TransWest Express Transmission Line

Importing wind power from Wyoming

TransWest Express (TWE) transmission project:

TWE’s plans call for building a 732-mile combined high voltage direct current (HVDC) and alternating current (AC) transmission line that has the potential to bring up to 3,000 megawatts (MW) of clean Wyoming wind power into California and other states in the desert Southwest as early as 2027. The line splits at the end of the HVDC portion in Utah, allowing 1,500 MW to go to the Los Angeles Department of Water and Power, while the remaining 1,500 MW can serve the ISO and NV Energy.

Costs for the $3 billion project will be recovered through TWE tariffs from subscribers using the transmission lines to move power and would not affect the ISO’s transmission access charge. The subscriber rights would pay for the generation, transmission, and congestion on the portion of the line used by the subscriber.

This model is also significant because it is the first in the nation that enables development of out-of-state generation to be provided using the subscriber approach. The subscriber model also allows development of out-of-state renewable generation identified in the CPUC’s Final Decision Ordering Supplemental Mid-Term Reliability Procurement, the CPUC resource portfolios used in the ISO’s 2023-2024 transmission planning process, and the new transmission facilities required to reach identified resource locations.

These portfolios call for out-of-state wind generation that requires new transmission to reach the ISO border: 1,000 MW from Idaho, 1,500 MW from Wyoming, and 2,328 MW from New Mexico. These volumes build on the amounts provided as part of the ISO’s 2022-2023 transmission planning process. They also match the values that the ISO used to size transmission needed from the ISO border to load centers in the 2022-2023 plan and they align with the longer-term requirements set out in the scenario provided by the CEC and the CPUC to the ISO for the ISO’s 20-Year Transmission Outlook.

The idea of connecting a reliable source of wind energy with a high capacity factor from remote areas to high-demand centers across the Western U.S. has long been recognized as a way to help unlock a more diverse portfolio of renewable energy resources that can help meet clean energy goals in a cost-effective and efficient way. Adding diverse resources from different areas at varying times of the day would add flexibility to the system and help with the transition to a cleaner grid.

California ISO - A big step forward on transmission infrastructure.


The sentence above is from the linked article in the original post, and it is nonsense. Wind energy is in no way a “reliable source” of producing power. The “high capacity factor” claim is laughable.

I looked at four wind farms in Wyoming of larger capacity. The yearly capacity factor of all of them is less than 50%.

There are 24 x 365 = 8760 hours in a year.

Top of the World wind farm has a capacity of 200 MW. The 2022 production was 404,226 MWh.
404,226 / (200 x 8760) = 0.23 = 23% capacity factor

Ekola Flats wind farm has a capacity of 250.9 MW. 2022 production was 805,728 MWh.
805,728 / (250.9 x 8760) = 37% CF

TB Flats wind farm has a capacity of 503 MW. 2022 production was 1,488,986 MWh.
1,488,986 / (503 x 8760) = 34% CF

Roundhouse wind farm has a capacity of 226.6 MW. 2022 production was 969,526 MWh.
969,526 / (226.6 x 8760) = 49% CF

Roundhouse is pretty good, but still below 50%. For all four of these wind farms, the combined CF is 35%. That is close to the US average for wind power, and is not “high capacity factor”, no matter what some people want to believe.

Looking at all Wyoming wind farms, and using the wind power generation data from the EIA, the entire state was also at 35% CF in 2021.

  • Pete
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You are looking at one old wind farm and three others that have no bearing on the new wind farms that will be connected to TWE.

The Top of the World wind farm was built in before 2010 with small wind turbines (2MW).
The Ekola Flats wind farm is using small wind turbines (2MW - 4MW).
The TB Flats wind farm is using small wind turbines (2MW - 4MW).
The Roundhouse wind farm is using small turbines (3MW-4MW).
New wind turbines are over 10MW capacity and achieve much higher capacity factors.

Wind farms of the future will have capacity factors over 50% and equivalent to the current capacity factors for:
Hydro: 37.4%
Coal: 49.3%
Nat Gas: 54.4%

Your argument is meaningless because high voltage transmission lines are built for hydro, coal and natural gas power plants. With wind farms of the future having capacity factors greater than 50% makes them Ideal for high voltage transmission lines.

I’ve never seen any onshore wind farm with a long term capacity factor above 50%.

Notice how generation from the Top of the World wind farm has steadily declined over the years. 2011 production was 679,217 MWh, but 2022 production was only 404,226 MWh.

  • Pete
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Wind turbines are increasing in size and capacity factors are increasing as new wind turbines are introduced and old small wind turbines replaced.

Hydro and coal are less than 50% capacity factor.

Hydro and coal (as well as natural gas) are dispatchable power sources. This means their output can be controlled by the grid system operator to match output to the electrical demand at any given time. Output must always exactly match demand for a stable grid, to keep the frequency at the desired 60 Hz or whatever it is for a given country.

See this exemplified in the following link.

In the first graph down, labeled “US electricity overview”, see how the generation goes up and down each day in a kind of sine wave. The daily peak occurs in the late afternoon or early evening, and the minimum occurs in the early morning hours after midnight. Scroll further down to the graph labeled “US electricity generation by energy source”. Natural gas, coal and hydro go up and down, being dispatched to provide the right amount of power at the right time. From this graph, wind actually goes up and down a little, but it is out of phase. Wind often goes down when power is needed the most, and then goes up later at low demand. (Nuclear remains pretty much at the same value all the time. There is a certain amount of base load that is always required, and US nuclear plants provide that function quite well.)

Wind farms are not load-following dispatchable sources, nor are they constant base load generators. If the wind happens to blow a particular day, then the turbines provide what they can.

  • Pete
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We all know that wind rises in the evening, peaks at night and fades away by noon. But solar is rising in the morning, peaks during early afternoon and fades way with sunset. Thus wind and solar complement each other. With the new TWE the wind and solar durations and peaks are broadened/extended by an hour or two. This is a step toward making wind and solar available for an extra hour or two. The longer that wind and solar are available - results in less need for natural gas and/or coal to be used and less CO2 emissions.