Design parameter overview

The design process requires the person performing the design to select values for various different design coefficients that will be used through the rest of the design process. Some of desiggn coefficients have values that are recommended based upon industry practices, but there are others that will require the designer to make a determination that strikes the right balance between the available weather and solar resource, load and usage estimates, and budget vary for each off-grid PV project. Different values for critical coefficients like Depth of Discharge, Days of Autonomy, and System voltage should be tested during the design process to find the optimal design for the system.

• Depth of discharge value: Coefficient that determines the percentage of the energy storage system that be considered usable for the design.
• Days of autonomy value: Value that determines the number of days that the system will be able to meet energy needs without additional charging.
• System voltage value: Value for the nominal voltage for the direct current (DC) system.
• Charge controller efficiency value: Value for the estimated efficiency of the type of charge controller that is anticipated to be used with the system.
• Module degradation value: Value for the estimated degradation of PV modules over time.
• Irradiance safety value: Value to ensure that system components can handle periods of high irradiance.
• Continuous duty safety value: Value to ensure that system components can handle periods of sustained current.
• Low voltage disconnect value: Value that determines when the system will shut off due to low voltage/insufficient stored energy.
• Maximum system charging voltage value: Value that determines the maximum charging voltage for the energy storage system.