IEC TS 61724-3:2016
(Main)Photovoltaic system performance - Part 3: Energy evaluation method
Photovoltaic system performance - Part 3: Energy evaluation method
IEC TS 61724-3:2016(E) defines a procedure for measuring and analyzing the energy production of a specific photovoltaic system relative to expected electrical energy production for the same system from actual weather conditions as defined by the stakeholders of the test. The energy production is characterized specifically for times when the system is operating (available); times when the system is not operating (unavailable) are quantified as part of an availability metric. The aim of this technical specification is to define a procedure for comparing the measured electrical energy with the expected electrical energy of the PV system.
The contents of the corrigendum of February 2018 have been included in this copy.
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IEC TS 61724-3 ®
Edition 1.0 2016-07
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic system performance –
Part 3: Energy evaluation method
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IEC TS 61724-3 ®
Edition 1.0 2016-07
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic system performance –
Part 3: Energy evaluation method
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-3531-7
– 2 – IEC TS 61724-3:2016 IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references. 8
3 Terms and definitions . 8
4 Test scope, schedule and duration . 11
5 Equipment and measurements . 11
6 Procedure . 12
6.1 Overview. 12
6.2 Calculation and documentation of predicted energy and the method that will
be used to calculate the expected energy . 14
6.2.1 General . 14
6.2.2 Definition of test boundary to align with intended system boundary . 14
6.2.3 Definition of the meteorological inputs used for the prediction . 15
6.2.4 Definition of the PV inputs used for the prediction . 15
6.2.5 Definition of measured data that will be collected during the test . 16
6.2.6 Definition of the model calculations . 17
6.2.7 Predicted energy for the specified system and time period . 18
6.2.8 Uncertainty definition . 18
6.3 Measurement of data. 19
6.4 Identification of data associated with unavailability . 19
6.5 Identification of erroneous data and replacement or adjustment of such data
and preparation of model input dataset . 19
6.5.1 General . 19
6.5.2 Data checks for each data stream . 20
6.5.3 Shading of irradiance sensor . 20
6.5.4 Calibration accuracy . 21
6.5.5 Final check . 21
6.5.6 Using data from multiple sensors . 21
6.5.7 Substitution of back-up data for erroneous or missing data . 22
6.5.8 Out-of-range data or data that are known to be incorrect . 22
6.5.9 Missing data . 22
6.5.10 Partially missing data or partial unavailability . 22
6.5.11 Curtailment because of external requirement . 23
6.5.12 Inverter clipping (constrained operation) . 23
6.5.13 Planned outage or force majeure . 23
6.5.14 Grid support events (e.g. deviation from unity power factor) . 23
6.6 Calculation of expected energy . 23
6.6.1 General . 23
6.6.2 Measure inputs . 24
6.6.3 Acceptability of data . 24
6.6.4 Time interval consistency . 24
6.6.5 Time stamp alignment . 24
6.6.6 Calculate expected energy during times of unavailability . 24
6.6.7 Calculate expected energy during times of availability . 24
6.6.8 Calculate total expected energy . 24
6.6.9 Analyse discrepancies . 24
6.7 Calculation of measured energy . 25
6.8 Calculation of metrics from measured data . 25
6.8.1 Calculation of energy performance index and availability . 25
6.8.2 Calculation of capacity factor. 25
6.8.3 Calculation of performance ratio . 26
6.9 Uncertainty analysis . 26
7 Test procedure documentation . 27
8 Test report. 27
Annex A (informative) Example calculation – Calculations for the energy performance
indices . 29
Bibliography . 30
Figure 1 – Schematic showing relationship of predicted, expected, and measured
energies to reflect how the model is applied consistently to historical and measured
weather data . 14
Table 1 – Example PV performance input parameters to the model for the initial
prediction . 15
Table 2 – Example table documenting the meteorological and other input parameters
to the model for the calculation of the expected energy . 17
Table 3 − Example of data filtering criteria, to be adjusted according to local conditions . 20
Table A.1 – Fictitious data to demonstrate calculation . 29
– 4 – IEC TS 61724-3:2016 IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC SYSTEM PERFORMANCE –
Part 3: Energy evaluation method
FOREWORD
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