DEPCOM Power is a leading EPC provider of solar and energy storage solutions in the U.S., helping utilities build energy-efficient operations that strengthen the grid and enhance operational reliability.

DEPCOM Power was hired by a local utility to design, build and maintain a Battery Energy Storage System (BESS) that delivers 800 megawatt hours of stored solar and wind power to some 42,000 customers. This 10-acre project consists of highly modified 20-foot ISO containers with Lithium Iron Phosphate (LFP) batteries which are connected to centralized inverters, and are then interconnected to a transmission substation. The batteries require a substantial amount of auxiliary power, primarily for temperature control, so an expansive 480V 3P AC network is utilized to distribute power to each of the 360 battery containers. The auxiliary protection components consist of a network of switchboards and panelboards which all contain Siemens 3WA and 3VA line circuit breakers. The batteries must run at an optimal temperature range, requiring an HVAC system to keep them from overheating.

The HVAC system has to operate continuously. If power from the grid goes out, an auxiliary switchboard engages a generator for backup power. DEPCOM Power contracted North Carolina-based electrical switchboard provider EPEC and its agent, ReBoSS, to deliver a highly customized auxiliary power switchboard system to control the HVAC and monitor the current flowing to the batteries. This auxiliary power system is made up of a network of switchboards and panelboards that are each equipped with a fleet of Siemens 3VA6 molded case circuit breakers and two Siemens 3WA main air breakers, both of which are assembled at the Siemens Mayfield plant in Grand Prairie, TX.

Adding grid stability

Expected to reach completion in summer 2025, the project is a 200-megawatt standalone energy storage project delivering over 800 megawatt hours of energy. Its primary purpose is to provide grid stability by storing excess solar power and distributing it after sundown to nearby homes when they need it most. The project delivers enough electricity to keep about 42,000 homes powered for four hours after sundown.

Solar energy is harnessed during the morning and early afternoon, when the sun is strongest. “Excess solar that is produced during the daytime is utilized to charge these batteries,” said Mark Sauls, Vice President of Sales and Operations for EPEC Solutions. “And then after the sun goes down, the batteries discharge and you have an extra four hours of power.” This BESS project fits into the local utilities aggressive sustainability strategy. The utility is striving for net zero direct greenhouse gas emissions by 2050. The project is one of the largest battery storage systems in the American Southwest, using its storge capability to add stability and reliability to energy sources that are inherently intermittent.

“This site is actually located relatively close to a population center, so it's available – and not transmission- constrained – to deliver power to the city,” said Walker Wentzler, Sr. Director of Electrical Engineering at DEPCOM Power. “It is really making up for those peaks and valleys when people get home and turn on all their appliances.”

Maintaining a steady operation

Energy arrives at the project’s BESS through the local power distribution network. It is then stored in the lithium iron phosphate batteries. These batteries leverage newer technology that delivers longer life and make them safer to operate. “The batteries need to stay cool or within a relatively finite temperature band for them to operate for their entire life and continue performing,” said Wentzler.

The liquid heating and cooling system controls the temperature of the circulating fluid within the battery modules to keep the battery cells in ideal temperature range – and should the utility power go out, the cooling system must continue operating. That’s where the EPEC switchboard comes in, providing power to the HVAC and maintaining the batteries in a steady state.

DEPCOM Power turned to EPEC for the auxiliary power switchboard for a number of reasons. The system is highly flexible and customizable and delivers the functionality the facility needed while keeping people safe by reducing arc flash, said Wentzler.

The switchboards were assembled by EPEC’s manufacturing arm, QT Corp., and delivered by ReBoSS. They are double-ended, low-voltage units with two electrically switchable Siemens 3WA main breakers and 14 3VA6 circuit breakers in each switchboard.

“The dual 3WA main breakers have a purpose,” said Drew Vermillion, president of ReBoSS. “We have a backup breaker in case the substation goes down. The second main breaker is then powered by a secondary utility feed to keep the HVAC running on the battery storage system. The main breakers feed the 3VA6 molded case circuit breakers that feed out to auxiliary distribution panels and the HVAC systems.”

The Siemens advantage

“EPEC has equipped its switchboards with Siemens circuit breakers for years. Units like the 3VA6 offer a host of features ideal for grid stability projects, starting with build quality," Sauls said. “The reliability, efficiency, and communication capabilities of the 3VA6 molded case circuit breaker far exceeds other big-name competitors.”

For this project, EPEC used its innovative solar-specific UL 891 dead front switchboard, which minimizes cable sizes, reducing implementations by 40%. Thanks to the reduction in cabling, the switchboard is more cost-effective and quicker to install.

This project is another example of how Siemens technologies are enabling its customers to be energy diverse, efficient and resilient.