What Challenges Affect Solar Energy in Coastal Areas | Salt Air, Humidity, Wind Exposure
Coastal salt spray easily leads to PID attenuation, efficiency annual drop exceeding 3%.
12-grade strong wind need bracket anti-pressure 2400Pa.
Under high humidity must select IP68 protection, suggest every week regular fresh water wash surface salt scale, prevent frame oxidation.
Salt Air
Salt spray erosion
Within the coastal coastline 30 kilometers range, the air middle average every cubic meter suspended 400 to 600 micrograms' sodium chloride particles. One burst wind speed every second 15 meters' sea wind blows through, 1 hour then can let area about 2 square meters' photovoltaic board surface accumulate thickness reach 0.05 millimeters' salt grains. When the ambient temperature rises to 35℃, the chemical reaction rate of the salt module's panel surface will than 20℃ time speed up approximately 2.5 times.
One piece rated power 400W's solar board continuous at containing salt amount 5%'s humid air inside exposed 120 days, overall generation conversion efficiency will drop 1.2% to 1.8%. Every morning from 6 o'clock to 8 o'clock, the morning dew and panel surface's high concentration salt grains mixed, forming a salt water solution with a pH value usually between 5.5 and 6.5, to various types of metal modules' corrosion depth every year can reach 0.03 millimeters.
Aluminum frame becomes brittle
Market occupancy rate exceeds 80% Solar panels all adopt thickness at 1.5 millimeters to 35 millimeters interval's anodic oxidation aluminum as external frame structure. On the beach, not more than 2 kilometers away from the open-air installation point, this kind of aluminum alloy material's 15-micron anti-corrosion protection film will be completely dissolved by chlorine ions inside in 18 to 24 months. Lose protection layer's aluminum material every month will due to electrochemical reaction lose 0.005 grams' mass, lead to frame's anti-pull strength from originally nominal's 250MPa sudden drop to 180MPa.
In experience 100 times above's day-night temperature difference from 15℃ sharp climb to 45℃'s heat expansion cold contraction cycle after, brittle aluminum frame four corners will appear length intervene 0.2 millimeters to 1.5 millimeters' tiny physical cracks.
l For repair single piece damaged panel's frame structure, operation maintenance team average need spend 45 dollars' labor and material budget.
l Purchase anti-corrosion grade reach 25 microns oxidation layer's special aluminum frame, every piece photovoltaic board's manufacturing cost will extra increase 2.5 dollars.
l In wind speed reaching every second 25 meters' typhoon day, attached with crack's frame has 15% probability will happen 0.5 centimeters above's deformation even complete breakage.
Glass becomes blurry
Photovoltaic board front side's 3.2 millimeters ultra-white embossed tempered glass surface factory time coated have one layer thickness as 120 nanometers' anti-reflection coating. The air middle concentration exceeds every liter 2 milligrams' salt spray sediments in hot sun under continuous bake exceed 300 hours, will take anti-reflection coating's light penetration rate from optimal's 94% pull down to 89% around. Lose chemical coating protection's glass surface roughness will increase 0.5 microns, lead to solar light's diffuse reflection phenomenon increase 12%, single board every day collected effective radiation amount will follow that decrease 0.45 kWh.
l When the glass surface's salt accumulation amount reaches every square centimeter 5 grams, the panel's working temperature will abnormally rise 5℃ to 8℃.
l Silicon wafer temperature every rise 1℃, internal working voltage will then drop 0.35%.
l Light penetration rate decay and high temperature effect superimposed, finally make 1MW photovoltaic system's daily average generation benefit decrease about 35 dollars.
l If hire machines every 30 days, use electric conductivity lower than 5 microsiemens' pure water wash one panel, every year's cleaning fee will occupy the total budget's ratio will lift to 4.5%.
Junction box water leakage
The panel's back side's plastic junction box is usually standard equipped with IP68 grade's waterproof dustproof operation standard. In relative humidity long term maintain at 85% above's sea wind environment middle, junction box shell's polycarbonate material after 3 years high intensity ultraviolet and 5% concentration salt spray's double irradiation, physical pull stretch toughness will drop 40%. Sealed silicone ring's elastic modulus every year will happen 15% irreversible decay, lead to junction box's water vapor penetration rate from every day 0.1 grams to every day 0.5 grams.
l Infiltrated tiny amount of salt water contact to internal 3 pieces of bypass diodes' metal pins, will in 48 hours inside trigger contact resistance from normal's 0.01 ohms soar to 2 ohms above.
l Short circuit generated heat will make the diode's local temperature exceed 120℃, then melt the surrounding 0.8 millimeters' plastic shell.
l Replace one unit by salt water complete burned junction box, count on 75 dollars' replacement parts cost and stop machine triggered electricity amount loss, single time maintenance fee approximately equal to 120 dollars.
Wire skin aging
Connect each piece panel's diameter 4 square millimeters photovoltaic special DC cable, outer layer cross-linked polyethylene insulation skin's experimental design life is 25 years. Exposed to salt content exceeding 3%, marine climate, cable outer skin's breakage elongation rate index every pass 10 months then will large scale drop 12%. Insulation skin surface because salt corrosion generated tiny cracks will accommodate volume 0.01 cubic millimeters' high concentration salt water, lead to cable to ground insulation resistance value in rainstorm day instant fall to 100 kilo-ohms' dangerous trip interval.
l System leakage not only will trigger string type inverter every day 5 times above's automatic stop protection mechanism, also will lead to whole string 1500 volts DC energy's line loss increase 2.5%.
l To avoid aging leakage trigger DC arc fire, every interval 5 years, then need every meter 1.5 dollars' price re-purchase lay double layer salt spray resistant cable.
l One strip length 50 meters' damaged cable if not replaced in 14 days, the whole array's generation amount every month will flow away 350 kWh.
Humidity
Water vapor entered
The coastal area's relative humidity has 240 days maintain at 80% to 95% high position interval. When the environment temperature reach 35℃ and the relative humidity is 85%, the air's water vapor partial pressure will soar to 5.62 kilopascals.
Standard PET backsheet in the above environment under water vapor penetration rate is approximately every day every square meter 1.5 grams. The area is 2.5 square meters. 72 pieces of cell module in outdoor continuous place 36 months, cumulative will have exceeded 410 grams' water molecules penetrate backsheet enter module internal.
By widely used EVA encapsulation film after absorbed weight ratio 0.2% moisture, will happen hydrolysis reaction and release pH value at 4.5 around's acetic acid. An acidic environment will let the silicon wafer surface's anti-reflection layer thickness from 75 nanometers dissolve to 50 nanometers below.
Potential Induced Degradation effect follows that the explosion, module glass and aluminum frame between's leakage current will from normal's 0.5 microamps fierce increase to 50 microamps. Single piece rated power as 550W's solar board, its output voltage will in 90 days inside drop 15% to 25%. Whole string by 20 pieces modules series connected DC loop every day will due to voltage fluctuation lose about 2.8kWh's generation amount.
Film bubbling
Water vapor infiltration changed the encapsulation film's physical characteristics, encapsulation material, and the 3.2 millimeters thickness tempered glass between's peeling strength will from initial's every centimeter 40 Newtons sudden drop to every centimeter 15 Newtons below. Experience every day an average of 12 hours' sunlight irradiation, module internal working temperature from 25℃ climb to 75℃, residual water vapor will fast expand.
Film layer start appear diameter intervene 2 millimeters to 15 millimeters' irregular bubbles, single bubble internal's air pressure can reach 1.2 standard atmospheres. Light passes through a bubble, due to refraction rate from glass's 1.52 sudden change to air's 1.0, local light reflection rate will increase 4.3%.
Bubble area's heat dissipation thermal resistance rose 0.8 (m²·K)/W, local silicon wafer's working temperature will break through 95℃'s dangerous critical point. Deal with high reach 85% environment humidity, purchase water vapor penetration rate only as every day every square meter 0.1 grams' POE film became one must-select item.
Change to full POE encapsulated module, manufacturing cost every watt will increase 0.025 to 0.035 dollars, can in 25 years cycle inside take photovoltaic board bubbling probability from 18% down to 0.5%. Investment recovery period model shows, early stage input's extra 3% purchase budget, can in number 8 years through reducing 22% module replacement rate complete recover cost.
Electrical equipment dampened
String type inverter hanging outdoors, in the early morning from 2 o'clock to 4 o'clock, the air temperature if in one hour inside sudden drop 8℃, 90% humidity condition under's air then will at equipment internal happen condensation phenomenon. Inverter mainboard's IGBT module, at the surface attached 0.1 millimeters thickness's condensation water drops after, its switching loss will instantly increase 12%.
Long-time work in an environment with humidity exceeding 80% will shorten the nominal average no-fault operation time of the power module from 100,000 hours to 45,000 hours. Circuit board's electrolytic capacitor after absorbing water vapor, the internal electrolyte happens expansion, equivalent series resistance will in 12 months inside rise 150%.
Inverter internal modules | Humidity trigger conditions | Fault rate increase range | Single unit power loss increase | Replacement material cost |
Power semiconductor module | Relative humidity >85% | Increase 35% | 12.5 Watts | 185 dollars |
DC bus capacitor | Environment condensation frequency >30 times/year | Increase 42% | 8.3 Watts | 45 dollars |
Heat dissipation fan bearing | Air water content >20 grams/cubic meter | Increase 28% | 2.1 Watts | 18 dollars |
AC output terminal | Long term humidity maintain 90% | Increase 15% | 5.4 Watts | 12 dollars |
Inverter shell although nominal IP66 protection grade, but waterproof breathable valve's PTFE membrane intercepts high density water vapor 6 months after, micropore blockage rate will reach 40%. Equipment's internal heat dissipation efficiency drops 15%, machine at noon with 100% full load output 100kW power, internal environment temperature will reach 65℃.
High temperature and high humidity environment lead to inverter every year's generation conversion efficiency from 98.6% to 97.2%, one 5MW power station every year will because inverter dampened extra evaporate nearly 80,000kWh's electricity amount.
Internal rusting
Water vapor and module internal's metal conductive structure contact after, width only as 0.05 millimeters' silver paste main busbar surface layer will generate thickness about 0.002 millimeters' silver oxide insulation layer. Responsible for connecting silicon wafer's tin-plated copper ribbon, width usually at 1.2 millimeters around, in water vapor and acetic acid's common corrosion under, surface resistivity will increase from initial's 0.0175 ohm·mm²/m to 0.025 ohm·mm²/m.
Metal oxidation leads to the whole piece photovoltaic module's series resistance from standard's 0.5 ohms slowly climbing to 1.8 ohms. Solar panel's fill factor parameter will follow that from factory time's 78% fall to 68% below.
In every square meter, 1,000W's standard light intensity under, series resistance increase brings ohmic loss, will let one piece board every year white white consume away 12 Watts' effective output power. Operation maintenance personnel use 8 to 14 micron wave band's thermal imaging drone at 30 meters high altitude to conduct infrared inspection, can find rusting ribbon position's temperature higher than surrounding normal silicon wafer high out 15℃ to 22℃.
Hot spot position's local reverse leakage current high reach 8 Amps, monocrystalline silicon wafer will in continuous 120 hours' high temperature heating middle appear irreversible physical burn damage. Repair 1MW array middle due to metal corrosion leads to hot spot fault, every 3 years need expenditure infrared detection and single board replacement fee approximately equal to 3500 dollars.
Wind Exposure
Gust
The coastline is 5 kilometers inside, and the open area averages 15 times above wind speed exceeding 28 m/s's strong gusts every year. When the wind speed in 3 seconds inside sudden increase to 40m/s time, the installed tilt angle as 20 degrees' solar array leeward side will generate every square meter 1400 Pascals' negative pressure pull-out force.
One piece size as 2,278 millimeters multiplied by 1,134 millimeters, total area 2.58 square meters' monocrystalline silicon module, at bearing instantaneous wind pressure time, equivalent to having nearly 360 kilograms' outward peeling load forced on aluminum alloy frame. Fluid mechanics model data shows, wind speed every increases 10%, acting on module surface's dynamic pressure will present square series rise 21%.
The windward side and leeward side's huge air pressure difference will let the module's center area generate an outward bulge of 18 millimeters to 22 millimeters' physical deformation. If the installation position distance from the ground exceeds 10 meters, the wind speed shear index will rise from 0.15 to 0.22, leading to the same level wind pressure under's destruction probability double.
Attack angle reach 25 degrees, time, wind tunnel tester recorded air aerodynamics drag coefficient will break through 1.4, single piece panel's instantaneous force peak will exceed 4500 Newtons, exceed conventional module 2400 Pascals mechanical load certification standard's 1.87 times.
Bracket blown crooked
Support whole photovoltaic matrix's C-type steel or aluminum alloy profile, in the face of coastal every year, long reach 1,200 hours' high frequency wind load alternating action under, extremely easy generate metal fatigue phenomenon. Section size as 41 millimeters multiplied by 41 millimeters, wall thickness 2.0 millimeters' standard hot-dip galvanized bracket column, at bearing wind speed 35 m/s's lateral impact time, its top end will happen 45 millimeters to 65 millimeters' elastic deflection offset.
Continuous gusts will let the whole bracket system generate frequency intervene 2 Hz to 8 Hz's resonance vibration, low frequency vibration will in 36 months inside consume away carbon steel material 15%'s fatigue life. For resisting strong wind-triggered torsion buckling, the project design stage must increase the main beam's section moment of inertia by 40%, the method usually is to take the profile wall thickness from 2.0 millimeters to increase to 2.5 millimeters or 3.0 millimeters. Structural strength's upgrade will let every MW system's steel material consumption from 35 tons soar to 48 tons, support structure's initial purchase budget will correspondingly increase 28%, converted down every watt increase 0.04 dollars.
Yield strength as 235MPa's ordinary carbon structural steel at bearing exceeds 1 million times' wind force alternating stress cycle after, its weld seam edge's microscopic crystal lattice breakage probability will reach 6.5%, leading to overall bracket's bearing redundancy drop 30%.
Glass cracks
Solar panel front side standard equipped 3.2 millimeters thickness high light penetration embossed glass, at wind speed reach every second 30 meters' continuous blowing under, its center position's every minute high frequency oscillation times high reach 180 times to 240 times. Be wrapped in EVA film internally, thickness only 130 microns' silicon wafer, at following glass happen up down amplitude exceed 12 millimeters' bending deformation time, internal originally existing micron level micro-cracks will by every day 0.02 millimeters' speed toward surrounding spread.
In the experience, the wind speed average exceeds 20 m/s, many wind seasons later, the operation and maintenance team use portable EL detection equipment at night time scanning time will find, about 12% of the modules internal appeared naked eye unable to perceive cross-type micro-cracks. Crack once cut off silicon wafer surface width to 40 microns' sub-busbar, block light-generated electrons' collection and transmission path, then will let damaged area's series resistance from 0.6 ohms climb to 1.4 ohms.
Micro-crack coverage area reaches whole piece cell 15%'s critical point time, local reverse leakage current will exceed 3.5 Amps, single piece 450W module's actual output power will in subsequent 90 days inside sharp decay 18 Watts to 25 Watts.
Lose screws
Fix photovoltaic board middle clamps and end clamps' M8 specification stainless steel bolts, in standard installation process, middle will usually be applied 18 Newton-meters to 22 Newton-meters' pre-tightening torque. In coastal areas, wind speed all year round maintains at 6-grade to 8-grade environment under, wind force triggered mechanical high frequency vibration will destroy threads between static friction state, lead to fastener's pre-tightening force by monthly 1.5% speed flow away.
When torque drops to 12 Newton-meters below time, the clamp and aluminum alloy frame between's clamping force will lose 60%, leading to module at bracket rail on generate at most 5 millimeters' lateral slip. Physical slip not only wears module frame thickness 15 microns' anodic oxidation layer, pulls back side's DC cable, more lets junction box internal's terminal bear exceed 30 Newtons' unexpected pull force. For maintaining the matrix's mechanical connection stability, operation and maintenance personnel must every interval of 6 months use a digital torque wrench to re-tighten tens of thousands of bolts in the whole field.
One occupied area of about 100 acres, installed capacity as 20MW's coastal photovoltaic power station, single time whole field bolt re-tightening needs consume 450 labor hours, every year due to wind load vibration brought's extra mechanical maintenance budget will exceed 12,000 dollars.