California approves energy export schedules for DERs

The California Public Utilities Commission has issued a decision allowing renewable energy systems to be approved to interconnect to the electric grid using an energy export schedule (a Limited Generation Profile, or LGP) designed to avoid grid impacts.

This approach, which leverages California’s public grid data, is meant to reduce the need for costly infrastructure upgrades and support higher levels of renewables on the grid.

In California, utilities are required to produce detailed hourly models of the hosting capacity for each node on their distribution system (known as the Integration Capacity Analysis). Under the Commission’s decision, clean energy developers can use the Integration Capacity Analysis to design an LGP to ensure that a project stays within hosting capacity limits, rather than paying for grid infrastructure upgrades that would otherwise be required. As defined in the order, “Limited Generation Profiles specify the maximum amount of electric generation a DER system will export to the grid at different times throughout the year, ensuring that the project is responsive to fluctuating grid constraints at different times.” 

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In addition to ruling that utilities in California must allow project developers to use LGPs based on the Integration Capacity Analysis in the interconnection process, the commission resolved other issues in its decision.

The Commission ruled that certified power control systems, devices that electronically control the power output of generating facilities, will be the primary option that developers can use to manage the LGPs of interconnecting systems. The LGP option will become effective nine months after UL includes the scheduling function in its certification standard for power control systems.  

Another issue addressed in the decision concerns the format of the LGPs, specifically how many different export levels a renewable energy system would be allowed to have throughout the year, and how often those levels may change (an LGP configuration). CPUC approved using a 24-value configuration, in which a system’s export levels can vary up to 24 times per year. The commission adopted three different formats of 24-value configurations; customers can choose the format that fits the conditions at their project site.

A third issue addressed in the decision involves instances in which utilities would be permitted to permanently curtail the power output of a renewable energy system, outside of emergency situations, in ways that deviate from the agreed-upon LGP due to changing grid conditions. Utilities expressed concerns that if grid conditions changed in the future grid, grid upgrades might be required after an LGP project is interconnected to allow it to continue to export power at the levels agreed upon in the LGP.

If such a case arose, utilities wanted permission to permanently curtail power generation from affected LGP-interconnected systems or to require the project developer to pay for the cost of needed upgrades. Aligning with recommendations from IREC, the Commission limited the instances in which long-term or permanent curtailment would be allowed. Such curtailment may only be done in instances when there is a “sustained load reduction.”

The Commission additionally asserted that the utility is responsible for upgrades to avoid such situations. In exceptional cases, a utility may “apply for a tariff deviation to request permission for permanent curtailment if they believe that undertaking an upgrade is not a reasonable use of ratepayer funds or is unreasonably costly.”

Originally published by Sean Wolfe on renewableenergyworld.com