An energy storage milestone: two batteries join ISO-NE Regulation Market

The presence of advanced battery storage technology continues to increase in New England, with two battery storage systems now participating in ISO New England’s Regulation Market, marking an important milestone in the region’s move towards a hybrid grid.

The batteries are a 3.4 megawatt (MW) system operated by Green Mountain Power in Rutland, Vermont, and a 16.2 MW system operated by NextEra Energy in Maine’s Casco Bay. Both are able to respond to the ISO’s new energy-neutral regulation dispatch signal that directs alternative technologies to cycle between electricity production and consumption over a short period.

About regulation Regulation is the capability of specially equipped resources to increase or decrease their energy output every four seconds in response to ISO signals. This “fine tuning” balances supply levels against small second-to-second variations in electricity use (demand) to help maintain transmission system frequency and maintain scheduled interchange. Because frequency must be kept at 60 hertz across the entire Eastern Interconnection, each grid operator within the system must maintain that frequency. Regulation also helps maintain scheduled interchange between regions and helps ISO maintain a secure and reliable operation of the grid. Using a complex software dispatch algorithm, the ISO selects resources that can meet system demand. The selected resources are then credited based on regulation capacity, service, and the Regulation Clearing Price

The ISO launched the energy-neutral regulation dispatch signal in 2015 so that batteries, flywheels, and other storage technologies can assist operators in regulating grid frequency and maintaining scheduled interchange—an important reliability service. The conventional regulation dispatch signal calls for generators to continuously produce electricity over a set period. This type of signal isn’t feasible for storage technologies that can lose their ability to follow this signal if they become fully charged or depleted.

In addition to participating in the Regulation Market, Green Mountain Power’s storage system is being used to help shave peak demand and smooth solar power generation, while providing the ability to disconnect from the grid and provide power for a nearby emergency shelter.

ISO efforts to assist integration

Storage technology is developing rapidly and is expected to have increased levels of participation in the markets in coming years as costs associated with storage continue to decline and levels of intermittent renewable resources in the markets continue to increase. Currently, more than 90 megawatts (MW) of storage systems are in the ISO’s interconnection queue.

As battery storage systems become more prevalent in New England, ISO New England remains prepared to integrate them into an ever-changing electric grid. To better assist energy storage facility owners, ISO New England has developed a paper on How Energy Storage Can Participate in New England’s Wholesale Electricity Markets, and recently held a webinar on the subject.