Thermography for solar O&M teams and why it is growing in demand, join us as we talk with Rogério Pinheiro who is the O&M manager at Exus Management Partners.
Drones are an essential tool used to conduct module thermography for solar O&M teams all over the world. O&M teams can use thermographic imagery to identify solar plant performance issues and inform O&M strategies. Before drone technology, solar plant operation and maintenance teams would collect thermal images of the solar panels using handheld cameras. This method requires more time and effort, in the past many solar plants would only have 10% of the modules inspected due to the labour-intensiveness of the task. Today, as solar PV plants grow in size and number aerial thermographic inspections, have been adopted to routinely inspect all of the PV modules.
In this seven-part series, Above’s Josh Kutler, Technical Account Manager, talks with Rogerio about how Exus Management Partners are utilising advanced aerial thermographic inspections as part of their data-driven maintenance strategy. Our first question in this series for Rogerio is ‘Based on Exus’s position in the solar PD market, how do you see the demand for thermographic inspections growing and/or the level of standards changing?’.
Let’s hear from Rogerio Pinheiro, O&M Manager at Exus Management Partners
We at Exus believe that the demand for aerial thermography for solar O&M will increase significantly in the short term. There are a couple of reasons for this. One of them is the new standards that were published, particularly the publication of the IEC62446-3: 2017 and the IEC62446-2:2020 which will make thermal inspections the norm for PV Plants. IEC62446-2:2020 outlines the minimum scope required for the operation and maintenance of a solar PV plant. One of the things that come from these two standards is the obligation or at least recommendation that thermal inspections are made over the entire plant for its entire operation. Another drive in the demand for aerial thermography is the relative size of the solar PV plant. They’re growing. They’re getting bigger. I mean when I started working in PV building big plants. They were 250 kilowatts. In 10 years, the average size of the PV plant is now 100 to 250 megawatts. So, this makes it impractical to make a handheld inspection on PV plants of this size. It’s not just impractical, it technically makes it impossible from a time point of view, uh, to make this inspection. So aerial thermography for solar O&M will grow in the short term and continue to grow in the long term. New best practice guidance and accreditations combined with the current, and planned growth in the size of PV plants, make aerial thermography the best economic, or even the only feasible way to perform an inspection of solar plant PV modules.
With Exus’s experience in conducting different types of thermographic inspections can you detail some of the benefits gained from conducting these types of inspections and what were some of the pros and cons of the various types available to the marketplace.
Without going into details regarding the different levels of inspection and abnormal thermal behaviour identification techniques the reality is that there are two different types of thermographic inspection: 1) handheld inspection and 2) aerial inspection. Handheld inspections are used for all BOS components in the PV plant as aerial technologies are not suited by obvious reasons. Modules on the other hand can be perform either by handheld or aerial inspection. Handheld inspections allow for higher level of detail and inspection on the backside and connectors, while aerial inspections allow for detection of polarity dependent degradation mechanisms. We have also found that aerial thermographic inspection tends to be less dependent on operator, in particular angle of view and reflections errors are very common when perform by operator and handheld devises. These tend to be less predominant in aerial inspections.
In the end at Exus we are taking a mixed approach when it comes to the module’s thermal inspection. Yearly aerial thermographic inspection by default. With this inspection being used to select sampling areas for handheld inspection if needed.
On completion of the different inspections you’ve had completed, how were the results put to use?
The results are put to use in a number of different ways. The most immediate and short-term use of that data is the corrective actions to be carried by the field services team. This is the one-off failures, the occasional activated bypass diode, or broken module, the things not presenting specific patters and related to external conditions. On a second phase we analyse specific patters and / or distributions to detect potential indications of degradation or serial defect (This would trigger specific actions for a warranty claim). After we make a YOY analysis of the failure rate to assess how the PV plant is evolving. The last step and arguably one of the most important is to store the data for future use if it becomes necessary.
We had a very interesting, recent, ongoing case, where aerial thermographic inspection data was used not to prove the existence of a specific degradation pattern, but rather to focus our efforts elsewhere. The data dismissed the initial, though to be, cause for the underperformance and prevented us from lunching a claim that in the end would be without merit. Re-focusing on the problem and by process of elimination, only possible with that data, allowed us to detect a one of a kind, never heard of, very specific degradation mechanism.
Can you detail some of the risks and liabilities associated with on boarding assets that lack adequate records
When it comes to onboarding new assets, there is always a risk associated. The less reliable are the records of the asset the greater the associated risk. To compensate the risk, the value of the project decreases, this will create a differential between the perceived value for the stakeholders involved. At this point, one of two things can happen, either the “deal” fails completely, or in-depth validation of the condition of the asset will have to be performed. This as tremendous costs, specially in terms of the time necessary to perform said assessment. Under this scenario
- Performance analysis (IEC61724-3:2016)
- Documental analysis and simulation model creation
- Base line performance based on simulation model
- Comparison with actual performance
- Periodic inspection of installed systems
- IEC62446-1 based (category 1 and 2 test regime)
- category 1 test regime – 100% of the asset
- category 2 test regime
- Thermographic inspection 100% of the asset
- IV curve tracing – sampling depending of thermographic inspection
- Test requirements require specific weather conditions -> delays -> cost
- Warranties and risk analysis
- The million-dollar question: without adequate records, are the OEM warranties still valid?
- IEC62446-1 based (category 1 and 2 test regime)
Across the different stakeholders responsible maintaining a solar PV plant, how do survey results such as thermographic inspections support their different service requirements.
For those responsible for operating and maintaining the PV plant the thermographic inspections provide actionable data. It’s a very strait forward process. An abnormality is identified, with a temperature difference and a corrective action is put in place.
But this is not the end of the cycle for that data. It can be stored and used at a later stage. We found that YOY analysis of thermographic inspection, in particular aerial inspection to modules, together with performance and other data of the PV plant can provide valuable information. PID degradation, micro cracks on specific batches of modules (or production lines) and many other.
The hope is that our PV plants never run in to problems, but if it comes to that, and a warranty claim is necessary, having this information, available on a user-friendly platform, with traceability, will make all the difference.
This is value, for the operators, for the asset managers and for the owner. On its own its added value for the SPV on its one
What level of experience does Exus’s have with managing module warranty claims?
This is a very interesting question. At this moment Exus as not yet been involved on a large-scale module warranty claim. But our approach from the start as been very simple, expect for the best, prepare for the worst. The entire technical asset management and maintenance service operates under the assumption that a warranty claim will be raised in the future. This believe make us be pro-active in this regard, we do not wait to start a warranty claim to realize that we do not have the necessary data to reach a successful claim. We perform today, the inspections and measurements that we may need in the future. It’s a risk management strategy. The cost of performing is marginal when compared to a large-scale module warranty claim settlement.
Depending on the claim, and the specific nature of the claim the information required by the OEM will vary. Project identification, module serial numbers and location are always required. A technical explanation of the problem and evidence are also required. Aerial thermographic inspection data covers a wide range of well-known pathologies making it the most valuable and most likely piece of information that you will need in the future to mount a successful claim.
In what ways would you see digitalisation (like Digital Twin, Mobile Inspection Applications and other data driven smart tools) impacting the Solar PV industry in the near- and long-term future?
To be clear, the digitalization is coming and there is no escaping it. I believe that this will have a tremendous impact in the future of the Solar industry, in particular Operation and maintenance of a PV plant. In the long run I predict that there will be a shift in the maintenance strategy. Preventive maintenance will disappear and be replaced by Predictive maintenance. The corrective maintenance will dominate the future, but unplanned will be a thing of the past. I call it the “just in time” maintenance, where a component is replaced just before it breaks down, but not before, eliminating both high preventive maintenance costs and unplanned stops.
However, we are not there yet! and there will be more than a few broken hearts along the way. Currently the hype is running the show, and people are deploying digital twins and other data driven tools left and right. My analysis is that most of these projects will fail, for a very simple reason: we are forgetting the basics. We can’t have good predictive models if the data being feed into those models is not correct. The installation of sensors and their accurate calibration is fundamental, and 9 out of 10 PV plants I visit have sensors incorrectly installed or calibrated. The GIGO concept (garbage in, garbage out) was first used in the late 50th and it’s as actual as ever.
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