Why Choose Polycrystalline Panels | Durability, Performance, Benefits

Polycrystalline silicon modules cost is lower by about 10%-15%, efficiency 15%-18%, weak light power generation is stable.

Suitable for large area roof installation, cleaning once every 3 months can lift power generation amount by 5%-10%, lifespan 25 years above.

Durability

Durable

Standard modules usually adopt a thickness of 3.2 millimeters ultra-white cloth-pattern tempered glass as protection layer. This kind of glass has a Mohs hardness level of 6 to 7 grades, able to withstand diameter 25 millimeters hail at a per second 23 meters initial speed vertical impact while maintaining structural integrity.

In mechanical load tests, polycrystalline modules' forward static load capacity usually reaches 5400 Pascals, which is equivalent to stacking 550 kilograms of snow on per square meter of panel, while back anti-wind pressure capacity also stabilizes at 2400 Pascals above. This physical toughness ensures panels in long as 25-year life cycle inside, able to resist wind speeds as high as 10 grade strong wind attacks. Because polycrystalline silicon ingots are formed in square quartz crucibles through directional solidification, its internal stress distribution is more uniform than pulled monocrystalline, effectively reducing the probability of generating micro-cracks in temperature difference violent fluctuation environments (micro-crack growth rate usually lower than 0.1%).

According to IEC 61,215 international standard test, polycrystalline modules after experiencing 1000 hours of high temperature high humidity (85℃ temperature and 85% relative humidity) cycle, its power loss is usually controlled within 3%. In actual outdoor electricity output monitoring, the first year initial degradation rate is about 2.0% to 2.5%, subsequent annual linear degradation rate then precisely locked at 0.6% to 0.7%. After using 20 years, panels can still maintain 80% above rated output power.

In order to protect circuit safety, module back integrated IP68 grade junction box, internal equipped with 3 above bypass diodes, able to under partial shading produced hot spot effect, rapidly shunt high as 15 Amperes current, control partial temperature rise within 85℃ safety threshold, prevent encapsulation materials due to long-term heating happening yellowing or delamination.

· Pressure resistance: Front maximum supports 5400 Pascals static load, anti-wind pressure 2400 Pascals, frame adopts 35-40mm anodized aluminum.

· Degradation rate: Within 25 years warranty period, power maintenance rate not lower than 80.7%, annual average performance decline about 0.7 percentage points.

· Insulation degree: System highest working voltage supports 1000V or 1500V DC, leakage current test lower than 40 microamperes.

· Environmental endurance: Working temperature range spans minus 40℃ to plus 85℃, salt mist corrosion and ammonia test pass rate 100%.

Its encapsulation material adopts high cross-linking degree EVA (ethylene-vinyl acetate copolymer) adhesive film, peeling strength usually greater than per centimeter 60 Newtons, this guarantees silicon wafer and tempered glass, backplane between tight bonding. Under 1500 Volts system voltage, polycrystalline module anti-PID (potential induced degradation) performance is excellent, in test power fluctuation range is limited within 5%.

In addition, polycrystalline cell surface metal grid lines usually adopt 9BB or 12BB (multi-busbar) technology, which shortens the current on the fine grid transmission path by about 20%, not only improving collection efficiency, but more significantly enhancing cell when receiving external mechanical pressure's conductive stability. Even in extremely harsh near-sea salt mist environment, its backplane moisture permeability is also low as per square meter per day 1.5 grams, passed a long as 96 hours continuous salt mist spray test, ensuring internal circuits not receiving corrosion, maintaining 20% above fill factor stability.

Performance

Power generation stable

Under Standard Test Conditions (STC, namely per square meter 1,000 Watts light, 25℃ environment temperature, AM 1.5 spectrum), currently mainstream polycrystalline modules conversion efficiency stabilizes at 17% to 18.8%. One piece specification as 1640mm×992mm 60-cell polycrystalline module, its peak power output is usually 275 Watts to 290 Watts. This kind of panel is internal by a large amount of irregularly arranged silicon crystals composed, due to the existence of grain boundaries, photons when entering the silicon wafer internally will happen multiple reflections and refractions. This kind of phenomenon is especially obvious at morning or evening sun incident angle large (for example, included angle at 15 degrees to 30 degrees between) time.

Compared to monocrystalline silicon's strong dependence on direct light, polycrystalline silicon panels' absorption rate for oblique light lifted about 2% to 3.5%. This directly caused the whole day power generation curve to be smoother.

In terms of actual power generation gain, polycrystalline silicon cells' short circuit current (Isc) is usually between 8.8 Amperes and 9.3 Amperes, and the open circuit voltage (Voc) maintains at 38 Volts to 39.5 Volts. Its Fill Factor (FF) is an important performance indicator, and high quality polycrystalline panel FF value can reach 76% to 80%, cell output power's actual efficiency is very close to its theoretical upper limit.

Polycrystalline silicon production using boron doping technology makes its initial light-induced degradation (LID) after installation first 100 hours inside only 1.5% around, far lower than part high efficiency monocrystalline cells. This kind of stable electrical characteristics makes polycrystalline systems when matching inverters, able to maintain extremely high maximum power point tracking (MPPT) accuracy, system end electric energy conversion loss usually compressed within 1%.

· Current stability: Working current (Imp) fluctuates between 8.3A-8.7A, current mismatch loss lower than 2%.

· Voltage interval: Maximum power point voltage (Vmp) is about 31V-33V, adapts to absolute majority grid-tied inverters' startup voltage.

· Module efficiency: 156.75mm cells composed of 72-cell module, power can reach 330W, efficiency 17.2% above.

· Low loss process: Adopts 5 busbar (5BB) or 9 busbar (9BB) technology, shortening current transmission path 30% above.

Hot weather not afraid

Most polycrystalline modules' peak power temperature coefficient (Pmax Temperature Coefficient) distributes at -0.38%/℃ to -0.41%/℃. When the panel surface temperature from 25℃ baseline rises to 65℃ (summer roof common temperature), the power decline range is about 15.2% to 16.4%. Comparison experiment data shows, in the same extreme high temperature environment, polycrystalline silicon cells internal hole mobility receiving temperature influence's fluctuation is smaller. Its Nominal Operating Cell Temperature (NOCT) is usually labeled as 45±2℃, under noon strong sunshine, panel internal hot spot formation probability is lower than high density encapsulation modules around 12%. This heat dissipation advantage guarantees modules after continuous running 8 hours, its output voltage offset amount will not exceed 1.5 Volts.

According to IEC standard, after minus 40℃ to plus 85℃ 200 times cycle pressure test, polycrystalline module output power degradation rate is usually smaller than 2.5%. This benefits from polycrystalline silicon wafer and EVA (ethylene-vinyl acetate copolymer) encapsulation material between excellent thermal expansion coefficient matching degree, both expansion difference rate maintains within 0.005%.

In temperature difference violent change areas, such as temperate desert or plateau environments, module internal ribbons due to thermal expansion and contraction caused fatigue fracture risk reduced 18%. At the same time, module backplane heat dissipation efficiency (Heat Dissipation Factor) stabilizes at 30 Watts/square meter·℃, effectively controlling internal working temperature within a safety threshold, extending semiconductor junction's effective life.

Scattered light also okay

Due to polycrystalline silicon wafer surface grains' random orientation, its sensitivity to diffuse radiation (Diffuse Radiation) is extremely high. At irradiance only being 200 Watts/square meter, low light intensity under, polycrystalline cell relative conversion efficiency still can maintain at 95% above, and will not like certain high efficiency modules that way appear cliff-style drop.

In every year, average rainy days exceed 120 days, and polycrystalline systems per Watt annual cumulative power generation (Yield per Watt) can often be equal to high-price systems. Polycrystalline silicon for 380 nanometers to 1100 nanometers wave band spectrum all has good response, especially in the morning from 5 o'clock to 8 o'clock this period, the blue light proportion is higher, its current gain is higher than the theoretical value by about 4%.

In actual observation, one set of 100 kilowatt polycrystalline system in a micro-light environment's startup voltage is usually lower than the rated value by 15% then the inverter can work, this is than monocrystalline system average 15 to 20 minutes earlier enter the power generation state, evening delayed 10 to 15 minutes stop work. Every day, accumulated extra 30 minutes of power generation time, although instantaneous power is lower, but in 25 years of operation, it can contribute extra 2% to 3.8% of total electricity output to investors. In addition, polycrystalline silicon panel surface 3.2 mm tempered glass through acid etching anti-reflection treatment, its light transmittance under weak light can still maintain at 91% above, further ensuring that every incident photon can be effectively converted into an electron flow.

Current smooth

Multi-busbar design shrinks fine grid lines' width to 0.1mm below, this not only reduced shading area by 1.2%, more importantly shortened current's lateral transmission distance by 20% above. On a 156.75mm cell, the current flow path impedance dropped about 15 milliohms, which directly lifted about 1.5 Watts of single piece power output. At the same time, polycrystalline silicon encapsulation loss (CTM Loss) is usually controlled at 1.0% to 1.5% at an extremely low level.

· Low impedance connection: Module internal busbars adopt tin-plated copper strip, contact resistance lower than 0.01 Ohm, reducing heat loss.

· Parallel redundancy: Junction box inside configured 15A or 20A Schottky diodes, when shaded power loss reduces 40%.

· Spectrum adaptation: Sensitive response to infrared wave band, in winter low color temperature environment power generation performance better than expectation.

· Charge collection: Back Surface Field (BSF) technology enhanced minority carrier life, making collection efficiency lift 0.8%.

In long-term current load experiments, module internal electromigration phenomenon (Electromigration) is extremely not obvious, even in continuous 2000 hours 1.5 times rated current impact under, grid lines' falling off rate is also lower than 0.05%. This micro-level conductive stability ensures macro-level whole set photovoltaic system's voltage stability within 0.5%. Polycrystalline modules when merging into a large power grid, its power factor can more easily reach 0.99, reduced demand for grid side reactive power compensation, thereby saving extra power equipment investment.

Benefits

Cost-effective

In the photovoltaic module manufacturing process, polycrystalline silicon adopts the casting method, saving the monocrystalline silicon growth process inside time-consuming and energy-consuming pulling rod procedure. This kind of process flow simplification makes polycrystalline silicon wafer production cost less than monocrystalline silicon wafer reduced by about 20% to 30%. Reflected to the terminal market, polycrystalline module per Watt procurement unit price is usually cheaper than same power grade monocrystalline module, cheap 0.15 dollars to 0.25 dollars.

For one 100-kilowatt (kW) medium-sized industrial and commercial roof project, only module procurement this one expenditure can save out 1.5 thousand to 2.5 thousand US dollars. This saved up initial budget can be flexibly re-allocated, for example, used for buying higher specification grid-tied inverters, or directly expand system installation capacity by 15% around, thereby obtaining higher total power generation.

Financial data quantification: Taking a 500 kilowatt scale distributed power station as an example, choosing polycrystalline panels can make the Balance of System (BOS) cost reduce about 8% to 12%. In the current electricity price subsidy and electricity use cost background, the polycrystalline system static investment recovery period is usually between 4.5 years and 5.8 years, while the monocrystalline system shortened about 10 months capital occupation cycle.

Due to polycrystalline modules' initial investment threshold being low, its Internal Rate of Return (IRR) in many situations can be higher than high-price modules' high out 1.2 to 1.8 percentage points. In the interest expenditure aspect, the total loan amount in the 20-year repayment period inside, interest expenditure can reduce 15% above. For those mainly focusing on Levelized Cost of Energy (LCOE) factory owners, polycrystalline silicon panels provided an extremely robust financial base.

In per degree electricity cost calculation, polycrystalline modules due to depreciation base small, its per degree electricity allocated cost can be low to 0.04 dollars/degree. In this fierce industrial and commercial electricity use environment, enterprises are able to save considerable operation profit, every year electricity bill saving quota can usually reach 22% above the installation cost.

Environmentally friendly

Manufacturing 1 Watt polycrystalline silicon cell's carbon footprint is about 2,500 grams CO2 equivalent, than monocrystalline silicon manufacturing process reduced about 18% carbon emissions. This is mainly because the casting process has the highest heating temperature and duration time far lower than the pulling monocrystalline process, electricity consumption per kilogram of silicon material can save about 15 to 20 degrees electricity.

At the same time, polycrystalline silicon manufacturing for silicon material utilization rate is extremely high, slicing process inside produced waste and scraps proportion lower than 5%, and these scraps can be 100% recycled and re-put into the casting furnace, realizing a closed-loop production. This low energy consumption, high recycling characteristic, makes polycrystalline panel Energy Payback Time (Energy Payback Time) shorten to 1.1 years to 1.3 years, that is to say, panel after installation running less than 16 months, its produced clean electricity just enough to cover its whole manufacturing process consumed energy.

· Silicon material utilization rate: 95% above, casting link almost no raw material waste.

· Unit energy consumption: Producing per Watt module electricity consumption only is 2.3kWh-2.6kWh.

· Carbon footprint: Lower than similar high efficiency modules 15%-20%, easier to pass green certification.

· Recyclability: After decommissioning aluminum frames, glass and silicon wafers recycling rate can reach 90% above.

From a land and space utilization perspective, although the polycrystalline panel unit area efficiency is slightly lower, its production process for water resources consumption is reduced 10% compared to the monocrystalline process. In arid areas, large-scale power station projects, the manufacturing stage ecological pressure is smaller. In panel after decommissioning treatment link, polycrystalline module structure is simple, impurity content is low, makes glass peeling and silicon material purification process cost reduced 12%.

For pursuing Environment, Social and Governance (ESG) indicators, institutional investors, polycrystalline panel lower Embodied Energy (Embodied Energy) is one important data plus point. In the carbon trading market increasingly maturing today, lower manufacturing carbon intensity every one degree electricity behind carbon emission reduction contribution value is higher, in future carbon credit settlement inside, this might convert into per kilowatt hour extra 0.005 to 0.01 dollars indirect revenue.

Easy to take care of

Polycrystalline silicon cell surface blue broken flower texture is not only for beauty, this kind of rough surface cooperating with 3.2mm ultra-white cloth-pattern tempered glass has natural diffuse reflection characteristics. In actual operation, polycrystalline panel surface dust shading for power generation sensitivity is lower than mirror surface modules by about 5%. In the same dust-falling environment, polycrystalline module cleaning frequency can be from every quarter once to every half year once, directly reducing about 30% manual maintenance fees.

In 25 years of operation, only cleaning fees for this one megawatt power station can save down exceeding 1.2 thousand US dollars. In addition, polycrystalline modules due to their internal grains distributed uniformly, for thermal stress bearing capacity is stronger, due to maintenance personnel stepping or improper handling caused micro-crack failure rate long-term maintains below 0.3‰.

Operation and maintenance detail data: Statistics data shows, polycrystalline system non-planned downtime annual average lower than 15 hours. Its matching junction box adopts potting technology, under IP68 grade annual failure rate of only 0.01%, this guaranteed in humidity exceeding 85% coastal or rainforest environment inside, circuit system still can maintain 100 megaOhms above insulation resistance.

In terms of electrical connection stability, polycrystalline modules usually equipped with 4 square millimeters standard photovoltaic cable, length at 1,000 mm to 1,200 mm between, this kind of specification able to withstand high as 30 Amperes short circuit current impact without happening overheating melting. Module internal bypass diodes when the environment temperature reaches 40℃, junction temperature can still be controlled within 75℃, greatly reduced due to Hot Spot effect (Hot Spot) causing panel scrapping risk.

For ordinary users, after installation, the first 10 years, almost no need for any professional technical maintenance. Due to polycrystalline technology maturity, its spare parts standardization degree reached 100%, even if running 15 years after, need to replace individual modules, the market on compatible parts stock is also extremely sufficient, procurement cost only is then mainstream module price 60% around, this kind of extremely low life cycle maintenance difficulty ensured the power station's continuous stable output.