Wednesday, September 24, 2014

A skeptic look at an $8-billion green energy initiative

Hey ho, another day, another "affordable" renewables story:

$8-billion green energy initiative proposed for Los Angeles - Duke Energy:
Four companies today jointly proposed a first-in-the-U.S., $8-billion green energy initiative that would bring large amounts of clean electricity to the Los Angeles area by 2023.

The project would require construction of one of America’s largest wind farms in Wyoming, one of the world’s biggest energy storage facilities in Utah, and a 525-mile electric transmission line connecting the two sites.

“This project would be the 21st century’s Hoover Dam – a landmark of the clean energy revolution,” said Jeff Meyer, managing partner of Pathfinder Renewable Wind Energy, one of the four companies involved in the initiative. 
The proposed project would generate more than twice the amount of electricity produced by the giant 1930s-era hydroelectric dam in Nevada – 9.2 million megawatt-hours per year vs. 3.9 million megawatt-hours 
A key component of the project – a massive underground energy storage facility – would yield 1,200 megawatts of electricity, equivalent to the output of a large nuclear power plant and enough to serve an estimated 1.2 million L.A.-area homes.
Read Duke Energy's full release, and if that floats your boat there's a video too.

This doesn't look equivalent to "a large nuclear plant" to me.

I've modeled the prospects of storage in Ontario, and revised that to just look at this proposal in isolation based on the information I've gathered, which is:
  • 2100MW of wind capacity
  • 1200MW output
  • 60,000 MWh storage
  • 9,200,000MW annual output
The fact the proposal anticipates using some existing transmission lines is problematic if those lines are already used during peak periods -and there's lots of other gaps -but there's enough information to show the problems.

My quick model is based on hourly data for Ontario, which can't be scaled up to profile Wyoming, but will be instructive anyway. Ontario's annual capacity factor is about 30% (the total output divided by the theoretical output if generating at nameplate capacity throughout the year); Wyoming would be, I'm guessing, around 40%, but they claim 50% if you do the math (there's a wind corridor in that region), but I do not know how that would break down hourly.

I do have a breakdown for Ontario, from previous work, so I've built on it in this spreadsheet. The spreadsheet takes the output from the 2100MW capacity of wind turbines, and delivers 1200MW - the remainder it puts in storage, up to 60,000MWh (which is never achieved in my model, but is likely for a scenario in Wyoming). When the wind output is less than 1,200MW, the model takes from storage (if it's available).

The delivered power is nothing like the profile of production from a nuclear power plant. The 60,000MW of storage for a 1,200MW generator is impressive (~28.6 hours), but wind production is also seasonal, and it turns out that in Ontario even 60,000MW of storage wouldn't be all that helpful in maintaining a 1200 MW output - 1200 MW can only be delivered 30% of the time.

90% of wind generation is immediately delivered. The 10% that is instead stored does always find storage available (it does get over 50,000MWh, but not to 60,000), which makes the annual capacity factor from the storage's 1200MW generating plant ~5.5%.

As I stated earlier, this type of analysis isn't available without an hourly wind generation profile for the site/region, but it's instructive in a couple of ways, one of which is hinted at by an example of a compressed air generator in the video, The McIntosh Power Plant - where the technology accompanies natural gas generation. Most of the energy-related writing that gets read ignores confusing operational issues, but there are cleaner ways to run traditional fossil fuel power plants, and the storage capacity can allow those plants to run cleaner. If we added a scenario with heat rates and maximum output well above minimum output, it might be possible to find a better twin for compressed air storage than the wind.
Storage might also be a good accomplice for baseload nuclear power plants - to store power everynight to generate power every day next.

The test for expenditure on storage should not only be how it accompanies wind, it should be how it eliminates the need for additional generators (this project might displace some gas, but in my model where it always tries to provide 1200MW, there are a couple of hours, in the high demand month of January, where it produces none), and how it compares in value to just dumping excess wind generation by feathering the turbines' blades. In short, the storage solution should be valued in scenarios that both include and exclude the wind proposal, and vice versa.

Based on what I know at this point, this doesn't look like the value supply it is being  presented as.

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