9 ms·

Gravitricity

• scottcanoni 12y ago
  Where can I buy one? I'll start digging in my backyard ;)
• gatehouse 12y ago
  Is 90% efficiency really feasible for electrical -> mechanical -> electrical?
  • KaiserPro 12y ago
    95% efficient each way, it does sound a bit much.
    • tormeh 12y ago
      Not really. Electrical engines and generators are incredibly efficient. It's not the transition there that is the problem. In fact, if it was only for that loss the efficiency would be more like 97%. The problem is the friction in the mechanical parts; the wires, gears and so on.
      • andrewflnr 12y ago
        Dang, that's impressive. I had no idea electrical<->mechanical conversion was so efficient.
        • bodyfour 12y ago
          Think about how little cooling is needed on a big electric motor. Even motors made 100 years ago are very efficient. By contrast anything that qualifies as a "heat engine" (including internal combustion) is limited by Carnot's law to be low-efficiency. If it weren't for the extraordinary energy density of combustible fuels they wouldn't be competitive.
          • tormeh 12y ago
            Yes, the theoretical efficiency limit on electric engines and generators is 100%.
      • tanzam75 12y ago
        Amtrak still uses motor-generators on some parts of the Northeast Corridor to convert 60 Hz AC grid power to 25 Hz AC traction power. It's exactly what it sounds like: a motor that is mechanically coupled to a generator. The motor runs on 60 Hz AC and turns the generator at the correct speed to produce 25 Hz AC.
        • tormeh 12y ago
          Haha, wow, a mechanical engineer was on duty that day.
  • troymc 12y ago
    Today, the majority of grid energy storage is done using pumped-storage hydroelectricity (PSH). "PSH reported energy efficiency varies in practice between 70% and 80%, with some claiming up to 87%." [1] [1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
• Zikes 12y ago
  I look forward to Elon Musk's proposal for unconventional energy storage, because he wouldn't dare call it anything other than Eccentricity.
  • slashnull 12y ago
    Eclectic energy
  • revelation 12y ago
    This is just a pun, but of course his proposal for energy storage already exists, and (surprise surprise) its lithium ion batteries. Significant parts of the projected gigafactory capacity are reserved producing cells for SolarCity home energy storage appliances and other storage systems. In fact, right now the Tesla factory has 4GWh of lithium ion batteries installed for smoothing energy demands and they are actively building 400kWh storage units: http://www.greentechmedia.com/content/images/articles/straubel1.jpg http://www.greentechmedia.com/content/images/articles/straub... I'm sure that the end game idea in his mind is using the 85kWh+ batteries of Teslas everywhere for distributed energy storage.
    • pm90 12y ago
      Yep, and as the maker of the most efficient of those batteries, he can make a nice clean profit. Good on him though, he (and the whole Telsa team really) did put in a lot of effort to get there.
• grondilu 12y ago
  What determines the depth of the whole? I mean, since E = mgh, you can get the same energy storage capacity with a less deep hole if you use a heavier weight. And you can get a heavier weight either by using more expensive material (why use a cheap one? it's not like it's going to wear or anything), or a larger hole. I'm not sure what determines the cost of digging a whole, but I suspect depth matters more than area. Also, does the shaft has to be vertical? You could dig it with a sharp slope, and put your weight on rails. That would make the shaft longer for the same depth, but it would probably be easier to build and maintain.
  • bsilvereagle 12y ago
    I suspect they plan on recovering the power with a generator. So the input shaft to the generator has to rotate. With a deeper hole, you get more 'clicks' on the generator so you can produce power for a longer period of time before having to pull the weight back up.
    • eknkc 12y ago
      Does it really matter? You should be able to get millions of rotations from a single centimetre hole, given that the mass is large enough and you have a good gear ratio..
    • grondilu 12y ago
      I suppose they plan on using a transmission mechanism that will turn one meter down to as many turns as you want anyway, so I guess the depth of the hole is at least partially determined by how good a transmission mechanism you can afford. But since they explicitly say the hole will be the most expensive part, I'm not so sure.
      • bsilvereagle 12y ago
        You're losing torque with every gear reduction, and I believe that current out of a generator is a function of torque. So there's some happy medium between hole depth & transmission ratio for the amount of power they want to generate.
• KaiserPro 12y ago
  So how many joules can it contain? I mean, technically I can get a super cap the size of jam jar to kick out 1 kw, just not for very long. A watt is a unit of how much energy is expended in a second, not how much energy is stored. There is a reason why hydrostations in wales use lakes to store energy, because you need a lot of mass at great height to be of any use.
  • bsilvereagle 12y ago
    Work = Force*distance, so theoretically the number of Joules would be mgh^2.
    • schoen 12y ago
      Your units got messed up there -- it's just mgh. There's no reason to square the distance. $ units Currency exchange rates from 2013-07-11 2562 units, 85 prefixes, 66 nonlinear units You have: 1000 kg gravity 1 km You want: J * 9806650 / 1.0197162e-07
      • bsilvereagle 12y ago
        That's what I get for doing intermediate thermo & fluids all day and then trying to make a comment on basic dynamics. Thanks for the catch.
        • schoen 12y ago
          Sure. This is also neglecting the compressed air part of this technology (which thermodynamics might actually be quite appropriate for modelling!).
• sz4kerto 12y ago
  This came up a long time ago. It doesn't work well, the amount energy it stores is simply too low. I've seen a calculation somewhere, but it's too late here so can't reproduce - does anyone remember? Edit: here it is. https://news.ycombinator.com/item?id=6739349 https://news.ycombinator.com/item?id=6739349
• elektropionir 12y ago
  The energy density for gravity is just immensely small, that's why you need dams holding back rivers to use them to generate electricity. For a 1km hole (that's in the middle of their 500m - 1500m range) you have an energy density of 10kJ/kg of the weight that stores the energy. The energy stored in a Tesla roadster battery pack is around 50kWh which is 180MJ. This means that you need a 18,000kg weight in a 1km deep (immovable) hole to have the equivalent of a Roadster battery pack. I'd go with the battery pack.
  • troymc 12y ago
    That's true. Unfortunately, current Tesla battery packs use lithium, which isn't super-abundant in Earth's crust. That's why companies like Ambri are looking at using other materials in the batteries they're developing for grid energy storage.
    • p1mrx 12y ago
      Other materials, like lead and antimony? http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%... Lithium: 33 Lead: 37 Antimony: 62
      • timdiggerm 12y ago
        Well they are more common
      • mtdewcmu 12y ago
        That table uses a mass-based unit, so wouldn't that tend to create the misleading impression that lighter elements are more scarce? Energy storage capacity depends on the number of atoms, not mass (as you can intuit by comparing lithium batteries to lead or nickel-cadmium batteries -- heavier doesn't mean more powerful).
        • p1mrx 12y ago
          Well, if Pb and Sb are more scarce than Li by mass, then they're even more scarce when you're counting atoms. If Ambri's technology does pan out, it will be due to a cheaper manufacturing process, not because they're avoiding lithium.
• Animats 12y ago
  OK, a typical mine hoist is about 10 metric tons. 10 metric tons descending at 1m/sec is very close to 100KW. So a 1000 meter deep hole can deliver 100KW for 1000 seconds, or 27 KWH. That's about $3 worth of electricity, and about 1/3 of the battery capacity of a Tesla Model S with the large batter option. Numbers not looking reasonable for this concept.
  • slashnull 12y ago
    I don't know how heavy are the planned weights, but it sure as hell will be heavier than 10 tons.
    • Retr0spectrum 12y ago
      Even if it was 1000 tons, it would still only be about $300 worth of power.
      • toomuchtodo 12y ago
        Depends on the spot price of power. Power on the open market (where utilities have to buy it to provide to customers) changes every minute. Its usually cheap at night until the early morning, starts to increase, and then spikes around 3-4pm (+_30-60 minutes, depending on the country). If you delivered power when it was most expensive (ie high demand) and consumed it in the middle of the night, the arbitrage may work out.
• deleted 12y ago
  [deleted]
• awjr 12y ago
  Is a 500m-1500m shaft is pretty much going to fill with water? I could see a well designed weight being able to work in water (although water turbulence would erode the shaft walls. I don't see how air compression would solve this. The principle however of storing energy by raising a weight could also be used anywhere with a steep enough hill/cliff/montain and the weight could in theory be on a rail not just suspended. Efficiency would potentially not be on par, however linked into solar/wind systems this is less about efficiency and more about creating a 1MW long term battery with a lifetime of 50+ years. Guessing cost of digging and maintaining a hole compared to installing a guide rail is significantly higher.
  • pbhjpbhj 12y ago
    >Is a 500m-1500m shaft is pretty much going to fill with water? // So you're saying you get a free well as part of the deal?
• AndrewDucker 12y ago
  Okay, so energy density is low - but what are the costs like? If you can build one of these cheaply, and the running costs are trivial, then it's worth doing. How many of them would you need to smooth out the energy of a wind farm, for instance?
• dmritard96 12y ago
  Been attempted before. Its interesting that below ground is preferable to above ground. Water tables in many places will be a problem.
• tasty_freeze 12y ago
  Although I think the idea isn't workable (energy density is too low, cost of boring the hole is tremendous), most of the other commenters here seem to think they'd just have one weight, whether it is 1000 KG or 50,000 KG. Any sane plan would be to have more than one weight. When the first weight hits the bottom, it would release from the cable and another weight up top would grab the cable and start dropping. To store energy, the top weight would get winched up, and when it hit the top it would lock into place somehow and the next weight at the bottom of the shaft would engage the lifting cable, etc. The cable would have to follow a circular track, rather than having 1KM of cable for each weight.
  • Sorgam 12y ago
    What advantage does this provide over combining all your weights together into one big one? If you want to limit the tension on the cable, just use more cables. You shouldn't be so confident that you know the only "sane" way to design such a thing. It's not a field anyone has experience in. These are only guesses.
    • Pxtl 12y ago
      Well, it does mean your cables and dynamo can be smaller. But then you've got a new problem of coupling the cables to the load at the bottom and somehow storing loads at the top that the cables must reach past/through.
      • tasty_freeze 12y ago
        You have a shaft 1km or 1.5km deep. You can afford to stack a lot of weights vertically. Imagine each has a hole running through the middle, where the cable runs, and a mechanism whereby the weight can engage/disengage from the cable. The cable forms a circular loop that passes through all the weights from the top of the shaft to the bottom, then circles around past a large pulley and back to the top, completing the loop. At the top of the shaft there would be hefty prongs that retract when the weight needs to start dropping, and when the weight returns during a recharge cycle, the prongs reinsert themselves in to the shaft when the weight is lifted back into position. Most likely each weight would have a "C" cross section with a nearly closed mouth -- just a slot from the edge of the weight to the larger central opening so that the weight can be removed/replaced from the cable if needed.
• pbhjpbhj 12y ago
  So basically clock-type counterweights. PSH seems like it would be far more efficient - there's surely a lot of mechanical losses in the sort of system in the OP? If the hole could be used for some sort of heatpump too then maybe that would weigh off [no pun intended!] some of the problems.
• madaxe_again 12y ago
  This is neat, but not novel. I used to live in a house (UK, middle of nowhere) that had a deep borehole that was used for this purpose 130 years ago. The weight and winding were long gone, but the dynamo was still sat there. Oh, and it wasn't raised by water, rather, servants, back in the day.
• throwawayaway 12y ago
  > Most expensive component – the hole in the ground – can have a life of well over 50 years Well well well, I must buy a well.
  • ZoFreX 12y ago
    They missed a perfect opportunity to use "sunk cost".
• phacops 12y ago
  Seems like this would be more cost effective as a component of sky-scrapers. Generator on top, series of weights on rails down the sides.
  • gtremper 12y ago
    I wonder if you could somehow combine it the counterweight system.
  • ars 12y ago
    Not even close. First a 1KM tall skyscraper? Second they are talking quite a lot of weight - the skyscraper would have to be MUCH stronger.
    • jacquesm 12y ago
      http://en.wikipedia.org/wiki/Kingdom_Tower http://en.wikipedia.org/wiki/Kingdom_Tower
  • bluthru 12y ago
    No, the additional load is not worth it. It would be one of the least sustainable things you could do due to all of the heavier columns you'd have to use.
• andrewliebchen 12y ago
  Good thing HN wasn't around durning the development of most of humanity's great inventions. "So your telling me I'm going to have to hold my food over this fire for 15 minutes before I eat it? No thank you, I'd stick with my raw meat."
  • msandford 12y ago
    The majority of humanity's great inventions didn't have basic physics saying "this isn't brilliant" long before a prototype got built. Most of humanity's great inventions were things that were difficult because human beings thought they were difficult, or complicated or intricate or whatever. On their webpage they say " The biggest single cost is the hole, but it is expected that firstly this will have a very long life and secondly, as the technology rolls out, the costs of drilling will reduce significantly. So the economics will improve in time." Drilling will not get cheaper without a serious reform of the law, and that's unlikely to happen. There are two primary kinds of drillers; water and energy. Folks involved in water have VERY protective rules in all states. The reasons are 1. good lobbying and 2. if you screw up you destroy the water supply. Energy drilling is no cheaper. Drilling rigs are huge machines that aren't moved easily and cost at least $50k a day on land and $500k a day for seagoing. That's before you pay another $20k per day in staff and god knows how much for fuel for everything; a rig will produce at least 5MW of power. Could they custom build a rig just for drilling for their idea and would that work? Sure. But they'd probably spend several million and then you've got to have it running 24/7 for it to pay off. The regulatory hurdle is going to be non-trivial as well. They're going to case it which helps. But the casing would probably need to be cemented in place which is a non-trivial cost as well. And convincing lawmakers that this doesn't quack like some other kind of well is going to be no easy feat.
    • mtdewcmu 12y ago
      The hole for this has different requirements than holes for water and petroleum: you'd not want to drill one of these holes into an aquifer, because then it would fill up with water. Oil and gas wells have to be drilled in specific places where the oil and gas are, naturally. In this case, you'd want nothing but a dry, empty hole. A dry, empty hole would be the kind of hole least likely to interact with anything underground. I'm not sure this has much to do at all with water and energy drilling. They're talking about using abandoned mine-shafts. Those are much wider and shallower than the kind of holes used to reach petroleum.
• apsec112 12y ago
  Let's do out the math on this... A subway tunnel might have a diameter of about 6 meters, so cross section = 3 * 3 * pi = 28 square meters. Digging subway tunnel through rock costs about $100M per kilometer. On the one hand, these holes would be vertical, which is harder than horizontal; on the other hand, they wouldn't need ventilation and train tracks and stuff. Let's handwave and say it's $100M for a 1 km deep hole. Now, you can't fill the whole tunnel perfectly or the air can't escape, so our total volume of mass will be about 25 m^2 * 1000 m = 25,000 cubic meters. If the weights are made from lead, that's a total mass of ~280,000 tons or 2.8 * 10^8 kg, at a mean depth of 500 meters, so our total potential energy is 2.8 * 10^8 * 500 * 9.8 = 1.4 TJ, or 1.3 TJ net assuming you get the efficiency they claim. 1 kWh is 3.6 MJ, so you can store ~400,000 kWh at $100M capital cost (ignoring for the moment the cost of weights, generators, etc.), which is $250 per kWh installed capacity. That's pretty good... but you also have to pay for weights and a bunch of other stuff. Bulk lead costs about $2,000 per ton on the current market, so that's $560M for the weights, which puts you back in the $2,000 per kWh range which doesn't beat lithium batteries. So you have to use iron or some cheaper material... but then you don't have as much storage capacity because the density is lower, and even with iron you're paying $400 per metric ton or $80M for all your weights. So this isn't obviously impossible like Solar Roadways, but even in the best case it won't make storage dramatically cheaper.
  • tempestn 12y ago
    One major advantage this would have over chemical batteries (Lithium-Ion or otherwise) is that it should allow for many, many more cycles. You would have to replace cables and motors and such at some point, but the expensive components - the hole and the weight - should last near-indefinitely. It certainly appears more expensive than pumped storage, but as they say, it doesn't require a convenient mountain and lake. That makes for much more flexibility in placement, and the closer you can place the storage to the demand, the less is wasted in transmission, and the less storage you ultimately need. That said, the pumped heat storage design[1] that hit the homepage yesterday would have all those same advantages, and although the efficiency would be slightly lower, it looks much cheaper to build. [1]: http://www.windpowerengineering.com/featured/business-news-projects/didnt-think-electricity-stored-temperature-difference/ http://www.windpowerengineering.com/featured/business-news-p...
• phragg 12y ago
  Drilling into the ground should almost never happen.
  • ars 12y ago
    Why?
• ramses0 12y ago
  I think the coolest thing about this concept (for me) is viewing it as a "whole-system" energy storage procedure. It is effectively 100% renewable, 100% distributable, using 100% commodities (ie: rocks in a hole). As a thought experiment: if on average you can meet 110%+ daily power expenditure captured from renewables (solar, wind, whatever), and store it by lifting up these weights, then you've broken into the "free energy" loop. More specifically, don't look at the power input or storage, look at the power output / usage. If your input + storage capacity is greater than your output rate then energy effectively becomes "free forever". Simulate it on a small scale. Get a pinwheel to run a small motor that winds something up. Attach a small LED to it that you only run occasionally. Basically, just so long as you have a really small output draw compared to your input rate and storage capacity, this "battery" will give you energy when you want it with minimal maintenance costs and minimal consumables.
• Stately 12y ago
  I'm far from being even slightly knowledgeable in this topic, but would it be possible to build this in very deep waters? Like a massive column containing a tunnel? Seems cheaper than digging a 1km hole.
  • delinka 12y ago
    You'd be anchoring a buoyant tube to the ocean floor, trapping all that energy. Instead, float a barge in deep enough water, drop a weight to generate power, raise it to store.
  • lovemenot 12y ago
    At the base of a 1000m shaft you'd have approximately 100 atmospheres of pressure. Not saying it cannot be done, but construction and materials cost would still be very high. Maintenance too. Plus you've lost the advantage of locating it anywhere.
• abdullahkhalids 12y ago
  The key figure of merit for comparing energy storage is not $/KWh, but rather $/KWh*Number of cycles. Li-ion only has about a 1000 cycles. Assuming one cycle per day (solar charge during day+discharge during night) in 50 years there are 18000 cycles. The figure of merit for Li-ion is 250x1000=2.5e5. My estimate (and those of others) is that this costs up to about $2000/KWh. So the figure of merit for this is 1000x18000=0.9e7. Two orders of magnitude better than Li-ion. Edit: I am ignoring the cost of capital, interest rates etc. Somebody should do this analysis.
  • mikeyouse 12y ago
    Sandia National Labs has done the math but it's quite the PDF at 340 pages describing just about every variety of energy storage: http://www.sandia.gov/ess/publications/SAND2013-5131.pdf http://www.sandia.gov/ess/publications/SAND2013-5131.pdf
  • jpau 12y ago
    I did some quick analysis comparing the proposed project against Li-ion, adjusting for storage and lifespan, and the result is very hopeful. I used values for $/KWh and lifespan from abdullahkhalids' comment. The analysis shows that if you can get more than one cycle per day out, the proposal offers fantastic value. Model visible here - http://imgur.com/KmQPb8P http://imgur.com/KmQPb8P Finance uses something called 'equivalent annual cash flows' (EACFs) to compare projects of different lifespans. Using EACFs makes this analysis very simple. Using abdullahkhalids' figures and assuming a single cycle per day, the equivalent annual cash flows per KWh are equal when the cost of capital is about 4.35%. Something magical happens when you assume can get more than one cycle per day. At two cycles per day, your funding costs could be 10% and the project still feasible! At four cycles per day and with a 5% cost of capital, Li-ion costs almost four times as much as the proposed project. Could someone shine some light on how many cycles per day is realistic for both Li-ion & the proposal? PS if you find this sort of analysis interesting and want to hit me up to talk about such things, feel free to send me an email (available in my profile).
• michaelbuckbee 12y ago
  This is just rampant speculation - but what if they used depleted uranium as the weight? They could get paid to take the material off others hands (instead of buying lead) and it's almost 70% more dense.
  • bequanna 12y ago
    Wouldn't the initial cost savings be offset by the ongoing challenges of dealing with a big moving chunk of hazmat?
    • tempestn 12y ago
      Probably... but it's still an intriguing idea! Especially since their pressurized gas proposal already calls for a sealed cavity; maybe there actually is potential there. (Of course, there would probably be a significant PR cost too.) That said, they can already get more weight by making the weight taller, so density likely isn't a huge benefit. Whatever's the cheapest cost/kg (and without the other issues of Uranium) would probably be best.
    • SolarNet 12y ago
      Well at least if it fell it would be buried in a giant hole.
• pm90 12y ago
  I really hope these guys succeed, even if they don't replace conventional batteries everywhere. One thing I've been thinking for a long while is that: the future of humanity is in how advanced drilling equipment we can make. Think about it: asteroid mining, colonizing planets or even just conventional mining...all require drilling. If this technology catches on, there will be so much research done in finding better drilling techniques. In fact there is so much resources to be found in our Earth itself, if we drill deep enough. Also, imagine if we have a base on the moon powered by solar cells: having the technology to drill quickly and cheaply would be indispensable in storing energy captured during lunar "days". Although I imagine you would need deeper holes because of the smaller g.
• Pxtl 12y ago
  There's interesting variations here - at first glance a single big weight is the same as many small ones, but you have to think of the engineering challenges of cabling and motors for a 1 kilotonne mass. So you could use many smaller objects in a stack and move them one at a time, but then you've got the problem of decoupling/recoupling the cable and reaching through the ones that are at the top while lowering/raising the ones at the bottom. Now, the next obvious consideration is using mountains instead of a pit. The rockies are full of 4000M peaks. But a mountain means suddenly we have so many new considerations - mountains aren't exactly a constant slope from peak to foot. But extreme loads on rails are a solved problem - the world's heaviest single fully-loaded rail-car was about a kilotonne (a special schnabel car carrying a reactor up to the Alberta tar-sands). Of course, then you've got a new construction problem - building a train-track that's a near-straight-line up a mountain and can support incredibly heavy trucks. It's probably not workable because of the energy-density concerns, but it sure is neat.
• jacquesm 12y ago
  http://www.launchpnt.com/portfolio/energy/grid-scale-electricity-storage/ http://www.launchpnt.com/portfolio/energy/grid-scale-electri... http://www.greentechmedia.com/articles/read/Gravity-Power http://www.greentechmedia.com/articles/read/Gravity-Power
• jmadsen 12y ago
  I love how every Tom, Dick & Harry with a bit of math & engineering thinks he can "dispel the myth" of HN Idea X with two minutes of off-the-top-of-his-head equations. Read about these two: http://www.gravitricity.com/#people http://www.gravitricity.com/#people Do they seem like complete morons? Do you think they haven't studied this just a little bit more than you have? It doesn't mean their idea is good or will work - just that you aren't going to rip it apart with two hastily written paragraphs. People who ask questions about the costs, process, etc. are in the right spirit. People who think they can show off how clever they are really make me /facepalm
  • bduerst 12y ago
    You don't need to be a carpenter to tell if a house is built poorly.
    • deleted 12y ago
      [deleted]
    • jmadsen 12y ago
      You don't need to be a carpenter to tell if the doors are hung straight. You DO need to be one to actually assess the overall build and structure.
      • aaron695 12y ago
        I think you need to re-read the point. Anyone can tell if a really really shoddy building is NOT structurally sound. What is hard to tell is if a building IS structurally sound. That is why engineers exist. Not for the previous.
      • bduerst 12y ago
        The picture they're drawing isn't very straight, as many have demonstrated. Until these "experts" provide evidence otherwise, it's useless to berate readers for pointing out the obvious.
        • 12y ago
• zaroth 12y ago
  I was really hoping it would keep scrolling down nearly forever, with something neat waiting at the bottom :-)
• krschultz 12y ago
  Keep in mind, we currently remove entire mountains to extract coal. If there is one thing we can do at scale it's dig holes, move concrete, and make steel cable.
• joering2 12y ago
  I have this idea in my mind for a while now and it seems great subject to share it with you. Imagine an elevator going kilometers into the oceans dept. A huge tank is mounted on the top of it. It gets filled in with pressurized air. Because its heavy it sinks to the bottom. Then an air is released. Air travels into the surface but on its way it is actually captured into a little traps. When enough air is trapped, the entire structure built from hundreds of traps is lifted into the surface, together with the tank. of course during this trip, it triggers friction and the dynamo mounted on the surface translates this movement into electricity. Once on the surface, the tank is filled in with air, and the process starts all over. With long enough elevator in deep enough ocean, the electricity produced thanks to the travelling elevator would be greater than electricity used to put air into the tank. If you ignore the rules of gravity and that trapped air travels to the surface of a water, this could be a perpetuate mobile. What's wrong with my idea?
  • jakobegger 12y ago
    The deeper you go, the higher the pressure. The higher the pressure, the smaller the (trapped) air bubbles. The smaller the air bubbles, the lower the upward force. As a result, the deeper you go, the more air you will need to pump into your tank. Or in other words: with a given amount of air inside your tank, there's a maximum depth you can go. If you go deeper, the air bubbles will no longer lift the tank.
    • joering2 12y ago
      Of course, and that's what happened to Kursk. But: The released air would go up, regardless how pressured it is. While going up it would decompress taking up more space and therefore having greater force to push the tank up (as I mentioned, released air would be capture in a construction similar to a tree with leaves. Imagine leaves upside-down capturing the air. I'm sure you can find different type of mix that would be less-compressible and overal better for this experiment.
      • jakobegger 12y ago
        If the bubbles are captured higher up, say 500m above the tank, so that the increase in deplaced water can lift the tank, you couldn't lift the tank all the way up to the surface; it would be stuck at 500m below surface. It's the basic law of conservation of energy. You need to provide the energy required to lift the tank by compressing the air. The energy required to lift the tank is mgh (mass of tank, gravitational constant, height to lift the tank). The energy stored inside the tank is proportional to p*V (pressure times volume). You can't lift the tank further than the amount of energy you have available, so you can never have a surplus of energy.
• pizzashark 12y ago
  This sounded so much more interesting before I knew what it was.
• callmeed 12y ago
  Funny, I just finished Peter Thiel's book. In the final chapters, he discusses the cleantech flame-out companies of the 2000's and how many were run by old suits. He contrasts them with true technology innovators (like Elon) who are "t-shirt and jeans" people. Interesting to scroll down and see suits at this site.
• aetherspawn 12y ago
  If we had a dyson sphere around something heavy then the crank part could be in space with the weight dangling into the atmosphere: https://en.wikipedia.org/wiki/Dyson_sphere https://en.wikipedia.org/wiki/Dyson_sphere
  • k__ 12y ago
    How about the Moon? :D
    • aetherspawn 12y ago
      Yeah, I thought about that, but there wouldn't be enough gravity and it might be a bit too far to beam the energy back.
• ggchappell 12y ago
  FTA: > The key requirement is a deep hole in the ground; it could be a disused mineshaft brought back into use, or it could be a purpose drilled or sunk shaft. So, apparently, "sinking" a shaft involves making a hole using some technique other than drilling. What technique is that? Dictionaries are no help. Wikipedia[1] says: > Shafts may be sunk by conventional drill and blast or mechanised means. "Mechanized means" is pretty vague. Can anyone clarify? [1] https://en.wikipedia.org/wiki/Shaft_mining https://en.wikipedia.org/wiki/Shaft_mining
  • jmadsen 12y ago
    This may be of interest: http://en.wikipedia.org/wiki/New_drilling_technologies http://en.wikipedia.org/wiki/New_drilling_technologies
• aaron695 12y ago
  Good to see these's still a sucker born every minute. Intelligent people on HN are pointing out huge holes with this idea but some people are still defending their Nigerian princes, because... they want it to be true? The warning signs here are huge. It's an incredibly simple idea, if it was possible it'd be already done. Nothing here really seems to rely on scale either.
• rebootthesystem 12y ago
  They are using the wrong approach. It's the difference between Karate and Aikido. Can one use potential energy to, well, store energy? Duh. This, however, is the wrong way to do it.
• robertmarley 12y ago
  Digging that hole seems expensive.
• deleted 12y ago
  [deleted]
• blubbi2 12y ago
  I'm probably missing something, but what's the advantage of drilling a hole as opposed to "simply" building a kind of drain or sky scraper. I doubt it would be more expensive. Sure, the pressure-aspect would be away, but besides that...
• glassdoor 12y ago
  May be a look at second 2nd law of thermodynamic would help. Electric motors are efficient but there are still more losses that this company claims.
• goodmachine 12y ago
  If this catches on everywhere we'll run out of gravity in no time.
• transfire 12y ago
  I thought of this decades ago, and I am sure many others have too. And no the math does not come out favorably. While technically feasible, the cost is prohibitive. The reason is simple, you need LOTS OF WEIGHT to get any appreciable storage capacity. Try it yourself: http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html Note that 1 joule = 2.77777778 × 10-7 kilowatt hours
• cjbenedikt 12y ago
  At least you'll have to appreciate that these guys have started a viable enough business before for Siemens to buy it. However, when they started out it appeared equally unfeasible at the time..."impossible is an opinion not a fact"
• thisjepisje 12y ago
  What about springs for energy storage? https://www.youtube.com/watch?v=YCs002BywAE https://www.youtube.com/watch?v=YCs002BywAE
• arfar 12y ago
  He's managed to get a patent for it http://worldwide.espacenet.com/publicationDetails/biblio?CC=WO&NR=2013005056A1&KC=A1&FT=D http://worldwide.espacenet.com/publicationDetails/biblio?CC=...
• etamponi 12y ago
  If you drill a hole 1500m deep, and you use concrete as the material of the object used for energy storage, and the volume of the object is V [cube meters], when the object is at its maximum level you have stored an energy of: E = 10 x V KWh This means that with 10 cube meters of concrete you can store 100 KWh (more or less the energy consumed by 10 households per day). If what they claim about doubling the energy storage is true, with the same amount of concrete you can store 200 KWh. 10 cube meters of concrete would weight just 24 tons, not so much after all. Assuming a hole 1600m deep, and a system of cables capable of handling 250 tons (100 cube meters of concrete), you can store up to 2000 KWh (so you can serve 200 households for a day). I don't know the price of drilling a hole 1600 meters deep, but with these premises, if the price is in the range of 1-5 millions $, a medium neighborhood can afford the operation.