"VanWalleghem said there is room to push costs down as the company gains experience from these first few plants. The storage systems have a projected lifespan of about 50 years, which is an important data point when comparing it to battery systems, which have much shorter lives"

So both longevity and working towards reduced costs for future plants. I guess someone thinks the long-term costs will end up below Li-ion, and likely lower environmental impact, at least compared to the battery component.

Another benefit is it's all onshore, the US has energy security and independence of critical industries from China as a priority.

How do cycles and lifetime compare? More cycles over long time would lower final unit cost. That is price of kWh at time of release. Which I don't think will ever go down for load shifting.

In the end 3 figures really matter total capacity, power output and cost per "generated" kWh on average over lifetime.

The compressor/turbine part will have predictable wear rates, not substantially different from what you see in fossil plants.

The reservoirs will at some point see noticeable sediment buildup, but not at all comparable with surface pumped hydro based on blocking valleys, due to the cyclic nature of the water flow in the hydrostor facility. And occasional cleanout (measured in decades or centuries?) will be trivially cheap compared to construction cost. Very much unlike cleanout cost behind valley dams, which are would-be cleanout costs because that never ever happens as it would utterly dwarf the cost of the original dam. There's been an article linked here a few months ago (can't find it, unfortunately) about how the total capacity of pumped hydro is getting increasingly smaller each year, despite new sites getting built. This is because sedimentation already outpaces the buildup, and it will only get worse the more we build. The volumes accumulating behind a dam are just too big, unless you have zero natural flow from rainwater (and then just getting the working volume of water to the site would be prohibitively expensive, per capacity, even before you factor in evaporation - the cycle capacity per unit of water is just so much lower than what a hydrostor site would achieve with its much larger head plus the energy stored in air compressionand heat)

Me I work with a turbine (Rankin Cycle) we use about perhaps every day 22 or 3 reservoirs of 20 m3 just for the air instrumentation….

Surely to prove and improve the technology? Being able reuse gas technology as the article says, in Australia would be a boon - there’s an enormous CSG industry

Installing power capacity is not O(1) complexity.

A battery UPS under my desk doesn’t really affect my rent or mortgage. Buildings not only need to get built they also need to be maintained.

What about emissions from lithium batteries manufacturing?

And how long do lithium batteries last?

My guesses:

1. no degradation

2. cheap to expand? - simply expand the cave

"cheap to expand? - simply expand the cave"

That is not cheap. And we have very high pressure here and not only cave and rock, but technic around it. And pushing air in and letting air out again will have degradation of that expensive equipment.

These are the costs of installation, but what about maintenance and replacement costs?

> Both are more expensive than lithium ion

Are you comparing battery cell cost vs battery pack + structures + electronics + lines + land + installation + different continent + N other things I have no idea about?

BloombergNEF reports a cost of $115 per kWh for turnkey energy storage systems (in China) so their comparison is likely to hold up for complete systems in Australia and the US.

https://about.bnef.com/blog/global-energy-storage-market-rec...

Yeah, also it takes 3 years to build. I predict that there will be so much more lithium-ion batteries deployed by the time this is finished that it will change the economics of operating it.

One thing that hasn't been mentioned in siblings yet: the bulk of the money, more if you lean further towards capacity in the capacity vs throughput decision, is in the excavation. This is not only a "forever" investment, it's also money spent on the local economy. This isn't the case at all for battery cost, unless you happen to be the world center of the battery business, all the way from mine to recycling.

Another aspect, completely unrelated and I'm not sure hydrostor already makes that part of the design (but it could totally be introduced later, without invalidating any of the excavation investment): some of the energy stored in an A-CAES system is stored as heat. When you do need heat, for a district heating system, for a swimming pool site or whatever, you can decouple some of the heat from the pressure storage. Worst case some of the joules repurposed end up missing in discharge, but it's also possible that they are simply joules not lost to cycle inefficiency. And if you happen to need cooling (datacenter on site?), at the time of discharge you can just keep some of the stored heat untapped, substituting with energy from the warm end of the coolant cycle that you want to freeload on the A-CAES. Compared to other waste heat/cold coupling schemes, at hydrostor pressure levels you would get considerably higher heat/cold deltas to work with. Huge potential, and with the reservoir shaft having very few site requirements, coupling opportunities should be plentiful (as compared to e.g. opportunities that only ever arise in remote valleys)

The economics of batteries are a function of cycle limits (none in this case, probably) and how much energy you can store and discharge over time and the price difference between charging and discharging. All that minus the upfront installation cost.

The article says this thing should last at least fifty years. There's no good reason it couldn't last longer as it shouldn't really degrade over time. If you assume daily charge/discharge cycles, that would be about 18250K cycles over 50 years. Times 4GWh is about 73TWh of energy sold to the grid at, hopefully, some profit. Of course that all depends on demand, utilization, and whether there are any cheaper ways to store energy. It's probably going to end up some percentage of that. But best case that's energy you buy cheap and sell at a higher price. Even a few cents difference starts adding up to billions pretty quickly. And that's before you consider the alternatives (buying energy on the open market from another provider, investing in more energy generation, etc.).

The prices you cite are just the purchase price. And of course lithium batteries don't last forever. So you'd be writing them off at some point. But in fairness, there are some battery chemistries that are getting quite good cycle times. So, the comparison might become a bit more fair over time.

>I wonder what the case is for it.

That there is a finite supply of Lithium available on Earth?

Probably these costs have a lot faster learning curves as they are not as widely deployed yet.

Also curious since the CPUC storage credit maxes out at 4h, so 8h seems particularly pointless.