Before answering this question, let’s discuss what a PV monitoring system is

PV monitoring systems are software-driven devices that track the performance of a solar energy installation. They vary in terms of what they track and how it’s displayed, but most provide real-time and historical data, performance-based alerts, web-based (or cellular) monitoring and some give details on weather and some let you customize the presentation. A PV monitoring system essentially involves

  • Capturing the power plant/system performance indicators
  • Analyzing the plant/system performance indicators
  • Identifying the problems affecting the performance of the PV power plant
  • Reconfiguring/Re-calibrating the plant as required, eliminating the performance bottleneck.

The first is done using sensors/meters and data loggers. Quite a few data loggers and inverters have the ability to export data and let the operators look at it visually over the web.

      What kind of monitoring solutions are employed in solar power plants?

        Typically, there are 2 kinds of monitoring system solutions.

  • On-site/inverter monitoring solutions – For many customers, an inverter’s basic display is informative enough. It is easy to access—right on the front of the inverter—and provides a basic level of monitoring, which often includes instantaneous power output, daily energy production, and total to-date energy production.
  • Advanced Monitoring Solutions – Some power plants opt for advanced monitoring solution over and above the basic monitoring solutions that come with inverters. These solutions come with additional hardware and data loggers through which they will be able to collect data at a more granular level.

What are the extra features provided by extended monitoring solutions?

  • Easy-to-use dashboards that provide installers or developers a common platform to view the performance of all their power plants
  • Better alerts and analytics capability that provides stakeholders updates in the form of emails and SMSes
  • Spatiotemporal analysis of the generation from panels placed in different directions and thereby providing useful analytics for optimizing solar panel layout
  • Mobile platforms (such as android application) wherein information on generation details, historical data and status of inverters can be viewed anywhere
  • More data, in terms of volumes, parameters and also frequency of recording, stored in the data logger that enables better analytics
  • Calculation of performance parameters like Performance Ratio (PR) and Capacity Utilization Factor(CUF)
  • Root cause analysis to evaluate factors that impact energy production
  • Offline analysis in case the data has to be downloaded to your system for a much more in-depth analysis

How does a string-level or modular monitoring system perform over a conventional inverter-level monitoring system?

Several features in an advanced monitoring solution over a purely inverter based monitoring solution is described above. This section provides further insight into what exactly could be the difference between the two.

A solar plant deployed with a string-level monitoring system gathers inputs from inverters, string combiner boxes, weather station and net meter. The weather station comprises of the pyranometer as well as instruments for measuring cell and ambient temperatures. This adds a high degree of reliability and ensures that under-performance of the plant is mitigated. Through this advanced monitoring capability, a faulty panel or set of panels can be narrowed down to the string level by identifying the reduced power generation in a particular string. For example, if the fault is reduced to a string of 20 panels, it would be pretty straightforward to detect the faulty panel and replace it, unlike in an inverter-level monitoring system.

An advanced monitoring solutions can give you an additional 10-15% in generation every year through quick turn-around( repair) time , personalised alerts to the site engineer and other stakeholders, remote monitoring by experts for resolution of issues, quick and easy detection of DC side losses caused by shading, module mismatch, soiling of modules, etc. Hence, while you evaluate your power plant do not forget to give additional points to power plants with advanced monitoring provisions, especially in case of large scale, ground mounted plants.

Takeaway – Thus, understanding the type of monitoring solution deployed at the solar power plant could play an important role while evaluating the solar power plant’s overall potential for performance.

You might want to check out these questions on Solar Power Plant Evaluation- Components:

  • How well have the components been chosen?- Here
  •  Presence of local service support from component manufacturers?- Here
  • What have been the degradation rates in panels?- Here
  • How good are the inverters?- Here
  • What kind of trackers is employed?How do you ensure its quality?- Here
  • Are the components suppliers in business?- Here
  • What are the warranty clauses attached to key components?-Here
  • Can you retrofit additional components to an existing power plant to increase generation? – Here