Participants in a California Energy Commission workshop last week wrestled with the question of how the state can interconnect huge quantities of new storage and generation resources to its transmission grid in the next two decades to meet its climate goals.

State statutes require load-serving entities in California to serve retail customers with 90% carbon-free electricity by 2035 and 100% by 2045, while reducing greenhouse gas emissions to 40% below 1990 levels by 2030 and 85% below 1990 levels by 2045.  

“The punchline, of course, is that we need 86,000 MW added to our grid in 12 years,” said Sharon Eddy, executive director of the Large-scale Solar Association. “We need another 70,000 MW in the 10 years after that” to meet the 100% clean energy goal established by Senate Bill 100 in 2018. “This is unprecedented.”

The state’s transmission system needs major upgrades and additions in a relatively short timeframe to handle so much new capacity, panelists said in the workshop.  

“Our current transmission grid can’t accommodate an additional 86,000 MW without new lines, new poles, new substations, and we need it quickly,” Eddy said.

“Everyone is running into the fact that we just didn’t plan early enough to build out the transmission system,” she said. “The challenge isn’t that we have too many projects vying for too little grid space, it’s that our entire system and our planning processes weren’t set up to handle this kind of accelerated growth.”

541 Interconnection Requests

CAISO adopted what it called a “more strategic and proactive approach” to interconnections in its 2022/23 transmission plan, which identified 46 transmission projects costing $9.3 billion that California needs by 2032 to incorporate more than 40 GW of renewable resources. (See CAISO Retools Transmission Plan for Reliability, Renewables.)

Future transmission plans will have to address portfolios from the California Public Utilities Commission (CPUC) that call for adding 70 GW of new resources by 2033 and 86 GW by 2035, CAISO said.

The 2022/23 transmission plan broke with tradition by analyzing projected resource additions within 14 transmission interconnection zones. CAISO said the “zonal” approach will allow it to deal more efficiently with interconnection requests, which it previously evaluated in annual cluster studies.

Interconnection requests to CAISO have soared in the last three years, from 155 in 2020, to 373 in 2021, to 541 this year, in clusters 13, 14 and 15, respectively. This year’s requests totaled 354 GW on top of the 180 GW already in its queue, including 18 GW of requests for a single substation, CAISO said.

Performing cluster studies on “such a huge volume is inefficient and provides less meaningful study results,” said Neil Millar, CAISO vice president of infrastructure and operations planning. “This clearly calls on us to take action and move forward with more substantive, transformative changes, better prioritizing where we’re putting our energies.”

The ISO’s new zonal approach targets “energy rich zones” with current or anticipated transmission connections where CAISO wants utilities and resource developers to focus their efforts, Millar said.   

“We’re talking about volumes being required in next year’s transmission plan of over 7,000 MW of installed capacity to be added to the grid each year for the foreseeable future,” Millar said. “The challenge would be to maintain that pace year over year, which our current processes were not designed around.”

Transmission-owning utilities such as Pacific Gas and Electric also have been inundated with interconnection requests.

“For many years up to cluster 13, the number of applications never exceeded more than 70 and [involved] less than 20,000 MW,” said Marco Rios, PG&E’s manager of transmission planning. “That wasn’t the case in cluster 14, where we received 185 applications and over 46,000 megawatts of generation just in the PG&E system. That makes the study process very, very difficult.”

PG&E used to have a high withdraw rate, but fewer developers are withdrawing their projects from the queue, compounding the problem, he said.

‘Promising if Arcane’

The afternoon sessions of the all-day workshop dealt with possible solutions.  

Representatives of wind, solar and storage trade organizations urged CAISO to revise its generation deliverability study methodology.

Nancy Rader, executive director of the California Wind Energy Association, called it a “very promising if arcane topic.”

“Reforming that methodology could really accelerate generator interconnections and make more efficient use of our existing grid and every additional transmission project that we build,” Rader said.

The ISO launched a stakeholder initiative in December to review its deliverability methodology, she said.  

“CAISO uses this methodology to determine what reliability upgrades are needed for an interconnection customer to obtain deliverability capacity … which is what generators need to qualify under the CPUC’s resource adequacy program,” Rader said. “The point of the methodology is to ensure that a project will be able to deliver its generation to load when it’s needed.

“The prospect of reforming this methodology is exciting because it could immediately address the current lack of available [deliverability] capacity” on transmission lines, she said. “Without it, projects can’t qualify for RA and generally won’t be commercially viable. And so, in our view, the available capacity appears to be insufficient to meet the state’s mid-decade and certainly our longer term SB 100 goals. And that will remain the case until new transmission is planned and built and that’s about 10 years off…”

CAISO currently uses a more restrictive methodology for assessing deliverability capacity than other RTOs, Rader said. Adopting less stringent criteria such as that used by PJM and MISO could “free up more than 10 GW of capacity immediately across the CAISO grid in areas … where the grid is strong,” she said.

“Capacity is a function of the assumptions used in the CAISO’s deliverability study methodology, and in our view those assumptions are unnecessarily conservative,” she said. “Reforming those assumptions consistent with those used by PJM and MISO could dramatically expand [deliverability] capacity. And that capacity would immediately become available at no cost.

“So, we really might have a big free lunch here,” she said.

Rader said she and others were looking forward to discussing the issues in CAISO’s upcoming stakeholder process.