Photovoltaic power systems (PVPS) – Information model for availability
|Publication Date:||1 May 2019|
|ICS Code (Solar energy engineering):||27.160|
A common basis of understanding results from defined metrics that can be useful to the stakeholders, populated by data collected in the operation of the PVPS:
a) To provide a standarized approach to characterize availablity and unavailablity for a PVPS.
b) To provide standard methodologies for determining the appropriate forms of availability of the PVPS during varying time periods, including real-time capability assessment or longer, for reporting availablity metrics to stakeholders.
This document provides a framework from which the availability metrics of a PVPS can be derived and reported. It describes how data are categorized and defines generic information categories to which time can be assigned for a PVPS considering internal and external conditions based on fraction of time, system health, and condition by specifying the following:
• generic information categories of a PVPS considering availability and production.
• information category priority to discriminate between concurrent categories.
• entry and exit point for each information category to allocate designation of time.
The PVPS comprises all photovoltaic (PV) modules, inverters, DC and AC collection systems, grid interconnection equipment, the site, its infrastructure, and all functional service elements. This is further explained in 6.3 and 6.4.
Formulas in this document provide normative guidance for standardization. Beyond that, it is not the intention of this document to specify exactly how other undefined, time-based availability metrics shall be calculated. The annexes are examples and guiding principles for developing methods for calculation and estimation of availability metrics, subject to the knowledge and concurrence for use by the involved stakeholders. Estimates and calculations also have recommendations on how they are to be used as part of the informative function.
It is not within the scope of this document to determine the method of information acquisition. Relevant IEC documents on data collection and information acquisition are included in the following normative references. IEC 61724-1 has requirements and IEC TS 617243: 2016, 6.2.5, specifically identifies measured data on this topic.
Data generated during the operation of a PVPS are valuable, establishing who owns the monitoring data and who will have access to the data and for what purpose should be established. Different stakeholders will have different needs, as summarized in Table 1 (IEA). In Annex E, the monitoring systems are addressed in greater detail.
Availability metrics cannot be derived without important outage information. Questions can require the PVPS operation to properly collect the requisite data, such as what equipment or portion of the plant is failing, how long, how often, and how much energy is being lost and categorized by the information model. Asset management questions include the source of the outage (i.e., Whose clock is it on? Was the outage due to internal or external forces? What power and energy was generated? And, what was expected?).