Genel

Detecting faulty EL photos with machine learning (ML)

Can two EL photos of two panels be identical? No. Every EL (electroluminescence) photo is different. What if the same photos come from the factory for different serial numbers?

EL photos coming out of solar panel factory lines are very similar to each other. For this reason, your chances of saying “I have seen this photo before” are very low. During our inspection of a solar panel factory, we noticed an identical EL photo by chance. Of course, we had our doubts; what if there were other photos that we missed?

The EL images above are identical. The two panels have different serial numbers inside. And the solution? The solution is in software, in machine learning.

Python and Tensorflow came to the rescue.

Using the MobileNet library, which is pre-trained to detect similar photos using convolutional neural networks (CNN) inside Tensorflow, we ran our own code on thousands of EL photos and automatically generated reports. Below is an example from our report page; the first example at the top and two other files containing the same image below.

As a result of the software’s analysis, we found that some photos were used in more than one serial number. Of course, this is not something that the factories do intentionally; some problems in the software can also cause such problems. IT intervened quickly and eliminated the problem in about a week. After this stage, this control became our standard procedure and we encountered this problem in 77% of the factories we audited.

It is really important to have production inspected in solar panel factories. There is no rule that the manufacturer will necessarily make bad production, but why shouldn’t you buy the best product coming off the lines? If you are considering panel supply, you should definitely have your production line inspected. The more a factory is open to inspection, the more confident it is.

What Tests Are Performed on Solar Panels?

Photovoltaic solar panels constitute a large part of the solar power plant investment amount. At the same time, many performance and safety tests are applied to these solar panels by the relevant laboratories as there are many types of defects that cannot be seen by the eye. The IEC 61215 standard includes minimum design criteria that will affect the performance of solar panels, while the IEC 61730 standard focuses on design criteria that will affect plant safety in solar panels. The rapid development of technology brings along product diversity. For this reason, the International Standard Commission is developing test scopes and test diversity day by day. The IEC TS 63209-1:2021 standard is the first standard created in this context and includes a wide range of solar panel tests to comment on the long-term performance of solar panels.

Solar panels are entitled to receive a certificate if they successfully pass the tests according to IEC 61215 and IEC 61730 standards. Although all solar panel tests written in the standard are important, the definition of some tests is as follows.

Firstly, the power, temperature coefficients, insulation resistance, thermal measurements of the photovoltaic solar panel are checked with performance tests in accordance with IEC 61215 standard. After the performance tests, solar panels are subjected to aging tests under certain conditions. Below are examples of solar panel tests.

Thermal Cycle Test: The performance of photovoltaic solar panels at variable temperatures is tested successively by passing current between -40°C and +85°C through the solar panel. The damage to the solar panels due to test repetition is as follows.

Humidity Freeze Test: At high humidity, the ambient temperature is first raised to +85°C and then lowered to -40°C. This test is repeated consecutively. In this way, performance in freezing humidity is evaluated.

Damp Heat Test: Photovoltaic solar panels are kept at +85°C and 85% humidity for 1000 hours. The damage to the solar panels due to test repetition is as follows.

Mechanical Loading Test: At a minimum of 2400Pa, the front and back surfaces of the solar panel are pressurized in a row.

Photovoltaic solar panels are subjected to performance tests again after the aging tests mentioned above. In this way, the long-term performance capability and the amount of degradation of the solar panels are revealed and if they pass, they are certified.

In addition to the above tests, a PID test should be applied to solar panels. As the solar panels operate, sodium ions react with the potential formed on the conductive layer and the glass surface and a positive charge accumulates on the panel surface. This interaction is called PID and the loss it creates is called PID loss.

The solar panel quality control process respectively is as follows.

Pre-Production Control of Certificate and Annexes

Each solar panel with different technology and power coming out of a factory must be subjected to the solar panel tests specified in the standards. The certificate obtained for one solar panel cannot be used for another solar panel. For this reason, solar panels should be checked by expert engineers on the production line before they arrive at the site. This control first starts with the control of the certificate and its annexes for the solar panel to be used. All raw materials specified in the certificate, certificate annexes and raw material list must be valid and consistent with each other. If there is a discrepancy between these documents, there is a possibility that the solar panel is not certified.

Factory Control in the Production Phase

There are many controls that need to be carried out during photovoltaic solar panel production. These are the raw material warehouse, air conditioning, production line and shipment controls respectively.

It also accompanies the solar panel factory tests. It is very important to check the EL visual and Flash Test results that give the power value of the solar panel. EL and Flash Test results of all solar panels are checked. These checks and interventions extend the life of the solar panel and allow the factory to determine whether the solar panels are at the promised power.

After the production of solar panels in accordance with the standards and certificates is checked, their delivery to the field is approved.

Control of Photovoltaic Solar Panels in Power Plant

It is possible to measure the performance of photovoltaic solar panels with tests performed at the power plant. These tests are IV curve measurement, hot-spot measurement with drone and hand thermals – IEC 62446, hand (electroluminescence) test of solar panels – IEC 61215, insulation (hipot) tests – IEC 62446, grounding value measurement. You can reach our detailed sharing about the measurement services applied to solar power plants according to IEC standards here.

Benefits of SPP Audit by an Accredited Company

Solarian Enerji A.Ş. is a type A inspection body with TURKAK accreditation with file number AB-0649-M. The scope of accreditation includes all the standards mentioned above such as IEC 62446, IEC 61215, IEC 61730. You can access the full scope here . By having your solar panels inspected by our TÜRKAK accredited company, you can have information about the status of your solar panels and have an accredited inspection report valid all over the world. Fill out the form below to contact us.

Inspection and Verification Process in Solar Power Plants

The technical assurance of a solar power plant rests on it being independently inspected from construction through to operation. This page sets out how the inspection and verification activities within our accreditation scope proceed on site.

When this process is completed, all the details of the project, return, costs, expected productions related to the ges project are determined.

1 – Construction Phase

This stage covers the inspection activities carried out during the construction period.

The projects and products submitted at this stage are verified against both the specifications and the relevant IEC standards, and the findings are reported.

With the start of the field processes, the part we call employer engineering in solar power plants in the field begins. The personnel in the field regularly inspect the productions. All activities are reported daily and weekly. Regular meetings are held with the contractor to reduce the occurrence of problems.

At this stage, our biggest goal is to prevent irreversible problems with our experience and knowledge.

Accredited IEC62446 acceptance tests begin when the plant is completed.

At this stage, the performance of the solar panels is inspected and examined for thermal faults. The site is reviewed in general and any improvements that can be made are realized. When the tests are completed, an accredited report is submitted by the accredited ges audit company within the scope of IEC62446. These reports can be considered as the acceptance criteria of photovoltaic modules and the system. With this report, the construction phase is completed and the operation phase begins.

You can click here for more detailed information about acceptance tests according to IEC62446 standard.

2 – Operation Period / PR Verification / Periodic Tests

In this section, the performance of the products and system after the construction period is regularly inspected according to IEC61724 standard.

At this stage, we work together with the remote monitoring system and the radiation/production/temperature data from the system is uploaded to the verification software. This software compares the actual and simulated values for the relevant time zone and tells us whether the system is operating at optimum performance or not. Thus, we have information about whether the system is working efficiently or not and detailed analyzes are carried out in the system within this information. The performance of solar energy systems is calculated with IEC61724.

PR verification is repeated periodically and the results are reported.

This way, the performance of the system can continue to be checked on a regular basis. If you would like to learn more about precision PR calculation, please click here.

You can contact us via the contact form for solar energy engineering services.

This service is within the scope of our TURKAK accreditation (AB-0649-M). Scope of accreditation

Solarian Energy TÜRKAK Accreditation Scope

You can access the scope of Solarian Energy’s TÜRKAK accreditation here.

Why should you have your solar energy investment audited by an accredited organization?

1. What is accreditation and accredited organization?

Accreditation is a quality infrastructure established to support the reliability and validity of the work carried out by conformity assessment bodies and therefore the conformity confirmation documents (test and inspection reports, calibration certificates, management system documents, product certification documents, personnel certification documents, etc.) they issue as a result of these studies.

Accreditation of conformity assessment bodies is carried out on the basis of international standards that set the qualification criteria for the relevant conformity assessment bodies, relevant sector-specific requirements and globally accepted requirements set out in guidance documents determined by regional or international accreditation bodies.

A product or service with a certificate of conformity issued by an accredited conformity assessment body inspires confidence that it meets the requirements applicable to that product or service. Thanks to the systematic accreditation contributes to the removal of technical barriers to trade.

2. Why work with an accredited organization?

Accredited organizations perform their services in line with a quality infrastructure based on the relevant standards and norms in the sector. Tests, studies and examinations are not subjective but objective and reproducible. Accredited organizations show their work to the institutions they are accredited during regular audits. The accreditation of inspection bodies with non-compliance in their work is canceled.

Inspection services performed in solar energy facilities are studies involving precise measurements and experiments. Procedures that determine the quality of measurement, such as the calibration of the equipment used in these studies, the creation of an uncertainty budget, interim verifications, the competence of the inspection personnel who will perform this service, are part of accreditation. Accredited organizations provide repeatable and accurate measurement services.

3. Can every accredited organization provide services in the field of solar energy?

Accredited organizations have accreditation scopes that specify their competencies. Services offered outside the scope are not accredited. Solarian’s accreditation scope specializing in solar energy investment is available here.

4. Is Solarian an internationally accredited organization?

Solarian is an internationally accredited organization from TÜRKAK with accreditation number AB-0649-M. Solarian’s accreditation is internationally recognized as Türkak is a member of the European Accreditation Cooperation Program.

5. How do I know if an organization is accredited?

Accredited organizations in Turkey are registered in TÜRKAK’s database . You can search by typing the name of the organization at https://secure.turkak.org.tr/kapsam/search and see the scope of accreditation of the organization.

6. The organization states that it is accredited abroad. Is this accreditation valid in Turkey?

Organizations of foreign origin operating in our country and performing certification activities; If accredited by a national accreditation body that is a member of the European Accreditation Cooperation Program (EA) and the extension of the relevant company in Turkey is specified within the scope of this accreditation, there is no obstacle for these certification bodies to provide services to their customers in Turkey.

6. How can I contact Solarian?

You can contact us by filling out the form below.

Photovoltaic Solar Panel Production Inspection According to IEC61215 and IEC61730 Standards

In order to ensure that the solar panels produced are long-lasting, production supervision is carried out in solar panel factories throughout the production process, including before manufacturing, during manufacturing and before shipment. In this way, the quality production of solar panels produced for your project is guaranteed.

There are three standards that interpret the product quality of solar panels. These are IEC 61730, IEC 61215 and IEC 62446 standards. However, these standards specify minimum quality conditions. For this reason, each of the factories producing photovoltaic solar panels has its own quality acceptance criteria. It is important to determine these acceptance criteria based on engineering fundamentals and specific to the solar panel to be produced for the project.

Storage of EVA and Backsheet used in Solar Panel Production — Conditioned EVA Storage

Solar Panel Production Inspection Material Control — Glass Storage

Certified solar panels show that the solar panel manufacturer meets the quality and safety requirements of the certification bodies in the specified product. However, this approval is only possible if the raw materials are used and stored at the right climatic conditions.

If the inspection is not carried out in the solar panel factory, the possibility of the solar panels having physical defects will cause the life of the solar panels to decrease. In mass production factories, it is very important that the production line is controlled by a 3rd party eye. In addition, not all solar panels produced have the same electrical values. Solar panels that meet the values committed for the project must be selected and prepared for shipment.

Visual inspection of solar panels before packaging — Visual Control During Production

Not all defects in solar panels can be seen visually, EL visuals should be examined by experts. According to the determined acceptance criteria, the manufacturing of the solar panels suitable for the project must be inspected and selected and prepared for shipment.

EL control in solar panel production — EL Control in the Production Phase

Preparation for shipment is the last stage of solar panel procurement with a high probability of error. It is very important to determine the measures to be taken in advance to eliminate the risks of physical damage during the transportation of solar panels to the site and to carry out PV module manufacturing inspection in this process.

Packaging inspection in solar panel manufacturing — After the solar panels are packed, they are checked until loading.

If you want to ensure the quality guarantee of the solar panels to be produced for your project, you can contact us. Solarian Engineering and Inspection Team is ready to support you about the manufacturing inspection during the production of solar panels.

Please fill out the contact form to get in touch with us.

Solarian begins work on the YEVDES Project, of which the Ministry of Energy is the final beneficiary

Within the scope of the YEVDES PROJECT project funded by the European Union and implemented by the Consortium led by Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH, of which the Ministry of Energy and Natural Resources is the ultimate beneficiary, we have started our work to increase energy efficiency and renewable energy production in municipalities and universities in every corner of Turkey. As Solarian, we are very proud to be a part of this valuable project where our experts will benefit from the integration of solar energy technology.

Pushing the Limits in Electroluminescence (EL) Testing of Solar Panels

How should the hand test be done? How much detail do we need in the EL photo? We were puzzled by many questions, such as, if we can take a photo to see what details we can see, we can see whether it complies with the quality guidelines in panel production.

The EL test journey also brought with it a lot of trial, error and learning.

In order to take an EL photo, you first need to know what EL is. EL is not just a photo you can take with equipment; you need to turn a solar panel into an electroluminescence (EL) source. In other words, we energize the solar panel and turn it into a UFO heater. “What do you mean?” I can hear you ask. Yes, we light the solar panel like a lamp to take this photo.

Since the photo is a long exposure, you apply this voltage for about 10 seconds, so nothing happens to the panel, but if you apply it for a long time during the test phase, you will burn the panel. Don’t try it yourself at home 🙂

After learning the technology thoroughly, we built our own small test station and started our first trials.

Düşük çözünürlüklü ve net olmayan elektrolüminesans EL fotoğrafı — Our first EL attempts (First photo of this page)

Even though this EL photo was not clear and did not have enough pixel detail, it was an indication that we were on the right step. We immediately went to the field and made our first test.

Sahada ilk Elektrolüminesans EL testi çalışmalarımız — First works on the field

One night we conducted our first experiments at the facility of a company where we regularly carry out O&M processes. The goal was to use RaspberryPi to push files to the cloud and process them there.

Raspberry Pi ile EL testi cihazı haberleşmesi — The pleasure of creating a wi-fi hotspot on Raspberry Pi and using it on iPad by connecting with SSH 🙂

At this stage, communication and machine learning technologies were ready to be used. The infrastructure was there, but the images were not of high enough quality. So how do we define quality? How high quality should an EL photo be?

We took the records of a factory capable of taking high-end EL photography as a benchmark.

Örnek bir fabrika EL test cihazının görüntüsü — Image of a sample factory EL tester

Our aim was to capture at least this image quality in the field. For this reason, a serious sensor/lens hunt started for us. Which sensor should we use with which settings? Which feature of which lens should we utilize? Which filters were necessary, we went on a long journey. In every EL photo we took, we looked for the next step, which I believe we have reached at some point. But the solution was not only hardware-based.

In addition to off-the-shelf EL hardware solutions, you also need a post-processing process to get the required values in the image, so it’s both a hardware and software problem.

So where did we come from? Good question. See below the first and the last photo we took of the same panel.

İlk EL test fotoğrafımız — First photo of the test panel in the office (Same as the first photo of this page)

Güneş Panelleri İçin Elektrolüminesans (EL) Testi — Latest EL photo taken with Solarian’s EL tester (Click to see original version)

Isn’t the difference enormous? Where have we come from? Today, there is a very serious optical quality and optimization with software. We have a photographic technique that allows us to see even the finest details on the cell.

Moreover, our Raspberry device in the system can receive this data and send it to the cloud, where a python code analyzes and interprets it. Today, we developed the device you see above, we wrote the necessary photo manipulation codes and we are developing cloud applications. Maybe 5 years ago, these were dreams. Where is technology going?

Do not damage the panel while mounting the panel. All will be revealed when we come to the EL test 🙂

You can fill out the form below to get information about our EL tests.