How to Assess Solar Module Transport and Logistics: Why Transport Cracks Are Invisible Without EL or Lock-in Thermography (IEA PVPS), the IEC 62759-1:2022 Package-Unit Transport Test and Its 2026 Chinese Adoption GB/T 46989.1-2025, One Manufacturer's Handling Limits (Two-Layer Stacking, Forklift ≤5 km/h, RH <85%, −40°C to 50°C) and What ICC Explains About FCA, CIF/CIP Insurance Levels and DPU

Short answer. Some of the damage in module logistics cannot be seen. IEA PVPS Task 13 calls transport and installation 'the first critical stages in a PV module's life': glass may break, but cells in the laminate may also crack from vibration and shock, and such cell breakage is invisible and often not detectable by a power rating right after it happens — only electroluminescence (EL) or lock-in thermography reveals it. Its 2025 report adds that the micro-cracks laser cutting leaves at half-cell edges 'frequently grow into dendritic cracks during transportation and installation', and shows a batch with cracks on arrival that the factory's final EL did not see. The test standard for the package is IEC 62759-1:2022, which simulates transport of complete package units and now carries pass/fail criteria; China adopted it identically (等同采用) as GB/T 46989.1-2025, effective 1 April 2026. Manufacturers add their own handling limits — Trina's Vertex manual, for example, bars stacking portrait packages, caps forklift speed at 5 km/h and sets storage at RH below 85% and −40°C to 50°C — and states that not following them invalidates the limited warranty. ICC's Incoterms 2020 page explains the FCA on-board bill of lading option, the CIF (Institute Cargo Clauses C by default) versus CIP (Clauses A) insurance levels and the DAP/DPU unloading distinction. CNWattHub reading: because the cracks are invisible, the evidence each party holds at handover matters as much as the contract terms.

1. What transport does to a module

The 2014 IEA PVPS review lists the typical situations that crack cells without breaking glass: a module falling over; an insufficiently rigid pallet touching the lowest module in the stack; too-tight transport corners, so that during de-stacking the second module is lifted and drops; someone stepping on a module; and, 'even in well-designed transport containers', cracking during 'normal' transport — the case in which it is 'especially difficult to decide who is responsible'. The same report notes that IEC 61215/61646 type-approval mechanical load testing (test 10.16) considered only static loads, while real mechanical stress comes from transport, wind and thermo-mechanical loads. In its resonance measurements, resonances of 18 individual modules fell between 5.5 Hz and 18 Hz, and a sinusoidal resonance search at 1g induced an 8% power loss in one module; separately, its shipping-stack transport simulation was adapted from ASTM D 4169/4728 (truck PSD spectrum, assurance level II, gRMS = 0.52g, 180 minutes).

The 2025 report brings this to today's cut-cell, multi-wire modules. Laser cutting into halves or thirds introduces micro-cracks at the cut edge; these are ignored at production but frequently grow into dendritic cracks in transit and installation. For multi-wire PERC half-cells the cited loss is about 0.2% per dendritic-cracked half-cell, so about 25 such cells are needed for a 5% module loss — a low per-cell impact; the report's example batch was found by EL inspection on arrival.

CNWattHub reading: this is why an arrival EL sample is the evidence a transport claim will need, and why the sample should be agreed before shipment — even though, as the 2014 report says, responsibility for cracks in 'normal' transport remains especially hard to decide.

2. The package test: IEC 62759-1:2022 and GB/T 46989.1-2025

IEC 62759-1:2022 'describes methods for the simulation of transportation of complete package units of modules and combined subsequent environmental impacts'. The second edition replaced the 2015 edition and, among its changes, removed the requirement of at least 10 modules per shipping unit, added stabilisation as an intermediate measurement, added pass/fail criteria, changed the retest requirements and changed the number of cycles in the dynamic mechanical load test.

China has adopted it identically (等同采用). GB/T 46989.1-2025 光伏组件 运输试验 第1部分：组件包装单元的运输和装卸 was published 2025-12-31 and takes effect 2026-04-01; the national standards platform records it as identically adopting IEC 62759-1:2022, under TC90 with MIIT (electronics) as competent department, with drafters including Risen, CESI, CQC, Jinko, SPIC Huanghe, 常熟阿特斯 and Jianheng. Only the abstract and the records were read for this guide; the test levels themselves were not read.

CNWattHub reading: a buyer can now ask a Chinese supplier for a GB/T 46989.1 or IEC 62759-1 test report on the actual package configuration shipped, and the pass/fail criteria give the report a result rather than a description.

3. What a manufacturer's handling rules look like

A manufacturer's manual is not a standard, but Trina's, for example, ties its warranty to the manual: the Vertex user manual says it 'is not a warranty document', yet 'failure of the customers to follow the requirements outlined in this User Manual during the handling (including without limitation to packing/unpacking, loading/unloading, transportation, storage, installation…) of the products will result in the invalidity of product's limited warranty'. Its handling section is quoted here as one manufacturer's example; other brands' manuals were not read for this guide and should be read in the same way.

Two of these deserve emphasis for site logistics in particular. The 'no stacking' and 'two layers' limits apply 'in any circumstances', which includes the laydown yard. And the storage rule about rain is two-sided — cover, then uncover to dry — to prevent rain-caused package collapse.

4. Incoterms and insurance: what ICC explains

Check first whether the sales contract uses an Incoterms rule and, if so, which one. ICC's Incoterms 2020 page explains three points that matter for modules shipped from China. First, FCA was revised so that, where goods are sold FCA for carriage by sea and a party or its bank requests an on-board bill of lading, the parties may agree that the buyer instructs the carrier to issue the on-board bill of lading to the seller, who then tenders it to the buyer. Second, all costs of a rule are now listed in article A9/B9 of that rule. Third, insurance: under CIF the Institute Cargo Clauses (C) remain the default level of cover, with the option of agreeing higher cover, while CIP now requires cover compliant with Institute Cargo Clauses (A) or similar. ICC also explains that DAT became Delivered at Place Unloaded (DPU): under DAP the seller does not unload, under DPU the seller does.

CNWattHub reading: because transport cell cracks are invisible at handover (section 1), the practical question for either party is what evidence it has at the point where the goods change hands. A seller delivering FCA at a Chinese port and a buyer receiving DPU at a project site are both better served by an EL sample at the point where risk passes than by a visual inspection of cartons. The Institute Cargo Clauses themselves were not read for this guide; the (C)/(A) distinction is as ICC describes it.

5. A review sequence

1. Ask for the package-unit transport test report (IEC 62759-1:2022 or GB/T 46989.1-2025) for the package configuration actually shipped; check that it has a pass/fail result.
2. Read the manufacturer's handling and storage requirements and the warranty clause that refers to them; write the same limits into the EPC's and freight forwarder's scopes.
3. Fix the Incoterms rule and the insurance clause (C or A) in the contract, and note where unloading sits (DAP vs DPU).
4. Agree an arrival EL sample at the point where risk passes; cell cracks cannot be seen and in many cases are not detected by a power rating — EL or lock-in thermography reveals them.
5. Record the arrival check the manufacturer asks for — carton condition, type and quantity against the delivery order — on the day of delivery.
6. Plan the laydown yard to the storage limits (ground slope, humidity, rain cover, drainage) and the stacking limits.

Scope limits

This guide cites two IEA PVPS reports, two standard records (IEC abstract and the Chinese adoption record), one manufacturer's manual and ICC's explanatory page. It does not quote the text of IEC 62759-1, GB/T 46989.1, ASTM D4169, the Incoterms rules or the Institute Cargo Clauses, and it quotes no freight rate, damage statistic, insurance premium or Chinese customs or export rule. The manufacturer's limits are one company's for one product series and are not transferable to other brands.