How to Choose Poly Solar Modules | Power & Efficiency, Physical Characteristics

Select polycrystalline modules: prioritize power 300W+ (efficiency ≥ 17%), size ≤1.7m²;

Choose anti-PID (IEC 62804), with first-year degradation ≤2% models, to reduce cost and improve efficiency.

Power & Efficiency

Power is the maximum output of a module under Standard Test Conditions (STC: 1000W/m² irradiance, 25°C cell temperature) in watts (W), such as mainstream PERC modules reaching 540-600W.

Efficiency is the percentage of light energy converted into electrical energy (%), calculated as (Power / Illuminated Area) × 100%.

Current TOPCon efficiency is 22-23%, HJT is 23-24%.

Choose high power (to reduce system cost) if space is sufficient; choose high efficiency (to increase generation per unit area) if space is tight.

Also consider the temperature coefficient (-0.3%/°C compared to -0.4%/°C means 7.5% less loss in high temperatures).

Power

How is the power number derived?

Power (Pmax) is the maximum output of a module under Standard Test Conditions (STC), which includes three strict criteria: irradiance 1,000W/m² (simulating noon equatorial sunlight), cell temperature 25°C (laboratory constant temperature), and AM1.5 spectrum (typical sunlight composition at Earth's surface).

During testing, a solar simulator irradiates the module, and the peak of the voltage-current curve is recorded.

The corresponding power value is the rated power, in watts (W).

For example, the SunPower Maxeon 6 module is rated at 440W, meaning it can output that much electricity under this test condition.

Manufacturers specify a power tolerance, commonly ±3%. Q Cells' "positive tolerance" modules promise actual power ≥ rated value (e.g., a 550W module outputs at least 533.5W), while some low-cost modules may have negative tolerance, meaning actual power is lower.

A 2023 NREL (USA) spot check found that among negative-tolerance modules, 5% had actual power at least 5% lower than the rated value, directly impacting installed capacity.

Power ceilings for different cell technologies

Current mainstream technology paths overseas show clear power differences:

l PERC (Passivated Emitter and Rear Cell): JinkoSolar Tiger Pro uses 182mm wafers, power 540-560W; Trina Solar Vertex uses 210mm wafers, power 580-600W (2024 new product).

l TOPCon (Tunnel Oxide Passivated Contact): LONGi Hi-MO 7 uses 182mm wafers, power 570-590W; JA Solar DeepBlue 4.0 uses 210mm wafers, power 595W (lab data).

l HJT (Heterojunction): REC Alpha Pure-R uses 166mm wafers, power 430W; Meyer Burger Glass-Glass modules use 210mm wafers, power 480W (2024 mass production target).

l IBC (Interdigitated Back Contact): SunPower Maxeon 7 uses 166mm wafers, power 440W, with high efficiency of 24.1% but relatively low power.

Wafer size is a key variable: a 210mm wafer is 25% larger in area than a 182mm wafer, theoretically allowing more cells to be placed.

For example, Trina's 210 module uses 132 half-cells, power 580W;

The same brand's 182 module uses 144 half-cells, power 540W, a 40W difference.

Higher Power ≠ More Modules Can Be Installed

Take a 10m² rooftop as an example (assuming module width 1m):

l 540W PERC module (size 2.27m × 1.13m, area 2.57m²): 3 pieces can be installed on 10m² (7.71m²), total power 1620W.

l 580W TOPCon module (size 2.38m × 1.18m, area 2.81m²): Only 3 pieces can be installed on 10m² (8.43m², exceeding by 0.43m²), total power 1740W, but it must be confirmed if the roof edge can accommodate it.

Measured data from a residential project in California, USA: 10 households using 210 modules (580W) averaged 19.2kW installed capacity;

10 households using 182 modules (540W) averaged 20.1kW, as the latter could fit 1-2 more modules.

Power Discounts in Hot Weather

The module operating temperature is much higher than 25°C. Power decreases linearly as temperature rises. The temperature coefficient (%/°C) determines the magnitude of the drop. Measured data from overseas high-temperature regions (NREL 2024):

l PERC: Temperature coefficient -0.34%/°C. Power at 50°C = Rated Power × (1 - 0.34% × 25) = Rated Power × 91.5%. For a 550W module, that's 503W.

l TOPCon: -0.29%/°C. Power at 50°C = 550W × 92.75% = 510W.

l HJT: -0.25%/°C. Power at 50°C = 550W × 93.75% = 516W.

In Florida, USA, module surface temperature often reaches 55°C in summer.

HJT modules generate about 5% more electricity than PERC.

Power Must Team Up with the Inverter

Total module power must match inverter capacity. The DC/AC ratio (Total Module Power / Inverter Power) is typically 1.1-1.2. For example, for a 10kW inverter, pair with 11-12kW of modules:

l Using 540W modules: Need 21 pieces (11,340W, ratio 1.13), just right.

l Using 580W modules: Need 20 pieces (11,600W, ratio 1.16), also suitable. But if using 600W modules (210mm TOPCon new product), only 19 pieces are needed (11,400W, ratio 1.14). Fewer modules but each is more expensive, potentially increasing total cost.

SolarEdge recommends: For high-power modules (>550W), the DC/AC ratio should not exceed 1.15 to avoid inverter overload clipping (when exceeding 1.2, excess power cannot be converted).

Will Power Drop Over Time?

Module power degrades over time. First-year degradation (LID) and long-term degradation (LeTID) affect long-term output. Overseas third-party testing (PVEL 2023):

l PERC: First-year degradation 2.5-3%, then 0.5% annually, remaining 80.5% after 25 years.

l TOPCon: First-year degradation 1.5-2%, then 0.45% annually, remaining 82.75% after 25 years.

l HJT: First-year degradation 1-1.5%, then 0.4% annually, remaining 84% after 25 years.

JinkoSolar Tiger Pro modules (540W) installed in 2020 measured an average power of 525W in 2023 (2.8% degradation), consistent with PERC first-year degradation expectations;

LONGi Hi-MO 6 (580W TOPCon) installed in 2021 measured 565W in 2023.

Efficiency

How is efficiency actually calculated?

The formula is simple: (Maximum Output Power ÷ Module Illuminated Area) × 100%. For example, a module with 400W power and 2m² illuminated area has an efficiency of 20% (400÷2000×100%).

For instance, the SunPower Maxeon 6 module, with glass dimensions inside the frame of 2.27m long and 1.13m wide, area 2.57m², rated power 440W. Is its efficiency 17.1%?

No, it actually uses back-contact technology with no front busbars shading, giving it a larger effective area. Measured efficiency is 22.8%.

Note that the power used in the calculation is under Standard Test Conditions (STC), not the actual generation power.

For example, the REC Alpha Pure-R module has 430W power under STC, area 1.95m², efficiency 22.1%;

But in summer when module temperature rises to 50°C, power drops to 390W, yet the efficiency is still calculated as 22.1% based on STC power.

Where do the efficiency differences between technologies lie?

Mainstream overseas technologies show clear efficiency tiers. Data from 2024 PV Magazine reviews and manufacturer datasheets:

l PERC (Passivated Emitter and Rear Cell): Base models 20-21% efficiency. E.g., Q Cells Q. PEAK DUO 425W module, area 2.01m², efficiency 21.1%; upgraded models with multi-busbar (MBB) reach 21.5% (e.g., Canadian Solar HiKu6).

l TOPCon (Tunnel Oxide Passivated Contact): Rear passivation layer reduces electron recombination, efficiency 22-23%. LONGi (overseas version) Hi-MO 7 module, 585W, area 2.57m², efficiency 22.8%; JA Solar DeepBlue 4.0 using 210mm wafers, efficiency 23.1% (lab data).

l HJT (Heterojunction): Amorphous silicon layers + low-temperature silver paste, less carrier loss, efficiency 23-24%. REC Alpha Pure-R (made in Norway) efficiency 23.3%, Meyer Burger (Swiss) Glass-Glass module efficiency 23.5% (2024 mass production).

l IBC (Interdigitated Back Contact): Both positive and negative electrodes on the back, no shading on the front, highest efficiency. SunPower (USA) Maxeon 7 module, 440W, area 1.95m², efficiency 24.1% (current mass-production ceiling).

Do higher efficiency modules really generate more electricity?

Using measured data from European residential rooftops (Fraunhofer ISE 2023):

1. Scenario 1: 10m² south-facing roof (no shading), using 20% efficiency modules (400W power, 2m² area), can install 5 pieces (10m²), total power 2000W, annual generation 2,800kWh (based on German annual irradiance 1,100kWh/m²).

2. Scenario 2: Switching to 22% efficiency modules (440W power, 2m² area), same 10m² installs 5 pieces, total power 2,200W, annual generation 3,080kWh, 280kWh more (+10%).

3. Scenario 3: Roof only 8m², 20% efficiency modules install 4 pieces (8m²), total power 1600W; 22% efficiency modules also install 4 pieces on 8m², total power 1760W, annual generation 2,464kWh vs 2,240kWh, 224kWh more.

Measured in Tokyo suburbs, Japan (10 small roofs, average 8.5m²): Using 23% efficiency HJT modules (e.g., REC Alpha) compared to 21% efficiency PERC modules resulted in 300-350kWh more generation per household annually, equivalent to 25 kWh more per month.

Which details quietly drag down efficiency?

Efficiency isn't fixed; encapsulation, installation, and environment can all reduce it:

l Encapsulant material transmittance: Ordinary glass transmittance 91%, anti-reflective coated glass (e.g., used by SunPower) increases to 94%, directly boosting efficiency by 3% (440W module becomes 453W).

l Cell spacing: There's a 2-3mm gap between cells within a module. Larger gaps mean lower efficiency. Shingled technology (e.g., Panasonic EverVolt) overlaps cells by 1mm, almost eliminating gaps, making efficiency 1.5% higher than conventional modules.

l Temperature effect: Module efficiency decreases by 0.05% (PERC) to 0.03% (HJT) per 1°C temperature rise. In Arizona, USA, summer module temperature is 60°C, HJT module efficiency is 1.2% higher than PERC (23.3% vs 22.1%) due to its lower temperature coefficient (-0.25%/°C vs -0.34%/°C).

l Dust shading: Measured in arid California, 1mm thick dust on module surface reduces efficiency by 8-10% (sunlight blocked, conversion ratio unchanged but input light energy is less).

Overseas Measurements:

US NREL 2024 comparison:

How high can efficiency go in the future?

Lab data gives the upper limit: Perovskite-silicon tandem cell efficiency 33.7% (NREL 2023 record), but mass production is still far off.

Short-term, TOPCon efficiency is expected to reach 24% by 2025, HJT 25% (Meyer Burger roadmap).

Overseas manufacturers are already piloting production of busbar-less (SMBB) modules, using thinner ribbons to reduce shading, potentially adding 0.5-1% efficiency.

For example, SunPower is testing Maxeon 8, targeting 25% efficiency, using 210mm wafers + back contact, power possibly reaching 500W (area 2.5m²).

Physical Characteristics

Mainstream 60-cell modules are approximately 1.6m×1m (power 350-450W), 72-cell approximately 2m×1m (450-600W).

Single-glass weight 18-22kg/m², double-glass 22-26kg/m².

Must meet IEC 61,215 mechanical load standards (front ≥5400Pa snow load, rear ≥2400Pa wind suction), glass transmittance >91% (3.2mm ultra-clear tempered), IP65 protection rating (junction box IP67/IP68), materials include POE/EVA encapsulant (POE better for PID resistance), aluminum alloy frame (with grounding holes).

Dimensions and Layout

How to calculate module size to avoid wasting roof space?

Overseas residential roofs often have clear heights of 2.2-2.5 meters, commercial roofs over 3 meters. Module dimensions must meet:

l 60-cell modules: Length 1.63-1.68m (64-66 inches), width 0.98-1.01m (38.5-40 inches), thickness 3-4cm (1.2-1.6 inches), power 365-385W, power per unit area 220-235W/m².

l 72-cell modules: Length 1.95-2.01m (77-79 inches), width same as 60-cell, power 435-460W, power per unit area 213-225W/m² (slightly lower due to increased length).

l 78-cell modules: Length 2.17-2.23m (85-88 inches), width 1.01m, power 500-530W, power per unit area 228-242W/m² (highest power density).

Transportation and Handling:

Overseas truck transportation restrictions are strict. Module dimensions must match cargo compartments:

l Standard 53-foot trailer (mainstream in USA): Inner width 2.44m (8 feet), inner height 2.59m (8.5 feet). After loading 2.2m long 78-cell modules, only 12cm clearance remains on each side, prone to scraping during turns.

l European trucks: Common cargo compartment width 2.3m, 2m long modules need to be placed diagonally, reducing single-load capacity by 15%.

l Handling clearance: Stair landing width must be ≥1.83m (6 feet). 2m long modules need to be tilted 45 degrees to pass, increasing labor cost.

Data: A US installer statistics show 78-cell modules have 0.8% higher transport breakage rate than 60-cell due to oversize causing instability.

Racking and Spacing:

Module length and width determine racking span and inter-row spacing:

l Racking span: For 60-cell modules (1.65m long), racking span can be 1.2m; 72-cell (2m long) needs to be reduced to 1m, otherwise mid-span sag exceeds 5mm (IEC maximum allowed).

l Shading spacing: Distance between front and rear rows must prevent shading on the winter solstice. Formula: Spacing = Module Height × cot (Local Winter Solstice Noon Sun Elevation Angle). Example: Los Angeles, California (latitude 34°), winter solstice sun elevation angle 31°, spacing for 2m high module = 2 × cot (31°) ≈ 3.3m (actual distance needs plus 0.5m safety margin).

l Edge margin: Roof edges need 30-50cm (12-20 inches) safety distance to prevent wind uplift.

Case: A ground-mounted system in Florida using 2m long modules, arranged with 3.5m spacing, occupies 15% more land than 1.65m modules, but total power increases by 12%.

Layout Variations:

Layout isn't just about cell count; cutting methods and frame design also alter dimensions:

l Half-cut modules: Cells cut in half and connected in series, dimensions slightly smaller than conventional (e.g., 60 half-cells length 1.58m, width 0.98m), same power (365W), but hot-spot risk reduced by 40%.

l Shingled modules: Cells overlapped, dimensions reduced by 5% (e.g., 60-cell shingled length 1.55m), power increased by 5% (380W), but requires replacing the whole string for repair.

l Narrow frame design: Frame width reduced from 40mm to 30mm, 60-cell module width reduced by 4cm, allowing one more piece per row (when roof width limits to 3m, conventional fits 3 pieces, narrow frame fits 4).

Special Scenarios:

l Curved roofs (e.g., silos): Use thin-film modules (length 1.2m, width 0.6m, thickness 0.3cm), can bend to fit curvature, power 80-100W, saving 30% space compared to crystalline silicon modules.

l Balcony mounting: Choose micro-modules (length 0.8m, width 0.5m, power 120W), weight only 8kg/m², suitable for small urban apartment spaces.

l High-latitude regions (e.g., Canada): Use short modules (1.5m long) + high-tilt racks (45 degrees), reduce winter shading, generate 5% more power than long modules.

Weight

How is module weight calculated:

First look at weight per unit area (kg/m²), then multiply by module area to get weight per piece. Corresponding table for overseas mainstream module dimensions and weights:

l Single-glass module (1 glass + backsheet): 18-22kg/m². Example: 60-cell conventional module (1.65m long × 0.99m wide = 1.63m²), at 20kg/m², single piece weight 1.63×20=32.6kg; 72-cell module (2.0m×0.99m=1.98m²), weight 1.98×22=43.6kg.

l Double-glass module (2 glass, no backsheet): 22-26kg/m². Same size 60-cell module weight 1.63×24=39.1kg, 72-cell weight 1.98×26=51.5kg.

l Thin-film module (flexible substrate): 8-12kg/m². Example: 1.2m×0.6m micro-module (0.72m²), weight 0.72×10=7.2kg.

Where do different materials differ?

Materials determine the lower weight limit, and structural tweaks can also reduce weight:

l Single-glass vs. Double-glass: Double-glass uses an extra 3.2mm glass (single-glass backsheet only 0.3mm thick), increasing weight by 4-6kg per m². But double-glass has 5-8 years longer lifespan (no backsheet aging), suitable for high-humidity/salt-spray areas (e.g., Florida USA, North Sea coast Europe).

l Lightweight modules: Use thin glass (2.5mm) or composite frames, 16-18kg/m². Example: A brand's half-cut lightweight module (1.58m×0.98m=1.55m²), weight 1.55×17=26.4kg, 6kg lighter than conventional single-glass, suitable for old roofs.

l IBC/N-type modules: Due to complex cell structure, thicker frames, 2-3kg heavier per m² than PERC single-glass (e.g., 22 kg/m² vs 20kg/m², but 5% higher efficiency, power density compensates for weight difference.

Can the roof bear the load?

Load-bearing standards for overseas buildings of different ages:

l New residential (post-2000): Roof live load (including snow, wind, modules) typically ≥30kg/m², can bear single-glass (20kg/m²) or double-glass (24kg/m²) modules.

l Old residential (pre-1980): Mostly wood frame or early steel structures, live load limited to 20-30kg/m². Example: A 1950 farmhouse roof in the US Midwest originally designed for 25kg/m². After installing double-glass modules (24kg/m²), remaining margin only 1kg/m², requiring structural engineer to reinforce beams.

l Commercial roof (flat roof): Concrete structure bearing ≥40 kg/m², can safely use double-glass or large-size modules (78-cell weighing 51.5 kg/piece).

Risk case: 2021, a warehouse roof in Germany (built 1985, load-bearing 28kg/m²) installed with double-glass modules (24kg/m²), plus snow load (30kg/m²) totaling 54kg/m², causing partial collapse, losses ~€120k for modules + goods.

Don't overload during transport:

Weight directly impacts transportation cost and feasibility. Overseas logistics have strict limits:

l Road transport: US 53-foot trailer (mainstream) weight limit ~20 tons (including vehicle weight), European truck limit 18 tons. Example: Single double-glass piece weighs 39 kg, 20-ton trailer theoretically holds 512 pieces, but limited by dimensions (2m long modules take space), can only fit 300 pieces (11.7 tons), leaving 8.3 tons for racks/accessories.

l Sea container shipping: 20ft container weight limit 21 tons, 40ft container limit 26 tons. Shipping double-glass modules, a 40ft container can hold max 650 pieces (39kg×650=25.35 tons), overweight requires splitting into 2 containers, increasing freight cost 50%.

l Breakage rate correlation: Modules >45kg (e.g., 72-cell double-glass) have 2x higher risk of frame deformation during transport bumps (according to 2022 data from Dutch logistics company DHL).

Is it strenuous to handle?

Manual handling weight during installation determines labor hours and cost. Overseas installer standards:

l Single-person handling: Upper limit 20kg (e.g., thin-film 7kg, half-cut lightweight 26kg requires 2 people). Example: US NREL survey shows, 25 kg modules take 3 min/piece for one person, 35 kg modules require 2 people, increasing time 40%.

l Roof access: Sloped roof stair landing width ≥1.2m, 2m long module (43kg) needs 45-degree tilt to pass. Narrow roofs (e.g., attic) can only use 1.65m modules (32kg).

l Assistive tools: For weight >40 kg, use roof crane (rental $50/day), saves 60% time compared to manual lifting (California installer case).

Relationship between weight and wind/snow load resistance:

Weight affects mechanical load capacity, but must be combined with frame design:

l IEC 61215 test: Modules must withstand front 5400Pa (1.3m snow), rear 2400Pa (150km/h wind suction). Double-glass modules, due to double glass + thick frame (≥1.2mm Al), have 10% higher load capacity than single-glass (e.g., front 6000Pa vs 5400Pa).

l Wind load scenario: Coastal areas (e.g., Sydney, Australia) high wind suction, choose heavy modules (double-glass 43kg) + ballast fixation, more wind uplift resistant than light modules (single-glass 32kg); but in high wind zones (e.g., US Tornado Alley) use lighter modules to reduce wind resistance.

l Snow load scenario: Northern Europe (Sweden) snow depth 2m, double-glass modules (43 kg) have better snow load resistance, snow slides 30% slower (at snow density 200 kg/m³).

How to choose in special situations:

l Old houses/historic buildings: Load limit 20kg/m², choose thin-film (8kg/m²) or half-cut lightweight (16kg/m²), sacrificing 5% power for safety.

l Mobile PV (RV/boat): Use thin-film modules (7kg/piece), total weight <50kg, not exceeding vehicle/vessel structure limits.

l High-power ground-mounted systems: Choose double-glass large-size (78-cell 51.5kg/piece), heavy but 232W/m² power density (8% higher than single-glass), amortizing land cost.

Material Composition

Glass Cover:

Mainstream overseas uses 3.2mm ultra-clear tempered glass, transmittance >91% (ordinary glass only 89%), that extra 2% can increase annual generation by 2-3%.

Surface coated with anti-reflective coating (silicon dioxide + silicon nitride), further increasing transmittance to 93%, equivalent to adding a small module.

Thickness isn't always better: 3.2mm is the sweet spot—thinner than 2.5mm (used in lightweight modules), hail resistance drops 30% (25mm ice ball impact prone to cracking);

thicker than 4mm, weight increases 25%, putting more pressure on roof load.

Test data: 3.2mm glass passes IEC hail test (23m/s impact) 98% success rate, 2.5mm only 85%.

Example: A system in Arizona, USA used 2.5mm glass, 3 panels cracked in 5 years due to sand impact; after switching to 3.2mm, zero breakage.

Encapsulant Film:

Encapsulant wraps the cells, preventing moisture and oxidation. Divided into EVA and POE.

l EVA (Ethylene-Vinyl Acetate): Cheap, occupies 70% market share. But moisture vapor transmission rate (MVTR) 0.3-0.5g/m²/day. In high humidity areas (e.g., Florida) after 10 years, encapsulant absorbs water → cell corrosion, power degradation 8% more than POE. After 5 years of UV exposure, yellowing rate 15% (transmittance drops below 85%).

l POE (Polyolefin Elastomer): 20-30% more expensive, MVTR <0.1g/m²/day (60% lower than EVA), anti-PID (Potential Induced Degradation) performance 30%+ higher. A coastal power plant in Norway using POE maintained 88% power after 15 years, while EVA modules in the same period only 75%.

Detail: POE remains flexible at -40°C low temperatures (EVA becomes brittle), less prone to cracking in Nordic winters.

But POE has poorer flow, requiring lamination temperature 145°C (EVA 135°C), slightly higher energy consumption.

Frame:

The frame is the module's skeleton, aluminum alloy, thickness ≥1.2mm (mainstream 1.5mm). Anodized layer thickness 10-15μm (too thin prone to corrosion, too thick high cost).

l Weight proportion: Frame accounts for ~15% of single-glass module weight (e.g., 32kg module, frame weight 4.8kg).

l Deformation resistance: 1.2mm thick frame, deformation probability 5% after transport bumps; if <1.0mm, probability doubles (2022 data from a Dutch logistics company).

l Grounding design: Frame must have M8 grounding hole, grounding resistance <0.1Ω (UL 1703 standard), preventing lightning strike or leakage.

Case: An Australian project used 1.0mm frames; after strong winds, 12 module frames deformed, cell micro-cracks, 15% power loss.

Backsheet:

Mainstream TPT/TPE composite fluoropolymer film (outer PVF + middle PET + inner PVF), thickness 25-30μm.

l Weather resistance: After 1000 hours UV aging (simulating 10 years outdoors), tensile strength retention >80% (inferior backsheet <50%).

l Moisture barrier: MVTR <0.5g/m²/day (better than EVA encapsulant), but lifespan 5-8 years shorter than double-glass module backsheet (glass).

l Risk point: Backsheet cracking often due to edge sealant failure. A German brand had a 3% backsheet cracking rate in 3 years, causing water ingress and 25% power degradation.

Cells:

Cell material determines efficiency and cost:

l Monocrystalline Silicon (P-type/PERC): Wafer thickness 180-200μm, surface pyramid texture (increased light absorption), efficiency 22-24%. Silver paste usage 80-100mg/cell (15% of cell cost).

l Polycrystalline Silicon: Wafer thickness 200-220μm, blue granular surface (more impurities), efficiency 19-21%, silver paste usage 10% less, but temperature coefficient higher 0.45%/°C (monocrystalline 0.38%/°C, power drops faster in high temperatures).

l N-type (TOPCon/IBC): Thinner wafers (160-180μm), doped with phosphorus, efficiency 24-26%, but silver paste usage 5% more (IBC structure requires double-sided printing).

l Thin-film (CIGS/CdTe): Material thickness 3-5μm (50x thinner than crystalline silicon), flexible substrate (stainless steel/plastic), efficiency 16-18%, suitable for curved surfaces but faster degradation (1.5% annually vs. crystalline silicon 0.5%).

Junction Box:

The junction box houses diodes (prevent reverse current) at the cable exit. Material details affect safety and lifespan:

l Protection rating: IP67 (water immersion resistant)/IP68 (high-pressure water jet resistant). Inferior boxes IP65, prone to water ingress and short circuit in rain.

l Connector: MC4 compatible (global standard), contact resistance <0.5mΩ (poor contact causes heating, 10°C temperature rise halves lifespan).

l Cable specification: 4mm² cross-section for ≤15A current (500W module), 6mm² for ≤20A (700W module). Thin cables overheat (a case: 4mm² cable used on 600W module, cable sheath melted after 3 years).

l Heat dissipation design: Use thermal conductive silicone pad inside box (thermal conductivity 1.5W/m·K), temperature 10°C lower than ordinary plastic boxes (NREL test), diode lifespan increased 3 years.

Material composition is the module's DNA. 1% lower glass transmittance, 0.2g higher encapsulant MVTR, 0.2mm thinner frame, and power after 25 years could differ by 20%.

Overseas installers choose materials based on data: POE encapsulant's 0.1g MVTR, 1.5mm frame thickness, 3.2mm glass transmittance.

Environmental Tolerance

Can it withstand hail impacts?

Hail test uses IEC 61,215 standard: 25mm diameter ice ball (about golf ball size), impacts glass center at 23m/s (≈90km/h) vertically; passes if no cracks.

l Glass thickness effect: 3.2mm ultra-clear tempered glass pass rate 98% (UL USA data), 2.5mm lightweight glass only 85% (weaker impact resistance).

l Double-glass advantage: Double-sided glass cushions hail impact, 20% more resistant than single-glass. Case: A Midwest US farm used 3.2mm double-glass modules, zero breakage after 3 hailstorms in 5 years (largest 30mm); neighboring single-glass modules cracked 4 pieces in 2 years.

l Extreme test: Swiss manufacturer tested 35mm ice ball (≈tennis ball) impact, 3.2mm glass only micro-cracked at edges, still generating power (5% power loss).

Will salt spray at the seaside corrode the frame?

Salt spray test per UL 1703: Spray with 5% sodium chloride (NaCl) solution for 96 hours (simulating 3 years coastal salt spray), fails if frame/connector corrodes or coating peels.

l Frame material data: Anodized aluminum frame (15μm oxide layer) corrosion rate <0.1mg/cm² (almost no change); inferior frame (5μm oxide) >0.5mg/cm² (perforates in 3 years).

l Double-glass vs. Single-glass: Double-glass has no backsheet, frame directly exposed to salt spray, requires 316 stainless steel screws (3x more corrosion resistant than 304 stainless); single-glass backsheet (TPT fluoropolymer) blocks some salt spray, but edge sealant prone to aging and salt seepage after 5 years.

l Case: 10MW plant on Norwegian coast, double-glass modules with thick frames, no frame corrosion after 10 years; single-glass modules had backsheet edge blistering after 5 years, 12% power degradation.

Will ammonia from farms degrade it over time?

Ammonia test uses IEC 61701: Modules exposed to 40ppm ammonia (common near pig farms/fertilizer plants) for 96 hours; fails if delamination, discoloration, or >5% power drop occurs.

l Encapsulant difference: POE encapsulant ammonia permeability <0.05g/m²/day (almost impermeable), EVA >0.2g/m²/day (prone to delamination after 10 years of ammonia absorption).

l Backsheet risk: Single-glass module backsheet (PET based) prone to hydrolysis with ammonia, tensile strength drops from 150MPa to 80MPa (Danish pig farm measured data).

l Case: Danish pig farm used POE double-glass modules, no delamination after 8 years; adjacent EVA single-glass modules had backsheet blistering after 5 years, disassembly revealed yellowed, brittle encapsulant.

Will thermal cycling crack the materials?

High-low temperature cycling test per IEC 61215: Cycle from -40°C (simulating Arctic winter night) to +85°C (desert noon) 200 times (≈10 years seasonal temperature swings), no material cracking or delamination.

l Material expansion coefficient: Glass (9×10⁻⁶/°C) and EVA encapsulant (200×10⁻⁶/°C) have large expansion difference, prone to delamination after cycling; POE encapsulant (80×10⁻⁶/°C) closer to glass, 60% lower delamination rate.

l Double-glass advantage: Glass-glass sealing expands/contracts synchronously, no stress cracking after cycling; single-glass backsheet (PET, 20×10⁻⁶/°C) differs greatly from glass, 15% backsheet edge cracking rate after 5 years of cycling.

l Case: Alberta, Canada (-30°C to +30°C), double-glass modules no delamination after 15 years; single-glass modules had backsheet separation from glass after 7 years, 18% power drop.

Will glass stay transparent after prolonged sand abrasion?

Sand abrasion test uses ASTM G154: Quartz sand (particle size 0.1-0.3mm) blasted at 35m/s (≈130km/h) for 100 hours (simulating 10 years desert sand), passes if glass transmittance reduction <2%.

l Importance of coating: Glass without anti-reflective coating, transmittance drops from 91% to 85% after sand (6% drop); coated glass only drops 1.5% (remains 89.5%).

l Frame gap: When gap between frame and glass >0.5mm, sand particles easily embed, tripling the probability of glass scratching (Saudi desert plant measurement).

l Case: Australian desert plant used coated glass + seamless frame, transmittance remained 90% after 10 years; uncoated modules dropped to 82% after 5 years, 7% less annual generation.

Will encapsulant yellow after prolonged UV exposure?

UV aging test uses IEC 61345: Xenon lamp simulates UV (wavelength 280-400nm) for 1,000 hours (≈10 years outdoors), passes if encapsulant yellowing rate <5%.

l EVA vs POE: EVA encapsulant yellowing rate 15% (transmittance drops from 91% to 86%), POE <3% (remains above 90%).

l Temperature overlay: High temperature (>40°C) accelerates UV aging. In Florida (average 25°C, summer 35°C), EVA yellowing rate 20% in 5 years, POE only 5%.

l Case: Arizona, USA (strong UV + high temperature), POE modules 92% transmittance after 10 years, EVA modules 86%, 8% difference in annual generation.