M E M O R A N D U M. Go Sustainable Energy, LLC

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1 M E M O R A N D U M Date: December 21, 2011 To: Stefanie Campbell & Mark Dancer (Dayton Power & Light) From: Shawn Brown & George Mertz (Go Sustainable Energy) RE: AGC Automotive Air Compressor Metering (Rebate B8E4FDB2) Go Sustainable Energy was contracted by Dayton Power & Light (DP&L) to conduct pre-installation and post-installation metering of the air compressor system at AGC Automotive, located in Bellefontaine, Ohio under DP&L Rebate B8E4FDB2. This memo presents our pre-installation metering analysis. We conducted our pre-installation site visit on November 8, During this site visit we deployed our logging equipment and obtained spot electrical readings. We also recorded equipment specifications. Our points-of-contact were Mike Hicks and Terry Scott. In the baseline scenario, American Trim has eight air compressors: three 75-hp compressors, two 100-hp compressors, one 150-hp compressor, and two 200-hp compressors. The objective of the pre-installation metering was to determine an accurate baseline of electricity consumption and peak demand for the eight plant air compressors. The proposed energy conservation measure is to replace the 200-hp single-speed rotary-screw air compressor (ACP-020) with a 200-hp variable-speed rotary-screw air compressor. Based on our preinstallation logged data, we estimated the baseline peak demand to be about kw and energy consumption to be about 4,510,507 kwh per year. On the rebate application, AGC gave an estimated baseline demand and an estimated energy use for only the air compressor that was being replaced and not the total air compressor system. It is more appropriate to use the whole system demand and energy consumption rather than simply analyzing the savings for the single, to-bereplaced air compressor. Basic Air Compressor Information The constant-speed air compressor that is being replaced is a 200-hp rotary-screw air compressor, model Atlas Copco GA160 designated ACP-020 and is shown in Figure 1. Page 1

2 Figure 1: Air Compressor ACP hp Atlas Copco GA160 This air compressor is part of a compressed system comprising a total of eight air compressors. Our strategy was to meter the current draw on all eight air compressors. We also metered the air pressure of the system. While on-site, we took spot current, voltage, power draw, and power factor readings of the compressors. The air compressor specifications are shown in Table 1 and the air compressor spot electrical readings averaged over all three electrical legs are shown in Table 2. Air Compressor Make Model Motor Rating (hp) ACP-009 Joy ACP-010 Joy ACP-012 Joy ACP-01 Gardner-Denver EAPSMC 100 ACP-014 Gardner-Denver EAPSMC 100 ACP-015 LeROI WM150SS II 150 ACP-017 Sullair LS ACP-020 Atlas Copco GA Table 1: Air Compressor Specifications Page 2

3 Air Compressor Pre-Installation Metering Table 2: Air Compressor Average Spot Electrical Readings For pre-installation metering, loggers were placed on all of the compressors. We logged amperage on one phase of each compressor for a period of ten days. The logging interval was 20 seconds. We also measured the compressed air system s pressure during this same period. We log pressure to determine if the plant s pressure changes after the installation of the new compressor. The logged current draws are shown in the Logged Data Appendix. Baseline Electricity Consumption Average Amperage (A) Average Voltage (V) Average Power Draw (kw) Typically, motors are a balanced load and we need only measure the amperage on one of the three legs. Therefore, we will use the following formula to calculate the power draw, Power draw (kw) = Amperage (A) x Voltage (V) x Power factor (kw/kva) Average Power Factor (kw/kva) ACP ACP ACP ACP ACP ACP ACP ACP x 1 kva/1000 VA x # phases. The power draw on the motors is a three-phase, approximately 460-volt load. For the air compressors we obtained spot voltage and power factor readings and will use the averages for each compressor in the calculation of the power draw. Next, we show an instantaneous calculation for the power draw of the eight compressors at 12:00:00 AM on November 9, This same calculation is made for every 20-second interval of the logged current draw. Power draw ACP009 = 77.0 A x 452 V x 0.87 kw/kva x 1 kva/1000 VA x Power draw ACP010 = 81.4 A x 452 V x kw/kva x 1 kva/1000 VA x Power draw ACP012 = 8.0 A x 452 V x 0.81 kw/kva x 1 kva/1000 VA x = 50.5 kw, = 5.7 kw, = 52.9 kw, Power draw ACP01 = A x 460 V x kw/kva x 1 kva/1000 VA x = 74.1 kw, Page

4 Power draw ACP014 = A x 471 V x kw/kva x 1 kva/1000 VA x Power draw ACP015 = A x 467 V x kw/kva x 1 kva/1000 VA x Power draw ACP017 = A x 47 V x 0.80 kw/kva x 1 kva/1000 VA x Power draw ACP020 = A x 466 V x kw/kva x 1 kva/1000 VA x = 75.4 kw, = 80.7 kw, = kw, = kw, Total power draw = 50.5 kw kw kw kw kw kw kw kw = kw. Analyzing the amperage data we determined the percent runtimes for the air compressors during the period we metered. These percent runtimes are shown in Table. Runtime ACP-009 ACP-010 ACP-012 ACP-01 ACP-014 ACP-015 ACP-017 ACP-020 Active 100.0% 100.0% 100.0% 98.9% 5.0% 60.% 71.% 72.5% Off 0.0% 0.0% 0.0% 1.1% 47.0% 9.7% 28.7% 27.5% Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% Table : Runtime Analysis of Air Compressors during Pre-Metering During the weekend we metered, air compressors ACP-014, ACP-015, ACP-017, and ACP-020 were turned off while air compressors ACP-009, ACP-010, ACP-012, and ACP-01 continued to run. As there is no production during the weekend all the air compressors should be turned off. This would result in energy savings. Next, using the metered data, we calculate the power draw and annual energy use for each compressor. Table 4 summarizes the measured amperage, the calculated power draw, and the calculated annual energy use. Page 4

5 Baseline ACP-009 ACP-010 ACP-012 ACP-01 ACP-014 ACP-015 ACP-017 ACP-020 Total Ave Total Amperage (A) Ave Total Power Draw (kw) Ave Active Amperage (A) Ave Active Power Draw (kw) Energy Use - Go (kwh/year) Energy Use - AGC (kwh/year) Demand - Go (kw) Demand - AGC (kw) ,92 468,2 468, ,127 25,48 421,8 668,027 1,087,95 4,510, Table 4: Summary of the Pre-Installation Amperage Data and the Calculated Power Draw and Energy Use The annual energy consumption in the pre-scenario is Annual energy consumption = 4,510,507 kwh/year. Billed demand is based on the greatest on-peak electricity consumption over any 0-minute period. In order to determine the peak demand, we calculated an average rolling 0-minute power draw for the compressors. Figure 2 shows the compressors electricity demand over time in the pre-scenario. Based on this information, we determined the greatest 0-minute average power draw and the time in which this occurred. For the compressed air system, the peak demand occurred on November 14, 2011 at 4:5 PM with a peak demand of Peak demand = kw. Page 5

6 0-Minute Average Power Draw (kw) Go Sustainable Energy, LLC Figure 2: Pre-Installation Rolling 0-Minute Average Demand Table 5 summarizes the energy usage and peak demand based on our pre-installation metering. Plant Pressure 0 11/9 11/10 11/11 11/12 11/1 11/14 11/15 11/16 Date Energy Use Go 4,510,507 AGC - Demand Baseline (kwh/year) Baseline (kw) Go AGC - Table 5: Summary of Baseline Energy Usage and Peak Demand Typically, we prefer to log plant pressure during the period when we are also logging the current draws of the plant compressors. This is because we want to make sure that plant pressure has not changed between the pre- and post-scenarios. During the pre-metering period at AGC we were able to log the pressure in the compressed air loop. Page 6

7 The pre-installation pressure data are presented in Figure. The minimum production pressure in the pre-scenario was 121. psig while the maximum production pressure was psig with an average production pressure of 11.5 psig. The range of pressure was 19.7 psig. The variance in the pressure can be expressed mathematically by calculating the standard deviation of the production pressures. The standard deviation of a set of data shows how much variation there is from the average. Therefore, a low standard deviation indicates that the data tend to be close to the average. A high standard deviation indicates that the data are not as close to the average and are spread out over a larger range of values. In the pre-scenario, the standard deviation of the production pressure was 2.8 psig. Figure : Pre-Installation Logged Pressure Table 6 summarizes the minimum, maximum, and average production pressures and the standard deviation of the pressure in the pre-scenario. Pressure Baseline (psig) Minimum 121. Maximum Average 11.5 Standard Deviation 2.8 Table 6: Summary of Pre-Installation Production Pressures Page 7

8 Logged Data Appendix The logged post-installation current draws for the eight air compressors at AGC Automotive are shown below in Figure 4 through Figure 11. This data was used to determine the average power draw of each compressor, which was then used to estimate the annual electricity consumption and peak demand of the air compressors. We measured the amperage on a single leg of each compressor with a sampling rate of 20 seconds. Figure 4: Measured Pre-Installation Amperage on Compressor ACP-009 Page 8

9 Figure 5: Measured Pre-Installation Amperage on Compressor ACP-010 Figure 6: Measured Pre-Installation Amperage on Compressor ACP-012 Page 9

10 Figure 7: Measured Pre-Installation Amperage on Compressor ACP-01 Figure 8: Measured Pre-Installation Amperage on Compressor ACP-014 Page 10

11 Figure 9: Measured Pre-Installation Amperage on Compressor ACP-015 Figure 10: Measured Pre-Installation Amperage on Compressor ACP-017 Page 11

12 Figure 11: Measured Pre-Installation Amperage on Compressor ACP-020 Page 12