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Table of Contents Summary ......................................................................................................................... 1 Conclusions ........................................................................................................................................... 1 Systems Details ............................................................................................................. 2 Monitoring of Inverters........................................................
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Monitoring of Inverters During the Monitoring Period, many operational parameters of each inverter were obtained from the inverters and recorded. The information extracted from each inverter is listed in Table 3 below. The average daily run-times of the inverters during the Test Period are listed in Table 4 below.
Performance Evaluations Inverter Production The energy converted by the inverters over the Test Period are listed in Table 5 below. The energy converted by the inverters is a function of local insolation on each PV array over the Test Period and the DC capacity of each PV array.
Performance Evaluations 30 25 Power (kW) 20 15 10 Inverter 1 Power (kW) Inverter 2 Power (kW) 5 0 0 200 400 600 800 1000 1200 Irradiance (W/m²) Figure 3 Plot of AC output power versus irradiance for both inverters over the Test Period Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
Performance Evaluations Irradiance (W/m²) Inverter 1 (kW) Inverter 2 (kW) 15 400 10 200 5 0 0 4/20/2014 600 4/19/2014 20 4/18/2014 800 4/17/2014 25 4/16/2014 1000 4/15/2014 30 4/14/2014 1200 Power (kW) Irradiance (W/m²) Week 1 Figure 4 Plot of AC output power and irradiance for both inverters over Week 1 of the Test Period Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
Performance Evaluations Irradiance (W/m²) Inverter 1 (kW) Inverter 2 (kW) 15 400 10 200 5 0 0 4/27/2014 600 4/26/2014 20 4/25/2014 800 4/24/2014 25 4/23/2014 1000 4/22/2014 30 4/21/2014 1200 Power (kW) Irradiance (W/m²) Week 2 Figure 5 Plot of AC output power and irradiance for both inverters over Week 2 of the Test Period Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
Performance Evaluations Irradiance (W/m²) Inverter 1 (kW) Inverter 2 (kW) 15 400 10 200 5 0 0 5/4/2014 600 5/3/2014 20 5/2/2014 800 5/1/2014 25 4/30/2014 1000 4/29/2014 30 4/28/2014 1200 Power (kW) Irradiance (W/m²) Week 3 Figure 6 Plot of AC output power and irradiance for both inverters over Week 3 of the Test Period Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
Performance Evaluations Irradiance (W/m²) Inverter 1 (kW) Inverter 2 (kW) 15 400 10 200 5 0 0 5/11/2014 600 5/10/2014 20 5/9/2014 800 5/8/2014 25 5/7/2014 1000 5/6/2014 30 5/5/2014 1200 Power (kW) Irradiance (W/m²) Week 4 Figure 7 Plot of AC output power and irradiance for both inverters over Week 4 of the Test Period Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
Performance Evaluations Inverter Efficiency In order to evaluate the conversion efficiencies of the inverters over the Test Period, both DC input powers of the two (2) MPPT inputs of each inverter as well as the AC output powers of each inverter were measured and recorded at five-minute intervals. Measured data for which either the total DC input power (the sum of the MPPT input powers) is less than 0.5 kW or calculated efficiency is greater than 100 % are neglected from this analysis.
Performance Evaluations Figure 9 below is a plot of measured conversion efficiency versus output power of Inverter 2 over the Test Period. Inverter 2 100 95 Efficiency (%) 90 85 80 75 70 0 5 10 15 Output Power (kW) 20 25 30 Figure 9 Inverter 2 conversion efficiency versus output power (blue dots) and the resulting tenth-order polynomial fit (green asterisks) evaluated over the output power range at 1 kW intervals Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
S ol e c t r i aPVI 28T L
Performance Evaluations Table 6 below contains the coefficients of the tenth-order polynomial fits applied to the performance data of Inverter 1 and Inverter 2. Polynomial Coefficient Inverter #1 Inverter #2 c0 7.458E+01 7.422E+01 c1 2.308E+01 2.452E+01 c2 -1.056E+01 -1.146E+01 c3 2.712E+00 2.940E+00 c4 -4.246E-01 -4.534E-01 c5 4.245E-02 4.429E-02 c6 -2.761E-03 -2.805E-03 c7 1.162E-04 1.148E-04 c8 -3.050E-06 -2.929E-06 c9 4.531E-08 4.238E-08 c10 -2.908E-10 -2.
Performance Evaluations Inverter Operating Temperatures In addition to evaluating the conversion efficiencies of the inverters over a wide range of loadings, the external case temperatures of Inverter 1 and Inverter 2 were monitored over same the Test Period under the associated operating conditions. Figure 10 below are the temperatures measured at various locations on the inverter’s case as well as ambient temperature throughout the Test Period.
Performance Evaluations Figure 11 below are the temperatures measured at various locations on the inverter’s case as well as ambient temperature throughout the Test Period.
Authors and Contributors Jason Forrest Consultant Rajeev Singh, PhD Principal Engineer Rajeev@PVEL.com Zachary Stelly-Riggs PV Field Site Manager Report #316-2-3 CONFIDENTIAL | www.PVEL.com | 415.320.
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Installation Notes The following are substantive installations that were recorded by the field installers during the installations of Inverter 1 and Inverter 2 at PVUSA: 1. Installation of inverters a. The installation process was straightforward. b. Attaching the mounting bracket to the structure that supports the inverter was straightforward. c. Hanging the inverter on the mounting bracket requires two people but is straightforward. d.
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