Why don't we use sand to store energy?

Discussion in 'General Science & Technology' started by impaJah, Feb 24, 2012.

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  1. Captain Kremmen All aboard, me Hearties! Valued Senior Member

    Storing energy as weight is more difficult than storing it as fuel.
    It is far more bulky.

    Consider that you can store enough energy in a litre of fuel, to drive a one ton vehicle about ten miles.
    It doesn't convert exactly, because a vehicle runs on wheels, but I think you can see that you would have to raise one ton of sand quite high in the air to have the equivalent of just one litre of petrol.

    People do store energy by pumping water to higher reservoirs, I believe.
    Someone may have already said this.
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  3. Aqueous Id flat Earth skeptic Valued Senior Member

    One of my purposes was to demonstrate the enormous structure required to store on a small amount of energy. It is only a good idea if you willing to invest a substantial outlay into such a structure.

    In either case you need some kind of motor. If you were using windmills, you could take advantage of their existing towers to lift weights (anything would do, sand, water, old cars....)heh heh... But when you say "bucket" I'm wondering what size you have in mind. The elevators I spoke of were basically very large buckets that are lifting huge scoops of sand (say 100 m tall). If they were 10 x 10 m at the base, you would need 100 of them to do this project... that's one per home. So imagine building just one to store your own power for 3 days. All you need is a 10 m x 10 m x 100 m column of sand, in one huge bucket (which I'm calling an elevator), and all you need to do is lift it 10 m, and turn a generator, plus to stop it and start it on demand, plus a battery to smooth it, and then an inverter if your home runs on AC, and your basically there. Once you have a power source to lift it, that is. And we haven't talked about the drive train that will lift this baby and let it down gently. When we get to that discussion we can talk about friction. Then you will start to get a handle on the full scope of the problem. As an exercise, you might want to calculate the weight of a column of sand 10 m x 10 m x 100 m.

    I think you missed my point. If you built your own storage system, and it used mass (of sand) to convert between kinetic energy (of moving the sand higher) into potential energy (mass times "g" times height) then the only way to get that energy back is to let the sand fall (simplest example was the elevator). Now as this "pile driver" falls, the generators attached to it will ramp up to speed and begin producing electricity. However, it will need to stop and start on demand, not to give up any height unless power is needed. My reference to a smoothing function was to bring to your attention that in practice, load-leveling is a real problem.. Whatever device you use for lifting sand, needs a load-leveler on descent, not to waste valuable height. If improperly done, the users of your electric power would become disgruntled from the rising and falling power levels as their neighbor's refrigerator kicks on, or ten people happen to flip their lights on at the same time. It would make no sense to transmit your power through the power lines back to the power plant for load leveling. Your idea of how capacitors and inductors store energy to smooth power supplies is on target, except for one small detail. When the energy storage requirement becomes large, we go to a very large capacitor, which we happen to call a battery. It's just an electrochemical version of a high energy density capacitor.

    Yes GW is gigawatt. 1 GW-s = 1 GJ (Joule is the SI unit for energy). I was speaking of 1 million cubic meters of sand, which is a cube full of sand, the size of a football field on each edge. It's an enormous amount of material...a small mountain, you might say.
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  5. impaJah Registered Senior Member

    Thank you very much for the thoughtful replies Aqueous Id. The task of designing a device such as this to completion is a hefty one that I admit I don't quite feel up to at the moment (I've got other things to focus on).

    I'm left wondering, are you an engineer of some sort?

    In your opinion, because I'm curious, what do you think is the most efficient means of storing energy for long periods of time - and what about for short periods?
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  7. Captain Kremmen All aboard, me Hearties! Valued Senior Member

    If you can design a lightweight, low cost, efficient battery,
    you will be the world's first Trillionaire.
    It is that important.
    It doesn't sound exciting,
    but an invention even of a slightly better battery
    will make the inventor a fortune.

    To store energy as lifted sand, in a desert, with unlimited availability of solar energy.
    I think that is a great idea. Possibly impossible, but a great idea.
    Maybe the prevailing wind could blow sand into a trap.
    It may not be uneconomical.
    Last edited: Mar 1, 2012
  8. Cifo Day destroys the night, Registered Senior Member

    Transmitting extraterrestrial energy to Earth sounds like it will add to Global Warming.

    Or just store the solar energy (along with the wind power in a desert) in its electrical form.
  9. billvon Valued Senior Member

    It will. But it will add to warming far less than digging up coal, burning it to release heat, releasing CO2 into the atmosphere AND using the power generated.
  10. Trippy ALEA IACTA EST Staff Member

    Power-Co's do this as well, although it's more subtle.

    They effectively use Hydroelectric dams to store excess capacity. They do this by cutting back on their generation at the dams, and allowing the water to build up when other forms of generation are sufficiently high, and demand is sufficiently low.
  11. Aqueous Id flat Earth skeptic Valued Senior Member

    I posed this to you as an engineering design so you could walk through the issues and see for yourself that, in the final analysis, efficiency is going to rule the day. Usually all of the things we are looking for in a solution -- cost, size, weight, reliability, and of course achievability -- are the first things a designer will home in on.

    Earlier in this thread it was pointed out that hydroelectric dams are more efficient than lifting sand. The reason given was friction. It was already evident from the folks who mentioned that, since anyone who has ever tried to move sand will recall that moving water was made easier by a pump.

    I gave you an idea of how you can raise and lower sand indefinitely without scooping it over and over, so you could eliminate some of the friction and inefficiency of using buckets, plus I wanted to get to the point of how you recover the energy by letting it fall.

    I already knew it would take a huge volume of sand (and/or a phenomenal height). But I thought you might benefit from trying to solve it yourself. It's a good exercise to do problems like this so you can familiarize yourself with the way physics is applied to solve these problems.

    My personal opinion is that it makes no sense to do this, unless you are trying to solve a particular problem, like the one I mentioned in which a machine like yours might be useful in a primitive setting. In other words, we have more efficient alternatives (like hydroelectric dams) but in a primitive setting, there may be no alternatives. This is the other side of design: sometimes we choose to run below the best efficiency, because it works, and we have no more efficient methods available.

    Your original question wasn't attacking the efficiency of modern power generating systems, you were just thinking of using a free dead weight by taking it from nature in a way that would not impact the habitat (too much). So I just followed your train of thought.

    Now as far as the most efficient storage... that's a tough one. I assume you mean storing electricity, and I assume you mean large power grids. In that case I would have to guess that dams are the most efficient, in fact they are only known method, for storing huge amounts of energy. Here we are not talking about storage from a generator, but merely the collection of free water that falls down from the watershed above grade.

    You seemed to be interested in storage, so I had to guess why you were pursuing that. The main problem in energy delivery isn't storage, but generation. If energy were free, we could could waste all we wanted on cheap inefficient storage systems - in fact we wouldn't need to store it at all if it were free.

    Anyway, more to your point, the most efficient systems are going to be the ones commonly used, since armies of scientists (any one of whom was smarter than you and me put together) have already solved these questions long ago. This is why it helps to walk through the kind of problem you presented. You can arrive at the same conclusion someone else discovered 100 years ago (or even 1000 years ago!).

    For example, if you don't already know about these things, read up on Archimedes' Screw and then read about pumps. Or look at the Leyden Jar and read about the voltaic pile or battery. After a while you will notice how these ideas have been around a long, long time.

    That doesn't mean we don't need a fresh look. If you look over the comments above, most of them are showing that folks here have a familiarity with the concern over energy availability and efficiency. It was mentioned that a new battery design will solve a lot of headaches, just as the Lithium batteries are doing now.. so that marks progress.

    I can't tell you what's around the corner. What I can tell you though is to keep chugging along and you will get a deeper insight into fields like engineering or physics where these problems have been rolling around for ever and a day.

    At some point if you are sincerely interested in this you will want to familiarize yourself with the relevant relationships between the various parameters involved in machines, such as how energy, power, force, torque and pressure relate. And of course you will want to familiarize yourself with units. Obviously there is a ton of relevant stuff you can learn, but this is a start.

    I wasn't sure of your background, so I just started free-wheeling. But we can take this anywhere you want to go.

    As far as what is the most efficient method overall for storing energy, I would choose matter (E=mc[sup]2[/sup]) as my first choice, since every kilogram of matter theoretically contains (approximately) that much energy in Joules, followed by 19 zeroes. (I think it comes out to something like 285 MW for 1000 years, something like that.) Of course there's no highly efficient means to exploit this, leaving us with nuclear fission as the best option.

    My second choice would probably be photosynthesis, although I couldn't tell you offhand what kind of efficiency to expect, or how best to exploit it, but there are people working on that in all kinds of ways. Ethanol was one.

    Anyway, I would go with what Captain Kremmen had in mind, a better battery. It would be really great if it could be small, light, non-toxic and 100 times more dense in its energy storage. I realize that's a tall order, but if you could also make it possible at a fraction of current prices, you would be an instant hero, in fact you would probably make enough to buy the Sahara Desert, and set up your new, better, cleaner sand-based economy.

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    Last edited: Mar 1, 2012
  12. Trippy ALEA IACTA EST Staff Member

    Use an Archimedes Screw - pumping it as a slurry might make this easier, but it's not neccessary.

    Solve the photosystem II problem and you're there. At the moment although we have several structural analogs, we have no functional analogs of the water oxidation center in Photosystem II. The person that manages that, including pigments and electron transfer chains (to some extent, the easy part) willl have a means of using Sunlight to produce hydrogen and oxygen from water at (IIRC) useful rates.

    I have my own plans, but I lack the capital to fund them, and I'm reticent to share them with anybody else (consequently they stay in my head until someone else independantly comes up with the same solution and patents it).
  13. Aqueous Id flat Earth skeptic Valued Senior Member

    An artificial photosystem of some kind, with good efficiency, and especially if it could be done cheaply (that's the practical limitation) and people could actually see their way to going solar, I think.

    Just scanning for information, some of the ideas I've seen kicked around include attaching photosystems to the sides of nanotubes, growing polymers, a ruthenium complex/mica sandwich, some ideas about a non-fading dye, etc. There seems to be a fair amount of work being done on this, at least there seem to be plenty of books and papers on the subject.

    It would be really cool to read that a guy who goes by "Trippy" was in the headlines with a breakthrough. ....I would gladly take a job as lab janitor, just to be there for the eureka moment!
  14. Trippy ALEA IACTA EST Staff Member

    Yeah, I'd love to be 'that guy', but the odds are against it. My talents are elsewhere in chemistry, and the most original thing I have done recently is develop a method for mapping septic tank densities.
  15. Aqueous Id flat Earth skeptic Valued Senior Member

    Hah! I'll bet you all the chemists who have failed to crack the photosystem nut don't have that particular experience. It could just be requisite fieldwork that they are all overlooking. Look at it this way: even Einstein couldn't map tank densities, and look how far he got.

    Seriously: have you ever considered putting your ideas in the form of a grant proposal? It looks like there has already been some serious money spent on very conceptual investigations. I wouldn't think that a knowledgeable investor would expect an instantaneous miracle. (I offer this as words of encouragement, just in case you think you might pursue it some day.)

    I still think it's a fascinating subject, even if we're just batting the ball around. It makes perfect sense that nature exploited solar energy as soon as it could, sometime in the Archaean, in some primitive bacteria that set the stage for the success of cyanobacteria. How and why the photosystem architecture came into being is partly tied to its evolution, so I imagine that whoever manages to crack the nut open will have made some discovery of an underlying evolutionary mechanism that somehow leads to a breakthrough.

    The idea that plants have these little light antennas, just waiting for us to figure out how to exploit them, is quite an incentive. 1 kW-m[sup]-2[/sup] is quite a hefty resource, still barely touched.
  16. Trippy ALEA IACTA EST Staff Member

    I have some background in metallo-organic chemistry, but that's not where my interests or ideas are. I'm more likely to be the guy that develops the (albeit expendable) cartridge that plugs into the discharge pipes of your existing septic tanks and scrubs it to drinking standards. I'm also more likely to be the guy that turns Dairy Effluent into a valuable commodity (seriously, can you imagine the positive impact doing that would have on the environment?)

    Not really, my ideas aren't in that direction, my ideas are more in the direction of effluent scrubbing, and petroleum syntesis (not Bio diesel mind, but actual crude oil).

    I would love to meet someone that took my ideas seriously, the people I have spoken to (friends and family mostly) generally get very excited.

    That, essentially is the point of trying to make a functional analog. We have structural analogs, so we know, more or less what needs to be there to make it work, but so far what we don't have is a sign that says "You need at least this much arranged that way to make this work".

    Here's another interesting idea for you - Plants use the water oxidation center to set up a proton concentration gradient. Those protons then leave the cell to try and acheive equilibrium, and they do so by passing through a cellular mechanism (for want of a better word) that at its base has an array of I think) 12 or 13 carbonate groups. When the protons bond with the carbonate groups, it changes the chemistry of the bottom of the mechanism such that it forces it to rotate (seriously, to me the whole setup resembles a flagellum). This rotational energy is then used by the cell to do work, by forcing another center through a series of physical shape changes, that reacts ADP with Orthophosphate to make ATP, which is then released.

    Imagine if there was a way of making that rotational energy work for us using nanotechnology.

    Enough dreaming from me though.
  17. Aqueous Id flat Earth skeptic Valued Senior Member

    Oh, OK so your photosystem idea isn't where your interest lies? I suppose that's more of a microbiology lab situation, whereas you tend to be more involved in an applied chemistry in a practical business setting?

    Synthetic crude? I don't get it. Why not synthetic octane?

    Consider this such a meeting. I'll bet you could easily get a million followers if you just asked for their vote of confidence. Everywhere around the world people are on the edge of their seats waiting for a breakthrough, they just lack the skill to throw themselves into the mix.

    This is great. I mean really great. Already motors are turning in my mind. Not only flagella, but I immediately flashed to the way myosin causes muscle fibers to retract. Something like cinching a belt, drawing one fiber against the other? But the possibilities and the ramifications of developing mechanical power directly from light? Ahh that would be completely revolutionary

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    ! I want to be in a place like that right now, somewhere that's doing crazy cool and insanely ambitious projects like that.

    But seriously - this particular aspect you mention, in which the molecule rotates, through ADP-ATP energy transfer: presumably this was worked out in the Archaean? How and why that came about has got to be one of the the great success stories from among all the failed ways that prokaryotes may have "experimented with design" until hitting on this winner and giving rise to the line that evolved into cyanobacteria (which were, of course, prolific beyond compare). Cracking that back story, if it's ever possible, would seem to be a huge leap forward.

    Oh, and I almost forgot, one more molecular motor of interest, the ever-popular kinesin:

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    Well OK I for one got a kick out of it. Enjoyed it thoroughly. I can't believe we got here from sand....heh heh
  18. Trippy ALEA IACTA EST Staff Member

    Environmental Law Enforcement, but yeah, something like that. But the thing is, it's not just my knowledge of chemistry I get to apply, it's a large portion of what I have learned, right down to the scientific method itself.

    Using the process I have in mind, it's easier to create a mixture of alkanes, than a specific alkane.

    Maybe, self confidence is an issue as well.

    I think you misunderstood me, the rotation isn't caused by ADP-ATP energy transfer, it's caused by proton trasnfer and results into ADP to ATP ernergy transfer.
  19. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Back on the sand storing energy, this may clearly show why is not an interesting idea:

    I had a friend who replaced the shingle roof of his house. He spent a couple of long days climbing up a ladder to get the new shingles on the roof (wanted them there so old would be quickly replaced with new.) He was telling me how much work that was so we calcualted the cost of that much energy from the power company. As I recall, it was less than 2 cents.

    Lifting weight stores insignificant energy by almost any useful standard.
  20. impaJah Registered Senior Member

    Yah and on top of it all on a mass scale it would no doubt be quite ugly.

    That's the problem I'm seeing with everything that's done on a large scale, it never looks as good as nature and it messes up the balance of the ecosystem.

    Trees use photosynthesis but they do it so tastefully that they are a real pleasure to be around. Compare that to parking lots studded with solar panels - people want to get AWAY from them (and no touching! ..not that you'd want to).

    I think the permaculture people hit the nail on the head. The most far-sighted ingenuity will not neglect to make sure the cycle connects... if you catch my drift. What we have right now isn't a cycle, it's a divorce. Ingenious to be sure... like the mechanically consistent deductions of a mad genius on questionable premises, but a divorce nonetheless.
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