SGP worked in close partnership with The United Illuminating Company (UI) to develop conceptual designs for three critical facility BESS microgrids that support communities in Connecticut. This analysis was conducted in support of Connecticut State Legislature Public Act 22-55 and at the direction of the Connecticut Public Utilities Regulatory Authority (PURA) in Docket 22-06-05.

SGP provided a comprehensive analysis including BESS microgrid technical design and a benefit-cost analysis to support the regulatory filing. Key elements of the analysis included:

• Analysis of the critical facilities’ electrical configuration and historical load characteristics
• Historical outage analysis and optimal sizing of a BESS microgrid to provide back-up power to the critical facilities
• Microgrid configuration design including expandable tiers to island portions of the distribution system
• Analysis of four secondary economic application scenarios including direct ISO-NE market participation and bulk system load shaping to reduce UI’s cost to serve all customers.

SGP directly supported regulatory engagement in partnership with UI including a Microgrid Conceptual Design Report filing, Supplemental Technical Analysis, participation in a Technical Meeting, and support for interrogatories and data requests.

As a result of this analysis, CT PURA approved the three proposed projects in December 2023 as outlined in their Final Decision.

Key outcomes from this analysis include:

• Critical facility BESS microgrid conceptual designs tailored to the unique needs of facilities supporting vulnerable members of the community. Each design included an optimally sized BESS to support the critical facility (Tier 1) and, where technically feasible, the ability to expand the microgrid to provide back-up power for a larger number of customers when merited by operational conditions (Tier 2).

• Using historical outage data, SGP developed a reserve state of charge (SoC) schedule that enabled the BESS to be prepared for outages when likely while also enabling as much BESS capacity as reasonable to provide valuable grid support services, thereby offsetting project costs to ratepayers.
• Four different BESS applications were evaluated to determine which application could provide the most value while maintaining readiness for critical facility islanding when needed. This included modeling three ISO-NE direct market participation scenarios including operating as:

• • • • • Continuous Storage Facility (CSF) offering Day-ahead Energy, Real-time energy, and Regulation
        • Settlement-only Generator (SOG) offering Real-time Energy
        • Alternative Technology Regulation Resource (ATRR) offering Regulation

One bulk system load shaping application was modelled that would reduce UI’s cost to serve all customers by operating the BESS to reduce UI’s regional and local network system charges (RNS and LNS) and forward capacity market (FCM) allocation.

The analysis identified bulk system load shaping as scenario with the highest benefit-cost ratio.

• A benefit-cost analysis was performed using industry-standard benefit-cost ratios such as the Total Resource Cost Test and Utility Cost Test including elements that incorporated all relevant values and costs and conformed to regulatory guidelines in Connecticut.