw measurement is provided by Equation 3. EQUATION 3. ERROR ANALYSIS FOR INDEPENDENT VARIABLES kw kw V V 2 I I 2 Southern California Edison Page 25

APPENDIX B 1. Baseline 1 and Baseline 2 data Baseline Data_report.xlsx 2. DC system data DC System Data_report.xlsx 3. Savings calculations Savings Calculations_Report.x Southern California Edison Page 26