Maturity status | Beta |
This article explains what BESS optimization is, how it works, and how to configure it for a site.
What is BESS optimization?
Battery Energy Storage System (BESS) Optimization uses a large-scale on-site battery to increase EV charging capacity and reduce energy costs. The Energy Management System (EMS) controls the battery in coordination with Dynamic Load Management (DLM) — charging the battery when spare capacity is available and discharging it during peak EV demand.
Three objectives are supported:
Grid Capacity Expansion — discharges the battery when EV charging demand exceeds the grid connection limit, providing additional charging capacity without a grid upgrade
Self-sufficiency optimization — prioritizes locally generated renewable energy (for example, solar PV) by storing surplus generation in the battery and using it for EV charging
Self-sufficiency optimization (zero feed-in) — same as self-sufficiency optimization, but prevents the battery from ever feeding energy back into the grid
How does BESS optimization work?
The EMS monitors GCP consumption and controls the battery to keep the site operating within the grid import limit.
Grid Capacity Expansion (also Virtual Grid Expansion):
When spare grid capacity is available, the battery charges
When EV charging demand pushes GCP consumption toward the grid import limit, the battery discharges to provide additional power to the EVs
Self-sufficiency optimization:
The battery charges with surplus locally generated energy (for example, solar PV) rather than exporting it to the grid
Stored energy is used to supply EV charging demand, reducing grid import
EV demand still remains the most important priority so power is imported from the grid to support EVs if the battery and local production cannot completely cover demand
Self-sufficiency optimization (zero feed-in):
Operates the same as self-sufficiency optimization, but the battery always maintains a small level of grid import to ensure it never exports energy to the grid
This objective assumes that PV production is actively curtailed to zero by the PV inverter itself when feed-in is not permitted
What are the safety features for BESS optimization?
When the battery approaches its minimum state of charge (SoC), the EMS gradually reduces its maximum discharge power, starting at 5% above the minimum SoC. A hysteresis of 2% SoC prevents frequent switching between charging and discharging when the battery is near minimum SoC.
What are the requirements for BESS optimization?
Dynamic Load Management (DLM) must be active — BESS optimization is not supported with Static Load Management (SLM)
Exactly one large-scale, stand-alone BESS must be integrated and visible in XENON — multiple batteries are not supported
Minimum GCP import limit of 100 kW is recommended
How do I configure BESS optimization?
In XENON, go to the Energy Management Configuration for the site
Under Virtual Grid Expansion, enable the feature and set the following fields:
Minimum state of charge — the lower SoC boundary below which the battery will not discharge
Maximum charge rate (optional) — the maximum power at which the battery will charge
Maximum discharge rate (optional) — the maximum power at which the battery will discharge
Objective — Grid Capacity Expansion, Self-sufficiency optimization, or Self-sufficiency optimization (zero feed-in)
What are the limitations of BESS optimization?
Only supported with DLM — not compatible with SLM setups
Only one battery per site is supported — if multiple batteries are present, the EMS will not control any of them
Multi-fuse setups are supported, but the battery cannot be assigned to a cluster
Single-phase EVs can cause phase asymmetry: providing 1 kW of additional EV charging power may cause up to 3 kW of battery discharge across the other phases
The battery will always leave some power at the GCP for EVs to charge