In light of the widespread integration of renewable energy resources to the power grid, the imperative of ensuring optimally efficient, safe, and reliable energy storage infrastructure cannot be overstated. Among the critical domains offering such possibilities is the implementation of compact and flexible power connections in battery energy storage systems (BESS), as well as solar combiner boxes and inverters, electric vehicle (EV) charging stations, and utility substations, along with transmission and distribution (T&D) assets.

Traditional cable/lug arrangements and rigid busbar are effective for making dependable and cost-effective electrical connections in many types of applications. Recently, however, the engineering community is taking note of an alternative method that is more compact and flexible, offers low smoke and halogen-free properties in the event of a fire, and reduces installation time.

1. The need for reliable energy storage is growing due to increasing renewable energy production, such as at solar farms (here paired with storage), and the ongoing electrification of demand and supply-side utility infrastructure. Courtesy: nVent ERIFLEX

“Specific to BESS units today, OEMs [original equipment manufacturers] are trying to fit more in the container, which is a set amount of space you typically can’t change,” said Thomas Bockstoce, product manager for nVent ERIFLEX, which provides low-voltage connection and distribution products for many applications including energy storage systems, fast DC chargers, battery packs, inverters, transformers, combiner boxes, recombiners, and the interconnection between electrical systems. Bockstoce helps electrical panel and cabinet builders find alternative technologies to large cable and rigid busbar for connecting critical components. These solutions are more compact, safe, and efficient compared to what he calls “the way things have always been done” in electrical enclosures of all types, and increasingly where battery energy storage (Figure 1) is required.

2. The market is eager for more compact, safe, and efficient electrical connection solutions, as shown here. Courtesy: nVent ERIFLEX  

“When making connections, it might be a 500- or 1,000-kcmil (thousand circular mils) cable you’re using, so that can be very challenging for an installer to maneuver around the field or in a shop,” Bockstoce said. “We’re getting questions like, ‘What can I use here in place of cable?’ That’s also pointing to electrical power connections that are pre-engineered [Figure 2] and don’t require the same amount of physical labor to install.”

Keeping It Flexible

Bockstoce explained how flexible busbar, also known as a flexible electrical conductor or flexible bus, is a lesser-known type of power distribution component increasingly used in electrical panels and cabinets. The core structure of flexible busbar consists of multiple thin strips or layers of conductive material, typically copper or aluminum, layered or laminated together to create a substantial and flexible conductor. This design allows the bar to be bent or shaped into various configurations, making it a versatile solution for distributing electrical power within confined spaces.

3. Flexible busbar eliminates the cutting and crimping of large, bulky cable and offers more freedom to design well-ordered, compact connections compared to standard busbar. Courtesy: nVent ERIFLEX 

In one scenario that Bockstoce described, a flexible busbar (Figure 3) is formed from layers of thin electrolytic copper insulated with a high-resistance, self-extinguishing thermoplastic elastomer (TPE). The insulating sleeve is also grooved on the inner surface, which reduces the contact surface with the laminates to less than 20%. This enhances flexibility to make installation easier. Additionally, current-carrying capacity and efficiency are improved over cable and rigid busbar.

“You will sometimes see where the inside of the jacket is ribbed, so there is less surface area for the copper laminates to adhere to, so you have a smoother transition when you do your folds, bends, and twists,” Bockstoce said. “The laminates will slide between the central conductor and the insulation material, which will not cause any binding, so it’s easier to fabricate.”

Bockstoce continued: “What you get is a very small bending radius—it’s a more compact and orderly connection between your main power and distribution equipment, transformers and switchboards, switchboards and electrical cabinets, and so forth. With cable, when you’re designing to UL 508A for example, the National Electric Code requires a certain radius depending on the conductor size. I think the ‘aha!’ moment for designers is seeing how you can pretty much fold these connections on top of themselves, so now they’re realizing why they don’t need all of this space where the cables will go.”

Reducing Cost and Complexity

Bockstoce noted how significant size and weight reductions can be achieved with a flexible busbar solution. Compared to a 500 kcmil wire length for instance, an equivalent 3×24 flexible busbar solution represents a roughly 70% cross-section savings (where 500 kcmil = 253.35 square millimeters (mm 2) and 3×24 busbar = 72 mm 2). Reductions will vary depending on the specific product and ampacity utilized; however, these savings can be compelling in place of rigid power connections.

4. When making power connections with flexible busbar, be sure to specify products that meet the most stringent global compliance requirements. These include IEC and ANSI/UL, as well as DNV GL and ABS, allowing for the installation of flexible busbar in a vast range of electrical systems rated up to 1000VAC IEC/UL and 1500VDC IEC/UL, and for ampacities from 80A to 7400A. Courtesy: nVent ERIFLEX 

“You get dramatically smaller, easier-to-manage connections [Figure 4] so you’re not fitting all those cables on top of each other where it starts to look like spaghetti,” he said. “Integrating remote diagnostics into electrical panels is something that’s happening more these days, and here’s a way to have that same footprint but more space again for new devices. Other times, it can enable you to shrink your enclosures and pay less, and now you have a clean looking cabinet that uses short runs and is visibly organized.

“If you’re using flexible busbar for inputs or outputs, or for stacking distribution blocks, we’re seeing 30% to 40% average space savings over cable in many of those applications.”

Bockstoce said another advantage is the simplicity of making and maintaining flexible busbar connections.

“When you have a lug and cable, traditionally you want to perform some checks on it to make sure there are no hot spots. With flexible busbar, you tend to have one piece that’s not crimped—there is no separate mechanical connection you’re relying on,” Bockstoce said. “That also means you don’t have to perform extra inspections on the lugs to see if you have any hot spots.”

Enhancing Safety and Compliance

The use of low smoke, halogen-free power connections also takes into account personal safety, environmental impact, and equipment protection in the design and installation of electrical enclosures. Bockstoce said a main advantage is gained by using products that combine low smoke, halogen-free, and flame retardant (LSHFFR) qualities (Figure 5).

5. Workers can monitor energy storage systems digitally to check performance and more quickly spot anomalies. Busbar insulation should be halogen-free and flame retardant in accordance with ISO 5659-2 (measurement of smoke density generated from burning materials), IEC 61034-2 (measurement of smoke density of cables burning), and UL 2885 (assessment of halogens), making it ideal for use in enclosed spaces. Courtesy: nVent ERIFLEX 

“By having those three characteristics, especially in a BESS site or any type of closed cell system, if there is an incident the product will not emit toxic fumes or smoke into the air, which is a benefit to electronic componentry and everything inside that panel,” Bockstoce said. “What’s key is having an LSHFFR-style jacket on your busbar where the potential release of smoke or harmful byproducts is not the same concern as with some types of conductors.”

Flexible busbar allows for greater design flexibility by shrinking the space required to make connections in electrical enclosures. These solutions tend to be highly compatible within panels and cabinets, making it easier to configure and scale electrical systems in renewable infrastructure. Combining LSHFFR properties, these products are taking on increased importance where it is vital to minimize the rapid spread of fire.

For designers and installers, a flexible busbar solution can overcome spatial limitations and offer a lower cost of implementation in BESS containers, as well as solar arrays, and EV and T&D infrastructure. Their ability to efficiently distribute power while adapting to various layouts and configurations makes them an essential component in modern electrical systems. Where traditional cable/lug and busbar connections are rigid and restricting, flexible busbar is a more adaptable option that designers and installers are coming to appreciate, providing OEMs with a solution to add more inside an enclosure while minimizing the potential heat rise.

—This article was contributed by nVent ERIFLEX, which serves industries such as energy storage, e-mobility, data centers, and renewable energy.