The Gordon Butte Pumped Storage Hydro Project in Montana is moving forward, having previously received an assessment of no significant impact on the environment from FERC and having just received a 50 year license to operate the facility.
Looks to me like the project will substantially increase the cost of electricity.
Stored water concept
The concept is that electricity generated by wind farms plants or solar farms plants when there is no need for the electricity can be sent to the Gordon Butte facility. The otherwise unusable electricity will be used to pump water from a reservoir uphill to a reservoir at a higher elevation. That “stores” the potential energy.
Later, when consumers want more electricity than the slice-and-dicers and wing-toasters can produce, water will be drained from the upper reservoir to the lower reservoir through turbines thus generating electricity from the stored water.
The underlying issue is electricity must be used the instant is created. Since generation of electricity from wind only happens when the wind is blowing within certain parameters (not too slow and not too fast) and solar farms only generate power when the sun is up and the sky is clear and the snow has melted off the panels, wind and solar power is unreliable.
The concept of stored water is taking otherwise unusable electricity, storing it, then using it when consumers need it.
Let’s look at this project and then consider the staggering cost.
Overview of project
Here is some basic data, according to the project overview page at the facility’s website:
Each of the reservoirs will be approximately 4,000 feet long and 1,000 feet wide. Depths will run between 50 and 75 feet. Each reservoir is designed to hold approximately 4,000 acre-feet of water.
There will be a 1,025 foot difference in elevation between the two reservoirs.
Pipes moving water between the two reservoirs will have four generators to produce electricity.
Theoretical capacity of the generators is 400 MW.
Expected annual output is 1,300 GWh. That would be 1,300,000 MWh.
According to an Associated Press article on 12/22, License issued for $1B Montana power storage Project, the construction costs are estimated at $986M and the annual operating costs are estimated at $173M. The energy produced is estimated to be worth $220M each year.
Increased cost to consumers
Keep in mind this entire project is in essence a massively huge battery which stores electricity between the time it is generated until it is needed. Every watt of power from the site will have initially been generated elsewhere.
That means the entire project adds costs to consumers. The electricity will have to be generated by wind farms plants or solar farms plants thus incurring the costs from those sources. Cost of this project will be added on to that electricity and then sold to utilities. That means the costs for this project will be added on to whatever else the retail consumers were otherwise going to pay.
Now, let’s do some math.
Construction costs:
| construction cost | 986,000,000 |
| capacity, MW | 400 |
| cost per megawatt | 2,465,000 |
That makes it relatively expensive in terms of construction compared to other sources.
Production and utilization:
| annual energy, GWh | 1,300 |
| annual energy, MWh | 1,300,000 |
| days/year | 365 |
| daily production, MWh | 3,562 |
| hours/day | 24 |
| hourly production, MWh | 148 |
| – | |
| capacity, MW | 400 |
| uilization | 37% |
Now the amount of cost the water storage project adds to electricity, for a 1,300GWh hour output at annual operating costs of $176M:
| annual energy, MWh | 1,300,000 |
| annual operating cost | 176,000,000 |
| cost / MWh | $135.38 |
| KWh in MWh | 1,000 |
| cost / KWh | $0.135 |
Assuming I got the concept right, that means this massively huge battery for storing electricity will add 13.5 cents cost to consumers. Just as a really rough comparison that is somewhere in the range of what electricity would otherwise cost consumers.
Please check my math. Feel free to let me know if I slipped a digit or something.
Comparison to costs in Southern California
For comparison, let’s look at costs here in Southern California. My August electricity bill showed generation charges of 6.92 cents per kilowatt-hour, which is the cost from providers, which in turn is passed straight through to consumers.
The average costs per tier, which is the way electricity is scaled up to discourage consumption:
- $0.16 – tier 1
- $0.23 – tier 2
- $0.29 – tier 3
My average cost for August was 21.6 cents per kilowatt-hour.
So this storage facility would add costs of 13.5 cents compared to the 6.9 cents of generation costs or 21.6 cents average cost.
Unless I made a serious math mistake (which is possible) or a serious conceptual error (which is a significant possibility), looks to me like this project will significantly increase costs to consumers.
Other costs
The above analysis doesn’t count the cost of filling the reservoirs with 4,000 or 5,000 acre feet of water. Also doesn’t count the cost of annual evaporation.
Storage analysis above doesn’t count the loss in power of transmitting the electricity to the site, or the loss from pumping the water uphill, or the loss in converting falling water into electricity, or the friction loss of transmitting the power back across the grid a second time.
Oh, since the northern plains are still digging out from a nasty blizzard on Christmas day and still in freezing temperatures, how does a water storage project work when temperatures are below freezing, say in the sub-zero range?
My little brain knows that lakes freeze so hard in North Dakota that you can drive a truck across them. They are frozen hard for several months at a time. How do you transfer water between reservoirs in sub-zero temps when the top several inches of each reservoir are frozen solid?
Editorial comment from MDW
As happens so often, hat tip for finding the above story goes to The Million Dollar Way in an article on 12/22: Interesting $1 Billion Science Project Okayed For Martinsville, Montana.
Oh, one final editorial comment on 12/24 from The Million Dollar Way. The blog mentioned the blizzard that was then expected to clobber most of North Dakota on Christmas Day:
Blizzard warning for southwestern North Dakota. Wind farms will be off-line during the blizzard. It’s fortunate that we have solar farms backing up wind farms. LOL.
Lots of wind farms plants in that corner of the state. Keep in mind that if the winds are too strong, turbines must be taken off-line to avoid damage. Thus, there will be no electricity generated during this very windy time.
There is a high probability that the expected 8 or 12 inches of accumulation might, perhaps, possibly have an adverse affect on output from solar farms plants. Degradation of output from solar farms plants might possibly continue until some distant warming trend (on Tuesday and Wednesday temperature were forecast to climb to only 27 and there were one sunny and two mostly sunny days forecast in the following two weeks). Might take a while for all that snow accumulating on top of solar panels across the upper Mid-west to melt off.
Update: Post got a comment at Million Dollar Way: TGIF -Last Friday of 2016. Thanks for the mention!