Underwater Balloons – a new idea in Energy Storage?

Author's impression of the Underwater Balloon Energy Storage Facility

Author’s impression of an Underwater Balloon Energy Storage Facility

Guest essay by Eric Worrall

Hydrostor has created an interesting innovation in energy storage. The energy is stored as compressed air, in giant underwater balloons.

Hydrostor’s system works in several steps. Electricity is run through a compressor and converted into compressed air. This compressed air is then sent underwater.

“There, we have a whole series of what are effectively balloons, that fill… like lungs under a lake,” he added.

“They fill with air, and when they’re full you stop charging the system and it can sit there indefinitely. When you want power back, again, a valve opens … air comes rushing out, we run through a low pressure turbine called a turbo expander, and that reproduces power back to the grid.”

Energy storage is becoming increasingly important. In the United States, the Office of Electricity Delivery & Energy Reliability states that the development of technology to store electricity so it’s available on whenever it’s needed would be a “major breakthrough in electricity distribution.”

Read more: http://www.cnbc.com/2015/12/09/underwater-balloons-clean-energy-savior.html

This isn’t the first time I’ve heard of storing energy with compressed air. Hydrostor’s innovation is to reduce the cost, by using water pressure to maintain the storage compression, without the need to create high strength pressure containers.

Using water to supply the pressure to collapse the balloons might also improve the efficiency of energy retrieval. By storing the air underwater, and using the water pressure to collapse the balloon, the air would be retrieved at a near constant pressure, until the balloon was empty. Hydrostor claim an efficiency of 60 – 80%.

Hydrostor seem to be aiming at grid stabilisation rather than storing multiple days worth of grid supply, so it seems unlikely this proposal, as it stands, will fully solve the renewable intermittency issue.

Could compressed air storage be scaled up enough to solve intermittency? Even if you had enough renewable capacity to cover 100% of grid requirements, on average, if you wanted to go further than Hydrostor’s current plans, to completely eliminate the need for backup gas turbines for renewables, you would need to store enough energy to maintain full grid supply for at least a day, more likely several days.

My concern is energy stored as compressed air could, in principle at least, be released all at once, in the event of a storage system failure.

Imagine you wanted to store one day worth of energy to supply a major city, in case the wind didn’t blow that day – enough energy to maintain a 1 gigawatt supply to the grid.

To maintain a 1Gw supply of energy for one day, your storage solution would need to store;

1Gw x 1 day

= 1000,000,000 W x 86400 seconds

= 86,400,000,000,000 Joules of energy

= 86.4 TJ.

This amount of energy is the same magnitude as the energy released by Little Boy, the nuclear bomb which destroyed Hiroshima (63 TJ). An abrupt release of 84TJ of energy next to a populated area would cause serious damage.

How would such a release of energy manifest? During the Lake Nyos disaster, when 100,000 tons of volcanic CO2 at the bottom of Lake Nyos was abruptly released, the rising gas created a 25m Tsunami which did extensive damage to the thankfully mostly uninhabited shoreline.

In the case of Lake Nyos, the Tsunami damage was secondary compared to the lethal effect of normal air being displaced over a large geographic area, by an asphyxiating cloud of concentrated CO2. But a large Tsunami smashing into a densely populated coastal city, adjacent to the storage facility, could still cause serious loss of life, even if the gas bubble which created the Tsunami was breathable air.

Risk concerns aside, in my opinion Hydrostor’s solution is still a very interesting innovation. Storing energy underwater, utilising the natural pressure of the water, should substantially reduce the cost of creating storage “balloons”, compared to other schemes for using air pressure for energy storage, by dramatically reducing the required strength and potentially the cost of the materials used to construct the pressure containers.

223 thoughts on “Underwater Balloons – a new idea in Energy Storage?

  1. “Electricity is run through a compressor”
    The idea of compressing electricity fascinates me but I thing they mean electricity is used to run a compressor.
    Words are important.

    • The idea of compressing electricity fascinates me but I thing they mean electricity is used to run a compressor.

      Yes, I think this is to be used in conjunction with Wind and Solar to maintain constant energy at night and periods of no wind. I’ve also read of a version where H20 is pumped up into a water tower to power the turbines at night. Energy generated in off peak hours pump the water. To me all these “solutions” are interesting 4th grade science projects, but none of them will ever really compete with the unbelievably efficient and environmentally friendly petroleum. Here is the most idiotic solution I’ve seen. GE puts the wind turbines under water. Basically they are automatic whale sushi makers. Imagine the environmental disaster they things would be.

    • This is the value of having a sub-editor actually proof
      reading such articles, before publication, Is there such
      a process at WUWT. Perhaps we shall be told.
      Still I think this is some kind of Rube Goldberg machine, isn’t it.
      Does it do any useful work, or does it just present a loss to the
      system, and cost millions to develop and research to “get it right”.
      Add in the obligatory phrase …
      “with respect to atmospheric CO2 reduction”
      … and Lo, the grant moneis will pour in,
      ….. You Hope !

      • The idea is to store energy temporarily in a way that is quickly retrievable, rechargeable without wearing out, low cost etc.
        Of course there will always be rather large losses of energy in any such multistep conversion…the laws of thermodynamics ensure that.

      • Pressure from the combustion of fuel and air is what drives the pistons in an IC engine.
        Using compressed air to move a piston is the exact same mechanical process — so yes work will be done.

      • Sorry, Thum, but ALL mechanical systems have parts that wear out, corrode, or break. Repairs to, & periodic replacement of the whole system would be a large cost.

      • Dessie
        Windmills can grind corn, too.
        Auto – not prepared to defend their efficiency at corn-grinding . . .

      • DesertYote.
        A friend of mine recently told me of a fellow he met who uses a small windmill to compress air into a tank he then uses to run compressed air tools in his shop. Intermittent use and small scale, but perhaps a good “alternative” for locations away from any “grid”.

      • Methane and carbon dioxide is naturally released from numerous places on the sea floor anyway so there is no need to pump it down and compress it. Volcanic vents and microbial activity produces it. Sometimes it is released from water depths of over 2 kilometres where it will be under considerable pressure.
        Why not funnel these gas streams on the way to the surface and place a turbine in the funnel?
        That way there is no need for the storage or wasted energy to compress and for pumping.

  2. When air is compressed the temperature of the air rises, significantly. P1V1 over T1 equals P2V2 over T2. The balloons would lose the energy from the increased temperature, in the first place, and rubber is not free, in the second place. I am not putting my life savings into this concept…

    • So are you saying that widespread implementation of this concept would warm the oceans? Dang, we can’t win for losing!

      • “…widespread implementation of this concept would warm the oceans…”
        Never mind warming the oceans, widespread implementation of this concept would cause widespread displacement of seawater; causing the rising sealevels to rise even faster. It’s worse than we thought!

      • Menicholas,
        “But it would cool the atmosphere.”
        That’s what I was thinking . . as in low tech AC/refrigeration . . Could come in pretty handy in a remote hospital situation . .

      • John, that’s all AC is. Compress a gas, let it cool while maintaining constant pressure, then release the pressure.

    • I know that when I want to remove energy from a hot object I usually put it in bath of cold water. Oh wait…

    • And when the compressed air is released, it will cool. If it cool enough, ice may form and befoul the system. Might need an air dryer, which takes energy.

      • Unless the tubes are insulated, if the air in them cools enough, it will form ice on the surface of these tubes, which will put a lot of upwards pull on the tubes. I hope the tubes are well attached to the bottom.

        • If you read the proposal they intend to run that hot gas thru a heat recovery device and then when the flow is reversed they plan to recover that heat. I am not familiar with anything that can store heat for long periods but someone suggested a tank filled with bricks (and interstitial spaces for gas flow) would work to some extent.
          Heat recovery is very common in power plants, but the transfer occurs in real time and not with stored heat.
          I do not believe the efficiency claim either.

    • The big problem is with the laws of Thermodynamics. When you convert one form of energy (electricity) to another (compressed gas) you ALWAYS lose. Conversion efficiency of 50% is generally considered to be fairly good by engineers. So you convert 4 GW of electricity to compressed gas and you now have 2 GW + 2GW of waste heat, and when you convert that back to electricity by running the gas thru turbines you end up with 1 GW of electricity.
      So you’d need four times as many solar panels to run this scheme. It’s a joke, or it’s more likely sucker bait for the technically ignorant investors.

      • Age, and – Office of Electricity Delivery & Energy Reliability states that the development of technology to store electricity so it’s available on whenever it’s needed
        In order to have any to store, you must first have an excess. When has this happened.

    • And just how much electrical energy is required for those air pumps to overcome the water pressure that surrounds those deflated submerged balloons?
      Orr are they planning to inflate the balloons first …… and then sinking them underwater?

      • “And just how much electrical energy is required for those air pumps to overcome the water pressure that surrounds those deflated submerged balloons?”
        overcoming the pressure is exactly why and how this system works. otherwise, what’s the purpose of storing it under the ocean in the first place. the deeper you go the less amount of compress air you need to store the same amount of energy. the principle here is similar to a hydro-dam. you are in reality storing energy in the water you are displacing.

    • You can steal the adiabatic heat of compression (which is what you are describing) to do useful work like heat a working fluid.
      You can also use thermal energy captured elsewhere to increase the pressure of the stored air after it is exhausted into an intermediate plenum — thus increasing the pressure and useful work without causing the main pressure vessel to increase in temperature.

  3. Might work in MN others with access to lakes and oceans. Interesting but highly inefficient, seriously doubt their 60-80% efficiency projection.

    • You’re not the only one William! Compressor losses, thermal losses, head losses going down the feed pipes, head losses coming back up the feed pipes and finally turbine losses.

      • One of the problems Oregon has had with it “Wave Energy” projects is the Old Man of the North Pacific.
        how deep are these placed and how will the infrastructure to run it be made storm proof? let alone the placement of the solar panels in areas where the
        sun actually shines? Long way from say, Lakeview
        to Coos Bay…(about 240miles) …

    • when I was young I was really into the idea of renewable energy. I figured out you could run a dessicant HVAC system with almost no energy BUT…then I kind of took a step back at what I’d thought of and realized it was freakishly large. For large static systems, space isn’t a problem…but it really starts to become a problem when you’re talking about storing a month of energy for the US (300 TW for electrical generation alone).
      You quickly notice that the cost of the secondary systems are much higher than the costs of some of the energy producing systems…why pay 2 million for a high efficiency system when a low efficiency system along with much higher generating capability is cheaper. The cheapest way I could think of to store energy…was to basically double output and store it at around half efficiency. Basically convert the excess to hydrogen and store it in metal lined, bored out tunnels. Because of the ridiculous costs of inverters and fuel cells…turns out its a lot easier to just make more hydrogen and set fire to it to drive turbines and industrial processes.
      Now if you’re being realistic, anti-carbon types should be BEGGING for fracking to cover loads like this, since natural gas is abundant, storable, transferrable, safer than hydrogen, etc. With an energy storage system you need to be able to account for the daily/weekly/monthly/seasonal swings in production. For wind this means you need a ridiculously large storage…like a week to a month. And the wind system would need to be able to refill that system so it would need just a bit more excess production than normal (but not too much). So a 1GW/Day load would require 15-30 GW of storage.
      Now if you did the same thing with nuclear, it gets a lot simpler. Because nuclear power’s output is much more reliable, you’re not even storing enough power for a single day, you just need enough storage to cover the difference between average daily production and average daily load (assuming you’re running the reactor at around 90% of max to do that so you have reserves). Even a single day’s worth of energy storage would be sufficient to cover that difference between production and peak load for half a week…and even if the storage system ran dry, they could switch off parts of the grid and meet around 75% of peak load.

      • According to a study of ADEME (Agence de l’Environnement et de la Maîtrise de l’Energie), France can go 80% or even 100% renewable with a very small price increase.
        Of course, this is only for electricity (which is already mostly carbon free and also clean in France).
        Of course, this is assuming an extrapolated price decrease.
        Of course, this is assuming the rest of Europe keeps enough fossils to keep French lights on.
        It is less funny when you know you have paid for such crap.

      • I know a great way to store energy. Lets bury trees 2km underground for a million years & turn them into coal & methane.

      • (Note: “Buster Brown” is the latest fake screen name for ‘David Socrates’, ‘Brian G Valentine’, ‘Joel D. Jackson’, ‘beckleybud’, ‘Edward Richardson’, ‘H Grouse’, and about twenty others. The same person is also an identity thief who has stolen legitimate commenters’ names. Therefore, all the time and effort he spent on writing 300 comments under the fake “BusterBrown” name, many of them quite long, are wasted because I am deleting them wholesale. ~mod.)

  4. …This amount of energy is the same magnitude as the energy released by Little Boy, the nuclear bomb which destroyed Hiroshima (63 TJ). An abrupt release of 84TJ of energy next to a populated area would cause serious damage….
    ANY method of storing enough energy to operate a modern civilisation is going to have very great potential dangers. This doesn’t seem to figure in green propaganda at all….

  5. Let’s go back to the idea as to why someone would need to store the energy.
    There may well be a number of valid reasons to try to do this in certain places and conditions, but if the reason is solely to try to account for the fact that solar/wind is intermittent and unreliable and grossly more expensive to produce and therefore needs a backup……………

  6. This idea, like the railway storage method (aresnorthamerica.com), while interesting are not tried and proven like pumped hydro. All are limited by geography. The amount of space required is another issue. Maintenance of the underwater section is another question I have.

  7. IOW, they are lifting the oceans with air, causing man-made sea level rise. Will someone think of the children I mean, the shores?
    What about the sea creature who will bump into the balloon?
    What about the danger when a balloon collapses? What about the toxicity of the destroyed balloon?

    • They could have HUNDREDS of cubic kilometers of balloons and not appreciably raise sea level:
      Volume of the oceans 1.37 Billion cubic kilometers
      The volume increase needed to raise sea level 1 millimeter is approximately 350 cubic kilometers
      Take a sphere 6371.000001km (radius of earth at sea level plus 1 mm) and subtract a sphere of radius 6371 km — you get 510 cubic kilometers — multiply by 70% surface area — 350

      • “They could have HUNDREDS of cubic kilometers of balloons and not appreciably raise sea level”
        I was making with the funny.

  8. Tides, locations issues, connection to the grid, salinity issues and corrosion. It seems a very expensive solution for a very small benefit.

  9. A similiar system is used at Kinzua reservoir in Pa. They blasted the top off of a mountain, and during the night when they have excess electricity available they pump water out of the lake up the hill into the storage reservoir. During the day, they run the water in reverse through the turbines to create electricity without flooding the down river residents. Is blowing the top off of a mountain worse than destroying the habitat on the bottom of a lake? I dunno.

  10. n’t the best use of renewables be to run a coal gasification plant … store the gas use it later …

  11. So now they want to litter the ocean floor with giant balloons made out of Hydrocarbons ?? Not to mention it would be highly inefficient !

  12. There is a large drop in eff. due to heat loss when compressing the air. It is also poor performance in a turbine. It would probably be better to pump water up a hill and then run a turbine as it drains back during off hours. There is no compression loss this way and the increase mass of the fluid through the turbine would result in much higher energy recovery.
    After all it’s really just the change in sea level caused by the air bags that’s storing your energy. You alternately can inflate the bags when the tide is low…the recover the higher pressure at high tide. This would provide additional energy over and above what went in. ( you would need a high tidal area to make it most useful)

  13. The buoyancy of the balloons would be huge. I can’t see how they could be practically anchored and supported. A very modest 1000 cubic meter balloon (10 meters cubed) would have a lift force of 2,200,000 pounds.

    • I was actually expecting this article to leverage that fact. I was imagining steel tanks connected via cables to a pulley/generator. You pump air into the tanks to grant them buoyancy and let the lift crank a generator as they rise to the surface over X time (gear ratios, depth, etc, would need calculation and calibration, obviously… maybe not even possible. Just a thought experiment prior to actually doing real engineering. 🙂
      The crank could also be spring loaded so that as you start releasing the air at the top, it starts spinning in the opposite direction, generating power on the way back down. once it’s back at rest, you can pump air in again to prime it.

  14. No $ per MWh – my bet is the storage costs are about $1000/MWh, ($1/kWh). So ‘perfect’ for the green energy industrial complex, which seeks to make people freeze in the dark. The limit of what you can charge for electricity is based on the alternatives to the grid, which is about $0.20 / kWh in the US (home based natural gas to electricity). With the grid controlled by politics instead of physics, people/companies simply unplug and make their own, as is happening world wide in places like Germany, California, Ontario, etc.

  15. And what about anchoring really big storage balloons in quite deep water? That’s one gigantic anchor or a major drilling operation into what presumably must be hard rock. I suppose a huge mat or platform with tethering cables could be covered with thousand of tons of sand and rock with dredging equipment but that would be a feat too.
    And there’s only about half pound of air pressure gained per foot of depth. For example, 200 feet deep gives roughly 100 pounds per square inch of pressure and that’s not much in industrial terms.
    At scale, as the article mentions, there are serious safety concerns in case of failure. At least the balloons are invisible and quiet except for air compressors. These waste energy through Inefficiency and the as far as I know unavoidable heating of the air being compressed.
    The utility and practicality of this clever idea remains to be seen.

    • If the bottom of the storage vessel was open, wouldn’t the air dissolve into the water – albeit slowly?

    • Sly
      Anchoring probably will be a problem.
      The ‘lift’ – the force trying to ‘un-anchor’ the system is obviously related to the size of the container [balloon, dome, whatever].
      Looking at shipping, ships have anchors that hold he end of their anchor chains. It is the hundreds of tonnes [for a big ship] of weight in the chain that – tends to – hold the ship in position.
      [except in high winds. I tell my masters to leave anchorages, unless well-sheltered, very early, and make for the open sea. Do not get caught on a lee shore.
      One of my ships did that, some years ago, and caused $40,000,000 of damage to a sophisticated, and nearly new, ship. Nobody hurt, fortunately, and no pollution – bunker tanks located protectively.
      But $40,000,000 – not chump change . . .
      Corrosion – at depth – will not be as big a problem as it is on ships at the surface, where there is heat and moisture. . . .
      Saying that, but expert analysis will be needed.
      At the surface, on ships, we get the dreaded steel-worm – rust.
      Rust eats ships.

      • Auto, you said: “Anchoring probably will be a problem.” Personally, I would to change that to: “Anchoring WILL be a problem.” I was docked in Nassau several years ago over Christmas when the (US aircraft carrier) ‘Eisenhower’ came down from Norfolk. They arrived on a Saturday and anchored off Paradise Island for the weekend. The next day the shore patrol came to town to shuffle all the sailors back to the ship. She was dragging anchor! If the US Navy can’t solve the anchoring problem I would be surprised if anyone else has.
        Another potential problem is protecting the air bags from marine growth. Unless the technology has changed in the last several years, any decent antifouling coating either contains some rather nasty chemicals or has to be replaced fairly often.

    • Open bottoms would ensure that the air was saturated with water. Then as the air cooled as it decompresses that water would condense out, blocking the hose to the surface. If the pressure drop was high enough, problems with ice forming would be have to be solved.

  16. Where is 80-90% of energy in the form wasted heat from the compression processes going to be stored? Likewise, how will it be reheated when released? And no mention of the massive air dryers required to prevent the whole system from turning into a giant block of ice (air contains water vapor that would need to be removed).

    • My thoughts exactly. OTOH, one advantage of the underwater balloon storage is that the pressure is pretty much constant, so it should be possible to have a heat storage unit to absorb that during compression and release during expansion – probably want to make it out of a series of phase change materials to keep the temperatures at each stage more or less constant.

  17. stephana

    A similiar system is used at Kinzua reservoir in Pa. They blasted the top off of a mountain, and during the night when they have excess electricity available they pump water out of the lake up the hill into the storage reservoir. During the day, they run the water in reverse through the turbines to create electricity without flooding the down river residents. Is blowing the top off of a mountain worse than destroying the habitat on the bottom of a lake?

    Pumping WATER uphill, then letting the WATER run back downhill is a long-working solution that does, in fact, work.
    The premise requires a few things – It needs absolutely that the electric energy to pump the water uphill is available at all (first!), that this energy is not needed someplace else (after all, when a generator has to run to create the electricity to run the turbo-pump backwards for 6 hours, that generator cannot power anything else. Then, the water has to be available – a dry river cannot be pumped uphill. Then, the high-level storage facility (hundreds if not thousands of acres of land as you point out) has to be available at the same location as the river and the excess cheap power.
    So, the vast Niagara River hydrostorage “lakes” below the Niagara Falls are near ideal. Water power already available, and those generators NOT needed at night, a river with no drought-reduced flow nor flooding problems. But even then, there was tremendous legal and enviro pressure against even these “little” artificial lakes because one edge of one lake on one side of the river flooded an old Indian burial ground. And both sides of the river (Canadian and New York) needed large excavations and tremendous earth dikes to make the lakes.
    Air-fed turbines (to get power out) and air-pressure fans (to pressurize the air and pump it below the water level) are notoriously inefficient – either way – compared to water pumps and water-powered generator turbines.
    Basically, I don’t believe their numbers can be matched in practice. I could be proved wrong. But I will NOT believe a sales pitch for government money until they show test results using their own money and their own turbo-pumps into their own balloon under their own lake.

    • (Note: “Buster Brown” is the latest fake screen name for ‘David Socrates’, ‘Brian G Valentine’, ‘Joel D. Jackson’, ‘beckleybud’, ‘Edward Richardson’, ‘H Grouse’, and about twenty others. The same person is also an identity thief who has stolen legitimate commenters’ names. Therefore, all the time and effort he spent on writing 300 comments under the fake “BusterBrown” name, many of them quite long, are wasted because I am deleting them wholesale. ~mod.)

      • (Note: “Buster Brown” is the latest fake screen name for ‘David Socrates’, ‘Brian G Valentine’, ‘Joel D. Jackson’, ‘beckleybud’, ‘Edward Richardson’, ‘H Grouse’, and about twenty others. The same person is also an identity thief who has stolen legitimate commenters’ names. Therefore, all the time and effort he spent on writing 300 comments under the fake “BusterBrown” name, many of them quite long, are wasted because I am deleting them wholesale. ~mod.)

      • Yes that’s true Buster, still there is rather a lot of those oil sands. That picture represents just the Suncor workings at that one site. The whole field is ginormous and though to hold more than all the shale put together. Then there’s coal, gazillions of tons of the stuff, but still it will eventually all run out in a many hundreds or thousands of years perhaps.
        But recently we hear from both Russian and US scientists of the discovery of Abiotic Oil and Gas, produced from primary elements, cleaved from Carbonate Rock, and Water molecules under extreme pressures and temperatures, deep in the subduction zones of the Earth’s Crust. Such is the source for those very deep high pressure oil wells now being found below Carboniferous geological layers, it is postulated.
        Again the Earth’s core is thought to have immeasurably huge amounts of elemental Carbon, and with Hydrogen from subducted rock strata, we have all the ingredients to naturally and sustainably create oil and gas, ad infinitum. It is claimed that the Deepwater Horizon well which blew out in the Caribbean was one such attempt to access the deep oil and gas. They may have succeeded in tapping the “mother lode”, but they couldn’t control it, and it took five months, to seal the well up permanently again.The Russians have similar deep wells, which they are able to control.
        The oil sands may run dry,
        and the coal bed be mined out,
        but peak oil and gas, perhaps not.

  18. There are two compressed air grid storage facilities. 280MW Germany 1978, 110MW Alabama 1991. Both are solution mined salt caverns, airtight by definition. Much cheaper than submerged balloons.
    There are no others even though there are lots of thick salt strata that coild be used, for a simple reason. The round trip efficiency is less than pumped hyro. Turbine and compression heat losses. So Hydrostor is another technically possible but commercially infeasible idea, more expensive than what was already tried and abandoned.

  19. As has been mentioned earlier, this process will produce huge amounts of heat, which will be released to the ocean.
    Then, on recovery, there will be a lot of heat absorbed when the compressed air is used back on land.
    This seems like a giant scheme to move heat from the atmosphere into the ocean, and heat both up. Remind me again just what fundamental problem we are trying to solve here – ah, yes, the heating of the atmosphere and the ocean…

  20. Why not use depleted oil and gas wells? A natural gas field on the North Slope of Alaska has pressures of over 20,000 lbs.

    • You don’t need the power generated up there. Oil reservoirs underground are not really “voids” unlike a full-sized salt cavern (which is a huge single hole in the ground created by years of dissolving salt by water pumped underground, then evaporating the salt out topside into the sunlight. That makes a huge hole tens of thousands of cubic meters in size. A oil field is near-solid rock, with the oil “squeezed” towards the pump suction through very, very tiny individual cracks in the rock by the tons of pressure of the rock thousands fo feet above. Even after pumping out tons of oil, there just isn’t any real “holes” in the rock to fill back with air then release the air back to the turbine. In any event, 70 – 90% of the oil remains below in an economically-empty, ready for later drilling with different techniques, so even after the oil-filled rock is pumped dry, there is little room below.

  21. Thanks so much for using the Hiroshima unit of measure to explain energy requirements in your example.
    Conceptualizing a Joule is pretty hard but Mythbusters blowing up a huge truck in the middle of a lake, that I can do.

  22. Makes me think of how wavepower seems a great idea until you see that in practice the sudden turbulence can have so much power that it destroys your wavepower rig.

    • Wouldn’t you just need to use scale-appropriate construction methods? I mean, I’ve seen the windmills up close, as my brother-in-law works on them. They’re fairly flimsy, and can’t handle side forces very well. For collecting wave power, I’d envision concrete dam-like constructions made to withstand some serious waves.

  23. Underwater balloons sound impractical.
    But, if one insists on pursuing an energy storage system, I suggest trying a system of motor-generators that would lift huge weights to store potential energy.
    This system would bypass the problems of explosions or flooding.
    It would be identical to the system of the weights that run old grandfather clocks.
    The weights could run straight up and down in a structure or up the side of a mountain on rails.
    However, like windmills, this system has a poor ratio of the amount of raw materials needed to build it, compared to the number of watts generated.
    Losses would occur dependent on the efficiency of the motor-generators and in the gearing.
    Nuclear energy is the best option for minimal CO2 emissions, if the world insists on CO2 being “the problem”.
    I vote to try thorium.

    • I see now that there is a rail system by ARES in Southern California.
      It seems like a great waste of space for little power, like windmills.
      I estimate that the most efficient system for gravity storage would be straight up and down.

      • There are some areas of the western slope of the Sierras where a 10,000′ change in elevation should be practical. A 10,000 ton train would require about 100MWHr to haul up that 10,000 foot hill. Figuring rolling resistance at about 0.2% of weight and a 4% incline should give about 90% mechanical energy recovery. Then assuming 90% electrical/mechanical and mechanical/electrical conversion efficiency will give a round trip efficiency on the order of 70%.
        The idea looks OK from a simple technical perspective, but I have severe doubts about the economic practicality.
        On a historical perspective, the first run of an electrically auled freight train on the Milwaukee Road’s line over the continental divide resulted in more power being returned on the downhill portion than consumed going uphill (Butte i quite a bit higher in elevation than Three Forks). This run took place in late 1915.

      • kbray,
        The ARES proposal is basically an electrified railroad and my back of the envelope estimates were based on that. The ARES website claims a bit over 78% round trip efficiency – the 0.9×0.9×0.9 estimate comes out at a bit over 72%, which is a bit closer to 78% than 85%… I’d expect the efficiency to be better than a compressed air storage system with no associated thermal storage.

      • erikemagnuson,
        I agree that the gravity railroad is likely the most efficient storage system, as almost 100% of the stored potential is forced back through the electric motor when it changes direction. The only losses I see are in the motors, generators, and friction.
        Hydro pumping would probably be less efficient due to water power transfer losses on the turbine blades and losses in the up-pumping added to the electrical losses in the motors, generators, and friction.
        The compressed air storage system has a plethora of losses and for me is a non-starter.
        But if these energy storage systems are being pursued to smooth out the power from wind and solar, it’s just “putting lipstick on a pig”.
        My neighbor just put up 11 solar panels with less than 3KW output thinking he is going to save the planet.
        Trying to run an all electric / zero carbon household on 3KW is not going to work very well. Fortunately he is still tied to the grid.
        However to sum up, in my opinion, modern nuclear power is the only practical way as of today to generate enough 24/7 reliable electrical power to satisfy the needs of the planet to run all our machines, heat our homes, and melt our steel, with minimal CO2 production. (and personally I don’t think CO2 is a problem to begin with)
        Wind, solar, and energy storage is just “screwing around” trying to get to that “zero carbon” goal.

        • Pump water storage has good efficiency. Getting very close to 100% round-trip efficiency is NOT the issue here. The issues are cost of building, keeping in shape, risks, peek power, capacity…
          The comparison of “efficiency” as energy in at 8:00 energy out at 10:00 is a non issue when it is quite good already.
          The issue is efficiency as total energy in vs. total energy out. This includes the energy to build stuff, including part of the energy to build the tools and the energy to raise cattle to feed the people who built the storage system and tools used for raising cattle to feed the people and the energy used to make the energy storage system used to build tools to make a tractor to feed the cattle to feed the worker who built tools used to produce lubricant oil for the train used in the storage system (each in proportion of the production consumed, of course).

      • “(and personally I don’t think CO2 is a problem to begin with)”
        No, but chemically energetic linked carbon geopolitics is.

      • Pumped Hydro. ≈ 72% round trip Efficiency & uses approx 36% more power to pump the water uphill than it generates running down.
        I have intimate knowledge of the Dinorwig pumped storage station ‘Electric Mountain’; The station has six 300MW generators, giving it a total capacity of 1.6GW. for ~7 hrs.
        Britain currently has 4 operating major pumped storage schemes –
        Total Storage Capacity = 23•279 GWh
        Total Generating Capacity = 2•764GW. The UKs total pumped storage can only supply 4•6% of max demand for 6hrs then 0.8% for 4hrs. Full recovery time is approx 17hrs of surplus power. _
        You could dam & flood every valley in Britain and not have a days worth of storage…& the construction costs are eye watering.

      • https://en.wikipedia.org/wiki/Dinorwig_Power_Station

        Nuclear power stations must be run at close to full output all of the time

        Bovine excrement, as usual from WP.
        With link to https://en.wikipedia.org/wiki/Base_load_power_plant which says

        Baseload plants are the production facilities used to meet some or all of a given region’s continuous energy demand, and produce energy at a constant rate, usually at a low cost relative to other production facilities available to the system.

        Note “used” not “limited to”.

      • Kbray,
        The major source of loss on a typical electric railroad is in the catenary or third rail, though the electrifications are designed for lowest overall cost of providing transportation. A power storage RR would presumably be built to give lowest cost of stored energy.
        One other thing came to mind – the ARES proposal is a specialized type of Railroad. I wonder if the folks at ARES have ever been in touch with people experienced with the track and mechanical aspects of keeping a railroad running.

      • simple-touriste,
        I agree that some of these schemes use way too many resources for what they give back.
        That’s the problem along with the political component.
        Thanks for the info about Dinorwig.
        I’m surprised that it can drain that big reservoir in only 6-7 hours and takes 17 hours to refill.
        It seems like a lot of effort and resources for not much return.
        It does function as a buffer for the grid, but such a cost.
        I understand the third rail losses. Definitely distance related.
        I watched some of the ARES animations and the plan looks too complicated with 90 degree rotations of the trains and stacking against each other. Too many mechanical problems with that process. Firm believer in keeping it simple. Agree and hope they have access to real railroad folks with experience.
        I wish them good luck with that.

        • “I understand the third rail losses. Definitely distance related.”
          Why not use an efficient 25 kV standard overhead cable?
          (Not safe for the idiots trying to still cables, though.)

      • “I’m surprised that it can drain that big reservoir in only 6-7 hours and takes 17 hours to refill.
        It seems like a lot of effort and resources for not much return.”
        No, it’s by design.
        Some stations in Europe have been modified (at great cost) so that they could be emptied faster. The ability to inject lots of power is valuable. The ability to do it at any time on short notice is even more valuable.
        Think of a big nuclear power plant being attacked by aliens jellyfishes. Or mud. Or oil spill. Or anything. It happens. Rarely, but it does. Then the plant, not one reactor, has to stop. (It may have a back-up lake but it is not intended for normal operation.) Several GW maybe be missing with no prior notice.
        You want to have a big reserve of backup with the ability to inject power at any time, not for long period. You also have other thermal plants online (possibly including other nuclear plant not at full power) with the ability to power up in less than a few hours.
        The cost of these gigantic accumulators with a capacity of few hours at maximum power may be stunning (about as much as nuclear power plant capable for running 10 months per year with a relatively small fuel cost), but it they may still be economically viable.
        Diversity is essential: diversity of reliable plants at different places ready to take over.

  24. T*delta S losses alone will make air compression highly inefficient, but the adiabatic heating losses will also cut energy efficiency. I haven’t done the calculations which are straight forward, but this comment from the Bonneville Power Administration essentially says it all:
    Compressed air is often called the “fourth utility,” after electricity, natural gas and water. For many businesses, compressed air is a vital input to their production process. However, too often, compressed air systems are highly inefficient, resulting in significant wasted energy (and cost).
    • Is compressed air free?
    No, compressed air is not free. Although “it’s only air,” compressed air is actually very expensive because only 10 to 20 percent of the electric energy input reaches the point of end-use. The remaining input energy converts to wasted heat or is lost through leakage. For example, to generate 5 CFM it takes 1 HP!

    • This is why it would almost always be most efficient to give away surplus energy to subscribers and let them find a way to put the energy to use at the premises/factory. A battery might be charged or water or floor slab heated for instance.
      Most mass storage schemes waste significant amounts of energy: in the range of 20-80%, but simple low-tech solutions are available for sinking oversupply in many small increments and would reduce capital outlays for those proposed large low-efficiency schemes.

      • This is of course exactly the concept used by electric night storage heaters. These are little more than a pile of bricks in a metal case with a fan inside.

    • Lol, and most industrials know this. The plant I worked in used compressed air to run tools and to blow dust off of our clothes, and to air up tires. For the large machines, electric motors and gasoline were used, lol.

    • I wonder what a large lobster might make of this, or even
      a large shark? Snip-snap, Gnash-slash, Oops-bang ?
      Great White sharks especially have been know to tear “rubber”
      boats to sheds. Marine boring worms? Limpets will eventually
      grind deep grooves into the surface and weaken it, perhaps.
      But in the sea these people imagine, it is just an imaginary sea
      in some computer model maybe, and they can just turn off the
      Crustaceans etc., and even turn off the corrosive chemicals.
      This won’t be so easy with the actual real sea though.

  25. Wouldn’t all those inflated balloons cause the water level to rise? Another example of ‘it’s not a crime when we do it’.

  26. Isn’t this just a more complicated way of implementing a hydro solution?
    Instead of raising all the water up a hill you raise some of it at the bottom of a lake.

    • No this is a pneumatic system, which is being proposed.
      Still there is no “free lunch” and the energy losses, plus
      the cost of infrastructure, and inaccessibility of working
      parts, as well as the highly corrosive environment in the
      sea, makes this impractical at best, and horrendously
      costly into the bargain. Frankly there are easier ways
      to “store” large scale electrical energy than this, but
      all of them do incur large scale energy losses as well.
      The “Giant Crystal” seemed promising some years ago,
      and what became of that “breakthrough” in energy storage ?
      Then there were the “Photonic Crystals” that could store
      “Light” from a heat source, what happened to that ?
      You see maybe those folks should have said it
      was all about saving the planet from the daemonic
      CO2 Gas …aaaaarrrrgggh ! Then they would have
      had as much funding as Solyndra …. oooeeerr !

  27. Not as silly as the Kilometer high granite piston raised by water pressure, but less efficient then the molten salt converted coal power plants. This CAGW scam sure brings out the crazy ideas.

    • I like the “Water Hyacinth” idea. Supposedly the World’s fastest growing plant, You just set off in a boat, and rake them up, dry and burn them. Next day there is just as many as before, they grow so quickly. Trouble with that idea is you might need hundreds of lakes, the size of Lake Superior, and the plant only grows in the tropics. Ah well it seemed a good idea, at least for those living around Lake Victoria. The plant is a menace to the environment now, and out competes other plant species, The UN & World bank has spent Millions trying to eradicate the plant. But just rake it up and flaming well BURN IT IN FURNACES, to MAKE ELECTRICITY, also FERMENT IT IN VESSELS to MAKE BIO-GAS for cooking and transport.
      Still the UN and other halfwits, are trying to kill this plant off by using poisonous herbicides and infesting teh lakes with foreign predator insects, and so on. Hundreds of Millions wasted by imbeciles on half baked nonsense, when the answer to several local problems is STARING THEM IN THE FACE.
      Who are these fools that decide crazy policy ?
      The local people should not wait for UN approval,
      just get in the boat, collect a load of Water Hyacinths,
      and get started on your own local bio-gas business.
      Are there any readers from the Lake Victoria area in Africa ?
      Perhaps they might tell us what is happening with Water Hyacinth Power..

      • I worked near Lake Victoria years ago. Solutions to world problems are not being hatched in that country. They can’t even solve their own problems.

      • “Trouble with that idea is you might need hundreds of lakes, the size of Lake Superior, and the plant only grows in the tropics.”
        Use Sargassum seaweed instead. It floats on seawater in the tropics. Just put some in a net bag and attach it to a bouy. Come back later and collect the excess We have plenty of tropical ocean available to do this. It aso grows very quickly.
        Sargassum doesn’t cover the ocean because currently move into colder water where it dies or the accumulation of barnacles and corals causes the Sargassum to sink to the bottom . Putting it in a net bag attached to a bouy will prevent it from drifting into cold water and regular harvesting would prevent it from sinking.
        Also you would not need hundreds of lake superiors 3 or 4 might be enough to meet much the US natural gas demand. At one time the American natural gas association calculated that 23 quadrillion BTUs of energy could be created by harvesting kelp off the california coast.

      • OK Water Hyacinth don’t just grow in the tropics. Some missionary’s wife thought the flowers were pretty so she brought some back to the US and let it escape into the wild. It is now the bane of the southern states boaters, ecologists and fisherman since it covers vast numbers of lakes and ponds.
        The Florida Dept of Agriculture has spent millions trying to come up with a way to 1) get rid of the stuff or failing that 2) find some economic use for the stuff. They even invented floating hyacinth harvesters to collect the plants. And so far as I know they only method they found to dispose of the stuff is to try to make cows eat it. Cows apparently don’t much care for the taste.
        You can’t economically burn the stuff since it is 90% water and the energy required to dry it to a burnable condition vastly exceeds the energy recovered by burning. You can’t practically spread it on the ground to dry since that would take square miles of drying racks.
        I’m sure that this applies to any aquatic plant.

  28. This is a net consumer of energy just the same as pumped storage is. Do we have that much “clean energy” to throw away on this stuff?

  29. This company has no idea about the real world energy losses involved. Real world compression pumps run between 65% and 90%, with most topping out at about 80% to 85% efficiency, with 75% being a decent real world average of the varying types of pumps. This includes gas friction within the compressor, the mechanical losses (bearings, friction, seals, etc.), and gear-box losses.
    So, right away, one loses 25% of the energy, simply and ONLY at the compressor. Then we have to add in the pipe head losses – both incoming and outgoing, the heat losses, and overcoming the pressure of the water outside the balloons.
    This last is no little thing. The balloons will not inflate against greater water pressure from outside. (And if they don’t inflate, then why even use balloons instead of simple storage tanks on land?
    At every stage of this pie-in-the-sky idea, there are energy losses, and it seems to portray all of this as 100% efficient. It is anything BUT 100% efficient.
    The energy taken out will be much less than put into it. All in all, perhaps less than 50% available. This is a non-starter to anyone who has to deal with system efficiencies.
    The amount of work done just to inflate the balloons is incredible. And that stage alone will run at best at perhaps 65% efficiency, what with the heating up of the gases – which itself is LOST ENERGY. They are never going to get that energy back out of the system. So for every 1,000 kilowatts put into it they are losing 250 kilowatts. HOW is that supposed to be a good system? ONLY if there is so much energy being produced essentially for FREE does it make any sense. Because if they have to PAY to produce the electricity to drive the compressors, it’s a losing cause.
    Energy and cost-wise, the faster it goes the behinder it will get.
    Better to simply shut off the valves on the inlet end and not run any gases through this system at all. And then scrap all the equipment or sell it all on eBay.

    • “The energy taken out will be much less than put into it. All in all, perhaps less than 50% available. This is a non-starter to anyone who has to deal with system inefficiencies.”
      And yet people found cars (30% efficient at best) very useful . Incandescent light are also very inefficient (about 10%) and yet we have used them for almost 100 years. Just because something is inefficient doesn’t mean it is useless. Blissfulness primarily determined by a systems coast benefit analysis. If you have excess energy and CAES can store it at a ,lower cost than the compititionm it will be used.

      • Yes that’s true but cars can use a cheap high density fuel to get around their inefficiency, aka gasoline or diesel. Lamps are supplied mainly by cheap high density fossil fuels or nuke plants for the most part. Power plants make mighty efforts to recover a tenth of a percent of efficiency. And so do auto manufacturers (increased mileage).
        So you are trying to replace cheap high density fuel with expensive low density and unreliable solar or wind power. When you go that route every tenth of a percent of efficiency counts much more.

      • Incandescents are 10% efficient only when you’re not heating your home. When you are (as I am 7 months of the year), they are 100% efficient.

        • As a heating system, you need to take into account:
          – the normal heating system (thermal heating is less “efficient” in term of energy than electromotive heating, but more efficient in term of entropy)
          – where the lamp is (floor is better for convective heating)
          – radiant vs. convective heating

  30. Conceivably, the “balloons” could be made of graphene, which is incredibly strong a durable and also is impervious to gas molecules. If we can only learn to make graphene in large sheets economically and deal with its thinness.
    It would seem that moving the contaners up would be the equivalent of any pump needed to release the stored and pressurized gas as it expands.

    • “Conceivably, the “balloons” could be made of graphene, which is incredibly strong a durable and also is impervious to gas molecules. ”
      The balloons don’t need to be strong. The pressure on the inside and outside of the balloon is the same so very little stress will be on the balloon. A thin steel or concrete can with a open bottom would work. Most of the stress is on the the Anchor which would have to hold it down. We have built very large Anchors to hold floating oil platforms in place so the anchor is not a show stopper.

  31. Of course this uses up energy
    Energy is lost when air is compressed, through leakages and when converted back again.
    But all energy is wasted if it is generated when there is no demand for it.
    So if you have a system with lots of investment in unreliable energy sources (like wind and solar) then this may have a place.
    Better to not have such a system, of course, but many countries have been ill-advised.

    • Leakages are a minor part of the losses. When you compress air you generate a lot of heat and that energy is lost to the environment. When you expand it you have to put heat back as the temperature drops. You had also better dry the air or you will get the outlet lines plugged with ice. Compressed air is a TERRIBLE storage medium.

  32. A much more promising concept (which is not to say that it would be competitive with fossil fuels) is underwater concrete spheres that the water is pumped out of when there is power available, and allowed to run back in through when power is needed. Basically it is pumped hydro storage using the depth of the ocean rather than the height of mountains.

  33. These days the creator of an idea doesn’t need to genuinely interest themselves in whether the idea will potentially lead to a commercially viable system which generates or stores energy at a competitive cost per generated watt or stored joule.
    An idea is “successful” for its creator as soon as govt. agencies or gullible investors can be convinced to pour cash into the pockets of the creator.
    And the govt. is now the first port of call. Since the ideal investor is one who is infinitely gullible, with access to infinite funds. The govt. comes damn close to meeting those requirements.
    Intriguingly though, once a person has obtained a multi-million DOE grant or similar, then investors of private money seem to be reassured that the project is legit. They seem to treat this a proof of “due diligence”. It is anything but.
    They do not seem to have learned that the DOE is even more gullible and even more fast-and-loose with “other people’s money”, than even they are with their own.
    The Solyndras are going to keep coming until someone patches the faucet.

    • Good point inde. I have been amazed that the communist societies have been able to feed themselves at all with the kinds of things you wrote about going on in a much larger scale. Most beaurcrats haven’t a clue how anything except the human mind works.

  34. Seems like it can only store as much energy as the volume of the balloon multiplied by the geopotential energy due to the height of the water column above it. In other words the same as classical pumped storage which requires a large enough reservoir at the top of a local mountain of sufficient height.
    Except now you have to economicallybuild a whole bunch of interconnected underwater balloons a long way underwater with the cumulative volume equal to a valley-sized reservoir. Good luck with that.

  35. Assume an offshore 1 GW day facility at 1000 ft. How big would the balloon have to be. Just need some feel for the scale.
    There are tunnels around that are built in sections in a dry dock, towed to where they will rest on the ocean floor, flooded, and sank. The sections are bolted together and then pumped out. The builders of these tunnels must have solved the bouancy problem.

  36. There was a plan back in the late 60s to fill vast reservoirs near the Great Lakes at night by pumping the water while electrical use was low and then run the water through pen-stocks when there was peak demand during the day. So this is not a new idea just more recycling of an old one. Toronto Hydro is running a test of the system…it will be interesting to see if it is cost effective, which was the major hit against the water idea.

  37. Rube Goldberg would be proud, just a few additional complications to round out the idiocy of the whole project and it would be perfect.

  38. What appears to be overlooked is the buoyancy of these balloons. They would need to be massive. How do you anchor them to the seabed or lake bed. To store worthwhile energy they would need to be in deep water . Seawater increases in pressure at approx. 0.5 lbs per foot of depth. At a depth of 500 feet (a common offshore oilfield working depth) this would give a 250 psi pressure at the surface. To get worthwhile energy the pipeline infrastructure would need to be enormous. I don’t think this is a winner

  39. Have a pipe 20 meter in diameter and 1000 meters long made with 1/2″ walls.
    Have one end capped.
    Made from marine steel it weighs about 6300 tonnes.
    It basically it difference kind of ship and you make it as you make ships in shipyards.
    Once made in shipyard, you put temporary plug in open end- inflate a balloon to seal
    the end. So you launch it into the ocean, and tow it to so location [in deep water].
    Once towed to some spot, remove the temporary plug- deflate balloon end.
    Then the ocean water will enter the pipe,
    What will happen is water will enter the open end and air will trapped by closed end, and it will
    flip vertical.
    So you have 900 meter of pipe submerged and 100 meters of pipe above the waterline.
    Now rather than store energy, I would use this pipelauncher to launch rockets into space.
    Or one charge about $100,000 or more to accelerate rockets by about +100 mph.
    One accelerate a rocket by making the pipe go up vertically.
    By added or removing air from inside the pipe and pipe will go up and down.
    And the air pressure inside the pipe remain constant.
    And it floats by having enough air pressure to push the water inside the pipe
    below the waterline. And one need 1 atm pressure to push the water inside
    the pipe, 10 meters below the waterline.
    Or having water depressed below the waterline this causes displacement.
    So ships can displace +100,000 tons, but this type ship displaces less- tens
    of thousands of tonnes.
    The 20 meter diameter is has area of 10 meters squared times pi:
    314.16 tons per 1 meter of depth, or 3141.6 tonnes per 10 meters which requires
    14.7 psig.
    Since it weighs 6300 tonnes, this means it has have enough air pressure to lift
    this weight: 6300 / 314.16 is 20.05 meters . So needs about 30 psig to float,.
    If instead one adds 60 psi. it will have 6300 tonnes of upward force.
    The gross mass of Saturn V [largest rocket to ever fly]: 2,290 tonnes.
    So this require 60 psi to go up at 1 gee acceleration and to lift addition mass of
    rocket at 1 gee acceleration requires more than 60 psi.
    To add the needed air [one needs a lot]. One pour liquid air into the water inside
    the pipe- the warm sea water will vaporize the liquid into gas. And to use less
    liquid air, you also heat the air with burner- so a max average air temperature over a period
    of couple seconds could be 100 C.
    Without considering mass of rocket, if one adds enough air so there is constant pressure
    of 60 psi, the pipelauncher will accelerate upwards at 1 gee. And waterline level inside the pipe
    with constant pressure of 60 psi will cause water to be 40 meters below waterline.
    So keeping waterline constantly at 40 meters below waterline cause pipe to go up vertical, at speed like jumping off an office building.
    But anyhow, as far as underwater balloon. if had 30 psi with the pipelauncher and the top was floating say 5 meter above the water, and removed air so it top was barely floating above the water. And then put say 100 tons of concrete on top of it. Then it sinks.
    And as it sinks, the air inside become more compressed and it sinks faster [and faster].
    And were that to continue falling say 4000 meters below the surface, the air would compress until
    it was a liquid. and might impact the ocean floor at around 100 mph.
    Were you to add some helium inside the pipe, it could un stick itself from ocean bottom, and rise
    upward, gaining speed until it flew out of the water.

  40. Rube Goldberg is right How many levels of primitive and unrealistic logic is involved in all this? First the
    technologically primitive wind and solar (unreliable )power generators, then we try to avoid their disadvantages by creating more primitive technology “solutions”, which, by the way,, are not solutions at all. The wind might not blow for weeks or even months, and the skies can be cloudy for weeks as well. Storage systems STORE energy , they do not generate energy and they can’t store very much of it, and if something happens and all that stored enegy is used up, how are you going to both supply the grid and restore the storage when the winds blow again or the skies clear? This is elementary school logic. Compressed air storage has been atempted using abandoned mines, andthe problem was that when compressed air is released , it becomes cold and loses energy. Natural gas warmers were used to heat up the air that was released to drive turbines.What a joke – using fossil fuels to make a non-fossil fuel system work efficiently (more or less). So far , compressed air as a storage medium (for cars, energy, etc) has been a big bust.

  41. When you consider the efficiency of compressors not to mention the turbines sounds really energy wasteful.

    • Now, that’s the only sensible suggestion on this thread.
      All of a sudden, this looks to be doable.
      You really should present that on Indiegogo-a-gogo.
      With a flashy video.
      It’s going to be the next “solar pavements” smash money-spinner.
      i’m jealous of you already. I hope that you have the patent rights sorted.

  42. There is at least one advantage of using rubber pressure storages at bottom of the sea compared to steel storages: rubber storages gives guite constant pressure till end of volume.
    But you don’t utilize that sea bottom’s pressure without costs. You must do valuable work to pressurize the storages. When you compress air you are heating it. In some places (Finland, Alaska) you may utilize the excess heat in some others you can’t.
    The eternal rubber is not yet invented?
    If you made your storage at a hot place, such as a black smoker, there is a theoretical possibility it gives energy to your system.

    • I don’t want to start an argument.
      But there is no reason to use rubber.
      This system depends only on displacing the water, at high pressure relative to the compressor/turbine system. The use of rubber is a completely needless. Rubber used as a store of energy is actually quite rubbish anyway. It is a good way of throwing energy away. Hence its use as a shock absorber/damper in tyres and engine/machine mounts.
      Of course, it’s a handy store of energy for model aeroplanes for children.
      But that’s because children have boundless energy and they are oblivious to the fact that the elastic aeroplane drive system is quite lossy.
      You can see this from rubber’s hysteresis curve on a force/displacement stress/strain graph. The area in the middle represents the W.D. energy that is lost each cycle as heat.

      • indefatigablefrog: “But there is no reason to use rubber.”
        OK. I think you are right. A steel storage can be bell shaped and open at bottom. Then it can deliver near constant pressure to the turbine (whatever).
        My mistake thing only about closed steel storages.

        • It’s a rare thing when a thread on the internet builds on understanding, rather than ending up stuck in antagonism
          So what a rare treat!!
          However, I looked into this topic briefly and found a company using (or intending to use) butyl rubber bags.
          I expect that they are simply collapsing and filling the bags – rather than using the rubber’s elasticity.
          But, it does look to me as though this idea may have potential.
          Unlike most of the idiotic and implausible crap ideas that are flying around on a weekly basis.
          “Designed and developed for Garvey’s project by Canadian firm Thin Red Line Aerospace, the bags use a butyl rubber bladder and a polyester-reinforced fabric for the outer surface.”
          Read more: http://www.theengineer.co.uk/in-depth/the-big-story/compressed-air-energy-storage-has-bags-of-potential/1008374.article#ixzz3uEMkz22y

  43. Claiming “60%-80% efficiency” is a huge red flag for me. A simple, inexpensive small-scale test or two would give a real efficiency number … either they haven’t done the tests or they aren’t reporting the numbers.
    A red flag either way.

  44. Let’s visit Hydrostor for sake of reality check. Under Technology > How does it work? > Learn more you find

    How it works
    Hydrostor’s energy storage solution
    1. Convert Electricity to Air
    Electricity runs an air compressor which converts the electrical energy into compressed air.
    2. Thermal Management
    Heat from compression is captured during this step and stored to be used during generation, thus increasing the system efficiency. Additional heat can be added to further increase roundtrip efficiency.
    3. Pressurize Air
    The compressed air stream is pressurized to the same pressure found at depth where the accumulators are located.
    4. Store Air in Accumulators
    The air displaces the water in the accumulators and is held until electricity is needed by the consumer.
    5. Reverse the Air Flow
    To satisfy the need for electricity the system reverses the air flow allowing the weight of the water to force the air back to surface under pressure.
    6. Convert Air to Electricity
    The stored heat is added back into the air stream. The heated air travels to an expander which drives a generator efficiently converting the energy in the air back into electricity for the consumer.

    So the process is a bit more complicated than the one described at CNBC.
    Steps 2 & 6 are significant. If compressed air is stored at a depth of 30 m (90 feet), and input is at 4°C (39°F), then its temperature is increased to 139°C (282°F) while compressed to storage pressure due to adiabatic heating. On release temperature of compressed air stored at 4°C (39°F) decreases to -87°C (-125°F). This is why heat needs to be stored separately and added back before use. With 100 m storage depth (300 feet) these figures are 277°C (530°F) and -133°C (-207°F) respectively.
    Therefore thermal management is the key point. Design of heat exchangers and that of the well insulated heat storage facility are not described at the Hydrostor site, but if losses are to be kept low, they should be quite sophisticated and expensive.
    To make up for (inevitable) losses, they say under 2, that “Additional heat can be added to further increase roundtrip efficiency.” That’s true, but energy for heating has to come from somewhere. If not from burning fossil fuels, which would immediately destroy carbon neutrality, then from another source, presumably nuclear. However, in that case it would be much cheaper to skip storage and produce electricity directly from that source.
    Furthermore, to keep underwater balloons at the bottom, you need to anchor them to something. If it is concrete blocks, you need roughly the same volume of concrete as the volume of compressed air to be stored in balloons. That’s much, and cement manufacturing has a huge carbon footprint. Also, the balloons have to be made of something, presumably from plastic, which also adds to the footprint.
    Therefore the process is complicated, expensive and fails to be carbon neutral. Otherwise it’s perfect.

    • Come to think of it, as air becomes so cold on decompression, heat exchangers close to the surface can be used to deliver additional heat before stored heat is added back. That way energy efficiency can be improved and no additional heat source is needed. That is, it would act as a kind of heat pump.
      The cost is increased complexity of the system and the environmental damage done by industrial amounts of cold water output.
      I do not know, for example, how to prevent heat exchangers getting clogged by ice. It can certainly be done, but at what price?
      Neither do i know what the effect of a copious amount of cold water would be on marine or lake life, especially on plankton.
      Also, releasing large volumes of air inevitably generates high levels of noise, not only in the frequency range of the human auditory system, but well below it in the form of infrasound. Against which there is no effective insulation.
      These questions are not discussed at Hydrostore.

    • As I mentioned in a different post, one advantage of the system is that the air pressure in the reservoirs is almost constant from an empty reservoir to full reservoir. This means that the compressor and turbine can be designed for a specific pressure ratio, which should improve efficiency. The other aspect is that the temperatures on the outlet of the compressor will be almost constant, and should allow for use of a phase change material to store energy at a constant temperature. Using a series of phase change materials with decreasing phase change temperatures to cool the compressed air to near ambient should allow for a respectable fraction of the heat energy to be recuperated during energy recovery.
      Looks like they’ve got the thermodynamics at least somewhat right, though I’m not convinced of the practicality.
      Mechanical (electrical) energy storage is not easy.

  45. The loss points: Converting wind/solar to grid quality electricity; Line loss to compressing station; compressor inefficiency; loss from piping to balloons; air storage leakage; return plumbing; low pressure turbine inefficiency; generator inefficiency.
    Hmmm….Not including primary generation, that is 7 points of loss at the least.
    Not to mention lifetime reliability of balloons and plumbing.
    And remember: the air has to be pumped to *higher pressure* than the depth of the water, which ~16 psi per 33 feet of depth. And the balloons have to be tethered and anchored to resist the powerful buoyancy of each balloon.
    Once again the carbon obsessed come up with an idea that is impractical, inefficient, unworkable, crazy expensive, non-robust. and claim it cures the non-problem they are so neurotically focused on.

  46. Hydrostor’s innovation is to reduce the cost
    Well, that’s the idea.
    Not bad for a “Nature trick” — if it works.

  47. Before I read the article, I was thinking of pulling floats down, then releasing them to capture energy. But that is dependent upon density differences, so is not as scalable as pressure differences are.

  48. I propose we build giant spring driven devices, a bit like old fashioned alarm clocks. During the day when the millions of acres of solar panels are generating excess electricity this is used to drive motors to wind up the springs…at night the process is reversed the energy stored in the springs is fed back to the motors which turn into generators and hey presto!

    • There is nothing functionally bad about CAES. This underwater balloon idea is not the greatest. (understatement)
      However, CAES allows you to capture the adiabatic heat of compression, and also use any thermal energy to increase the pressure of the stored gas — thereby allowing for more work to be done.
      This is basically what a combined cycle NG/Coal plant does with some of the waste heat.
      Residential and distributed CAES would allow the use of solar thermal to create a combined cycle solar PV/thermal system that would allow for round the clock energy production.
      Is it super efficient? Nope — but sunlight and solar infrared don’t cost a thing unlike coal and CH4.

  49. What happens when the water is displaced by bags of air and air tries to do what it does best in water?

  50. Why do the “balloons” have to be flexible, as in Rubber?
    Can the reservoirs not be made of Concrete, in a clam shell configuration.
    One inside the other “floating” on the compressed air.
    If used in a high tidal area the tide comes “IN” then the air would be compressed and drive the turbine.
    Tide goes “out” the air gets sucked back in. Some control required of the air pressures.
    I know to simple But I do Like a KISS.

  51. Perhaps one should look into the history of Naval mines and the difficult and expensive process of maintaining a mine field against the ravages of the ocean environment before they get to wrapped around the axle concerning any of the other mechanics of such a system. It is a labor intensive operation.

  52. I’m not very concerned about safety with this storage system. Since the contents of the balloon is at the same pressure as surrounding water, even rupture of the balloon will only release a giant bubble, there will be no explosion or shock wave associated with it. So there will be little reason for other balloons to rip as well.
    What I am concerned about is the longevity of the system. Moving things have very serious issues under sea water as living organisms have tendency to stick to anything, and make it unmoving and fragile. Maintenance costs needed to keep these balloons working may be a limiting factor and serious hit to the efficiency figure.

  53. Sure, this would be a relatively inefficient way of storing energy, but so are all the other ways currently used for storing “surplus” generated electricity.
    The real problem, as I see it, is the massive size required to store practical amounts of electrical energy. It quickly becomes a very large and complex project. And then you have the teensy problem of regular maintenance and repair in a very hostile environment.

  54. The limitations of this system have been well explored in this thread. However, it seems to me that the most basic metric for understanding the proposal is yet missing. Maybe some of you with more engineering chops that I can easily do the calcs.
    Suppose we envision a test system: a 100 meter balloon, 100 M below the surface. What is the enemy capacity of a cubic meter of air in KWH under those conditions? With this info, e
    ven us amateurs can play with scaling a system, changing depth, balloon size, etc.
    Second question, after asking the first: Since the top of our balloon is at 50M and the bottom at 150M, the pressure is not going to be equal everywhere. Wouldn’t the top be bigger than the bottom?
    OK, one more. In the heat exchanger system they envision, there are two operational phases: Cheap energy time and expensive time.
    Cheap energy is used to compress the gas and waste heat is stored. However, during expensive time when the system is outputting, you need to add more “expensive” energy to make up for the heat exchanger losses. Unless you use more “cheap” energy to heat an additional storage system.
    Also, unless I am missing something, the efficiency of a heat exchanger drops as the delta T decreases. Thus the storage medium would have to be massive and store the heat at a much lower temperature. Problems at both ends of the cycle?

  55. Energy storage madness. All this to avoid the obvious solutions of atomic energy or fossil fuel.
    I have a battery operated sump pump, to avoid another flooded basement. By my calculations, a big 12 volt marine deep cycle battery rated at 122 amp hours stores, max, about 1.4 kilowatt hours.
    1 amp x 122 hours x 12 volts = 1465 watt-hours.
    Is this true?
    My system requires a battery charger and an inverter, with total capital costs in the hundreds of dollars. Neither the inverter, the charger,nor the battery will last forever, either. The sump pump might last for many years. My old sump pump lasted 40 years.
    Around here, a kilowatt-hour goes for about 13 cents. So, it costs me hundreds of dollars to store 13 cents worth of energy. My pump doesn’t run much normally and only draws 420 watts when it does.
    It would likely be almost as cheap to just buy a small generator, and, it would cover my pumping needs indefinitely, unlike the battery. But it would be a hassle to set up the generator every time the power went out in a rainstorm.
    I like the big spring idea, though. Imagine when that baby snaps. It could take your house down and kill anything standing nearby. I can just imagine the case report in the American Journal of Forensic Medicine, “Death due to sudden energy release in large alarm clock-like apparatus. Case report and review of the literature.” That would ring anybody’s bell.
    Like I say, all this madness is due to cheap money.

    • Unfortunately, that money isn’t cheap in the long run. Luckily, like CO2, much of the wasted money goes back into the economy somewhere, even if it all starts with bars and brothels in the DC area.

      • “the wasted money goes back into the economy somewhere”
        It’s called a “stimulus”.
        “even if it all starts with bars and brothels in the DC area”
        Hostesses are “stimulating”.

  56. This idea is not going to fly!
    Air motors ready to buy:
    Their motor: http://www.ingersollrandproducts.com/am-en/products/air-motors/specialty-governed-motors/series-551/modelspec/4613 gives 4kW/5hp at 4.53 m^3 per minute.
    Even with the efficiencies bought about by scale, it doe snot look good.
    These tethered bags on the sea bed, would each require a pipe to feed/extract the air, the pipe would need to enter the bag from the bottom, be self supporting and reach the top of the bag to ensure only air enters the pipe.
    To prevent each bag from over filling with air and wasting this expensively generated air, and to prevent water from entering the feed pipe, a valve would be required shore side, and instrumentation measuring water height in each bag to operate each valve.
    The figures of 4kW for 4.53m^3 per minute will allow people to scale this up.
    I suspect such a huge array of air bags and supporting valves/pipe work/instrumentation would be needed to give relatively little power.
    http://www.marineengineering.org.uk/page49.html discusses the issues relating to air compressors in marine environments.

  57. It is a much better idea to bury arrays of pressure vessels in the ground (insulated and inside concrete) for residential energy storage.
    You could use the adiabatic heat of compression to heat a working fluid
    You could also use thermal solar to increase the pressure of the exhausted air to allow more work to be done.
    Scuba tank level pressures (20 Mpa – 3000 PSI) are just fine — scuba tanks last for decades
    Charge discharge cycle number is effectively limited to valve/fitting survival

  58. Obviously your working pressures for driving pistons would be much lower than the storage PSI of 3000, so you would just exhaust the air into a plenum and then use that air at lower pressure to drive a piston assembly.

  59. Like I posted above.
    There is nothing functionally bad about CAES. This underwater balloon idea is not the greatest. (understatement)
    However, CAES allows you to capture the adiabatic heat of compression, and also use any thermal energy to increase the pressure of the stored gas — thereby allowing for more work to be done.
    This is basically what a combined cycle NG/Coal plant does with some of the waste heat.
    Residential and distributed CAES would allow the use of solar thermal to create a combined cycle solar PV/thermal system that would allow for round the clock energy production.
    Is it super efficient? Nope — but sunlight and solar infrared don’t cost a thing unlike coal and CH4.
    Furthermore it is simply Air — nothing special — Scuba tanks are routinely filled with 3000 PSI air, and people walk around with them on their back

  60. My eyes glazed over when I read ” Office of Electricity Delivery & Energy Reliability.” That’s an actual government job? Why not just pump money. But I felt a bit better when I found out this was in Canada. To quote Nelson on the Simpsons Ha Ha!

  61. A better idea would be to have ‘x’ windmills in a wind farm pump air directly (mechanically) to store energy and deliver energy when the mills are quiet. Indeed, I’m impressed (if engineers were involved) why this wasn’t built into each project. They knew at the outset what the expected wind frequency and strength would be and consequently the quiet time percentage. Just send me a tenth of a cent per kWh for the idea.

  62. To me the idea seems to be a complicated way of using conventional forms of energy to pump water from a lower gravitational potential to a higher gravitational potential, and then when needed recovering some of that energy by placing a dynamo in a pipe and letting the water drive the dynamo as it flows through the pipe on its return to a lower gravitational potential. Unless the plastic of the balloons can store massive amounts of energy by being stretched, isn’t the energy stored by such a system stored in the form of an increased water level? Nature does this all time time–think hydroelectric power from dams. Maybe the proposed method is more efficient than simply raising the water level using a pump–I don’t know; but it sounds like a lot of folderol to me. If used in local reservoirs the proposed “battery” does have the advantage, namely in drought stricken areas it will give the appearance of increased water supplies.

    • Few places are adequate for pumped water energy storage, you need two pretty large reservoirs.
      Air-lifted water energy storage has the advantage of not needing an additional big water reservoir.

      • steverichards1984 “To match pumped storage in terms of size and output, imagine the upper water catchment area, that’s what is needed in underwater in bags.”
        That’s only the volume, you also need depth to give pressure, ½psi per foot of depth, So if you you use a low pressure turbine say 100psi & 50psi to overcome pressure drops we are looking at water depths of 150-200ft. so can’t be inland. Most offshore wind turbines are in water <100ft.
        QED a crap idea !!

      • The necessary size of the reservoir would depend on the elevation of the 2nd reservoir, no?, like voltage in a D.C. circuit dictates how much power you will get with each amp of current.

        • “The necessary size of the reservoir would depend on the elevation of the 2nd reservoir, no?”
          Yes. You use natural geography and you can’t choose heights of mountains.
          Or maybe you can if you are “green” and can justify building up an artificial mountain with concrete.

  63. The buoyancy factor of large volumes of air under high pressure makes this crazy expensive.
    The balloons have to be sealed at the bottom because the air has to be held at higher pressure than the water pressure if the air is going to do any work.
    This is such an obviously unworkable concept as to raise questions about why anyone is willing to spend serous money to study it.

  64. Why is compressing air underwater any better than compressing it into a tank on land if you intend to use it to run a turbine what am I missing?

    • “Why is compressing air underwater any better than compressing it into a tank”
      The pressure in the balloon depends almost only on the depth of the ballon (and a little bit on the shape and tensile force of the rubber).
      The pressure in a tank is proportional to the amount of air and also to its temperature, which means the pressure would drop as the air cools down during standby.

      • (Note: “Buster Brown” is the latest fake screen name for ‘David Socrates’, ‘Brian G Valentine’, ‘Joel D. Jackson’, ‘beckleybud’, ‘Edward Richardson’, ‘H Grouse’, and about twenty others. The same person is also an identity thief who has stolen legitimate commenters’ names. Therefore, all the time and effort he spent on writing 300 comments under the fake “BusterBrown” name, many of them quite long, are wasted because I am deleting them wholesale. ~mod.)

  65. Hunter/Philip: Why underwater? Sealed/unsealed?
    Underwater the bags have the same pressure inside and out so can be weakly constructed, shore side pressure vessels are strong and costly.
    Unsealed – open at the bottom – can be weak and contain air at 1 Bar if the bag was 10m high.
    So tethered at 100m underwater the pressure of the air within a 10m bag would vary from approximately 9 Bar to 10 Bar, but you can only use the 1 Bar range.
    You would need hundreds of thousands of these devices to do anything near useful.
    A logistical nightmare.
    To match pumped storage in terms of size and output, imagine the upper water catchment area, that’s what is needed in underwater in bags.
    Time to put this idea to bed.

    • To match pumped storage in terms of size and output, imagine the upper water catchment area, that’s what is needed in underwater in bags.”
      That’s only the volume, you also need depth to give pressure, ½psi per foot of depth, So if you you use a low pressure turbine say 100psi & 50psi to overcome pressure drops we are looking at water depths of 150-200ft. so can’t be inland. Most offshore wind turbines are in water <100ft.
      QED a crap idea !!

      • The deeper you go, the more energy you store.
        … and the more problems you get for maintenance, the more uneconomical this stuff becomes.

    • “Unsealed – open at the bottom – can be weak and contain air at 1 Bar if the bag was 10m high.”
      I don’t understand.
      “So tethered at 100m underwater the pressure of the air within a 10m bag would vary from approximately 9 Bar to 10 Bar, but you can only use the 1 Bar range.”

  66. When you compress air, it gets hot. As you store the air, that heat escapes to the environment. This will happen even faster underwater.
    The claims for 60 to 80% efficiency sound really far fetched to me.

  67. I agree w/others — compressed-air storage is a non-starter due to glaring inefficiencies (where are the engineers in this scheme?). Particularly with the equipment on a sea-bottom — maintenance would be a nightmare. Even worse than constructing offshore pinwheels.

  68. MarkW December 14, 2015 at 9:52 am

    John, that’s all AC is. Compress a gas, let it cool while maintaining constant pressure, then release the pressure.

    Sorry, Mark, but as an erstwhile refrigeration technician I can assure you that your description is not correct. Air conditioning also includes a working fluid that undergoes a phase change from liquid to gas and back again …

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