The California ISO has begun a program to develop a product that would pay energy storage resources for absorbing energy from the grid and making it available later.
The program aims to reduce the need to curtail solar power during peak generation hours, combating negative prices that can sometimes result in California from midday solar generation.
The initiative marks a shift to a "load shift" product from "load consumption" products previously under consideration, emphasizing that excess clean energy should be saved for future use.
Spikes in solar power during the day can lead to negative power prices and the curtailment of solar power output. In spring 2017, low demand and high solar production routinely pushed spot prices below zero, stressing generator finances.
CAISO has been exploring ways to deal with that problem. One of the solutions on the table, termed "load consumption," was to incentivize the consumption of more electricity during periods of high renewable energy generation — "paid to wastefully consume energy," as CAISO put it.
But CAISO stakeholders such as Tesla, Stem and Green Charge Networks argued in favor of an alternative storage product that would shift peak solar output by absorbing peak energy and storing it for later use.
In a presentation, John Goodin, manager of infrastructure and regulatory policy for CAISO, said a "load shift" product would ensure excess power is "used productively at a different time to the benefit of the economy and environment" and would "avoid increasing the economy’s energy intensity."
The proposed load-shifting product falls under the third phase of CAISO’s Energy Storage Distributed Energy Resource (ESDER) program. The proposal is still in its early stages and will require several rounds of comment before it is sent for approval by the California Public Utilities Commission and the Federal Energy Regulatory Commission.