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Example Contract Exhibit

PROCEDURE – ENERGY TEST

I. General

a. Introduction

The Energy Test shall be used to determine that the Facility is performing as designed and shall be performed as a condition to Substantial Completion of the Facility when reporting conditions, such as shade, low irradiance levels, or persistent constrained operation, do not support a Capacity Test and as otherwise required pursuant to the Agreement.

b. Reference Standards

The reference standards for the Capacity Test include:

  1. IEC 61724-3 (2016) “Photovoltaic system performance-Part 3: Energy evaluation method”
  2. IEC 61724-1 (2021) “Photovoltaic system monitoring”
  3. ISO/IEC 17025 (2017), “General requirements for the competence of testing and calibration laboratories.”

These standards and their reference documents shall be used to perform the Energy Test, as defined in Section []. Allowed modifications from these standards are listed in Section II.

c. Final Results

The Final Results of the Energy Test procedure shall be reported in an unambiguous format per the selected Allowances and Acceptance Criteria.

II. Test Guidelines

a. Definitions

The following terms are herein defined for this Energy Test. The purpose of defining these key terms is to remove the ambiguity of terminology between the various reference standards.

  1. Constrained Operation. Operation of the Facility when the power injected into the grid is limited by the output of all the inverters either due to their AC rating (i.e. inverter clipping), Facility rating (i.e. POI clipping), or other grid requirements (i.e. curtailment, power factor response, etc.).
  2. Unconstrained Operation. Operation of the Facility when all inverters are freely following the DC power response to irradiance and output is otherwise not limited.
  3. Test Model. The simulation model of record or proxy model used to calculate the predicted or expected PV power generation based on the test model parameters
  4. Expected Energy. Energy generation of the Facility that is expected for actual weather data collected at the site based on the Test Model Parameters of the system.
  5. Predicted Energy. Energy generation of the Facility that is calculated with a specific performance model, using historical weather data that is considered to be representative for the site.
  6. Measured Energy. Energy that is measured by the Facility meter and injected into the grid or storage elements.
  7. Test Ratio. The ratio of Measured Energy to Expected Energy during the Test Period, defined in IEC 61724-3 (2016) as the Energy Performance Index (EPI).
  8. System Unavailability. Expected Energy that cannot be delivered because of inverters or other components being offline, as judged by the automatic indication of any DC to AC conversion, as a percentage of total Expected Energy.
  9. External Unavailability. Demonstratable periods of snow, curtailment, or grid unavailability.
  10. Excluded Periods. The time duration of data records during the test period that are excluded from the test due to errors of Excluded Conditions.
  11. Test Uncertainty. Expanded Test Uncertainty (K=2) As defined in the reference standard using the Guide to the expression of uncertainty of measurement (GUM).
  12. Test Model Parameters. Electrical design parameters that influence Expected Power, including but not limited to: DCstc capacity, AC system max output, DC static losses, DC and AC ohmic losses, module temperature coefficient, and inverter CEC efficiency rating.
  13. Test Period. Total hours of operations specified by the Acceptance Criteria, less Excluded Periods.

b. Test Model

The Test Model shall be agreed upon in advance of the Energy Test and used as the basis for calculating Expected Energy. The Test Model shall include a report or data file of all Test Model Parameters, including the shade scene and soiling assumptions.

c. Test Boundary

The system under test is qualified by a test boundary that includes Test Model design parameters calculated by total effective irradiance, both front and rear (if applicable) incident measurements, and module cell temperature. Expected Shade losses may be included in the Test Boundary, if defined in Section IV.

d. Data Collection

  1. Benchmarking and reporting for this test shall follow the requirements of IEC 61724-1 (2021). Measurement devices shall be consistent with the Test Boundary selection, including:

    1. Plane of Array (POA) and Rear Plane of Array (rPOA) irradiance measurements may include spectrally flat thermopile pyranometers, similar spectrum fast response photodiode pyranometers, or matched reference cells configured to report effective irradiance. Pyranometers or reference devices shall have a Calibration Uncertainty (K=2) < 2% and be calibrated within 1 year by an ISO/IEC 17025 Accredited Calibration Laboratory.

    2. Cell Temperature (Tcell) calculation shall be derived from Back of Module temperature (Tbom) measurements and applying the NREL Open Back conversion to Calculated Cell Temperature based on the Irradiance:

      Tcell = Tbom x (1+.003* POA Irradiance)

      Back of Module temperature sensors shall have validated temperature readings consistent with manufacturer specifications.

    3. Power generation shall be measured using an ANSI C12.20 Class .2 or higher meter, or as specified in the system design. Meter accuracy shall be documented in a certified statement of conformity by the manufacturer. Meter measurement shall be validated against inverter power measurements prior to the start of the Capacity Test to identify potential human error during set-up.

    4. Interim test point measurements from inverters, reclosures, tracking equipment, and other weather instrumentation, may be included to provide supporting analysis to support the Final Results.

e. Test Procedure

  1. Test Model
  2. Instrumentation and Calibrations
  3. Ongoing Data Quality
  4. Sensor Cleaning
  5. Array Cleaning
  6. Unavailability and Fault Detection
  7. Unavailability and Fault Resolution
  8. Curtailment Resolution
  9. Data Analysis
  10. Test Report
  11. Uncertainty Analysis

III. Test Report

The Test Report shall include all required information as outlined in the reference standards per the selected Test Methodology of Section IV, including the associated data file:

  1. IEC 61724-3 Section 7
  2. ISO/IEC 17025 Section 7

IV. Test Criteria

a. Test Options

The Final Results of the Energy Test shall include the following Options:

Table 1. Options for Energy Test

ParameterOptionExplanation
Expected Shade[included/excluded]If the Test Model includes a defined shade scene, including Expected Shade may be used to calculate effective irradiance (post-shade) for determining the Test Ratio.

b. Allowances

The Final Results of the Energy Test shall include the following Allowances:

Table 2. Allowances for Energy Test.

AllowanceValueExplanation
Soiling[ 0.5% ], or As Measured and agreed by parties to this AgreementAn assumed soiling level during the Energy Test that is not included in the Test Model. Irradiance measurement sensors shall be clean during the Test Period.

c. Acceptance Criteria

The Final Results of the Energy Test shall be derived from the following Acceptance Criteria and other Test Parameters defined herein:

Table 3. Acceptance Criteria for Energy Test

CriterionValue
Minimum Test Ratio[.98]
Maximum Test Uncertainty (K=2)[5] %
Maximum System Unavailability[1] %
Test Period[7] Days

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