Generally, distributed photovoltaic power generation systems mainly adopt the mode that the power generated by the solar cells is given priority to the load. When the load cannot be used up, the excess power is sent to the power grid. When the power supplied to the load is not enough, the power grid and solar power systems can supply power to loads simultaneously.

So, do you know how the conversion efficiency, load working time, etc. of the solar power generation system are calculated? This article has compiled 20 solar power calculation formula for your reference.

## 1. Solar power calculation formula

### ① Conversion efficiency

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

Pin=1KW/㎡=100mW/cm²

### ② Charging voltage

Vmax=V rated × 1.43 times

### ③ Battery in series and parallel

Number of battery modules connected in parallel = Average daily power consumption of the load (Ah) / Average daily power generation of the module (Ah)

Number of battery modules in series = System operating voltage (V) × Coefficient 1.43 / Module peak operating voltage (V)

### ④ Battery capacity

Battery capacity = Average power consumption of the load per day (Ah) × Number of consecutive rainy days / Maximum depth of discharge

### ⑤ Average discharge rate

Average discharge rate (h) = Number of consecutive rainy days × Load operating time / Maximum depth of discharge

### ⑥ Load working time

Load working time (h) = ∑ Load power × Load working time / ∑ Load power

### ⑦ Battery

In the solar power calculation formula, battery capacity = Load average power consumption (Ah) × Number of consecutive rainy days × Discharge correction coefficient/Maximum depth of discharge × Low temperature correction coefficient

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

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

### ⑧ Solar power calculation formula based on peak sunshine hours

Component power = (Electrical appliance power × Power consumption time / Local peak sunshine hours) × Loss coefficient Loss coefficient: 1.6~2.0, determined according to local pollution level, line length, installation angle, etc.

Battery capacity = (Electrical power consumption × Power consumption time / System voltage) × Number of consecutive rainy days × System safety factor

System safety factor: 1.6~2.0, based on battery depth of discharge, winter temperature, inverter conversion efficiency, etc. Use best solar inverter for high conversion efficiency.

### ⑨ Solar power calculation formula based on total annual radiation

Component (square matrix) = K × (Operating voltage of electrical appliances × Operating current of electrical appliances × Power consumption time) / Total annual radiation in the local area

• When there is maintenance + general use, K is 230;
• When there is no maintenance and reliable use, K is 251;
• When there is no maintenance + harsh environment + require very reliable use, K is 276.

### ⑩ Solar power calculation formula based on total annual radiation and slope correction coefficient

In the solar power calculation formula, square array power = Coefficient 5618 × Safety factor × Total load power consumption / Slope correction coefficient × Average annual radiation amount on the horizontal plane

Coefficient 5618: Based on charge and discharge efficiency coefficient, component attenuation coefficient, etc.

Safety factor: Depending on the use environment, whether there is a backup power supply, whether there is someone on duty, etc., the value is from 1.1 to 1.3

Battery capacity = 10 × Total load power consumption / System operating voltage

10: No sunshine coefficient (applicable to continuous rainy days not exceeding 5 days)

### ⑪ Multi-channel load calculation based on peak sunshine hours

• Current:

Component current = Load daily power consumption (Wh) / System DC voltage (V) × Peak sunshine hours (h) × System efficiency coefficient

System efficiency coefficient: including battery charging efficiency 0.9, inverter conversion efficiency 0.85, component power attenuation + line loss + dust 0.9, which shall be adjusted according to the actual situation.

• Power:

Total module power = Module power generation current × System DC voltage × Coefficient 1.43

Coefficient 1.43: The ratio of the component peak operating voltage to the system operating voltage.

• Battery pack capacity:

Battery pack capacity = (Daily load power consumption Wh / System DC voltage V) ×(Number of consecutive rainy days / Inverter efficiency × Battery depth of discharge)

Inverter efficiency: approximately 80% to 93%, depending on equipment selection. For TYCORUN inverters, no matter it is 500w inverter or 3000w inverter, the efficiency is 90%.

Battery depth of discharge: Choose between 50% and 75% according to its performance parameters and reliability requirements.

### ⑫ Solar power calculation formula based on the peak sunshine hours and the number of days between two rainy days

• System battery pack capacity:

Battery pack capacity (Ah) = Safety factor × Average daily power consumption of the load (Ah) × Maximum number of continuous rainy days × Low temperature correction coefficient / Battery maximum depth of discharge coefficient

Safety factor: between 1.1-1.4

Low temperature correction coefficient: 1.0 above 0℃, 1.1 above -10℃, 1.2 above -20℃

Maximum depth of discharge coefficient of the battery: 0.5 for shallow circulation, 0.75 for deep circulation, and 0.85 for alkaline nickel-cadmium batteries.

• Number of components in series:

In the solar power calculation formula, number of components in series = system operating voltage (V) × coefficient 1.43/selected component peak operating voltage (V)

• Average daily power generation of modules:

In the solar power calculation formula, average daily power generation of modules (Ah) = Peak operating current of the selected module (A) × Peak sunshine hours (h) × Slope correction coefficient × Component attenuation loss coefficient

In this solar power calculation formula, the peak sunshine hours and tilt surface correction coefficient are actual data of the home solar power system installation site;

In this solar power calculation formula, the component attenuation loss correction coefficient mainly refers to the loss due to component combination, component power attenuation, component dust coverage, charging efficiency, etc., and is generally 0.8.

• Calculation of the battery capacity that needs to be replenished during the shortest interval between two consecutive rainy days:

Supplementary battery capacity (Ah) = Safety factor × Average daily power consumption of the loads (Ah) × Maximum number of continuous rainy days

• Calculation of the number of components in parallel:

Number of modules connected in parallel = (Supplementary battery capacity + Average daily power consumption of the load × Shortest interval days) / Average daily power generation of the module × Shortest interval days

Average daily power consumption of the loads = Load power / Load operating voltage × Number of working hours per day

### ⑬ Photovoltaic array power generation

In the solar power calculation formula, annual power generation (kWh) = Local annual total radiant energy (KWH/㎡) × Photovoltaic array area (㎡) × Module conversion efficiency × Correction coefficient

Correction coefficient P = H·A·η·K

Correction coefficient K=K1·K2·K3·K4·K5

• K1 (=0.8): The attenuation coefficient of the component in long-term operation;
• K2 (=0.82): Correction for component power reduction caused by dust blocking components and temperature rise;
• K3 (=0.95): Line correction;
• K4 (=0.85 or according to the manufacturer’s data): The inverter efficiency;
• K5 (about 0.9): The correction coefficient for the orientation and tilt angle of the photovoltaic array. ​

### ⑭ Area of photovoltaic array based on load power consumption

In the solar power calculation formula, photovoltaic module array area (A) = Annual power consumption (P) / Local annual total radiant energy (H) x Module conversion efficiency (η) x Correction coefficient (K)

### ⑮ Conversion of solar radiation energy

1 cal = 4.1868 J = 1.16278 mWh

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

100 mWh/cm² = 85.98 cal/cm²

1 MJ/m² = 23.889 cal/cm² = 27.8 mWh/cm²

In this solar power calculation formula, when the unit of radiation amount is cal/cm²: Annual peak sunshine hours = Radiation amount × 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)

### ⑯ Battery selection

Battery capacity ≥ 5h×Inverter power / Battery pack rated voltage

For the best batteries, you can refer to the battery stores near me.

### ⑰ Electricity price calculation formula

Power generation cost price = Total cost / Total power generation capacity

Profit of power system = (Purchase price of electricity - Cost price of power generation) ×

Working hours within the life span of the power system

Power generation cost price = (Total cost - Total subsidy) / Total power generation capacity

Power system profit = (Purchasing electricity price - Power generation cost price 2) × Working hours within the life span of the power system

Profit of power system = (Purchase price of electricity - Cost price of power generation 2) × Working hours within the life span of the power system + Income from non-market factors

### ⑱ Calculation of return on investment

No subsidy: Annual power generation × Electricity price/total investment cost × 100% = Annual rate of return

With subsidies: Annual power generation × Electricity price / (Total investment cost - Total subsidy) × 100% = Annual rate of return

There are electricity price subsidies and power station subsidies: Annual power generation × (Electricity price + Subsidized electricity price) / (Total investment cost - Total subsidy amount) × 100% = Annual rate of return

### ⑲ Photovoltaic array tilt angle and azimuth angle

Tilt angle:

 Latitude Module horizontal inclination 0°~ 25° = Latitude 26°~ 40° = Latitude + 5°~ 10° (most areas in China adopt +7°) 41°~ 55° = Latitude +10°~ 15° >55° = Latitude+15°~ 20°

Azimuth angle: Azimuth angle = (Peak load time of the day (24h system) - 12) × 15 + (Longitude - 116)

### ⑳ Spacing between front and rear rows of photovoltaic array

D = 0.707H / tan [ acrsin (0. 648 cosΦ - 0. 399 sinΦ) ]

D: Spacing in front and behind of the component matrix

Φ: The latitude of the photovoltaic system (positive in the northern hemisphere, negative in the southern hemisphere).

H: The vertical height from the bottom of the rear row of photovoltaic modules to the top of the front row of shields.

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