About PV Power Calculation Formula

Solar System Calculation of Lithium battery backup for home
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Conversion efficiency

η= Pm (peak power of the cell)/A (cell area) × Pin (incident light power per unit area)

Note:Pin=1KW/㎡=100mW/cm²

Charging voltage

Vmax=V rated voltage×1.43 times

Battery components in series and parallel

Number of battery modules in parallel = average daily power consumption of load (Ah)/average daily power generation of modules (Ah)

Number of battery modules in series = system operating voltage (V) × factor 1.43 / peak module operating voltage (V)

Calculator:

Battery capacity

Battery capacity = average daily power consumption of the load (Ah) × number of consecutive rainy days / maximum depth of discharge

Average discharge rate

Average discharge rate = Number of consecutive rainy days x Load operating time/Maximum depth of discharge

Load operating time

Load operating time(h)=∑Load power x load operating time/∑Load power

Storage battery

Battery capacity=Average load electricity consumption(Ah) x Number of consecutive rainy days x Discharge correction factor/Maximum depth of discharge x Low temperature correction factor

Number of batteries in series=System operating voltage/nominal battery voltage

Number of batteries in parallel=Total battery capacity/nominal battery capacity

Simple calculation based on peak sunshine hours

Module power =( appliance power x time of use / local peak sunshine hours) x Loss factor, Loss factor: 1.6 to 2.0 depending on local pollution level, line length, installation angle, etc.

Battery capacity =(appliance power x time of use / system voltage) x number of consecutive rainy days x system safety factor

System safety factor: 1.6 to 2.0, depending on battery discharge depth, winter temperature, inverter conversion efficiency, etc.

Calculation based on total annual radiation

Component (square) = K x (operating voltage of the appliance x operating current of the appliance x time of use) / total annual local radiation

For manned maintenance + general use, K is taken as 230:
For unmaintained + reliable use, K is taken as 251:
For unmaintained + harsh environment + very reliable required, K is taken as 276

Calculation based on total annual radiation and slope correction factor

Square power = factor 5618 × safety factor × total load power consumption / slope correction factor × average annual radiation in the horizontal plane

Coefficient 5618: according to the charging and discharging efficiency coefficient, component decay coefficient, etc.: safety coefficient: 1.1 to 1.3 according to the use environment, whether there is a backup power supply, whether someone is on duty, etc.

Battery capacity = 10 × total load power consumption/system working voltage: 10: no sunshine factor (for continuous cloudy rain not more than 5 days are applicable)

Multiplex load calculation based on peak sunshine hours

Current

Component current = load day power consumption (Wh) / system DC voltage (V) x peak sunshine hours (h) x system efficiency factor

System efficiency factor: including battery charging efficiency 0.9, inverter conversion efficiency 0.85, module power attenuation + line loss + dust etc. Adjustments will be made to suit.

Power

Total module power = module generation current x system DC voltage x factor 1.43

factor 1.43: Ratio of the peak operating voltage of the component to the system operating voltage.

Battery pack capacity

Battery pack capacity = [daily load power consumption/system DC voltage] x [number of consecutive rainy days/inverter efficiency x battery discharge of depth

Inverter efficiency: between 80% and 93% according to equipment selection: battery discharge depth: between 50% and 75% according to its performance parameters and reliability requirements, etc. Read more: Top Lithium ion Battery Manufacturers in the world.

Power Calculation Formula

Calculation based on peak sunshine hours and the number of days between two periods of cloudy and rainy days

Calculation of system battery pack capacity

Battery pack capacity (Ah) = safety times x average daily consumption of load (Ah) x maximum continuous cloudy days x low-temperature correction factor / maximum depth of discharge factor of battery

Safety factor: between 1.1 and 1.4.Low temperature correction factor: 1.0 for above 0°C, 1.1 for above -10°C, 1.2 for above -20°C.The maximum depth of discharge factor of the battery is 0.5 for shallow cycle, 0.75 for deep cycle and 0.85 for alkaline Ni-Cd battery.

Number of components in series

Number of components in series = system operating voltage (V) x factor 1.43 / peak operating voltage of selected components (V)

Calculation of the average daily power production of the modules

Average daily module power production = (Ah) = peak operating current of selected modules (A) x peak sunshine hours (h) x slope correction factor x module attenuation loss factor

Peak insolation hours and tilting surface correction factors are actual data from where the system is installed:The module attenuation loss correction factor mainly refers to the loss due to module combination, module power attenuation, module dust cover, charging efficiency, etc., generally taken as 0.8.

Calculation of the battery capacity to be replenished for the shortest interval of days between two consecutive rainy days

Replenished battery capacity (Ah) = safety factor x average daily consumption of load (Ah) x maximum number of consecutive rainy days

How to calculate the number of components in parallel

Number of components in parallel = [replenished battery capacity + average daily consumption of load x minimum interval days] / average daily power production of components x minimum interval days

Average daily power consumption of the load = load power / load operating voltage x number of operating hours per day

Calculation of power generation from PV arrays

Annual power generation = (kWh) = total annual local radiant energy (KWH/㎡) x PV square area (㎡) x module conversion efficiency x correction factor.
P=H·A·η·K 

Correction factorK=K1·K2·K3·K4·K5

K1 attenuation factor for long-term operation of the component, taken as 0.8:
K2 correction for module power drop due to dust shading and temperature rise, taken as 0.82
K3 is the line correction, taken as 0.95:
K4 is the inverter efficiency, taken as 0.85 or according to manufacturer’s data:

K5 is the correction factor for the orientation and tilt angle of the PV square, taken to be around 0.9.

Calculate the area of the PV square based on the load power consumption

PV module square area = annual power consumption / total annual local radiant energy x module conversion efficiency x correction factor

A=P/H-η-K

Solar radiation energy conversion

1 cal (cal) = 4.1868 Joules (J) = 1.16278 milliwatt hours (mWh)

1 kilowatt-hour (kWh) = 3.6 megajoules (MJ)

1 kWh/㎡(KWh/㎡)=3.6 MJ/㎡(MJ/㎡)=0.36 KJ/cm²(KJ/cm²)

100 milliwatt hours/cm² (mWh/cm²) = 85.98 calories/cm² (cal/cm²)

1 megajoule/m² (MJ/m²) = 23.889 cal/cm² (cal/cm²) = 27.8 milliwatt hours/cm² (mWh/cm²)

When the unit of radiation is cal/cm²: annual peak sunshine hours = radiation x 0.0116 (conversion factor)

When the unit of radiation is MJ/m²: annual peak sunshine hours = radiation ÷ 3.6 (conversion factor)

When the unit of radiation is kWh/m²: peak sunshine hours = radiation ÷ 365 days

When the unit of radiation is kJ/cm², peak sunshine hours = radiation ÷ 0.36 (conversion factor)

Battery selection

Battery capacity ≥ 5h × inverter power / battery pack rated voltage

Tariff calculation formula

Power generation cost price = total cost ÷ total generation capacity

Power plant profit = (purchase price of electricity – cost price of power generation) x working time within the life of the power plant

Power generation cost price = (total cost – total subsidy) ÷ total generation capacity

Power plant profit = (purchase price of electricity – cost price of power generation2) x working time within the life of the power plant

Power plant profit = (purchase price of electricity – cost price of power generation2) x working time within the life of the power plant + non-market factor earnings

ROI calculation

No subsidies: Annual power generation x tariff ÷ total investment cost x 100% = annual rate of return

With power plant subsidy: annual power generation × electricity price ÷ (total investment cost – total subsidy) × 100% = annual rate of return

With tariff subsidy and power plant subsidy: annual power generation × (tariff + subsidy tariff) ÷ (total investment cost – total subsidy) × 100% = annual rate of return

PV square tilt angle and azimuth angle

Tilt angle

Latitude Component horizontal tilt

0°-25° Inclination = Latitude

26°-40° inclination = latitude +5°-10° (in most parts of the country take +7°)

41°-55° Inclination = Latitude + 10°-15°

Latitude > 55° Inclination = Latitude + 15° – 20°

Azimuth

Azimuth = [peak moment of load in a day (24h system) – 12] × 15 + (longitude – 116)

PV square front and rear row spacing:

D = 0 . 7 0 7 H / t a n [ a c r s i n ( 0 . 6 4 8 c o sΦ- 0 . 3 9 9 s i nΦ) ]

D: Component square front and rear spacing

Φ: Latitude of the PV system (positive for the northern hemisphere, negative for the southern hemisphere)

H: is the vertical height from the bottom edge of the rear row of PV modules to the top edge of the front row of shade

Want To Learn More About Lithium Battery industry?

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