Project Overview
Mortenson engineered, procured, and constructed the Seven Flags BESS project for Spearmint Energy. The system marked the second installation of Sungrow’s PowerTitan 2.0 energy storage technology (Tierra Seca was first) to enhance grid reliability and flexibility.
Key Takeaways:
- 100 MW / 200 MWh of energy storage
- Mortenson-built 34.5 kV / 138 kV substation
- Second installation of Sungrow PowerTitan 2.0 technology
- Added flexible capacity that supports (ERCOT) reliability
- Newly developed greenfield site in Webb County, Texas (near Laredo)
- Completion Date
December 2025
- Delivery Method
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Engineer, Procure, and Construct
- Additional Project Facts
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EMS Provider: Indie Energy, Inc.
Battery Chemistry: Lithium Iron Phosphate (LFP)
Enclosure Supplier: Sungrow Power Supply Co., Ltd
System Integrator: Mortenson/Indie Energy, Inc.
50 Batteries
Interconnecting Utility: AEP
Strengthening Texas’ Grid for a More Reliable Future
Seven Flags brings 100MW / 200MWh of battery energy storage to a newly developed greenfield site in Webb County, Texas (near Laredo). The region’s growing demand for flexible, large‑scale energy infrastructure makes Seven Flags a strategically placed asset for strengthening grid stability and responsiveness.
Seamless Integration with AEP’s Network
The project interconnects directly with AEP, requiring tight coordination across engineering, protection, and commissioning teams. This collaboration ensured the system could support regional reliability needs while aligning with AEP’s operational standards and long‑term grid planning.
Overcoming Energization and Site Challenges with Purposeful Planning
Seven Flags’ delivery required navigating both technical and civil complexities. Extended delays in utility backfeed and energization threatened to slow commissioning progress, prompting the team to deploy temporary generators that supplied interim power and kept critical testing on schedule. At the same time, difficult site access conditions demanded a tailored civil approach.
To safely accommodate oversized BESS deliveries, the team constructed a temporary access roadway, ensuring equipment could reach the site without disrupting construction flow. Together, these proactive strategies demonstrated the team’s ability to anticipate obstacles, adapt quickly, and maintain momentum throughout the project.
Partnership in Action: How Collaboration Brought Seven Flags to Life
We are pleased to achieve commercial operation for Tierra Seca and Seven Flags. This milestone is an important step toward expanding access to reliable, safe, and cost-effective energy in ERCOT as power demand continues to rapidly grow. We appreciate the collaboration with our construction partner, Mortenson, whose team worked closely with us throughout development and construction to help bring energy storage capacity online across the region.
Mortenson is proud to partner with Spearmint Energy as Tierra Seca and Seven Flags reach commercial operation. These projects add flexible capacity that supports ERCOT reliability and demonstrate how strong collaboration can bring complex energy infrastructure online safely and on schedule.
Community Support Beyond the Project Site
Seven Flags’ impact extended beyond the project footprint through meaningful local engagement. Team members participated in a playset build in San Antonio with the Roc Solid Foundation, creating a positive experience for families facing pediatric cancer.