The BESS sites were picked for their close proximity to substations owned and operated by Oncor — the major regional utility serving the area — in order to optimize efficiencies and manage the costs of interconnecting the battery capacity to the area grid. The project owner, Sustainable Environmental Renewable (SER) Capital Partners had gained approval from the Electric Reliability Council of Texas (ERCOT) to construct the facilities and to utilize the Oncor substations to add the power to the grid. ERCOT is the transmission authority that manages grid operations serving more than 90% of Texas.
SER contracted with Oncor to add the necessary equipment and construct power lines to connect with the BESS facilities at all three locations. An integrated engineer-procure-construct (EPC) team from Burns & McDonnell coordinated all remaining overhead construction, including installation of overhead power lines, transformers and reclosers at the metered interconnection point.
The three BESS facilities utilize LG JH4 and JH3 lithium-ion batteries connected to EPC Power CAB1000 inverters for conversion of the DC power to AC. Automated control systems were provided by Emerson’s Ovation platform to enable integrated monitoring and asset control. This open-source platform increases battery operational visibility and simplified overall system management. Project scope included setting the battery containers, inverters and inverter step-up transformers; installing battery protection units; loading battery modules; installing battery busbars and jumpers; interconnecting cables (including DC, 480VAC auxiliary power), communications and 12.47 kV distribution lines; and implementing a site controller.
As it became increasingly apparent that the scheduled in-service date would be challenging to meet, construction and engineering staff met to brainstorm new approaches that could streamline some of the repetitive installation tasks faced by crews in the field. The team came up with an innovative design for a custom battery module installation jig that enabled four modules to be combined and lifted as one unit into the container racks. Once the modules were placed into the jig, the crews used a forklift to lift and insert the modules into the battery rack, allowing bolts to be torqued into place to secure the unit. The jig was fabricated by AZCO, a construction division of Burns & McDonnell. Field construction was self-performed by Burns & McDonnell.
In addition, delays in the schedule for distribution line interconnections were offset when the team rented mobile diesel generators so that backfeed commissioning work could proceed. The auxiliary power provided by the mobile generators allowed cold commissioning of the batteries, control systems and inverters, a step that allowed the systems to connect and begin communicating so that they were working properly before energizing the equipment through the point of interconnect, or energized commissioning work began. Had this step been delayed until the interconnect was completed, the project would have been delayed by one to two months past the contractual deadline.