Anti-PID and Anti-LID Requirements for Hot Climates
Key Takeaway
Anti-PID is a claim about potential-induced degradation. Anti-LID is a claim about light-induced degradation. In a hot climate both mechanisms, plus light and elevated temperature induced degradation, belong on the evidence list. A temperature coefficient is not that evidence. This note does not cite a Weltrus test report number. The report that names the model on the purchase order is the document to request.
Table of Contents
When the Logo Replaces the Report
Hot-climate specifications often add two adjectives to the module line: anti-PID and anti-LID. The adjectives travel well. They fit on a slide, a stamp, and a comparison column. Two quotations can both carry them and still rest on different tests, an older bill of materials, or no report at all. The array that will sit at high cell temperature for years does not experience the adjective. It experiences voltage, heat, humidity, and light.
The cost of a vague claim shows up after the first hot season, when a power shortfall has to be sorted into ordinary temperature behavior, a warranty schedule, or a degradation mechanism the quotation said had been designed out. Those are three different files. Mixing them produces a claim the warrantor can refuse because the buyer measured the wrong thing, and a design review that never asked for the right report.
Buyers in deserts and buyers in humid tropics are not asking the same stress question, even though both sites are hot. A dry site still pushes cell temperature. A humid site adds the moisture path that potential-induced degradation uses. Write the climate you are actually building. Then ask for evidence that speaks to that stress, on the bill of materials you will receive.
Name the Mechanism, Then Name the Test
Potential-induced degradation
Potential-induced degradation is power loss driven by the system voltage between the cells and the grounded frame or glass, in the presence of heat and humidity. Leakage current through the encapsulant and the glass can polarize or shunt cells. The stress is higher when the system voltage is higher, when the module is hotter, and when moisture is available. It can also matter at night, when the array can sit at voltage without the light that produces operating current. A daytime-only story is an incomplete description of the mechanism.
The three Weltrus TOPCon tables used in this note, 465-490 W, 540-560 W, and 645-670 W, each print a maximum system voltage of 1500 V DC. That rating tells you the electrical ceiling of the module. It does not tell you the result of a potential-induced degradation test. It does tell you which voltage a relevant test should be compared against. A report run at a lower system voltage is a weaker stand-in for a 1500 V plant unless the report itself explains how the result scales. Ask for that explanation in writing. Do not invent it.
Buyers commonly ask for IEC TS 62804-1, the crystalline-silicon method for detecting potential-induced degradation. The report has to name the method actually used. The series includes more than one setup, including an environmental chamber and a contact-foil approach. A frequent chamber stress people expect to see is 85 degrees C, 85% relative humidity, at the intended system voltage, for 96 hours. Treat that quartet as a checklist of what to look for, not as proof that a given Weltrus report used it. This note does not supply a report number. If the report used a different temperature, humidity, voltage, or duration, the numbers in the report are the ones you have. A slide that says anti-PID does not fill them in.
Light-induced degradation, and the hot-climate relative
Light-induced degradation is power loss after the module is exposed to light. The classic boron-oxygen form is associated with p-type cells. TOPCon production is commonly n-type, which means that particular boron-oxygen path is the wrong mechanism to assume and the wrong mechanism to waive. Saying “it is TOPCon, so there is no light-induced loss” skips the test. Hot climates add a related question: light and elevated temperature induced degradation, often shortened to LeTID, which appears under light and high temperature together. That is close to how a module on a hot roof actually spends its afternoons.
Current editions of IEC 61215 include sequences aimed at light-induced degradation and at light and elevated temperature induced degradation. A certificate cover that says IEC 61215 is the start of the file, not the end. Ask for the edition, the sequence name, the measured loss of maximum power, the sample description, and the bill of materials. Glass, encapsulant, cell, and frame can change leakage and light stability. A pass on a different power class, or on a cell generation you are not buying, is context. It is not the result for the serials on your bill of lading. IEC 61215 and IEC 61730 remain type tests. They are not a 30-year outdoor dataset.
Three numbers that are easy to misread as test results
The temperature coefficient of maximum power on these three tables is -0.26% per degree C. It describes instantaneous power versus cell temperature. As a piece of arithmetic, a cell at 65 degrees C is 40 degrees above the 25 degree C standard-test cell temperature. Forty times 0.26% is 10.4% lower power than nameplate at that instant, from the coefficient alone, before other losses. When the cell cools, that term comes back. It is not potential-induced degradation and it is not light-induced degradation. The 65 degree C figure is an example temperature for the arithmetic. It is not a rated operating temperature, and these tables do not print one.
The degradation line on the same three tables is first year 1.0% or less, then 0.35% per year. Twenty-nine steps of 0.35% after a first-year floor of 99.0% put the end of year 30 at 88.85% of nameplate. That is a warranty schedule if the limited warranty for the model prints it. It does not state that a potential-induced or light-induced test was run, and it does not state a measured loss from those mechanisms. If the warranty covers power loss from them, the warranty text says so. A datasheet adjective does not.
The 465-490 W table prints a low-light figure of at least 96% at 200 W per square meter. Low irradiance is not a degradation mechanism. Do not file that line as anti-LID evidence. The other two bands are not given that low-light figure in this note. The datasheet for those models controls.
Evidence to Request, Field by Field
Ask for one packet per mechanism, tied to the model code and the bill of materials. Empty cells are gaps. They are not passes.
| Field | What you are checking | What does not answer it |
|---|---|---|
| Mechanism named in full | Potential-induced degradation, light-induced degradation, or light and elevated temperature induced degradation | A combined “anti-PID / anti-LID” stamp with no split |
| Standard, edition, and method | For example IEC TS 62804-1, and whether the setup was a chamber or a foil method; or the IEC 61215 sequence and edition | The words anti-PID or anti-LID with no standard |
| Stress | Voltage and polarity, temperature, humidity, irradiance, and duration | A pass at a voltage below the 1500 V system, unless the report explains the scaling |
| Pass limit and measured loss | The maximum loss of maximum power the report used, and the value measured | “Passed” with the limit left off the page |
| Recovery | Whether power was recorded before any reverse-bias recovery step | A result shown only after a recovery the plant will not apply |
| Bill of materials and model | Cell, encapsulant, glass, and frame match the code on the purchase order | A report on a neighboring wattage presented as the family |
| Report holder and date | The laboratory name, the report identity, and the date | A cropped logo. This note does not provide a Weltrus report number to fill the cell |
Read the pass limit before you read the word “passed.” Some project specifications treat a loss under 5% of maximum power as the commercial bar for a potential-induced degradation test. Use that only when the report prints it. If the report uses a different bar, quote the bar it used. A module that loses less than the lab’s measurement uncertainty may be inside the noise. Ask how uncertainty was handled. Do not assume a small miss is automatically a failure, or that a small pass is automatically field performance for 30 years.
Recovery deserves its own sentence in the file. Some potential-induced loss can be reduced by applying the opposite voltage. A test procedure that allows that step, and then reports the recovered power, can look better than an array that never sees the recovery bias. Ask whether the official number was taken before recovery. If the plant’s inverter and grounding scheme will not apply a recovery bias, a recovered number is the wrong number to file.
Sample identity closes the loop. The report should describe the power class, the cell technology, and the major materials. The three bands in this note share a degradation line, a bifaciality factor, a maximum system voltage, and a maximum-power temperature coefficient. Sharing those lines does not mean a single potential-induced degradation report covers all three, and it does not mean a report on one of them covers a 100 W or a 700 W code outside the tables. Match the model. If the match is partial, say so in the bid comparison.
Selection Boundaries
- A desert and a humid tropic are both hot, and they are not the same PID stress. Ask which climate the test was built to represent. Still use the site design temperature in the energy model. The coefficient of -0.26% per degree C remains the power-versus-temperature term, separate from the degradation file.
- Do not accept a family claim for every wattage from 100 W to 700 W. Evidence is per model and bill of materials. These three bands do not, in this note, share a cited report number.
- Do not treat n-type TOPCon as a waiver of light-induced or elevated-temperature light testing. Ask what was run. Architecture is not a result.
- Module evidence does not replace system design. Grounding, equipotential bonding, and the inverter’s isolation topology set the voltage the cells actually see. The module test assumes a stated stress. The drawing has to be consistent with that stress.
- A type-test pass is not a serial-level warranty and not a 30-year outdoor record. Keep IEC 61215, IEC 61730, the PID or LID report, and the limited warranty as separate documents. The year-30 floor of 88.85% applies only where the warranty prints the 1.0% and 0.35% schedule.
- Do not invent a report number, a UL file, or an insurance backing to fill an empty cell. Record the absence and request the document.
Put the climate, the system voltage, and the model code in the request. Ask for the potential-induced degradation report and the light-exposure report as two files. When they arrive, check voltage, temperature, humidity or irradiance, duration, pass limit, recovery, bill of materials, and the laboratory name. A quotation that cannot produce those fields has not yet substantiated anti-PID or anti-LID. It has used the words.
Ask for the Test That Names the Model
Send the model code, the system voltage, and whether the site is hot and dry or hot and humid. Weltrus can confirm which report, if any, matches that code. This page does not assign a report number in advance.
Frequently Asked Questions
What do anti-PID and anti-LID mean on a module quotation?
Anti-PID is a claim about potential-induced degradation, which is power loss driven by system voltage together with heat and humidity. Anti-LID is a claim about light-induced degradation, which is power loss after the module is exposed to light. Each claim needs a named test, a stress, a pass limit, and a model match. The words alone are not the evidence.
Does a Weltrus report number appear in this note?
No. This note does not cite a Weltrus potential-induced degradation report number or a light-induced degradation report number. Ask for the report that names the model on the purchase order. A logo that says anti-PID or anti-LID does not replace that report.
Is the -0.26% per degree C coefficient an anti-PID or anti-LID result?
No. On the three TOPCon tables it is the temperature coefficient of maximum power. It describes how power changes while the cell is hotter or colder than 25 degrees C. The change reverses when the cell temperature returns. It is not a degradation test and it is not a pass-fail result for potential-induced or light-induced loss.
Why does a 1500 V system change the question without answering it?
The three tables print a maximum system voltage of 1500 V DC. Potential-induced degradation stress rises with system voltage. A test run at a lower voltage is a weaker stand-in for a 1500 V plant unless the report explains the scaling. The 1500 V rating itself is not a test result.
Does TOPCon mean there is no light-induced degradation to test?
No. Classic boron-oxygen light-induced degradation is associated with p-type cells, and TOPCon production is commonly n-type, so that particular mechanism is not the one to assume. Hot climates still raise the question of light and elevated temperature induced degradation. Ask which sequence was run, on which bill of materials, and what power loss was measured. Do not convert the cell architecture into a waiver.
