Using Energy Storage Systems to Optimize Datacenter Reliability and Sustainability

Energy is critical and costly for datacenters. The addition of a battery energy storage system (BESS) can enhance datacenter reliability and sustainability by supporting renewable energy sources, ensuring continuous energy availability, and reducing operating costs. Battery pole connectors are a key component enabling a BESS to deliver maximum benefits.

BESS battery pole connectors require features such as strong mechanical durability, an IP67 environmental rating, and safe, reliable connections to handle high currents and voltages. They should also be easy to install and maintain, with polarity protection to prevent connection errors, and latching mechanisms to prevent inadvertent disconnection. They must also comply with the requirements of UL Standard 4128.

This article reviews the factors driving growing energy consumption in datacenters and how that’s changing the design of uninterruptible power systems (UPSs). It then considers the reliability and sustainability benefits of using modular BESS in datacenters and looks at the performance requirements for battery pole connectors with a focus on UL 4128. It concludes by demonstrating how battery pole connectors and cable assemblies from Weidmüller can support proactive energy management and contribute to the successful and high-performance implementation of datacenter BESS installations.

The increasing rack density in cloud datacenters, driven by the rise of artificial intelligence (AI) and machine learning (ML), is significantly increasing power requirements. Datacenter energy consumption is expected to triple as a percentage of overall electricity consumption between 2024 and 2030, rising from about 3 to 4 percent of total demand in the U.S. in 2024 to between 11 and 12 percent in 2030 (Figure 1).

Figure 1: Between 2024 and 2030, datacenter energy consumption in the U.S. is expected to triple as a percentage of overall electricity consumption (shown on the vertical axis). (Image source: Weidmüller)

Evolving power architecture

The surge in power consumption is causing significant changes in datacenter power architectures, including a rethinking of how UPSs are structured to support the need for robust power availability, improving sustainability, and helping to manage spiking energy costs.

Previously, a UPS was primarily used to provide short-term power during the startup of a motor-generator that was designed to power the datacenter during outages of the main utility power. That has changed.

A UPS is increasingly seen as the primary source of back-up power to reduce or eliminate the greenhouse gases produced by motor generators. That demands more from UPS designs. Scalability and flexibility have become important features.

A modular design enables the BESS to be scaled up in size to support longer runtimes and other capabilities, such as integrating renewable energy resources. Additionally, traditional valve-regulated lead-acid (VRLA) batteries are being replaced with lithium-ion (Li-ion) batteries. The new battery technology has longer life cycles, faster charging times, and higher energy densities — all highly prized features in datacenters with growing energy demands.

Modular UPSs using Li-ion-based BESSs are also easier to maintain compared to VRLA solutions, which require much more frequent battery replacement. Adding and removing modules using battery pole connectors is also a cost-effective way to address changing datacenter power needs.

Battery pole connectors are also important to support safety and efficiency in modular BESS. Those BESS designs can be conventional racks of batteries inside the datacenter. Still, they can also be collocated next to the datacenter in a containerized solution, freeing up valuable space inside the datacenter for servers, memory, communications, and other critical electronics that support the increasing demands for processing power and connectivity (Figure 2).

Figure 2: Modular BESS installations can be based on containerized solutions, as illustrated above, or built using racks of batteries and power converters located inside a datacenter. (Image source: Weidmüller)

Integration with renewable energy sources

Not only are datacenters consuming more electricity, but the kilowatt-hour (kWhr) cost of that electricity is increasing, compounding cost and sustainability challenges. To address these concerns, renewable energy sources such as solar power are being integrated into datacenters. Again, modular BESS designs utilizing battery pole connectors can provide the necessary flexibility.

The growing energy consumption of datacenters is also resulting in the expectation that datacenter operators will be good stewards of the environment. In addition to direct energy cost reductions, datacenter operators can also leverage peak shaving, demand response, and other tools to achieve secondary cost benefits.

BESS can provide valuable grid services, such as frequency regulation and voltage support, thereby enhancing grid resilience. In a campus setting, a BESS can be part of a microgrid that supports islanding and operates independently of the grid.

BESS can shift energy consumption patterns by storing renewable energy during periods of low demand and utilizing it during peak demand periods, thereby reducing demand on the grid and leveling costs, as utilities often charge higher rates during peak hours.

UL 4128 for BESS connectors

UL Standard 4128 details requirements for the mating halves of connectors used to join battery cells (intercell) and battery tiers (intertier) in a BESS. The standard covers cables, cable connectors, and mating inlets rated for up to 2,000 V that are not intended for connection or disconnection under load.

It requires that the connector be fully plugged in and interlocked before it is energized. Even a little movement from the connector could reduce the contact area, increase contact resistance, and create a hot spot, which could lead to a fire. This locking feature is important for BESS safety. Additionally, the tensile load on the connectors in a cable assembly must not exceed the specified upper limit.

The connectors are designed for use with copper or copper alloy conductors, rated for at least +90°C. They are intended for factory or field assembly and can be used in both outdoor and indoor locations, handling over 100 operations of mechanical connection and disconnection (without load).

UL 4128-rated connectors are not intended for use in hazardous locations; therefore, a protective cap should be installed on any unused connectors. Finally, burn warnings may be required when using connectors in high ambient temperature conditions.

Battery pole connectors

Battery pole connectors, especially those that meet UL 4128 requirements, were developed to provide superior performance and safety in a high-power BESS compared with simple and inexpensive cable lug wiring assemblies.

Cable lug connections don’t provide the flexibility needed in a modular BESS. They require manual connection and tightening of the nuts on each lug. That takes too much labor and is prone to errors. In addition, if the nut is not tightened correctly, a high-resistance connection results, generating heat, wasting energy, and creating a potential fire hazard.

The lack of environmental protection and the ruggedness of cable lug connections can lead to unreliable operation over the longer term. Lug connections are not touch-safe and can pose a serious safety hazard for installers when high energy levels are present.

Instead of cable lugs, designers can turn to color-coded battery pole connectors that meet UL 4128 (Figure 3). Color coding, as defined in the UL standard (orange for positive and black for negative), is used on the cable connectors and busbar connections to create a visual key and speed assembly.

Figure 3: Battery pole connectors enable quick and efficient connections in modular BESS and are important to support safety and efficiency. (Image source: Weidmüller)

In addition to being color-coded, both sides of the battery pole connectors are mechanically keyed for positive and negative connections, preventing any possibility of assembly error when mating the connectors. Keying in the battery pole connectors from Weidmüller allows for the plugging of the connector together in any orientation, minimizing mechanical stress in the cable assembly.

The locking mechanism meets the UL requirement that the connector is fully plugged in and interlocked before it is energized. The contacts are separated before the connector can be unplugged, eliminating the potential for a dangerous arc fault in the event of an unintended disconnection under load.

The contacts are made of copper alloy plated with silver to minimize contact resistance, are approved according to UL 4128, and are rated for more than 100 operations of mechanical connection and disconnection.

Weidmüller battery connectors (WBCs) are designed to withstand harsh environmental conditions and are rated for ingress protection class IP67 for protection against the intrusion of dust and water. They are touch-safe due to the protected mounting side.

UL 4128 does not specify the material of the connector body, only its performance requirements. WBCs are made using polyamide 66 (PA 66), a modified thermoplastic well-suited for use in battery pole applications. The advantages of PA 66 over regular PA include improved fire protection and a higher continuous operating temperature. PA 66 also meets the strict requirements for use in railway vehicles. Other benefits of PA 66 include:

• Improved fire resistance
• Contains no halogen or phosphorus
• Low smoke and fumes

The WBC family enables the connection of conductor cross-sections ranging from 16 mm², to 95 mm², rated for up to 200 A on the connector side. Cable assemblies are also available that significantly reduce the amount of labor required for BESS wiring (Figure 4). Examples of Weidmüller battery pole connectors and cable assemblies include:

• 2905330000, male minus connector, rated for 120 A and 1,500 V
• 2905290000, female minus connector, rated for 120 A and 1,500 V
• 2905320000, male plus connector, rated for 200 A and 1,500 V
• 2905380000, female plus connector, rated for 200 A and 1,500 V
• 2938270000, 324 mm (12.75 in) long cable assembly rated for 120 A and 1,500 V

Figure 4: Examples of male and female WBCs and a battery pole connector cable assembly. (Image source: Weidmüller)

Conclusion

Changes in the power architecture of large datacenters are being driven by a combination of increasing rack power densities to meet the computing and storage needs of AI and ML, as well as to manage the rising cost of electricity. This is resulting in new UPS designs based on modular BESS, utilizing battery pole connectors to provide scalability and modularity.

In addition to ensuring reliable power delivery, the modular BESS designs enable the integration of renewable energy sources, such as solar energy, which can address the expectation for higher levels of environmental sensitivity, sustainability, and resilience. The battery pole connectors that support these needs must meet the requirements of UL 4128 to ensure safe and efficient connectivity of high and potentially dangerous battery energy levels.

Recommended reading:

1. How Microgrids and DERs Can Maximize Sustainability and Resilience in Industrial and Commercial Facilities
2. How to Use Intelligent Power Distribution to Maximize Network Availability
3. How to Connect the Blocks in Commercial Energy Storage Systems
4. How to Implement High-Performance Modular Connectivity for Enterprise Datacenter Equipment
5. Addressing the Energy Demands of AI Servers with Cutting-Edge Technology