Case study: Battery energy storage system is solution for pharma warehouse

BESS insights

• Battery energy storage systems (BESS) can offer uninterrupted power solutions for buildings seeking to integrate renewable energy.

• Explore a real-world example from United Therapeutics’ Project Lightyear, which ensured a seamless transition to sustainable and resilient renewable energy solutions.

Spanning 55,000 square feet, United Therapeutics Corp.’s Project Lightyear serves as a current good manufacturing practices (cGMP) warehouse facility and logistics center designed to store and distribute United Therapeutics’ pharmaceutical products. Maintaining these products within a meticulously temperature-controlled environment is imperative, with rigorous monitoring for Food and Drug Administration validation standards.

What sets Project Lightyear apart is United Therapeutics’ unwavering commitment to achieving zero-carbon operations, relying solely on electrical systems to help the building achieve this goal. This ambitious goal, coupled with the stringent demands of cGMP facilities, medication production and the desire to complete the project from contract to construction in two years, presented formidable design challenges.

Figure 3: The chart illustrates Affiliated Engineers Inc. calculations of the expected battery energy storage system (BESS) performance with an eight-hour fire pump reserve using the lowest average solar week from historical data. The left index is a bar chart of building load/photovoltaic production. The right index is the battery state of charge (SoC). Courtesy: Affiliated Engineers Inc.

In addition to achieving zero-carbon operations, Project Lightyear was driven by several other design priorities. These included ensuring occupancy and operational readiness by the second quarter of 2023, sourcing building materials from the United States whenever possible, completing the project within budget, minimizing embodied carbon and ecological impact and securing U.S. Green Building Council LEED or other certifications to validate the fulfillment of these objectives, underscoring a holistic approach to sustainable project delivery.

To expedite the schedule, United Therapeutics opted for a design-build project delivery method, engaging Affiliated Engineers Inc. (AEI) as the mechanical, electrical, piping/plumbing and fire protection engineer; Hanbury Architects as the architect of record; and DPR Construction Inc. as the construction manager. This approach allowed for close collaboration with manufacturers, local authorities like the fire marshal or code officials and utility providers during the design phase to ensure timely completion.

Implementing BESS for reliable backup power

Eliminating on-site carbon use, natural gas, diesel and other fossil fuels, the warehouse required reliable backup power. Given the critical nature of pharmaceutical warehousing, any disruption in power supply resulting in temperature fluctuations could lead to significant financial loss and product waste. Thus, implementing a battery energy storage system (BESS) emerged as the sole viable solution to ensure an uninterrupted power supply.

To calculate the required battery capacity, AEI assessed the facility’s needs for continuous operation through a power outage, resulting in a tiered approach: 48 hours for cold storage, 24 hours for the balance of the warehouse and eight hours for the code-required fire pump.

With the project targeting net zero energy, the facility must generate enough power to offset its energy usage. Integrating a roof-mounted photovoltaic (PV) system featuring 1,186 PV panels, which connect to form a microgrid using the BESS as the anchor resource, ensures sustained power generation during grid outages. While the microgrid will remain connected to the utility grid most of the time, its design allows it to operate in “island mode,” relying on the battery backup system to support the loads described above.

The required inverter capacity is identified by aggregating the building loads, including the starting current needed to support a fire pump. Compliance with NFPA 70: National Electrical Code (NEC) 695 necessitates sufficient capacity from the microgrid switchboard to the fire pump automatic transfer switch. The inverter must support this load in addition to the simultaneous operation of other building systems.

Figure 4: Project Lightyear’s battery energy storage system, featuring the Tesla Megapacks on the left with firewall separation and a combiner switchboard and grounding transformer on the right. Courtesy: DPR Construction Inc.

It was necessary to verify the starting curves for a 100-horsepower wye-delta fire pump motor, confirming adherence to the 600% motor current rule specified in NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection Section 9.2.3.4.1. The analysis determined a total required inverter capacity of 1,000 kilowatts (kW), accounting for both the fire pump startup and the ongoing building loads.

Next, AEI determined the required battery capacity to sustain 48 hours of operation through an energy model assessment. Leveraging AEI’s Building Performance Practice and incorporating 1,000 kilowatt-hours (kWh) reserve capacity for the fire pump, the calculated battery capacity totaled 5,310 kWh. This capacity also necessitated implementing multiple levels of load shedding within the microgrid. Essentially, the focus was on maintaining critical operations, such as the 7,000-square-foot cold room and warehouse heating, ventilation and air conditioning (HVAC) systems, rather than sustaining all building systems for the entire 48 hours (see Figure 3).

Figure 5: Project Lightyear’s microgrid switchgear. Courtesy: DPR Construction Inc.

Having determined the battery and inverter size of 1 megawatt (MW) at 5,310 kWh, the next step was locating a system aligned with the required UL label for integrating with the building system under NEC regulation rather than utility grids. The project team opted for two Tesla Megapacks featuring lithium iron phosphate batteries. These Megapacks offer a combined total of 6.2 MWh initial battery capacity and 1.54 MW inverter output capacity, with a warranty covering approximately 85% of battery capacity over 20 years. Fully self-contained, the Megapacks require only uninterruptible power supply (UPS) power for the controller, which is housed in the electrical room (see Figure 4).

Careful consideration is required when connecting three-phase inverters to their power supply. The traditional method involves using a large pad-mount transformer, but this approach was not feasible for this project due to extended delivery times.

The project team instead opted for an outdoor combiner switchboard at the BESS, featuring a built-in line reactor and a zigzag grounding transformer mounted adjacent to it. This system design establishes a neutral fourth wire for the BESS and balances currents at the inverter inputs. Implementing an outdoor switchboard with a load bank connection also facilitates safe battery commissioning and regular load bank testing (see Figure 5).

Throughout the planning and design phases, the project team regularly consulted United Therapeutics, Duke Energy, FM (United Therapeutics’ insurance company), the local fire marshal and other stakeholders to ensure comprehensive planning.

Addressing safety and compliance concerns

Figure 6: Overhead photo showing the battery energy storage system (BESS), BESS switchboard and solar photovoltaic system. The Megapacks are located more than 50 feet from the building as required by United Therapeutics’ insurance agent. Note that shading from the large building prevents adding solar to the smaller building. Courtesy: DPR Construction Inc.

Discussions with FM highlighted two critical considerations. First, they required a 50-foot separation between the BESS and the building, exceeding the current 10-foot code minimum. Second, the fire pump must be capable of operating from either Megapack.

In response to Tesla’s experience with the Victoria, Australia, Megapack fire incident, the project team incorporated several design enhancements. These included a fire-rated wall to separate the two battery packs and prevent cascading failures and programming the microgrid controller to shut down the BESS if temperature controls fail, as seen in the Victoria incident.

Lastly, the microgrid must interface with the building’s HVAC controls. Given their cGMP facility expertise, the project team collaborated with Schneider Electric’s microgrid group. Inside the building, a Square D switchboard with a Schneider Electric microgrid controller equipped with its own UPS manages all aspects of the building’s power distribution. This includes BESS charging and discharging, solar PV production and load control during battery operation.

BESS success and certification

Despite the inclusion of a few non-U.S.-made components, Project Lightyear’s BESS successfully met all United Therapeutics’ objectives, achieving on-time, on-budget and fossil fuel-free operation. The building’s efficiency was pivotal in obtaining LEED Gold certification, propelling the facility as close to operating at net zero energy as possible, given the limited rooftop space available for solar PV as the project team refrained from additional land disturbance for ground-mounted solar PV.

Project Lightyear exemplifies the successful integration of evolving technologies into complex systems, navigating regulatory requirements while achieving client goals.

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