The Western Interconnection’s transmission network, including assumed transmission additions between now and 2020, will enable energy flow without significant congestion, Bradley Nickell, director of transmission planning for the Western Electricity Coordinating Council, said Sept. 23.
The WECC board on Sept. 22 approved a 10-year regional transmission plan, the first transmission plan for the Western Interconnection. The Plan was developed through WECC’s Regional Transmission Expansion Planning (RTEP) project, as part of a $14.5m grant from the U.S. Department of Energy.
WECC is responsible for coordinating and promoting electric system reliability in the Western Interconnection.
The plan assumes that all 44 regionally significant transmission projects identified in the Foundational Projects List will be completed by 2020. The project list was provided to WECC by the Subregional Planning Group (SPG) Coordination Group (SCG), which was formed to facilitate WECC’s transmission planning efforts.
The projects identified have a “very high probability” of being in service in the 10-year period, according to the SCG’s parameters.
These projects add about 5,500 miles of transmission lines to the Western Interconnection and are estimated to cost $20bn.
With the exception of the Montana-Northwest Path, the Pacific-Tie Path and California-Oregon Intertie, or Paths 8, 65 and 66, respectively, most of the major transmission paths, including the Foundational Projects, do not appear to be significantly congested in 2020, according to the study.
In the study, WECC recommended that decision-makers consider transmission upgrades or other mitigating measures that relieve congestion on Paths 8, 65 and 66, which see continued use and congestion under most scenarios analyzed.
The study evaluated future population growth, generation retirements and additions, resource relocation alternatives and their capital costs, and public policy requirements in the Western Interconnection.
WECC found that the generation mix by 2020 will be a “significant departure” from the past, which is largely attributable to the amount of renewable generation coming online, as well as gas-fired retirements, Nickell said.
“We’re seeing a large increase in our models on the amount of cycling of the traditional fleet,” he said. “Basically, they’re moving around a lot more to follow the variable generation, and there’s a lot of both costs and potential reliability impacts” to that.
The Western Interconnection’s population is expected to grow by 10 million, Nickell said. One-third of the load is in California; tacking on the rest of the coastal states takes that to one-half of the Western Interconnection’s load.
About 12,000 MW of gas-fired generation in California will retire due to once-through cooling regulation. In WECC, about 33,000 MW of renewable energy is expected to be added, on top of the 17,000 MW already in place.
California comprises about two-thirds of the renewable energy demand, which is fueled by its 33% renewable portfolio standard.
“When we talk about why people are building renewables, much of it is to serve the California state renewable portfolio standard,” Nickell said.
In looking at resource relocation alternatives, a central question from WECC stakeholders was about renewable resource procurement in other states, Nickell said. As a proxy, the study relocated about 12,000 GWh of renewable generation from California to eight different locations in WECC to study the resulting need for transmission to deliver those resources back to California, as well as capital and variable costs.
In most cases, the annualized capital costs for the California resources exceeded those in the relocated areas, which Nickell attributed to the type and quality of renewable generation replacing California’s resources. Wind energy in Montana, for example, has a higher capacity factor than solar energy in California.
The study also took some of the lowest-ranking resources out of California and replaced them with the best available resources in other areas, Nickell noted.
Furthermore, the study includes recommendations about how to increase coordination in planning across the Western Interconnection, environmental and cultural considerations to take into future transmission planning, water resource impacts on the future generation mix, and gaps in regional transmission planning processes.