Peak Sun Hours And Energy Storage: How Do Sun Hours Affect Battery Sizing?

Question

Accepted Answer

Understanding Peak Sun Hours Peak sun hours are a measure of the amount of solar energy available in a given location over a 24-hour period. This measurement is typically expressed in peak sun hours per day (PSH) and is used to determine the capacity of a solar panel system. For example, if a location receives 6 peak sun hours per day, it means the solar panels can produce 6 hours of maximum power per day.
Calculating Battery Size Based on Sun Hours To determine the required battery size, you need to consider the amount of energy generated by the solar panels and the energy usage of your off-grid system. A general rule of thumb is to size the battery bank to store 2-4 days’ worth of energy usage. For example, if your system uses 1 kilowatt-hour (kWh) of energy per day, you would need a battery bank that can store 2-4 kWh of energy. Based on the number of peak sun hours, you can then calculate the required battery capacity. For a location with 6 peak sun hours, you may need a 1,000-2,000 watt-hour (Wh) battery, while a location with 4 peak sun hours may require a 2,000-4,000 Wh battery.
Example Calculation Let’s consider a location with 5 peak sun hours per day. If the solar panel system generates 5 kWh of energy per day, and the system uses 1 kWh of energy per day, you would need a battery bank that can store 1 kWh of energy. To calculate the required battery size, you need to consider the depth of discharge (DOD), which is the percentage of the battery’s capacity that can be safely discharged. A typical DOD is 50%. Based on this, you would need a battery with a capacity of 2 kWh (1 kWh / 0.5 DOD) to store 1 kWh of energy.