11. Multiplex load calculation based on peak sunshine hours
11.1 Current
Solar module current=load daily power consumption (Wh)/system DC voltage (V) × Peak sunshine hours (h) × System efficiency coefficient
System efficiency coefficient: The charging efficiency of the storage battery is 0.9, the conversion efficiency of the inverter is 0.85, and the power attenuation of the solar module+line loss+dust is 0.9. The specific adjustments will be made according to the actual situation.
11.2 Power
Total power of solar modules=current generated by solar modules × System DC voltage × Coefficient 1.43
Coefficient 1.43: The ratio of the peak operating voltage of a solar module to the system operating voltage.
11.3 Battery capacity
Battery capacity=[Load daily power consumption Wh/System DC voltage V] × Continuous rainy days/inverter efficiency × Battery discharge depth
Inverter efficiency: Between 80% and 93% depending on equipment selection; Battery discharge depth: Between 50% and 75% depending on performance parameters and reliability requirements.
12. Calculation method based on peak sunshine hours and the number of days between two rainy and cloudy days
12.1 Calculation of System Battery Capacity
Battery capacity (Ah)=safe number of times × Average daily power consumption of load (Ah) × Maximum consecutive rainy days × Low temperature correction coefficient/maximum discharge depth coefficient of the battery
Safety factor: between 1.1 and 1.4: Low temperature correction factor: 1.0 for temperatures above 0 ℃, 1.1 for temperatures above -10 ℃, and 1.2 for temperatures above -20 ℃. Maximum discharge depth coefficient for batteries: 0.5 for shallow cycles, 0.75 for deep cycles, and 0.85 for alkaline nickel cadmium batteries
12.2 Number of solar modules connected in series
Number of solar modules connected in series=system operating voltage (V) × Coefficient 1.43/Selected solar module peak operating voltage (V)
12.3 Calculation of average daily power generation of solar modules
Daily average power generation of solar modules=(Ah)=peak operating current of selected solar modules (A) × Peak sunshine hours (h) × Slope correction coefficient × Attenuation loss coefficient of solar modules
The peak sunshine hours and slope correction factors are the actual data of the system installation site. The correction factor for solar module attenuation loss mainly refers to the losses caused by solar module combination, solar module power attenuation, solar module dust cover, charging efficiency, etc., generally taken as 0.8:
12.4 Calculation of battery capacity to be replenished for the shortest interval between two consecutive rainy and cloudy days
Supplementary battery capacity (Ah)=safety factor × Average daily power consumption of load (Ah) × Maximum consecutive rainy days
Calculation of the number of parallel solar modules:
The number of parallel solar modules=[supplementary battery capacity+average daily power consumption of load] × Minimum interval days/average daily power generation of solar modules × Minimum interval days
Average daily power consumption of load=load power/load working voltage × Daily working hours
13. Calculation of photovoltaic array power generation
Annual power generation=(kWh)=Local annual total radiation energy (KWH/㎡) × Photovoltaic array area (㎡) × Solar module conversion efficiency × Correction coefficient. P=H · A· η· K
Correction coefficient K=K1 · K2 · K3 · K4 · K5
The attenuation coefficient of K1 solar module during long-term operation is taken as 0.8: K2. The correction for the decrease in solar module power caused by dust blocking and temperature rise is taken as 0.82: K3 for line correction, 0.95: K4 for inverter efficiency, 0.85 or based on manufacturer data: K5 is the correction coefficient for the orientation and tilt angle of the photovoltaic array, taken as around 0.9.
14. Calculate the area of the photovoltaic array based on the power consumption of the load
Area of photovoltaic solar module array=annual power consumption/total local annual radiation energy × Solar module conversion efficiency × correction factor
A=P/H· η· K
15. Conversion of solar radiation energy
1 cal=4.1868 joules (J)=1.16278 milliwatt hours (mWh)
1 kWh=3.6 megajoules (MJ)
1 kilowatt hour/square meter (KWh/square meter)=3.6
Megajoules/square meter (MJ/square meter)=0.36 kilojoules/centimeter ² (KJ/cm) ²)
100 milliwatt hours/centimeter ² (mWh/cm) ²)= 85.98 calories/cm ² (cal/cm) ²)
1 megajoule per meter ² (MJ/m) ²)= 23.889 calories/centimeter ² (cal/cm) ²)= 27.8 milliwatt hours per centimeter ² (mWh/cm) ²)
When the unit of radiation is calories per centimeter ²： Annual peak sunshine hours=radiation amount × 0.0116 (conversion factor)
When the unit of radiation is megajoules per meter ²： Annual peak sunshine hours=radiation amount ÷ 3.6 (conversion coefficient)
When the unit of radiation is kilowatt hours/meter ²： Peak sunshine hours=radiation amount ÷ 365 days
When the unit of radiation is kilojoules per centimeter ²， Peak sunshine hours=radiation amount ÷ 0.36 (conversion factor)
16. Battery selection
Battery capacity ≥ 5h × Inverter power/rated voltage of battery pack
17. Electricity price calculation formula
Power generation cost price=total cost ÷ total power generation
Power station profit=(purchase price – generation cost price) × Working time within the lifespan of the power station
Power generation cost price=(total cost – total subsidy) ÷ total power generation
Power station profit=(purchase price – generation cost price 2) × Working time within the lifespan of the power station
18. Calculation of return on investment
No subsidy: annual power generation × Electricity price ÷ total investment cost × 100%=annual return rate
Subsidies for power stations: annual power generation × Electricity price ÷ (total investment cost – total subsidy amount) × 100%=annual return rate
Electricity price subsidy and power station subsidy: annual power generation × (Electricity price+subsidy electricity price) ÷ (total investment cost – total subsidy amount) × 100%=annual return rate
19. The inclination angle and azimuth angle of the photovoltaic array
19.1 Slope angle
Latitude solar module horizontal tilt angle
0 ° -25 ° inclination angle=latitude
26 ° -40 ° inclination angle=latitude+5 ° -10 ° (+7 ° is adopted in most regions of China)
41 ° -55 ° inclination angle=latitude+10 ° -15 °
Latitude>55 ° Dip angle=Latitude+15 ° -20 °
19.2 Azimuth
Azimuth angle=[peak time of load in a day (24-hour system) -12] × 15+(Longitude -116)
20. Distance between front and rear rows of photovoltaic arrays:
D=0. 70 7 H/t a n [a c r s i n (0.6 4 8 c o s Φ- 0 3 9 9 s i n Φ) ]
D: The distance between the front and back of the solar module array
Φ： The latitude of the photovoltaic system (positive in the northern hemisphere and negative in the southern hemisphere)
H: Vertical height from the bottom edge of the rear photovoltaic solar module to the top edge of the front cover
