BESS – Battery Energy Storage Systems: architectures, applications and service continuity

The evolution of the energy transition has made Battery Energy Storage Systems (BESS) fundamental assets – not only for optimizing self-consumption from renewable sources, but above all for the resilience of grid infrastructure. In the commercial and industrial (C&I) sector, BESS units play a crucial role as advanced backup solutions.

For companies operating uninterruptible critical loads — such as data centers, continuous chemical processes, or hospital departments – integrating a BESS ensures operational continuity, eliminating the risks of micro-interruptions (flicker) or blackouts that would cause substantial economic losses and equipment damage.

Through peak shaving and load shifting functions, combined with response times on the order of milliseconds, these systems stabilize the internal grid, guaranteeing Power Quality.
At the heart of managing these machines is the EMS (Energy Management System), the software “brain” that oversees energy flows, communicates with grid nodes, and optimizes charge/discharge cycles based on predictive algorithms and market logic. Currently, the technology landscape is divided into three hardware macro-categories, differentiated by modularity, capacity, and installation flexibility.

Modular, Stackable BESS

This category represents the ideal solution for the C&I sector, which requires flexibility and ease of sizing. Unlike single-block units, this architecture features structurally separate hardware components: the power conversion unit (inverter) and the battery modules (usually Lithium Iron Phosphate chemistry, LFP) are installed individually but are designed to integrate natively into a single communication and thermal management ecosystem.

• Inverter power: these systems use three-phase hybrid inverters, DC-coupled or AC-coupled, with scalable rated power typically ranging from 25–30 kW to 100–125 kW per single unit, often paralleled to reach overall power outputs on the order of a MW.
• Storage capacity: capacity is highly scalable thanks to the independent-module design. Each battery pack typically has a rated capacity between 5 and 12 kWh. By connecting multiple modules in series on a single tower or paralleling multiple towers, the system can configure overall storage clusters ranging from 5 kWh up to 250 kWh per single inverter group. The dedicated EMS manages energy optimization at the individual module level, preventing the aging of a single cell from penalizing the entire bank.

Cabinet BESS (engineered enclosures)

Cabinet systems represent the standard solution for the mid-sized commercial and industrial (C&I) segment. These are pre-assembled, certified rack enclosures for outdoor or indoor installation (with high protection ratings such as IP55), integrating batteries, fire safety systems, and thermal management inside a single unit.

• Power and capacity: the power conversion section (PCS), integrated or tightly coupled to the cabinet, generally ranges from 50 kW to 125 kW. The internal energy capacity of the racks typically varies from 50 kWh up to 250 kWh per single cabinet, with the possibility of connecting multiple cabinets in parallel to meet larger-scale business needs. Thermal control is handled by forced-air or liquid HVAC systems to stabilize the cells.
• STS (Static Transfer Switch) integration: the management of electrical continuity during a blackout depends critically on the presence of a static switching device:
  • Cabinet WITH STS: the inclusion of a thyristor-based static switch allows the system to continuously monitor grid parameters. In the event of voltage fluctuations or interruptions, the STS disconnects the main line and switches critical loads over to the BESS in under 4–10 milliseconds. This seamless transition prevents computers, servers, and sensitive industrial machinery from shutting down, functioning effectively as a large-scale UPS.
  • Cabinet WITHOUT STS: in this configuration, the system lacks the fast semiconductor-based switch. While it can still operate in island mode, the transition from grid to battery power occurs via external mechanical contactors. This results in a slower switching time, typically between 20 and 50 milliseconds (or more), causing a micro-interruption that shuts down electronic loads not protected by local UPS units. This solution is suitable for general-purpose emergency power backup, but not for protecting continuous-cycle industrial loads.

Containerized BESS (utility-scale and large industry)

For energy-intensive industries, large renewable generation plants, and grid-stability services for network operators, the only applicable architecture is the containerized system, mounted on standardized 20- or 40-foot structures.

• Power and capacity: these infrastructures manage centralized or distributed power well in excess of 500 kW, reaching up to several megawatts (MW) via dedicated medium-voltage conversion stations. Energy capacity is massive, starting at 1 MWh and exceeding 4-5 MWh per single container in the latest high-density generation.
• Management characteristics: these systems leverage highly sophisticated liquid cooling technologies and multi-stage safety systems. In this scenario, the EMS is a centralized, industrial-grade software platform that interfaces directly with the plant’s SCADA systems and with transmission system operator (TSO) platforms to operate in dispatching services markets.