Hydrostor Gigawatt Compressed Air Energy Storage

Hydrostor, a long duration energy storage solution provider, today announced the development of 1,000 MW of long duration energy storage in the state.

The California Public Utilities Commission has identified a need for up to 1,600 MW of long duration energy storage by 2026. Long duration energy storage is critical to achieving California’s decarbonization and renewable goals. Hydrostor is proud to play a critical role in the clean energy transition for the state, and looks forward to continuing to work with the Commission to establish its commercial pathway for long duration energy storage.

Hydrostor has two major projects now in active development – one in southern Kern County and one in Central California – representing a combined investment of over $1.5 billion USD, creating economic opportunities for Californians while supporting the transition to a carbon-free and renewable energy grid. Project development work including transmission interconnection, engineering and permitting activities are well underway. These are major capital projects that establish long-term clean energy infrastructure to the state using highly skilled union employment and provide significant economic benefits to the region.

A-CAES provides long duration energy storage like pumped hydro but with the key advantages of flexible siting where needed by the grid and with significantly less environmental impacts. A-CAES is much more cost effective than batteries at large scale and has a life of 50+ years making the asset ideally suited for the long duration energy market required for decarbonizing of electrical grids globally.

Hydrostor’s patented and commercially proven A-CAES technology provides 8-12+ hours of energy storage, versus the 1-4 hours that current battery technologies can feasibly provide.

It has lowest installed cost per kWh for large-scale, long-duration energy storage (100+ MW)

A-CAES in 4 simple steps

1. Compress Air Using Electricity
Off-peak or surplus electricity from the grid or a renewable source is used to run a compressor and produces heated compressed air.

2. Capture Heat in Thermal Store
Heat is extracted from the air stream and stored inside a proprietary thermal store preserving the energy for use later in the cycle. This adiabatic process increases overall efficiency and eliminates the need for fossil fuels during operation.

3. Store Compressed Air

The compressed air is stored in a purpose-built cavern where hydrostatic compensation is used to maintain the system at a constant pressure during operation.

4. Convert Compressed Air to Electricity On Demand
Hydrostatic pressure forces air to the surface where it is recombined with the stored heat and expanded through a turbine to generate electricity on demand.

29 thoughts on “Hydrostor Gigawatt Compressed Air Energy Storage”

  1. Actually, yet again, you put your foot thru your mouth. Seems like you (again!) didn't read my top-level comment. Perhaps an oversized Ego?  My point isn't whether your objection to 'MW' vs 'MWh' was wrong, but the tone of your comment, and that it reflects poorly on YOU, as author.  

    The right response might have been, "gee, I'm sorry. You're right… but the author still needs to edit the article text and change it to MWh".  That would have been gentlemanly and well received.  

    I expect you'll come up with some sort of mental shit-ball as a reply to this though. One of those personalities that simply cannot accept critique of their bawdy commenting style.  

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  2. GoatGuy always liked those ocean concrete ball systems for energy storage, or the ocean balloon bag types.

    These terrestrial systems using CAES, now with water hydraulic head assist for compression duties, are part of a wide swatch of similar systems though.

    For terrestrial pumped hydro in an engineered format though, I always liked Gravity power with their vertical bore water tunnels with a piston. They finally are getting to engineering prototype in Germany.


  3. That's the fundamental issue, isn't it. To store a lot of energy means you've got a whole lot of energy stored, which will release a whole lot of energy if it all escapes at once.

    That's the advantage of fuel. It won't release the energy until it's combined with oxygen from the atmosphere. And we mostly have the technology and operating procedures to prevent that mixture from happening except in a slow, controlled fashion. Mostly.

    Also the advantage of nuclear power (except for risky, highly enriched, military only reactors). The maximum possible rate of energy release is slow. The problem there is that even a slow 1GW or so soon builds up to enough heat to produce a moderate sized boom if you aren't converting that energy to electricity and hot air as quickly as it is made (Chernobyl). But much better than having the entire GW.year come out in one second.

  4. Hi Goatguy – I'm very odd. 😉 I remembered that many elements come to us via colliding neutron stars, and others come to us by supernova, but couldn't be bothered looking up which bling forms where, so just typed it up (from my brain) as a kind of metaphor. My humanities brain works in sweeping catch-phrases and metaphors and hyperbole. So thanks for your awesome unpacking of the more probable sources of uranium etc – and your description of our early solar system calls to mind a David Tennant Dr WHO episode with Martha checking out the formation of the solar system. Thanks for that reminder! Love your work.

  5. In case you didn't think it through … the last place on Earth you would want to inject high pressure air, would be a fruitless defunct oil well. Seriously…

    Just 'cuz an old gusher ain't economically viable to pump (or frack) any longer doesn't mean the oil is gone. Plenty still there.  

    What happens when you mix high temperature, high pressure air with oil? Hmm… let me guess. It burns.  Slowly at first, then KABOOM.  We really don't want a spent oil well with 250 atm of compressed air (within its safety margin) suddenly ramping up to 2500 atm as the oil burns. Bad things come from there. Really bad things.  

    500 kton TNT per 1,000,000 m³ of oil well. 5× the overburden pressure, so it's also going to blow. One BIG boom. Big bada boom.  And that's for a 1.4 GWday capacity underground chamber.  

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  6. Well … attribution is odd, but … rest of the story is right!  

    Far more likely (10000×) is that an ordinary supernova of 10-15 M-sols blew up 4.8 Gy ago, blasting away all but a tiny white dwarf remnant; the outer shells had a few percent of ²³⁵U in the mix, and the nebular mixing was efficient.  

    Outward velocities exceeding 10,000 km/s, combined with (in the same astrophysical neighborhood) other supernovæ and of course plenty of prior-art molecular clouds, compressed to overcome dispersion pressure; these then gravitationally collapsed into (at the very least) Sol and Alpha Centauri, but it likely also another few score others, along with millions-to-billions of planetary-and-moon sized orbs.  

    Sol's nascent system had tens-of-thousands of these blobs, basically planets and asteroids, along with the great aggregating central mass of Sol herself.  

    Celestial billiards rapidly collided … or flung off … most of the smaller bits, leaving a few dozen proto-planets a few million years along. Over the next ¹⁄₁₀ Gy, they continued to perform rearrangements and condensations, yielding our present planetary mix.  

    At least that's how I read the modern astrophysics literature. It changes in both subtle and large ways, every 25 years or so, as more things are discovered both locally and far, far, far away.  

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  7. You didn't even bother to read other comments, before wailing on the author of this otherwise kind-of-interesting science piece?  And you have the temerity to call our Dear Science Leader a STEM-illiterate? Bah, humbug!!! 

    I already wrote a nice, mannerly comment that called out the MWh vs MW issue. Read, and take a social-graces lesson home. You don't need to cast aspersions at people while correcting their innocent mistakes. Teach, don't punish.  

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  8. Lose has one 'o'. 
    But yah. 

    Thing is, there's a thing called adiabatic compression which realistically works well to conserve the efficiency of a compression-decompression cycle.  Basically, air, a non-ideal gas, both rises in pressure when compressed AND rises in temperature. 

    If air is compressed into a nearly-ideal tank that doesn't leak out or add heat to the compressed air, then minus all the usual mechanical lossy aspects, the energy-of-compression is almost completely recoverable. Well over 95% (bidirectional!) for well engineered systems.  

    Also (see top level analysis), so long as the operating pressure doesn't significantly come close to the overburden 'pressure', then such systems in abandoned-and-repurposed mines is pretty compelling. Lots of capacity, cheap to maintain, plenty of potential for HIGH energy delivery and absorption when required.  As fast, or even faster reacting than say 'gas turbines'.   

    Compressed air has quite a bit of specific recoverable energy, well over 25 kWh per cubic meter at 200 atmospheres. And spent salt mines (nearly ideal) are quite large. The real problem is that most salt mines aren't terribly deep, nor are they ubiquitously scattered all over the place … and between the solar/wind farms and the cities needing the juice. 


    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  9. See top-level analysis … which might be off by a factor of 1,000× but I really did try to check it carefully. Who knows. Might work. California is already using a compressed air system (and has been for over 25 years).  Small beans, but it is working. just sayin…

  10. Lets say each cubic meter of Terra has a mass of about 4 tons.  

    4,000 kg.  

    So, the downward pressure if 4,000 kg × 9.81 N/kg ÷ 1 m² is about 40,000 Pa(scals)/m of dirt above the chamber.  
    That is about 0.4 atmospheres of pressure.  
    If our chamber is 2,000 ft (⅔ km) below the surface, then ⅔ × 1000 m × 0.4 atm = 267 atm of overburden pressure. 
    That's about 3,700 PSI ± 10%.  

    Above that and a lens-shaped bubble will rise up, set to burst.  
    Don't want that.  
    Bad mojo, for sure. 

    About 125 MJ/m³ at 267 atm… 30 kg/m³ of TNT of compressed energy… 35 kWh/m³ in electrical;

    Now, multiply that by say a 1,000,000 m³ (not terribly big) cavern, and you have 30 kton of explosive contained energy. 
    It also happens to be 34 GWh of energy.  

    More than one might realistically NEED to store underground?
    Let's see … 34 GWh ÷ 24 hr = 1.4 GWd of energy.  

    Still, if running down at 1 GWd per day for 50 windless, cloudy winter days, then this is woefully insufficient storage at 1 GW drain. Only 1.4 days worth. 

    40× larger is about 55 GWd. 
    Also 1.2 megatons of potential disaster.

    Seems kinda risky.

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  11. Compress air storage has losses far larger than battery storage. That should go into the cost calculation.

  12. I think the term "long term" needs an exact definition here.

    Storing heat for months is not feasible, storing it for hours is totally feasible (thought I shan't comment on the economics). The article explicitly mentions 8 to 12 hours.

  13. Exactly! I was just explaining to my son the other day that watts are like measuring the flow of water coming out of a tap, and watt-hours are like the size of the tank that little tap is attached to. 1 GW is the flow of watts – but if that's only for a minute, why do I care?

  14. Neutron stars collided together and provided us with the ultimate in energy storage – uranium and thorium. Oh, and this safely provides power 24/7 for about 18 months till it needs refuelling on a predictable basis.

  15. So… since I wasn't writing the article, of course the single most important letter was likely left off the purported quantitative performance specs.  

    'h' (or 'd' or 'mo' or 'y')

    1000 MW is a specific power figure. Delivering (or receiving) an instantaneous maximum, or continuous charge/drain load of one billion watts.  Marvelous!  

    1000 MWh is a quantity-of-energy figure. That little 'h' out there means, said air-battery can deliver a total of 1,000,000 kilowatt-hours of energy, whether at 1,000,000 kW for 1 hour, or 1,000 kW for 1,000 hours, or any multiplicative equivalence therein. In many regards, so long as the specific power (first bit) is sufficient for the demands placed on the system, the ENERGY content is far, far more important.  

    As a good example, you can buy off the shelf a big stack of marvelously dangerous (when charged) capacitors, and hook them in series-parallel to handle being charged to 1,000 volts.  24 ea, 165 F at 48 V … $30,000 or so from mouser.com. What do you get?

    4,500,000 joules.  About 1.3 kWh. However, the instantaneous power output can be gigawatts. If the hookup wire is thick enough! Again, however, for only tenths of a second. See?  The bank of joules is enough to shoot a small projectile upwards of 5 km/sec. But total power is small.  

    Same with the article's air capacitor. Reservoir.  

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  16. Not really. That's when you need distributed distribution. You need storage to manage peaks. If an earthquake severely impact CA, many businesses will shut down and reduce electrical load.

  17. I don't think anti-fracking people have any desire to preserve rock. They don't like the massive amounts of toxic mystery water produced and methane leaks caused by it. Mining rock is not at all the same thing.

  18. There were other outfits (including Hydrostor) that looked as balloons. I think the technical challenges are greater. Hydrostor had a demonstrator balloon set-up in Lake Ontario at Toronto. Lake Ontario is not the ideal depth, but I think they moved on to use mined storage instead due to more flexible siting and perhaps less challenging conditions.

  19. There are 10,000's windmills generating electricity in West Texas, right beside gas/oil wells that already have drilling shafts down into impermeable shale where the air could not escape. I wonder if this is a viable (economically practical) solution for backup for the Texas grid? The powerlines have already been built from West Texas to major metropolitan areas (Dallas/Fort Worth, San Antonio, Houston).

  20. Umm, so the solution is to use an underground cavern as a compressed air storage bottle. In seismically active California? Interested in knowing how they handle that failure case, as an earthquake would seem to be one of the use cases where long term energy storage could be needed to supply the grid.

  21. Even better if the fuel is uranium (or thorium). Use the waste heat from the nuclear plant to heat the expanding gasses.
    Of course this is too sane an idea to be politically acceptable.

  22. "How do you create those storage chambers for the compressed air?"

    "Oh, we frack them out of hardrock."

    Heads explode in the background.

  23. Since you always loose in converting one form of energy into another what are the losses. How much thermal warming can you extract from the earth? A geothermal area would probably be a good place. I think its doable just has to be in the right location.

  24. The nice thing about any storage system that runs on heat and/expanding gases is that they can build in an easy fuel backup.

    Run on stored air and heat for 12 hours, then switch over to gas, hydrogen, ethanol, RNG for fuel to run for as long as the plant is needed.

    For this sort of arrangement, you want about 2-4 hours of storage and 1-10 days of fuel in most markets.

  25. Nimbys in coastal communities will sue and require an extra 30 years of environmental impact reviews. At the end of 30 years, they will determine that the system might disturb a fish.

  26. I see a certain degree of conflict between "long term storage", and the system relying on 'sensible heat storage' (Which is to say, NOT phase change.) for its efficiency. 'Sensible' heat storage is difficult to pull off long term unless at a VERY large scale.

    I'm also disturbed, though not surprised, that California is doubling down on using unreliable energy sources, and just attempting to compensate by throwing money at energy storage, which will radically increase the system cost of those sources.

    California has an ocean available to it. Why do hard rock mining when you can just sink tanks under water? At sufficient depth, the tanks scarcely need to be more than balloons.

Comments are closed.