Design decision
PV supplies energy when sunlight is available; BESS stores usable energy, while PCS converts power and EMS coordinates constraints. Specify kW for conversion and charge/discharge limits, and kWh for usable storage within the agreed state-of-charge window. An illustrative 100 kWh of usable energy supplying 50 kW would last two hours in an ideal constant-load calculation; conversion losses, temperature and reserve requirements reduce the usable duration.
When this approach fits · Limits and alternatives
Solar and storage may help align generation and charging or limit peaks. They do not guarantee an islanded supply or eliminate grid-connection obligations. Assess interval load data, seasonal generation, grid-import and export limits, storage degradation and control ownership. Request a site-specific fire and emergency plan, safe isolation, applicable electrical design, grid approval evidence and a tested response to EMS or communications failure. A smaller non-storage solution may be appropriate when the evidence does not support the added complexity.
Procurement checks
- Separate battery energy in kWh from PCS output power in kW
- Assess thermal safety, grid code, fire protection and insurance
- Test EMS, PCS, PV and EVSE integration and dispatch logic
Evidence to request
Define the installation country, supply, arrival and departure times, energy per session and operating constraints. Ask for an electrical design, exact configuration, test evidence and acceptance plan. Include support responsibilities and data ownership in the written scope.