Innovative Utility-Scale Battery Solution for Data Centers Eliminates Need for UPS Infrastructure

Here comes a utility-scale battery designed for data centers that doesn’t require uninterruptible power supply infrastructure

June 11, 2025
By Paul Gerke
4 min read

If there’s one lesson we can learn from Spider-Man’s uncle, or perhaps Voltaire, it’s that with great power comes great responsibility. In today’s world, where data centers are experiencing unprecedented load growth due to resource-intensive and always-on operations, this saying holds significant relevance. The increasing energy demands driven by artificial intelligence (AI) training, high-density computing, and rapidly fluctuating loads are stretching the capabilities of conventional power infrastructure within data center facilities, highlighting the need for innovative solutions.

Two industry leaders believe they have found such a solution. Battery energy storage company FlexGen Power Systems is collaborating with Rosendin, the largest employee-owned electrical contracting firm in the United States, to integrate proprietary technologies and solutions into utility-scale Battery Energy Storage Systems (BESS) that can support data center operations without the reliance on traditional uninterruptible power supply (UPS) systems.

### The Project

FlexGen and Rosendin are developing a utility-scale battery solution that will be located outside data center buildings, as part of the medium-voltage (1,000V to 35,000V) infrastructure. Together, they aim to introduce a pioneering BESS that serves as a reliable and high-performance alternative to conventional UPS systems while simplifying system architecture and reducing capital expenditures.

This project will incorporate Rosendin’s patented BESSUPS design and methodology, along with FlexGen’s patents for Soft Grid Interconnection and Island Grid Transient Frequency Stabilization. Additionally, they will leverage FlexGen’s Innovation Lab to implement its powerful HybridOS energy management system, supported by Rosendin’s extensive experience in data center delivery and thought leadership in energy storage.

According to Rosendin, the BESSUPS system offers several advantages, including providing CEBMA-quality power on an uninterrupted basis at a massive scale while eliminating the need for generators, which is particularly beneficial for clients focused on decarbonization. This approach also allows for dispatchable power to the utility upon demand, facilitating the evolution of power dispatch methods and consumption dynamics using proven utility-scale systems.

Through this initiative, FlexGen and Rosendin are conducting real-world, grid-connected tests to demonstrate that:

– Existing grid-forming Power Conversion System (PCS) technology can meet fast-response and waveform control requirements.
– Modifications to the current AC Power Conversion System (PCS) firmware enhancements from Original Equipment Manufacturers (OEMs) can support seamless UPS replacement functionality.
– Utility-scale BESS can support mission-critical loads, enhance resiliency, and simplify the transition between grid-connected and islanded modes.

“As data centers scale to meet the exponential demand from AI and hyperscale computing, we need to rethink how we deliver power resilience across the modern data center campus,” stated Pasi Taimela, Chief Innovation Officer of FlexGen. “This partnership with Rosendin allows us to offer a smarter, leaner, and more responsive approach to energy design for data centers, eliminating the need for redesigns within the data center walls—where battery systems can deliver both power quality and grid services without compromise.”

“Data center developers are seeking scalable and flexible power solutions that do not compromise performance,” added Bill Mazzetti, Senior Vice President of Rosendin. “With FlexGen’s Innovation Lab and our expertise in building complex electrical systems, we are well-positioned to validate a solution that enables our clients to build faster, smarter, and with greater confidence.”

Utilities in the Midwestern United States face significant challenges due to increasingly severe weather events, aging infrastructure, and the ongoing need to integrate renewable energy while ensuring grid reliability. State decarbonization laws complicate the process of bringing new power generation online. As utilities transition from fossil fuels to cleaner alternatives, they must also navigate supply chain issues, labor shortages, and emerging cybersecurity risks.

Service providers are tasked with modernizing their infrastructure to meet rising demand while keeping costs manageable, a challenge for utilities of all sizes. A new regional DISTRIBUTECH event, DTECH Midwest, will offer a unique opportunity to address specific issues faced by the power industry in the Midwest, including tailored content for municipal and cooperative utilities. Registration is now open for the event, scheduled for July 14-16, 2025, in Minneapolis, MN!

### The Benefits of a Better BESS

BESS configured as interactive UPS alternatives provide significant value throughout the development lifecycle. They can reduce the electrical footprint and construction complexity while enhancing energy efficiency and operational resiliency. Flexible interconnection options are emerging as a promising method to expedite project timelines, and paired battery storage is often faster to deploy than co-located gas generation, making this solution appealing for data center developers.

Rosendin and FlexGen believe that the outcomes from their integration efforts will inform system architecture standards, procurement planning, and large-scale deployment strategies for future data center projects and suppliers across the industry. Last December, FlexGen announced plans to collaborate with Eos Energy, a manufacturer of zinc-based long-duration energy storage systems, to introduce the first domestic BESS option to the U.S. market. The companies signed a joint development agreement to create and commercialize America’s first fully-integrated domestic storage solution, combining Eos’ Z3 zinc-bromine batteries with FlexGen’s HybridOS EMS and a domestic inverter and transformer package. The final product will offer a customizable solution for various applications, ranging from grid-scale to behind-the-meter energy storage systems.