The continued growth of renewable energy as a source of capacity has created new opportunities and challenges for grid operators and asset owners across the country. One such challenge occurs when more energy is generated in one location than can be transmitted safely across the distribution and transmission network. When this congestion occurs, grid operators often curtail the output of renewable energy assets to maintain system balance. This practice can be seen in grids across the country, with Dispatchable Intermittent Resources (DIRs) in MISO, or Intermittent Renewable Resources (IRRs) in ERCOT.

Until recently, solar power plants in New England had been largely exempt from curtailment rules seen in other regions. Since 2016 ISO-NE has required wind and run-of-river-hydro assets to operate as Do-Not-Exceed (DNE) Dispatchable Generators (DDGs), requiring that they reduce their production in response to a curtailment dispatch. While solar assets have always needed to respond to Minimum Generation (MinGen) Emergencies, they have typically been exempt from DNE requirements. The continued growth of renewable energy resources in New England led ISO-NE to file rule changes with the Federal Energy Regulatory Commission (FERC), which were approved in 2021. Starting in December 2023, all modeled solar assets in ISO-NE (typically projects >5 MWac) will be required to comply with DNE dispatches.

Complying with new rules will likely create new challenges for both existing and new solar projects in New England. Chief among them is the need to install a Remote Terminal Unit (RTU) to provide real-time telemetry to ISO-NE and the relevant Local Control Center (LCC). Storage developers in New England have experience with RTUs, as they are required for batteries participating as a Continuous Storage Facility (CSF) or Alternative Technology Regulation Resource (ATRR). End-to-end installation of an RTU can take upwards of a year for some sites, and as a result ISO-NE has been urging assets owners to take action to prepare for the DNE requirements. Once an RTU is installed and configured, asset owners will need to work with their Lead Market Participant (LMP) and Designated Entity (DE) to ensure they are able to receive and respond to ISO-NE DNE dispatch signals.

Beyond the ability to respond to DNE signals, the possibility of partial curtailment increases the need for accurate, reliable, and on-time data points that have long been required for modeled solar assets. These points include Real-Time High Operating Limits (RTHOL), Solar High Limits (SHL), meteorological points, and asset output information in Volts, Vars, and Frequency. Inaccuracy of these points or of your day-ahead offers can have real economic impacts, including involuntary curtailment of an asset at a time when it wasn’t really needed.

As the share of renewable and storage offerings increases, grid operators will need to adapt their operations and rules. ISO-NE’s changes serve as one example of the dynamic landscape developers and assets owners will face in the coming years. SYSO specializes in helping renewable energy and storage asset owners navigate the complexities of power markets, especially amid change. Our extensive experience leverages our data platform to monitor data points, create alerts, and optimize operations, including for a number of clients we have helped navigate the new landscape for DNE solar assets in ISO-NE.