Basic components for a standalone PV system includes Solar modules, Battery Bank (typically with 5 days autonomy or more), Charge Controller (for DC loads) and Inverter (for AC loads).
Typical Solar System Design Configurations
Standalone PV systems (DC, AC or both)
Deployed generally in remote and inaccessible areas where power is required and not the grid is not accessible.
Hybrid Solar Systems working with Wind, Generators, ETC.
Basic components for a standalone hybrid system includes Solar modules, Battery Bank (typically 2.5 days autonomy), Charge Controller (for DC loads), Inverter (for ac loads) and Diesel Generator.
The Generator plus rectifier allows the battery bank to be fully charged in the event of consecutive rainy days with no sun.
Other energy sources and combination can also be added to this system e.g. wind generators, bio mass & bio gas generators, etc to make up a hybrid system.
Grid Connected Systems
Basic components for a grid connected system includes Solar modules, Grid Inverter and Grid Utility. Battery Bank and Charge Controller are optional and may be included for a backup system.
Unused power from system during daylight is actively sent to utility power grid, giving the system a credit.
Large grid support systems (1MW-50GW) and distributed home systems send power directly to inverter and then to grid, and operate only when grid power is active (not during outages) as a safety precaution.
Utility independent systems utilize special “bi-directional” inverter that can power dedicated circuits which remain energized even during utility power outages.
Solar System Sizing
Designing solar systems is the single most important criteria in ensuring a reliable system. It is based on these 4 key components namely Load (watts or amps), AC or DC, Hours of operation and Location.
Solar sizing is done taking into consideration the solar insolation data for that area (if available). Otherwise 4hrs of peak sunshine per day is used to calculate the module output.
The minimum battery autonomy is ~5 days. Any lower and system reliability will be compromised.
Loss of Load Probability, LOLP should be as high as possible within economic limits. The Array to Load Ratio, ALR should also be >1.2 for all months.
Other factors that need to be considered are system voltage, module & battery configurations, type of charge controller & inverter to be used and proper grounding issues.