Quick Answer
To achieve a 24-hour off-grid supply, a solar panel array with a minimum of 2.5-3 kW peak power output is typically required, assuming a moderate load and battery efficiency. The exact amount of solar input needed can vary greatly depending on the specific application, load profile, and desired battery state of charge. A more detailed assessment is necessary to determine the optimal solar array size.
Determining Solar Array Size
The first step in determining the required solar array size is to calculate the daily energy load. This involves analyzing the load profile to determine the average daily energy consumption. For a 24-hour off-grid supply, the load profile should be examined to identify the peak and trough periods. A common approach is to use a load profile with a moderate load during the day and a reduced load at night. Assuming an average daily energy consumption of 20-25 kWh, the solar panel array should be sized to meet this demand.
Battery Bank Sizing
When sizing the battery bank, it’s essential to consider the depth of discharge (DOD). A DOD of 50-60% is generally recommended to ensure battery longevity. Based on this assumption, a 20 kWh battery bank would be required to meet the 20-25 kWh daily energy demand. The battery bank should be sized to store excess energy generated during the day, which will be used during the night or on cloudy days.
Calculating the Required Solar Array Size
To calculate the required solar array size, the daily energy load (20-25 kWh) is divided by the daily solar irradiation (5-6 peak sun hours). A common value for daily solar irradiation in the US is 5.5 peak sun hours. Based on this assumption, the required solar array size would be 3.64 kW (25 kWh / 5.5 hours) to 3.18 kW (20 kWh / 5.5 hours). To account for inefficiencies and variability, a 10-20% oversize factor is commonly applied, resulting in a required solar array size of 4-4.5 kW.
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