Case Study
Relay solution for Rule 21 solar + storage interconnection
Client Type
Project developers
Project Type
Commercial scale, Industrial scale, Solar + storage
Location
California, PG&E, SCE, SDG&E
Challenge
California Net Energy Metering (NEM) laws and Rule 21 interconnection process forbid battery storage from exporting power back to the grid. For sites that have existing solar, utilities require a verifiable method to ensure NEM integrity.
Solution
HRE developed a novel monitoring and relaying scheme to prevent battery export. This solution requires multiple real-time data inputs feeding otherwise “off the shelf” relays.
Results
The HRE relay solution is a cost effective way to enable interconnection of new energy storage systems for customers that also want solar. Dozens of solar + storage systems have received permission to operate from California utilities thanks to the HRE design.
