Monitoring of photovoltaic systems: good practices and systematic analysis
Trends in PV System Performance
Researchers have observed a continuous improvement of performance ratios (PR) over the last 20 years. Detailed and more reliable monitoring campaigns have played a significant role in improving this trend.
The International Energy Agency’s Photovoltaic Power Systems Programme (IEA PVPS) includes a taskforce dedicated to improving the performance, reliability and therefore yield of PV systems (Task 13). This international task-force focuses on performance assessment techniques and specifically on monitoring as one of the remaining levers for improving performance of PV systems further. 3E is a key contributor of the IEA PVPS Task 13 expert group. We presented new IEA PVPS results at EUPVSEC in October 2013, in the paper “Monitoring of Photovoltaic Systems: Good Practices and Systematic Analysis”. The paper is part of the EUPVSEC proceedings from WIP.
Good Practice in PV Monitoring: What to Watch for
Being able to rapidly detect and diagnose these factors and issues specifically is therefore of key importance in monitoring for optimal performance.
Getting the Right Input
Being aware of the limitations and uncertainties related to measurement equipment is a first step in getting more insight from the data collected.
For electricity yield measurements, energy meters or true-rms power meters should be used. The inverter-integrated measurements are usually not sufficiently precise but can deliver useful information for relative analyses over time.
The way irradiance data is processed and integrated in PR calculations, for example through third-party monitoring software, will also be key to getting maximum value from monitoring systems. Ensuring that irradiance data is available at all times and treated transparently, is a strong feature for a monitoring software platform which should be assessed carefully. 3E’s own independent platform, SynaptiQ, integrates the lessons learned from our research team and provides multiple reliable fall-back options and clear categorizations of PRs indicating the underlying irradiance source.
Data Mining and Analysis
The main purpose of a monitoring system is to assess PV system performance to identify design flaws and malfunctions.
Our IEA PVPS Task 13 paper points out a few of the most well-known methodologies and introduces a new analysis based on regression-based linear modelling. This technique consists in describing key behaviour of a PV system with simple linear relationships to be mapped out over time and checked for deviations. Examples of various issues throughout the energy conversions chain show that with weekly reviews of these relationships, deviations can very clearly and quickly be identified.
To carry out such analyses and to manage the whole performance assessment process most effectively, a monitoring system must combine:
We are continuously enhancing our own SynaptiQ monitoring tool around these capacities. Contact us for more information about SynaptiQ’s new scatter plot and data mining tools.