Comment by OliverJones | Hacker News Reader

Comment by OliverJones | Hacker News Reader

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There's a pumped-water electricity storage facility near where I live, called Northfield Mountain. It entered service in 1972 and has been in use since then.

When electricity demand is low, the grid operator uses the excess to pump water uphill. When electrity use is high, the water flows back down into the Connecticut River. Horthfield Mountain can deliver just over a gigawatt of energy for eight hours with the generators running at full bore.

It was originally built as a complement to the (now-decomissioned) Vermont Yankee nuclear power plant. That plant generated 0.6 gigawatts continuously, and functioned most efficienty if it wasn't ramped up and down to meet instantaneous demand. So, the storage facility provided a way to vary the power output from the grid.

The Times piece contained these words:

...utility-scale lithium-ion batteries cost 26 cents a kilowatt-hour, compared with 15 cents for a pumped-storage hydroelectric project. The typical household pays about 12.5 cents a kilowatt-hour for electricity.

It's a little misleading. The 26 cents and 15 cents figures are for capital expenditure to build storage capacity, which can then be used over and over (for 45 years in Northfield Mountain's case). The 12.5 cents is for a kilowatt hour consumed.

Also, I fear the 12.5 number represents lazy journalism. The current residential rate in Los Angeles is 17.8 cents/kWh, and in New York City (home of the Times) it's 21.0 cents/kWh. Rates vary a LOT geographically.

I hope journalists can learn to understand energy economics better, because they are a way for the rest of us to learn about them. And learn about them we must when fossil fuel use diminishes.

Northfield Mountain is a great plant. The company I work for used to own it before we foolishly sold it off. A pension plan bought it, which is a good indication of how stable it's economic outlook is. It's also an important black-start resource in the northeast.

The difference between Northfield and Lake Mead / Hoover Dam is that dedicated pumped-storage plants have two reservoirs: upper and lower. They are generally able to move water between them as needed with few restrictions because there is no downstream water user who's going to suffer damage because water was released from the upper reservoir (or taken from the lower reservoir).

The Colorado River is pretty much the ultimate opposite case. The existing Hoover Dam operations are dictated entirely by downstream flow requirements. If water has to flow downstream (because it's needed by agricultural users), it flows, and power generation follows. If flow needs to be restricted for flood control, power generation is reduced accordingly. Other than emergency spillways, there's no way for water to flow downstream except through the turbines, so there's no flexibility based on the needs or conditions of the power grid. In power industry terminology this is called a 'must-run' resource.

This article doesn't address that at all, although I imagine that if there is a serious engineering paper proposing this that it would look at the consequences of this in detail. It's extremely questionable to invest this scale of money in an energy storage resource that will likely never attain its full operational potential because the operator would not be allowed to ramp up or down arbitrarily. Batteries are more expensive - right now - but far less risky and can easily be deployed to any location, in precisely the size and scale required, with minimal financial risk or exposure to changing climate patterns.

26/15 is the estimated cost per kwh. Really there is a huge variance, especially for pumped storage because because of highly variable capital cost.

Capital costs are in the 100s-1000s dollars for kw of pumped storage.[0]

[0]http://large.stanford.edu/courses/2014/ph240/galvan-lopez2/

Similarly for the batteries. If lithium-ion could be had for $0.26/kWh then a Tesla Model S battery would be $26.

As it stands, Tesla batteries are estimated to be around the $100/kWh level for individual cells and projected to fall below $100/kWh at the pack level in a couple of years [1].

[1] https://cleantechnica.com/2018/06/09/100-kwh-tesla-battery-c...

The 26 cent figure for a kWh of storage must be the cost per cycle, and assuming it gets thousands of cycles. 1 kWh of Li-ion battery capacity is orders of magnitude more expensive than 26 cents.

Also they fail to mention cyclic efficiency and life cycle cost. Hydrolic storage are most efficient with their short comingss being too large and location dependaance.

Funny I used to think of capacitor as water bucket and now we're smoothing power grid with a big water bucket.

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