How Do You Calculate Potential Solar Output | Sun Hours, Wattage, Efficiency Loss

The calculation formula is "power × sunshine duration × efficiency coefficient".

Take a 200W panel as an example. If local sunshine is 4 hours, deduct inverter and circuit about 20% loss (coefficient take 0.8), daily average actual get about 640Wh electricity quantity.

Suggest according to a 0.75 conversion rate estimate, to offset temperature rise brought about by efficiency attenuation.

Sun Hours

Calculate latitude difference

Geographical latitude coordinate every towards north move 10 degrees, winter sun highest zenith angle will drop 10 degrees, leading to penetrate atmosphere air mass (Air Mass) index from AM 1.5 rise to AM 2.0, further attenuate off about 15% to 20% ultraviolet and visible light photon penetration rate. In north latitude 36 degrees, Nevada, Las Vegas, July's daily average peak sunshine duration reaches as high as 6.8 hours, arriving in the 12th month then plummets to 3.2 hours, presenting a reach as high as 52.9% obvious seasonal fluctuation variance. Panel tilt angle set at 30 degrees, in spring and autumn two seasons can capture 98% direct light, but if flat lay on a 0 degree slope roof, winter produced kilowatt-hour electricity quantity will plummet 25% to 30%.

The incident ray angle deviates from the vertical normal by every increase of 1 degree, according to the cosine law, the panel surface absorbed usable radiation power will according to a 1.5% rate present linear decrement. Balance 12 months' electricity generation quantity median require installation team refer to local latitude value minus 15 degrees to set summer best tilt angle, thereby will whole year total electricity generation hour number's system deviation control in plus minus 4%'s extremely narrow interval inside.

Look at cloud layer quantity

Cloud layer thickness and water vapor humidity will according to 40% to 80% drastic proportion will direct normal irradiance (DNI) refract into diffuse horizontal irradiance (DHI). In the cloud layer, block rate reaches 85% overcast rainy day, originally per square meter 1000 watts' nominal irradiance will rapidly collapse to 150 watts to 250 watts' trough interval. One set of 8 kilowatts (8 kW)'s residential array in clear sky ten thousand miles time one day can produce 45 degrees electricity, under a thick heavy cloud layer, daily production quantity will drop to 8.5 degrees electricity, single day electricity generation loss rate reaches as high as 81.1%. Refer to the USA's northwest part, Washington state, Seattle city's meteorological statistics. Every year, 201 overcast rainy days have an extremely high appearance frequency, pulling local's annualized average peak sunshine forcefully pull low to every day 3.1 hours. Arizona state Phoenix city relies on every year average 300 cloudless clear days' absolute climate advantage, its 365 days' daily average peak data stable at 5.7 hours' high position. Reach as high as 83.8% of regional light duration difference, because Seattle residents need to spend extra 6,000 US dollars to buy rated power high out 40% of panel system, just to maintain every month 900 kilowatt-hours' predetermined output load.

Avoid shadow

One root diameter 0.3 meter's chimney at afternoon 2 o'clock project out area only occupy single block panel 10%'s shadow, not activate built-in's 3 bypass diodes words, will trigger entire 12 blocks series panel array's output voltage suddenly drop 33%. Micro inverter with 99.8% maximum power point tracking (MPPT) sampling frequency, will this 10% local block attenuation strictly isolate a single piece 1.8 square meters' module inside, successfully retrieve this circuit in other 4.4 kilowatts (4.4 kW)'s effective output power.

Yard in one tree with every year 0.6 meter speed growing oak tree, at 5th year time its tree crown volume will increase 120%, and at 3 o'clock in the afternoon after intercepting the originally shoot towards the roof southwest corner panel 45% photon flow rate. On-site survey personnel use 360-degree panoramic lens's pathfinder analyzer, extract from morning 9 o'clock to afternoon 3 o'clock, for a period of 12 months' sunshine window period obstacle outline, ensure entire 25 years life cycle inside's total solar resource fraction (TSRF) always maintain in 90% above's healthy standard.

Calculate total duration

l Pull past 15 years to 20 years' National Weather Service TMY3 (Typical Meteorological Year) historical data set, extract library in accurate to every 60 seconds 1 time sampling's GHI measurement record, calculate out 8,760 hours sample capacity's sunshine median.

l Will system panel's installation azimuth angle benchmark set at 180 degrees' due south absolute direction, towards due west 270 degrees direction offset will make afternoon 2 o'clock to 5 o'clock time period's peak sunshine receive absolute value increase 18%, whole day 24 hours cycle's total kilowatt-hour production capacity however will decrease 8.5% to 11.2%.

l Apply 3D polygon photovoltaic simulation software establish length width height physical error strictly less than 0.05 meters' house panoramic mapping model, substitute local air temperature from winter -12°C to summer 42°C's 54 degrees huge temperature difference amplitude, calculate semiconductor crystalline silicon 2.5%'s heat loss.

l Put every day 6.2 hours' July highest peak value and every day 2.8 hours' 12th month lowest trough value according to 365 days calendar day number conduct weighted average, deduce out one for example 4.65 hours' annualized standard parameter, bring into system 240 months loan recovery cycle's internal financial return rate table in.

Wattage

Look at the nameplate number

The market for residential type module's rated power distribution from 380 watts to 460 watts presents a normal distribution, commercial level's large size module highest peak value already breaks through 600 watts. The one-block open circuit voltage is 41.5 volts, short circuit current is 13.5 amperes, 400-watt panel connected to multimeter, at noon 12 o'clock, actual measured usable working voltage usually falls back to 34.2 volts, working current maintains at 11.7 amperes.

According to California Energy Commission adopted's PTC test conditions, the environment temperature will be set at 20 degrees Celsius, wind speed per second 1 meter, 400 watts nominal panel's actual output power median will inevitably shrink 10.5% to 12%, drop to 355 watts around. If the roof area is restricted to only 35 square meters, the conversion rate reaches as high as 22.8% 450 watts high density panel, compared with use conversion rate 19.2% 350 watts panel, can in the same physical space inside will total installed capacity from 6.3 kilowatts elevate to 8.1 kilowatts, installed density growth rate reach 28.5%.

Single piece silicon wafer thickness from 180 micrometers cut down to 150 micrometers after, material manufacturing cost drop down 15%, at the same time, put multi busbar technology from 5 busbar upgrade to 16 busbar, make series resistance loss reduce 3.2%, single block module's rated power therefore net increase 15 watts to 20 watts.

Calculate attenuation

Crystalline silicon material exposed to wavelength 280 nanometers to 400 nanometers' ultraviolet radiation under's 1st year, light-induced degradation physical effect will cause rated power to appear 1.5% to 2.5%'s initial drop. One block factory power 400 watts' panel in operate 8760 hours after, the highest output will be locked at 390 watts' upper limit scale. From 13th month to 300th month, high quality N type silicon wafer every year's linear power attenuation rate be strictly controlled in 0.25% to 0.4%'s tiny variance interval inside.

Cumulative operate full 25 years, nameplate calibrated as 8,000 watts' total array, maximum direct current output capability will slide down to 6,760 watts to 6,920 watts between, whole life cycle total capacity loss rate is 13.5% to 15.5%. Panel manual on indicated's temperature coefficient every degree Celsius negative 0.35%, explicitly quantified when surface working temperature exceeds 25 degrees Celsius' standard red line time, temperature every climb 1 degree Celsius, real-time output power will same proportion deduct 0.35%.

In July, the air temperature reaches 38 degrees Celsius, and the roof panel surface temperature soars to 65 degrees Celsius. Climate sample under, 40 degrees' temperature difference will produce a reach as high as 14%'s negative power deviation, let 400 watts' real-time output drop to 344 watts' trough value.

Match inverter

Will 8,000 watts' direct current convert into 120 volts or 240 volts alternating current merge into the family power grid, need to configure maximum continuous output alternating current power is 7,600 watts' series inverter or micro inverter matrix. Electrical design specifications universally adopt 1.15 to 1.25's direct current and alternating current capacity ratio, will 8,000 watts panel match to rated power 6,400 watts' inverter on, able to put overall equipment procurement budget shrink 800 US dollars to 1,100 US dollars.

Every day from morning 10 o'clock to afternoon 2 o'clock's 4 hours high light band inside, exceed inverter 6,400 watts processing limit's 1,600 watts peak direct current will be by system actively peak shave discarded. Reach as high as 20% instantaneous power loss in the whole year's 365-day statistical cycle inside, only occupy year total kilowatt-hour electricity generation quantity's 1.5% to 2.5% tiny error, and inverter in low irradiance time period situate at relatively high load rate under operate, can average conversion efficiency from 92% push elevate to 97.5% peak interval.

Select single unit rated alternating current output power is 349 volt-amperes' micro inverter one to one hang mount on 400 watts panel back surface, direct current to alternating current's conversion efficiency can reach 96.5%, highest working environment temperature support 65 degrees Celsius.

Measure physical area

Install one set standard capacity is 8,000 watts' residential power generation facility, if adopt every block physical projection area 2.17 square meters' 450 watts large power panel, in total need to procure 18 blocks modules, occupied's roof physical total surface area is 39.06 square meters. Add on panel between interval's 2.5 centimeters aluminum alloy guide rail heat dissipation gap, and edge reserved's 0.9 meter fire fighting channel, rectangle array's actual coverage area usually will expand 20% to 25%, reach 47.5 square meters' occupy volume.

According to building load-bearing standard test, 18 blocks weight distribution is 24.5 kilograms' glass panel plus 125 kilograms' metal bracket system, will at roof every square meter exert 11.8 kilograms' static dead load pressure. If the roof only has 30 square meters of usable south-facing area, only 13 blocks of the same size panel can be accommodated, and the total power system upper limit will be compressed to 5,850 watts, and the highest output will drop to 750 kilowatt-hours every month.

Upgrade adopt cost unit price high out 18%, conversion rate reach 23.2%'s 480 watts heterojunction panel, in same 13 blocks' quantity limit under, can will total nominal capacity pull elevate to 6,240 watts, every day extra increase 1.8 degrees electricity's output benefit.

Efficiency Loss

Calculate conversion rate

Single-phase string inverter in execute direct current to alternating current's waveform conversion task time, its European weighted efficiency index usually calibrated in 96.5% to 98.2% variance range inside. In the system load rate drops to 20% in the morning and evening low sunshine period, inverter's switch loss and standby power consumption will put instantaneous conversion efficiency pull low to 89% to 92% low position interval. The market price is 1200 US dollars' 7.6 kilowatts (7.6 kW) series inverter, inside's IGBT power module at full load operating time will produce as high as 150 watts to 250 watts' heat dissipation.

When the inverter's direct current side input voltage deviates 380 volts' best MPPT (maximum power point tracking) voltage median, rise to 480 volts or drop to 250 volts, electrical energy conversion error rate will expand 1.5% to 2.5%, leading to every year losing about 180 degrees to 300 degrees' usable electricity quantity.

In 15 years' hardware life cycle, due to internal electrolytic capacitor aging, inverter's output precision every year will produce 0.1% tiny deviation, at 180th month time cumulatively cause extra's 1.5% conversion rate decrease.

Afraid heat wave roast

Silicon-based semiconductor's photoelectric conversion efficiency and surface physical temperature present a high degree of negative correlation. Monocrystalline silicon module's temperature coefficient median is usually negative 0.35%/C. When California's July outdoor environment air temperature climbs to 38 degrees Celsius, the absorbed 90% invisible infrared radiation black panel, its actual working temperature will soar to 65 degrees Celsius. Will 65 degrees Celsius' actual measured temperature subtract 25 degrees Celsius' standard test laboratory temperature, 40 degrees' positive direction temperature difference bring into the temperature coefficient formula, will get out one 14%'s fixed loss ratio.

One block factory calibrated as 400 watts' panel in 65 degrees Celsius' high temperature oppression under, its real-time output power peak value will instantly shrink to 344 watts, 20 blocks panels composed's 8000 watts array at noon's true output total quantity only remain 6880 watts.

Will panel through 10 centimeters high's aluminum alloy bracket suspended install at asphalt roof above, can increase per second 1.5 meters to 2.5 meters' air circulation speed, put backplane's working temperature forcefully lower 5 to 8 degrees Celsius, thereby retrieve back 1.75% to 2.8% power attenuation.

Calculate dust thickness

In annual rainfall quantity lower than 250 millimeters, desert edge zone, like Nevada state, panel glass surface in continuous 45 days no rain after accumulated's 2 millimeters thick tiny sand dust particles, will put light transmittance cut down off 4% to 7%. The USA National Weather Service's statistical sample indicates that the tilt angle is 15 degrees, compared with the 30-degree tilt angle system, its surface particulate matter retention probability is high out 35%, every year produced's dust block attenuation rate reaches 5.2%.

Spend 150 US dollars to hire a professional cleaning team in the spring season, conduct one-time water pressure is 1500 PSI's high pressure wash, able to immediately will by dust swallowed's 450 degrees electricity (according to local 0.14 US dollars/degree's average price convert to 63 US dollars) re-release back power grid.

If the surrounding 200-meter range inside exists a large-scale construction site, the air in concentration reaches per cubic meter 150 micrograms' PM10 suspended particulate matter, will in short short 3 weeks inside the system's overall output load pull low 8.5%'s peak error. Even if it is in the rainwater-abundant Oregon state, Portland city, pollen and bird excrement form local irregular stain spots, if not timely cleaned up, still will bring every year 1.5% to 2.0% basic optical loss.

Look at cable loss

One set of physical span reaches 15 meters' 8 kilowatts (8 kW) residential module, in connect roof panel and garage distribution box's process, need to lay total length reach 30 meters to 40 meters' 10 AWG specification pure copper direct current cable. When the ambient temperature reaches 40 degrees Celsius, the cable carries a current of 15 amperes' peak load time, and the copper conductor's ohm resistance will cause about 1.5% to 2.0% of the voltage drop amplitude (Voltage Drop).

According to the USA National Electrical Code (NEC)'s strict engineering standard, the direct current side and alternating current side's circuit loss budget must be forcefully controlled within 3% of the upper limit threshold, otherwise it will be unable to pass the grid connection acceptance test.

Put wire diameter from 10 AWG upgrade to thicker's 8 AWG specification, although will make cable procurement cost increase from 120 US dollars to 180 US dollars, but can put direct current side's resistance attenuation rate from 1.8% to low to 0.9%, in 25 years' cycle inside extra exchange back value 450 US dollars' 1800 degrees electricity quantity benefit. Due to panel leave factory time's short circuit current and open circuit voltage exist plus minus 3%'s manufacturing tolerance, including 20 blocks panels series connection after produced's mismatch loss (Mismatch Loss), still will extra eat off total rated power's 1.0% to 1.5%.

Calculate aging rate

Semiconductor wafer in receive per square meter 1000 watts strong ultraviolet bombardment's initial 365 days inside, will inevitably trigger light-induced degradation (LID) physical phenomenon, cause rated power benchmark line fall 1.5% to 2.5%'s amplitude. From 13th month start until 300th month, N type monocrystalline silicon cell panel's standard linear power attenuation rate is controlled every year at 0.25% to 0.4%'s tiny variance inside.

When this set spends 18000 US dollars on an 8 kilowatt (8 kW) system, it operates for 25 years, the last one day, its overall panel's maximum direct current output load will irreversibly shrink to 6720 watts to 6960 watts between, whole life cycle total capacity loss rate reached 13.0% to 16.0%.

Equipment aging not only stays at the panel end, the micro inverter's solid electronic module undergoes a long up to 87600 hours' thermal expansion and contraction cycle after, its working conversion efficiency will also appear 0.5% to 0.8% long-term downward drift. Engineers established long-up to 25 years' net present value (NPV) and internal rate of return (IRR) financial calculation model time, usually will set one every year 0.5%'s comprehensive aging loss rate, with this accurately calibrate 10th year to 20th year between continuously slide down's every kilowatt-hour degree electricity return curve.