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Industry urges Cal-ISO to speed fixes to help hybrid renewable, battery resources


Current rules could 'strand' half a project's capacity

Hybrid projects could be uneconomic without fix

Washington — California Independent System Operator should quickly fix rules that block the grid operator from using some capacity from hybrid resources that combine technologies like wind, solar, and storage, according to renewable industry stakeholders.

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The requested change is significant because current rules could hurt the economics of the types of hybrid projects that are expected to help the state reach its goal of decarbonizing the electric sector.

"It is hard to see how such projects could ever be economic if this problem is not fixed, and these modifications should be among the top priorities (if not the top priority) for the [Cal-ISO] from this effort," EDF Renewables said in its comments.

A hybrid resource can sign up to be considered a single resource or it can have its components be considered multiple resources. There are benefits of having multiple resource IDs, for instance, because this approach gives the ISO more visibility into the components of a hybrid resource, according to an issue paper it released in July.


But the ISO's current rules limit the output of each component of a resource with multiple resource IDs to the total injection rights of a project. For example, if a hybrid project had 100 MW of solar capacity, 100 MW of battery capacity and 100 MW of injection rights, each component would be limited to putting 50 MW onto the grid.

In this situation, the hybrid project's battery would only be able to use half its capacity, even at night when the sun is not shining and no solar capacity is available.

The ISO floated the idea of fixing the problem by creating a new hybrid resource constraint that ensures these resources' output remains less than or equal to the hybrid resource's project's maximum injection rights without stranding capacity from either of the components of the overall hybrid resource.


Stakeholders are backing this idea, and some say the grid operator should act on it immediately.

Removing the maximum output constraints on the individual components allows the operator to efficiently adjust output to minimize stranding, the American Wind Energy Association said in comments posted Wednesday.

"Given this issue's immediate impacts on current and future hybrid resource proposals, AWEA strongly encourages the [Cal-ISO] to isolate this issue from the ongoing hybrid resource stakeholder process, and expedite this implementation of the hybrid resource constraint as the first, very expedited phase of this initiative," AWEA said.

SPower agreed the issue is urgent. "Much of the inherent efficiency of hybrids -- for both the resource owner/operator and the CAISO as grid operator -- is due to the flexibility to switch between components to more fully utilize the capacity at the [point of interconnection] and provide services to the grid accordingly," said SPower, which owns and operates solar and wind assets.

The treatment of the maximum capacity of hybrid resources affects resource adequacy payments, and then has an impact on the overall projects' economics, explained Felix Maire, a lead author of the S&P Global Platts Analytics US Power Storage Outlook.

In the case of hybrid assets with solar PV and storage, the solar PV asset will not generate during evening peak hours, Maire noted. "Technically, this could leave space for a battery to dispatch at its full nameplate capacity during these peak hours, which in turn should get RA payments for its full nameplate capacity," he said.

-- Kate Winston,

-- Edited by Valarie Jackson,

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