How to Calculate Seasonal Variations in Solar Production?

Understanding Solar Irradiance

To calculate seasonal variations in solar production, it’s essential to understand solar irradiance, which measures the amount of solar energy received per unit area per unit time. The solar irradiance chart for your location will provide the monthly average solar irradiance values in kWh/m²/day. For example, a location at 40° North latitude might have an average solar irradiance of 4.8 kWh/m²/day in June and 1.7 kWh/m²/day in December.

Calculating Seasonal Solar Production

Using the solar irradiance chart, you can calculate the monthly average solar production for your off-grid system. For a 5 kW system, you would multiply the system size (5 kW or 5000 W) by the solar irradiance value (e.g., 4.8 kWh/m²/day) and the number of days in the month (assuming 30 days for simplicity). This will give you the monthly average solar production in kWh. For example, in June, the monthly average solar production would be 5000 W x 4.8 kWh/m²/day x 30 days = 720,000 Wh or 720 kWh.

Worksheet for Seasonal Solar Production Calculation

To simplify the calculation, you can create a worksheet with the following columns:

• Month
• Solar Irradiance (kWh/m²/day)
• System Size (W)
• Number of Days in the Month
• Average Solar Production (kWh)
• Energy Storage Capacity (kWh)

Fill in the values for your location, system size, and solar irradiance chart, and calculate the average solar production for each month. This will give you a clear picture of your seasonal solar production variations and help you size your energy storage capacity accordingly.