What Should You Know About Solar Energy | Efficiency, Maintenance

Mainstream photovoltaic panel conversion rate reaches 22%.

Daily maintenance suggests every half year use a soft hair brush to clean one surface dust. This operation can then effectively avoid about 15% power generation loss, ensuring equipment as long as 25 years' high efficiency stable running.

Efficiency

Measure calculate condition
Solar energy cell panel factory nameplate on marked's 20% or 22% conversion efficiency, completely is under laboratory set's standard test condition (STC) measure calculate out's number value. The test cabin's inside's light illumination radiation intensity was precisely set at every square meter at 1000 watts, air mass maintained at AM 1.5's fixed parameter standard, simultaneously panel's physical surface temperature was strictly locked at 25 degrees Celsius.

In reality, the installation environment inside, when noon's actual solar radiation degree only reaches every square meter 800 watts, one piece rated nominal 400 watts' module, its actual direct current terminal output power will synchronously shrink to 320 watts around. Light illumination intensity every produces 10% natural fluctuation, panel short circuit current's test number value then will appear 9.8% to 10.1% equal proportion linear deviation.

Too afraid of heat
Monocrystalline silicon module possesses -0.34%/℃ to -0.38%/℃'s typical temperature coefficient. When the outdoor environment air temperature reaches 35 degrees Celsius, the roof black panel absorbs solar short wave radiation, and its glass surface's actual physical temperature will rapidly soar to 65 degrees Celsius to 70 degrees Celsius. Compared to 25 degrees Celsius' laboratory baseline, panel surface every elevate 1 degree Celsius, its maximum output power will then absolutely drop 0.35%.

· Under panel temperature reaches 65 degrees Celsius' working state, its actual output voltage will be compared to open circuit voltage drop 14% to 15%.

· Originally nominal 400 watts' module, under high temperature load's actual power output will attenuate 56 watts to 60 watts, real working power only remains 340 watts around.

· System's overall energy conversion efficiency will slide from nominal's 21% to 18.2% range.

· Environment relative humidity if synchronously exceeds 85%, panel surface layer's wet hot steam will make light ray refractive index increase 1.2%, leading to arrive cell piece's effective photon quantity further reduce about 2%.

Look cell panel
Currently, N-type TOPCon cell piece inside's minority carrier lifetime exceeded 1,000 microseconds, mass production cell's average photoelectric conversion efficiency reached 25.2% to 25.8% data range.

The single piece dimension being 182 millimeters multiply 182 millimeters' silicon wafer, assemble into 72 layout type's standard double-sided double-glass module after, the overall length width physical dimension is 2.27 meters multiply 1.13 meters, effective receive light physical area is about 2.56 square meters. This kind of module's front side rated highest power usually is 570 watts to 590 watts, and the convert down every square meter's peak power density is 222 watts to 230 watts.

If the same area's roof adopts a photoelectric conversion rate of only 19% polycrystalline silicon panel, every square meter's power density will fall to 185 watts to 190 watts, and the same area's total installed capacity will produce about 16% number value deviation.

Double-sided reflection
Double-sided double-glass module at back surface installed a layer thickness being 2.0 millimeters' high light transmittance half tempered glass, absorbs light from the ground's environment reflected light, realize 5% to 25% back surface power gain.

· When the module is installed on a light color flat roof, and ground clearance is maintained at 0.5 meters to 1.0 meters' standard height, ground's reflectivity (Albedo) data is usually between 20% and 25% at this time. This time, the overall power generation efficiency of this system can increase by about 7% to 9%.

· Installed on paved high reflection white waterproof material's flat surface, ground reflectivity indicator will elevate to 60% above, back surface attaching produced's power gain able to break through 15% critical point.

· In winter, accumulated snow thickness exceeds 5 centimeters. The environment inside, pure white snow land's reflectivity can soar to 80% to 90%, one piece originally 500 watts' single-sided panel, through back surface's photon absorption, its actual comprehensive output peak value able to stage-ly reach 560 watts to 575 watts' measure range.

Inverter loss
String type inverter takes direct current (DC) and converts it into frequency being 50 Hertz or 60 Hertz's alternating current (AC) process inside, its maximum conversion efficiency parameter is generally marked as 98.2% to 98.6%. Under equipment daily running load rate locates at 40% to 60% range, inverter's European weighted efficiency indicator is about 97.5%. Equipment built-in's multi-route maximum power point tracker (MPPT) possesses 99.9% static tracking precision, its working voltage range is usually set at 160 volts to 1000 volts between.

When morning light illumination is weak, string input voltage is lower than 150 volts' startup threshold time, inverter will locate at standby state, internal standby loss power is limited at 1 watt to 3 watts. When the machine casing external running temperature exceeds 45 degrees Celsius, the inverter will automatically start derating the run mechanism, and the environment temperature every elevates 1 degree Celsius, the output power limit ratio will increase 1.5%.

Direct current cable step down
From roof photovoltaic array extend to indoor distribution box's direct current cable, usually uses cross-section area being 4 square millimeters or 6 square millimeters' special double layer insulation tin plated copper core wire. According to IEC industry test specification, from panel to inverter between's full link direct current cable voltage drop amplitude, must be controlled in total output nominal voltage's 1.5% to 2.0% within.

· The used length exceeds 50 meters, and the cross-section area is only 2.5 square millimeters, so the copper wire's direct current resistance number value will rise to 0.008 ohms/meter.

· Working current reaches 13 amperes' full load working condition time, this strip 50 meters' cable two ends will produce exceeding 5.2 volts' voltage deviation.

· According to the power physical formula, this root cable every runs one hour will produce about 20 watts to 30 watts' invalid heat energy loss.

· Inverter connects to the main distribution board's alternating current terminal cable, alternating current voltage loss parameter needs to be controlled at 1% baseline below, ensure 230 volts' standard alternating current voltage in pass through 20 meters physical distance transmission after, arrive at smart meter's actual test voltage maintains at 227.7 volts above.

Maintenance

Wash panel

In rainfall quantity less than every year 400 millimeters, arid or semi-arid climate region, photovoltaic panel statically run 90 days after, surface's accumulated dust thickness usually will reach 0.2 millimeters to 0.5 millimeters, this will lead to short circuit current parameter drop 4.5% to 6.2%.

Wash panel time, water quality's total dissolved solids (TDS) indicator must control at 200 ppm below. Used contain high concentration calcium magnesium ions' hard water carry out flush, water evaporate after will on panel's anti-reflection coating (ARC) on leave down thickness about 50 micrometers' calcium carbonate white scale crystal, leading to glass panel towards 380 nanometers to 780 nanometers visible light wave band's light transmittance permanently lower 1.5%. Wash operation's time window must be strictly limited at sunrise before or sunset after, when panel surface temperature drops to 30 degrees Celsius below time, then can supply water.

Solar energy panel's 3.2 millimeters half tempered glass in bear exceeding 20 degrees Celsius' cold hot water temperature violent alternate time, its inside will produce exceeding 40 megapascals (MPa)'s thermal stress, glass will happen micro cracks even completely burst's probability will present exponential level growth.

Measure hot spot

Every 12 to 18 months, needs to use thermal sensitivity (NETD) smaller than 0.05 degrees Celsius' industrial level infrared thermal imager towards full array carry out scan. When the panel's diameter is only 2 centimeters, a bird dropping or fallen leaf blocking object time, this region's cell piece will instantly convert from power generation state to consume electricity load, consume the whole strip series circuit on other normal cell pieces produced's current.

Blocked region's local physical temperature will in short short 15 minutes inside soar to 100 degrees Celsius to 150 degrees Celsius between, encapsulate cell piece's ethylene-vinyl acetate copolymer (EVA) adhesive film in experience exceeding 85 degrees Celsius' high temperature roast after, its light transmittance will from 98% suddenly drop to 80% below, and in 10 days inside appear irreversible's yellowing phenomenon.

When the local hot spot module's temperature difference (ΔT) exceeds 15 degrees Celsius, the junction box inside's bypass diode will automatically trigger the conduction mechanism, take one third of the internal cell string circuit to carry out physical isolation, and the single piece rated power 400 watts' panel output power will instantly fall to 260 watts around.

Check wire

Exposed to outdoor ultraviolet (UV) radiation's direct current cable, its external polycarbonate or cross-linked polyethylene (XLPE) insulation skin's tensile strength will degrade every year at a rate of about 1.2% per year. In carrying out annual maintenance, must use a megohmmeter towards photovoltaic direct current cable inject 1000 volts (V)'s direct current test voltage, continuous time length is 60 seconds.

Standard's insulation resistance reading must be greater than 1 megohm (MΩ). If the system's location environment's relative humidity long term maintains at 80% above, wet gas will along broken's insulation skin seep into copper core, leading to leakage current number value break through 30 milliamperes (mA)'s safe red line. Roof's MC4 standard waterproof joint is also a key point. Normal metal terminal contact resistance should be smaller than 0.5 milliohms (mΩ). Once the internal tin-plated copper pin oxidizes, the contact resistance elevates to 5 milliohms or above, under 12 amperes (A)'s continuous working current passes through time, the joint inside's temperature will rise to 40 degrees Celsius, trigger plastic casing melt ruin's risk.

Inverter

Wall-mounted type string inverter's heat dissipation aluminum die-cast back plate once accumulated thickness exceeding 2 millimeters' flocculent dust, its passive heat dissipation efficiency will cliff style drop 20% to 30%. When the inverter's internal IGBT (insulated gate bipolar transistor)'s working junction temperature exceeds the 125 degrees Celsius limit threshold time, equipment every run 1 hour then will lose about 0.8% of its conversion life cycle. Built-in direct current cooling fan's design life standard generally is 40000 working hours, but in environments containing high concentration salt fog or tiny sand dust, fan bearing's mechanical wear rate will increase 3 times. Usually, after accumulating 15000 hours of run, then needs to carry out preventive replacement.

Inverter's alternating current output terminal equipped multi-group metal film filter capacitor, its equivalent series resistance (ESR) parameter in experience 5 years about 18000 times' charge discharge cycle after will increase about 15%, leading to output current's total harmonic distortion (THDi) indicator breaking through 3% grid connection electric energy quality red line.

Tighten screw

Photovoltaic aluminum alloy bracket system in as long as 25 years' service cycle, needs to bear wind speed as high as every second 35 meters' gust load as well as every square meter 5400 pascals (Pa)'s static snow load. Fix panel's middle press block and side press block use's usually is M8 specification's stainless steel hexagon socket bolt, maintenance personnel must use calibrated digital display torque wrench, take fasten torque precisely control at 14 Newton·meters (N·m) to 16 Newton·meters.

If the torque is lower than 12 Newton·meters, in a continuous frequency of 2 Hertz to 5 Hertz's breeze vibration environment, the panel edge and bracket between's gap will expand to 1.5 millimeters above, long-term mechanical friction will lead to border frame anodic oxidation layer fall off; if the fasten torque exceeds 18 Newton·meters, exceeds aluminum alloy border frame's yield strength, border frame bear pressure deform will squeeze internal glass layer, produce naked eye unable perceive and length in 50 micrometers to 100 micrometers between's hidden crack, ultimately lead to panel power happen every year 0.8% above's abnormal attenuation.