The resource buildout of the western grid used to support the early coal retirement scenario pricing and analyses incorporates many of the common assumptions that are used throughout the scenario work, but also accelerates the planned retirements[1] of all the coal plants in the western grid to occur before the end of 2030.
The associated buildout is similar to the baseline but replaces the coal retirements with predominantly renewables, and due to lower capability acquired per nameplate there are more early builds than in the baseline buildout.
Early Coal Retirement buildout
The buildout in the early coal retirement included over 453 gigawatts of nameplate build by 2041 as seen in the figure above. Nearly 84% of the new resource buildout was either stand-alone solar or solar plus battery hybrid resources, and over 90% of the buildout was solar or wind. Like in the baseline significant amount of the renewable buildout appears to be to meet the policies enacted by states or municipal governments, and/or goals by utilities and limitations on gas plant builds[JO3] [2] further increased renewable and storage resource builds. There were not enough renewables to meet clean policy requirements within the current operations and transmission without adding an emerging technology[3] by 2030 that is referred to as a proxy clean resource[JL4] .
As can be seen below, significantly less stand alone solar is built in the early years, but more is built later. More hybrid solar plus storage is built in general and displaces or defers the builds of other resource types like wind and short-term storage. The proxy clean resource defers some of the offshore California wind resource until the end of the study.
Build Comparison to Baseline
Also like the baseline results the large amount of renewable generation built, causes renewable curtailment[4] to become significantly more prevalent throughout time, especially during midday hours. In 2021, as can be seen in the graph below, the maximum renewable curtailment in any hour of the day averaged under 20 megawatts and by 2041 grew to over 257,000 megawatts. This is less renewable curtailment in the early years and more renewable curtailment later years of the early coal retirement study than in the baseline.
Renewable Curtailment
This extensive renewable curtailment made it challenging to enforce compliance with some of the clean policies and goals with the current technologies as can be seen in the graph below. By 2040[5], with current system operations,[6] transmission infrastructure and the assumed buildout the system is forecasted to not be able to meet all of obligations implied by the clean policies and goals[7] even though the buildouts contain sufficient capability to generate that much power. The state renewable portfolio standards are met for all years of the study.
Clean Policy Versus Capability Baseline
The following spreadsheets contain further supporting information on the early coal retirement scenario buildout:
Buildout Information for Early Coal Retirement Scenario
Buildout Comparison to Baseline Conditions
Renewable Curtailment in Early Coal Retirement Scenario
[1] The planned retirements assumed in the baseline conditions and other scenarios.
[2] Initial studies showed upwards of 70 nameplate gigawatts of gas, but advisory committee and Council feedback made it clear that was much higher than the expected gas plant build. Thus, for the baseline gas plant build was limited, but the removal of those limits was tested in the No Gas Build Limits sensitivity.
[3] This proxy clean resource characteristics used to represent an example of something from the emerging technology clean resource stack in the studies were the attributes and estimated costs associated with a small modular nuclear reactor.
[4] Renewable power is often limited by how much “fuel”, insolation and wind, is available at any given time. Sometimes, more power is generated than is needed, or can be sunk to the grid due to transmission, demand or operational constraints on other generators. In this case, the power is “curtailed” or “spilled.”
[5] Technically, the policies are missed in 2035 but since many of the policies are based on multiple year averages of generation for compliance the narrative reports the first year after which the policies are missed persistently.
[6] It is possible that revised system operations or different policy structure might reduce renewable curtailment, but the current market structure is devised to reduce production cost not to eliminate emissions.
[7] From a physical compliance inside the WECC perspective, there may be alternative compliance methods.