The Beyond the Datasheet Edition

Over the last few issues, we have looked at conditions that can shape PV module performance in India: monsoon light, partial shading, coastal humidity, dust and heat. This issue closes that thread by revisiting a condition that repeatedly came up in the discussion, looking at how durability is evaluated, and ending with one practical question for supplier conversations.

Insight: A recurring condition, and how to design around it

Across these conversations, heat kept returning as an important design consideration.

PV modules are rated under Standard Test Conditions (STC), which use a module temperature of 25°C. In field operation, module temperature can differ from that reference as weather and operating conditions change. NCPRE, IIT Bombay, includes module temperature, ambient temperature, wind and solar irradiance among the parameters used when evaluating PV-system performance. This is why temperature is better read as a site condition rather than a fixed datasheet value. (Source context: NCPRE, IIT Bombay, PV Systems Testing and Characterization)

Heat should also be read alongside other factors that influence long-term module behaviour. In its combined analysis of the All-India Surveys of PV Reliability, NCPRE, IIT Bombay, reported higher observed degradation rates at hot-climate sites than at non-hot sites within the surveyed data. The same work also highlights the importance of how field measurements are corrected to STC when degradation rates are estimated. This supports treating temperature as an important contributor to field performance, rather than as a standalone explanation for degradation.

The temperature coefficient is visible on a datasheet. Long-term durability is more complex and cannot be inferred from that value alone.

Cell architecture is one part of the picture. Indian research institutions including NCPRE, IIT Bombay, have studied PV temperature coefficients and module performance in hot Indian climates, reinforcing the value of evaluating temperature response at module and site level rather than inferring it from a technology label alone. For SLR's current Bifacial N-TOPCon G12R product, the technical datasheet lists a maximum-power temperature coefficient of -0.30%/°C and describes the design as having very low LID. These are product-level specifications, and their contribution to field energy yield will still depend on operating conditions and system design.

System-level thermal behaviour is also influenced by local operating conditions. NISE publications include work on wind-effect modelling for PV module temperature, while NCPRE's system-testing guidance monitors module temperature alongside ambient temperature, wind, humidity and irradiance. In practice, this supports evaluating thermal behaviour in the context of the site and overall system configuration rather than relying on a single datasheet parameter.

For many Indian projects, temperature is therefore worth treating as a site-design input rather than only a datasheet parameter.

From the floor: Validating durability

Durability is best evaluated through a combination of qualification testing, manufacturing controls and field evidence. The useful question is what each layer of evidence can actually establish.

In India, BIS lists crystalline-silicon terrestrial PV modules under compulsory registration against IS 14286 and IS/IEC 61730. IS 14286 (Part 2):2023 is the Indian Standard covering design-qualification test procedures for terrestrial PV modules. NISE's NABL-accredited PV testing facility lists thermal cycling, damp heat, humidity-freeze, mechanical load and electroluminescence among its module testing services. These tests provide evidence against defined qualification criteria; they should not be read as a site-specific prediction of field lifetime.

Meeting the applicable qualification requirements indicates that the tested module design satisfied the defined test criteria. It does not, by itself, establish exactly how long a module will operate at a particular Indian site, where environmental exposure, system design, installation and operation can differ.

Qualification certificates are one layer of evidence. Additional quality-control information, such as electroluminescence images, power measurements across a stress sequence and consistency across tested samples, can provide more context about manufacturing control. NISE includes electroluminescence and several accelerated-stress tests among its PV-module testing services. The value of any internal quality data still depends on the test method, sample size, acceptance criteria and traceability to the product being supplied.

MNRE's revised 2025 series-approval guidelines define a PV module product family around common design, construction, parts or assemblies that are essential to conformity. The guidelines also state that changes in bill of materials (BOM) or process modifications require retesting as per IS/IEC 62915:2023 to maintain certification. This makes certification records and manufacturing traceability complementary parts of supplier evaluation.

For buyers, the practical takeaway is to look beyond a certificate number alone and ask how quality data is generated, recorded and linked to the module construction being supplied.

One thing worth knowing: A question to ask every supplier

Here is one practical question worth carrying into a module procurement conversation.

Can you show me the test reports for the exact bill of materials I am buying, rather than the model family as a whole?

The reason it matters is traceability. MNRE's revised 2025 series-approval guidelines state that when there is a change in the BOM within a product family, the applicable retesting requirements are to be followed; the guidelines refer to IS/IEC 62915:2023 for BOM changes or process modifications. This does not mean every change carries the same retest scope. It does mean that the construction being supplied should be traceable to the applicable certification and test records.

A manufacturer with clear material and process controls should be able to explain its bill-of-materials traceability and identify which certification or test records apply to the supplied construction. Where that relationship is not clear, procurement teams can ask for supporting documentation before relying on a model-family certificate alone.

It is a simple question, but it can make supplier evaluation more evidence-based.

Source context

1. Bureau of Indian Standards (BIS), IS 14286 (Part 2):2023 / IEC 61215-2:2021, Terrestrial Photovoltaic (PV) Modules - Design Qualification and Type Approval - Part 2: Test Procedures. BIS source

2. Bureau of Indian Standards (BIS), Scheme II Registration Scheme - Solar photovoltaic modules listed under compulsory registration against IS 14286 and IS/IEC 61730. BIS source

3. Ministry of New and Renewable Energy (MNRE), Revised Guidelines for Series Approval of SPV Modules for implementation of the Solar Systems, Devices and Components Goods Order, 2025, dated 19 December 2025. MNRE source

4. National Institute of Solar Energy (NISE), Testing of Solar PV Modules - NABL-accredited testing facility and listed module qualification/characterisation tests. NISE source

5. National Centre for Photovoltaic Research and Education (NCPRE), IIT Bombay, Insights from Combined All-India Surveys of PV Reliability: 2014, 2016 and 2018. NCPRE source

6. NCPRE, IIT Bombay, PV Systems Testing and Characterization - system performance factors and monitored weather/module parameters. NCPRE source

7. National Institute of Solar Energy (NISE), Publications - including Wind Effect Modeling and Analysis for Estimation of Photovoltaic Module Temperature and studies on PV performance/degradation under different climatic conditions. NISE source