What Are Centralized and String-Type ESS in C&I Projects?

As commercial and industrial energy storage expands across factories, logistics centers, commercial buildings, and microgrids, multi-cabinet parallel operation has become a core system design. In parallel applications, integrators must choose between centralized and string-type ESS architectures. Although both use lithium iron phosphate (LFP) batteries and similar cabinet capacities—such as 100–144kWh air-cooled systems, 215–241kWh C&I systems, or 372kWh liquid-cooled solutions—their internal structures and control methods differ significantly.

Centralized architecture focuses on unified power conversion, while string-type emphasizes distributed control. Understanding these differences helps buyers, EPC companies, and overseas project owners choose the most suitable structure for system reliability, safety, and scalability.

Types of ESS Architectures

1. Centralized ESS

A centralized ESS connects multiple battery cabinets to one large PCS (Power Conversion System). All battery modules share the same DC bus, and the PCS handles charging, discharging, and grid interaction.

Characteristics:

• Single PCS with high power density

• Unified scheduling through EMS/BMS

• Lower redundancy

• Sensitive to differences in SOC and internal resistance

• Suitable for stable industrial loads and large power blocks

Systems like 215–241kWh air-cooled or 372kWh liquid-cooled ESS are often used in centralized architectures due to their higher continuous output and simplified grid interface.

2. String-Type ESS

A string-type ESS assigns a dedicated PCS to each battery cabinet, allowing independent operation. Cabinets communicate with the EMS individually, forming a distributed architecture.

Characteristics:

• One PCS per cabinet (similar to PV string inverters)

• High redundancy; one cabinet failure doesn't affect the whole system

• Works well with different cabinet capacities or aging levels

• Easy to scale by adding more units

Modular air-cooled systems in the 100–144kWh range are commonly deployed in string-type configurations, especially in commercial buildings or microgrids.

Key Differences Between Centralized and String-Type ESS

System Architecture

Centralized ESS offers a single conversion point, reducing hardware quantity but creating a single point of failure. String-type ESS distributes power conversion, increasing flexibility and redundancy.

Control Logic

Centralized ESS uses unified control for voltage, current, and SOC balancing.
String-type ESS uses distributed logic—each PCS adjusts parameters independently, allowing better adaptation to cabinet health differences.

Result:

• Centralized = simpler but less flexible

• String-type = more adaptive and tolerant of battery aging

Parallel Operation Behavior

Centralized ESS

• Parallelization occurs at the battery level

• Requires tight consistency among battery packs

• Large PCS bears all balancing responsibility

• Expansion after installation is complicated

String-Type ESS

• Each cabinet controls its own current output

• No DC bus imbalance issues

• Easy to add or replace cabinets

• Better suited for phased investment or gradual load growth

This makes string-type systems more attractive for Southeast Asia microgrids and European distributed C&I projects.

Installation and Maintenance

Centralized ESS

Pros:

• Fewer PCS units

• Simpler wiring

Cons:

• Heavy PCS installation

• Entire system may stop during PCS maintenance

String-Type ESS

Pros:

• Lightweight PCS per cabinet

• Fault isolation and hot-swap capability

• Faster commissioning for modular deployments

Cons:

• More PCS units to inspect

Safety Considerations

String-type ESS provides stronger circuit isolation because each cabinet can disconnect independently. This is especially beneficial in liquid-cooled systems—such as 215kWh and 372kWh cabinets—where module-level protection and thermal stability are critical for safety compliance in Europe and North America.

Centralized systems rely more on the health and protection of the large PCS. A PCS failure may impact the performance of all battery cabinets connected to the same bus.

Applications in Global Markets

Different regions favor different architectures based on regulatory, installation, and energy-use patterns.

• Europe

Strong preference for modular string-type systems

Strict grid codes value high redundancy and cabinet-level control

• North America

Combination of centralized blocks for utility-scale

String-type for C&I buildings and EV charging hubs

• Southeast Asia

Rapid load growth makes scalable string-type designs attractive

Microgrids benefit from cabinet-level PCS control

Manufacturers offering both air-cooled and liquid-cooled ESS—like 100–144kWh air-cooled, 215–241kWh air-cooled, and 372kWh liquid-cooled systems—gain flexibility across these diverse project demands.

Price Considerations

ESS architecture selection directly affects cost due to differences in:

• PCS quantity

• Installation complexity

• Cooling method (air-cooled vs liquid-cooled)

• Communication and control components

• Local certification requirements

For export projects, integrators typically request a full technical design before pricing because system configuration varies widely across regions.

How Long Do These Systems Last?

Modern LFP C&I energy storage systems generally achieve:

• 8000+ cycles

• 15+ years service life

• Stable performance under both air-cooled and liquid-cooled environments

Liquid-cooled systems typically provide lower temperature variance, contributing to slower battery degradation.

Conclusion

Centralized and string-type ESS architectures both play important roles in C&I parallel projects:

• Centralized ESS delivers high power density and unified management, ideal for large industrial loads.

• String-type ESS provides flexibility, redundancy, and easy expansion, making it suitable for commercial buildings, microgrids, and export markets with incremental capacity needs.

Choosing the right architecture depends on project size, power requirements, redundancy expectations, and future expansion plans.

If you are interested in centralized or string-type ESS solutions, feel free to contact Dagong ESS at sales@dagongess.com.