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Comment by foota | Hacker News Reader

I'm going to compare this plant to the largest pumped storage plant (https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta...).

It has a listed cost of 1.6 billion USD built in 1977-1985, a capacity of 70,000,000 cubic meters of water (the sum of the lower and upper reservoirs on the wikipedia page) which at the max flow rate of 51,000 cubic meters per second is ~24 hours of generation at capacity. The page lists the generation capacity as 3000MW and so you can calculate a storage capacity of 72,000 MWH.

These numbers give $533,333/MW of generation capacity and $22,222/MWH of storage.

The article seems to show the cost for the Tesla station at $38 million. This gives $475,000/MWH of storage capacity and $1,900,000/MW generation capacity.

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Based on the wikipedia article, I think the 1.6bn USD is in 1977 USD. That's going to be roughly 4 times as much by 2017 [1], or 6bn USD, giving about $2,000,000/MW capacity at Bath vs $1,900,000/MW for Tesla.

Compensating for the fact that only the upper reservoir provides power, storage cost is around $180,000/MWh for Bath vs $475,000/MWh for Tesla.

Still significant but at least in the same order of magnitude, and this technology is still improving more rapidly than pumps and turbines. And, the batteries I could put close (or in) cities, potentially saving another 5-20% on transmission losses.

I'm now wondering how the operational cost of this will look. Rotating equipment will show wear and I'm assuming Bath has quite some cost on that side. However, that thing has been in operation for over 30 years, and tesla only gives guarantee for 5000 cycles on the powerwall, or about 15 years (assuming 333 cycles a year). If you would actually need to replace the batteries after 15 years then I don't see them beating pumped hydro in the short term, if you can use them for 10'000 cycles with just a loss of capacity, then I think the finances can make a lot of sense.

1: https://www.wolframalpha.com/input/?i=100+USD+in+1977+conver...

Here's an apple, there's an orange.

This battery project can be built in small increments and does not require local land in a proper geometry that can be flooded. Most good pumped storage possibilities in the US are built out already. Pumped storage also wastes more of the stored energy.

It took 7 years to build the hydro facility? Wow.

The recently rebuilt (2010) Taum Sauk reservoir only manages a 70% efficiency according to Wikipedia. I'm not seeing a number published for the Powerpack but I'd guess a 90% ballpark.

While those are interesting comparisons, keep in mind pumped storage has other negatives that make it less appropriate for some needs (besides the fact that pumped storage has a larger ecological impact).

Batteries can be installed much faster: it's been 4 months since the announcement of Tesla's selection making it ~ 24 times faster to implement than that pumped storage station.

Because they don't have to rely on natural features and since they're smaller so they can be scattered more, they can be placed nearer to the population they serve or their power sources.

> ~24 times faster to implement

But these two generators don't deliver the equivalent power, 72,000 MWH versus 80 MWH so 900 times difference. Are we going to say that to generate the equivalent power the battery plant would need to be 900 times bigger and therefore take up to 900 times longer to build? 900 x 4 months = 3,600 months = 300 years.

> they're smaller

Again, these two generators don't deliver the equivalent power, 72,000 MWH versus 80 MWH so 900 times difference. Are we going to say that to generate the equivalent power the battery plant would need to be 900 times bigger or that we'd need 900 of them, each with their own facilities and connectors and security placed near the population they serve?

Also there has been roughly 400% inflation since 1977, so you have to multiply the older cost numbers by 4.

None of these numbers make any sense, because they don't account for the longevity of the capital investments (10 years? 60 years?), as well as maintenance costs.

You're off by at least a factor of 5 on the $/MWH for this pumped storage plant, even without the longevity and O&M. A factor of 2.2 on the cost, and a factor of 2.4 on the capacity. The $1.6B cost is in 1985 dollars[1]. In 2016 dollars, the cost is $3.5B [2]. The capacity at 3GW is only 10 hours, not 24 hours [3].

The solution is to look at Lazard's analysis of the levelized cost of energy storage. [4]

For the purposes of the transmission system:

    Pumped Hydro:  $152 -- $198  / MWH
    Lithium Ion:                 $276 -------- $561 / MWH

Note that these costs are per MWH delivered to the grid, accounting for all the costs over time of that system.

When lithium ion battery prices fall by 50%, they now match the most cost effective storage out there. This will happen within 10 years.

It's amazing how fast the technology is changing. Pilot projects like this one should be happening all over the country right now, because within 10 years, it will be the only cost-effective way to do these things.

[1] http://www.crcnetbase.com/doi/pdf/10.1201/b10778-1

[2] http://www.in2013dollars.com/1985-dollars-in-2016

[3] http://www.energystorageexchange.org/projects/4

[4] PDF: https://www.lazard.com/media/438042/lazard-levelized-cost-of...

Hydro is always going to be superior to pretty much anything out there. The problem with hydro is that we already tapped every possible source for both generation and storage. It's done.

You can put a Tesla station anywhere in whatever size you need.

At the current rate of tech change, which has been sustained for decades, within a couple decades hydro will be more expensive than battery technology. And that's even with the vastly improved scalability, responsiveness, and sitability characteristics of batteries!

We need to build these industries, as they are our future. And if we're not building them, we'll just be buying from somebody else.

Nonsense, just have to make more rain.

Bath County is not the World's largest pumped hydro storage plant. At 24GWh it is smaller than TVA Raccoon Mountain, which is 34GWh. There may be bigger ones, but unfortunately nobody makes rankings of the energy stored in pumped hydro plants.

Re-read the description of Bath County and you will find that they pump from the upper reservoir into the lower reservoir. Therefore, adding the capacity of the two reservoirs and dividing by the flow rate is a bad assumption.

Can you flip the Tessa numbers around so they match up respectively to the pumped storage plant numbers?

So Tesla's new technology is within a factor of 4 of the old technology before economies of scale.

That's pretty damn good actually.

>...at the max flow rate of 51,000 cubic meters per second is ~24 hours of generation at capacity

The max flow rate is 51,000 cubic meters per minute (not per second) according to the article you link to. That changes the math quite a bit.

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