The difference between co-location and hybrid energy storage plant models

Co-location power station

Modeled as an independent power station, energy storage facilities co-located with new energy power stations have independent metering arrangements, submit outage requests independently, receive dispatch instructions independently, and can be operated by different entities.

CAISO has adopted several policy changes to help regulate co-located plants in participating markets. In 2021, CAISO implemented the Aggregate Capacity Constraint (ACC) function [2] [3] to ensure that dispatch orders to co-located power plants behind the utility grid connection point do not exceed the constraints of the utility grid connection point. ACC can also limit the battery's FM wins. CAISO has adopted rules allowing co-located energy storage plants to deviate from dispatch orders in certain circumstances in order to allow renewable energy plants at the same public grid connection point to generate electricity while meeting ACC limits.

These changes will introduce optional features to prevent energy storage plants from receiving charging orders that exceed the dispatched operating targets of new energy plants at the same public grid connection point. The changes will also allow co-located storage plants to deviate from market charging orders to avoid charging from the grid when the actual output of renewable resources at the same public grid connection point is lower than predicted.

hybrid power station

Hybrid plants are modeled as single plants because they have a single bidding curve for all their components and receive unique dispatch instructions from CAISO. Hybrid plant operators self-optimize their resource components to meet dispatch directives.