Power Your Home With A Water Battery

Quint explaining his water turbine

I’ve stated it before on Hackaday but one of the most interesting engineering challenges posed to me this year was “how could you store enough energy to power a decent portion of a home for several hours without using batteries, all while staying within the size of a typical suburban plot?” [Quint Builds] attempts something up that alley by using solar power to pump water up onto his roof and later releasing it for power generation. (Video, embedded below.)

Earlier [Quint] had built a water collecting system using his gutters and a bell siphon but wasn’t satisfied with the overall power output. Using the turbine he had created for that system, he put a 55-gallon drum on top of his roof with the help of some supporting structures. We’d like to advise the public to consult a professional before adding a large heavy weight on top of your roof, but [Quint] forges ahead after studying his trusses and determining it to be a risk he is willing to take. A solar panel runs a small pump that pumps water from a reservoir up to the top of the roof when the sun shines with a float switch in the roof barrel stopping the motor once it’s full. A valve at the bottom allows water to spin the turbine and fill back into the bottom reservoir, forming a closed loop. There were a few snags along the way with prototype circuits not being fully contacted and the motor needing water cooling, an issue fixed by a custom CNC’d heat sink. The fixes for the various issues are almost as entertaining to see as the actual system itself.

It’s incredible to see lights come on powered by water alone but also sobering to realize just how much water you’d need to power a typical home. Perhaps if [Quint] upgrades, he can swap out the small motor for a larger 3D printed water pump.

52 thoughts on “Power Your Home With A Water Battery

      1. Not quite; a reasonably good Li-ion 18650 battery stores 3350mAh at 3.6V nominal, so that’s 12Wh per cell. Also, this battery has a cycle efficiency of over 95%, if the current is reasonable, while the pumped hydro has a cycle efficiency of about 25%, probably a lot less with this really crappy pump (it gets hot for a reason).

        It may have been a fun build, but it’s very impractical, and economically absolutely unviable.

        1. “while the pumped hydro has a cycle efficiency of about 25%, probably a lot less with this really crappy pump (it gets hot for a reason).”

          I agree that the efficiency of this setup is likely near zero, but why are you mentioning 25%? Pumped hydro normally has a cycle efficiency pretty comparable to lithium-ion batteries at grid scales. The battery *itself* has a cycle efficiency of ~95%-ish, but that’s like comparing it to the actual energy difference between “water high” and “water low” – so by that metric the cycle efficiency is 100% for hydro!

          The losses come in how you’re moving the water, just like the losses for a lithium ion battery come in how you regulate and deliver the power. The whole “95%” number typically ignores those losses. Typically at grid scale, both of them are around 80% round-trip efficiency at a system level.

          1. “Pumped hydro normally has a cycle efficiency pretty comparable to lithium-ion batteries at grid scales. ”

            This guy’s setup is not grid scale and a completely useless metric.

            ” The battery *itself* has a cycle efficiency of ~95%-ish, but that’s like comparing it to the actual energy difference between “water high” and “water low” – so by that metric the cycle efficiency is 100% for hydro!”

            What? No.

            “The losses come in how you’re moving the water, just like the losses for a lithium ion battery come in how you regulate and deliver the power.”

            What? No. The efficiency of a flashlight I plug into the battery is irrelevant.

            Assuming even 100% efficiency, 14.2kJ is enough to generate 23W for…10 minutes.

            He will never recoup the energy his computer wasted editing, rendering, and transcoding the video. The guy is an absolute moron.

        2. The author himself says that it’s totally impractical, and economically absolutely unviable.

          It’s just a little experiment to show how pumped storage power plants works, with a real example.

      2. 55gallons at 10m is nowhere near that. It’s gallons x psi (10m is 20psi on a good day) /1714, that gives you HP at .64, then you multiply that by 745w/hp and get 500w’s of power, not 5,000.

        1. My god, the mental gymnastics you have to perform to cope with imperial measures.
          Makes you look stupid.
          55 gallons = 200 liters = 200 kg.
          energy stored is 200 kg x 10 m x 10 N/kg = 20,000 J. Or 5.6 Wh. Yeesh.

          For the unenlightened who want to follow the units longhand: a joule is a newton-meter.
          A newton is a kg-m/s^2.
          The 10 N/kg is the force due to gravitational acceleration, dimensionally identical to m/s^2.

          What the heck is “500 w’s” anyway? Doesn’t look like any unit of power. And, anyway, we really want to know energy stored, not power.

        2. While we’re at it: 10 m of water head x 1000 kg / m^3 x 10 N/kg = 100 kN/m^2 = 100 kPa = 1 atmosphere. Last I heard, that was around 15 psi. Not 20 psi.

          But, heck, the American gallon is smaller than a regular one. Maybe there’s a stunted American-size pound too.

    1. I believe his intentions aren’t much on the economy of this, but to show his kids and his subscribers how to store solar power. If we wanted to really curb his power bill, it would be better to get some lead acid batteries.

      Or he should use a better turbine, a better pump, a better generator, a larger tank, and a 30-store building…

      1. … or shift the whole thing down 30 stories. Put the storage tank on the ground, drill a vertical shaft for the gravity drop. It’s possible to do this with only a well-style shaft, but a large diameter tank at the bottom of the drop does improve efficiency.

        With careful engineering, you can combine your water well and your power storage, although the risk of compromising your water quality might not be worth it.

          1. An artesian well, by definition, does not require either a pump or a foot valve.

            But, yeah, that’s a heck of a deep well. Ours was the deepest in the area, at 220 ft. The pump was 20 ft. off the bottom — an awful lot of pipe, power cable and lift chain. Thankfully, we never had to lift it. It’s a half century old now though, so I imagine the new owner has had to pull it at some point.

    2. This is simply a demonstration of how a « pumped storage power plants » (PSP) works. The main purpose is not to generate electricity, it’s a “battery” which can deliver a lot of power quickly, to compensate when demand is high for example.
      It is precisely used to smooth the electrical network, when Nuclear plants generate extra power they will use it to pump water.

    1. What?!?

      While I highly doubt that an individual moving mass up to their roof and back down could hope to store a useful amount of energy either way I really have a hard time believing that moving a solid mass would be simpler than moving water.

      A lot of water can be pumped a little at a time. All that’s needed is a pump and a hose. A solid mass would require quite a gear box to get enough torque to move it, thick steel cables and a structure even higher than the height the mass will be raised to hang it all from. That structure would have to be braced to support all that weight hanging off one side. Unless the structure was hollow and big enough to surround the weight.

      Water sounds a lot easier. To do this on a useful scale I would think what one would need is a place next to a mountain, some dynamite to excavate a hole somewhere up the mountain and the rest is just plumbing.

      1. I didn’t see anyone mention that in some municipalities, it’s against ordinances for homeowners to collect rainwater in any fashion as the city believes that water belongs to them and depend upon it in the form of runoff and collection to supply citywide water.

  1. Here is the root of the problem , it is called conversion when you change the form of the power you get increased losses and his system converts the energy twice from electrical to mechanical and then back again. the loss is more than additive in fact it is probably (math is not my profession!)more like a log function. Economy of scale would play into this to help with justifying the losses the heat energy wasted at the pump is not a small loss, the heat sink solves the pump wanting to melt down but the heat soaked up by the water and allowed to escape is lost energy that was expended with no benefit. The generator he uses is not shown but I suspect it would get warm also again another loss, pelton wheel another loss (turbine water generator is much better not perfect but better) If he was using the solar to do a task like pump water to the roof after his main battery bank was fully charged and it was used to supply domestic water pressure the pump would be a secondary task and more acceptable as inefficient as the pumping is it is better to use the solar for something than to let it go un used ! Batteries are not as expensive or hard to maintain as they were in the past, nor do they weigh tons and tons taking up valuable space, leaving D.C. power as D.C. and storing it in batteries is the most efficient way to utilize the power. When using the stored power use D.C. where possible only converting it to A.C. for loads where D.C. is not available or an option such asto run some power tools. I understand his efforts were to show what was possible and how much energy is stored in water etc… as far as his demo goes it would be so much better if he used a more proper sized pump for the task so it ran with out such massive losses as his system has also a large loss with small pumps is the small diameter of the tubing friction between the water and the tube carrying it is a real significant loss. as to improvements in his generator he needs to go online and find a small fully sealed and efficient hydro generator designed for generating power for high end shower fixtures where the water going to the shower powers up the controls and led lighting, Ebay had hundreds of them listed for 10 to 20 usd prices for the same part varied by free shipping or not and shipped from china or from the U.S. no water loss and connect with same tubing he was using , he could parallel say 3 or 4 of those units to get more current, valve above each to allow throttling or scaling to fit use.

    1. You can do very very efficient gravity powered energy store, possibly even vastly blowing batteries away for longer term store as your ‘electrical’ storage methods self discharge meaningfully and with the right pump and turbine used at their most efficient rates you can get damn close to or even beat most battery techs energy in to out in the short term too..

      The only thing ‘wrong’ with this setup is it wasn’t built for efficiency, or peak power delivery, or any practical metric, but as a demonstration and at that it does well.

      p.s – worth pointing out not all energy storage methods scale very well – some loose efficiency quite badly as you build larger, and others really come into their own at the bigger scales – so the right choice is always down to the use case!

  2. This is a classic “what if” to throw at engineering students.

    You can pump water uphill then run it through the system to recapture power – with all the attendant inefficiencies involved, or you can use batteries for more direct capture etc. But wait, there’s more! Batteries deplete over time, supercapacitors moreso so….what’s the best scenario for an hour from now? Overnight? A year from now? Does it scale to grid proportions?

    1. Don’t forget to include lifetime maintenance, amortization and opportunity cost of capital. Not engineering concepts, but crucial in calculating the practicality of the thing.

      And none of that calculates the value of a youtube click. Which is, to be brutally honest, the entire purpose of this endeavor.

      1. It would be even easier if he didn’t use those funny stunted American “colony size” gallons. A real gallon of water is ten pounds. And the standard size drum is 45 (real) gallons. Or 200 liters, for less important 95% of the planet.

        Now, if you want to be really pedantic, weight is in Newtons. Mass is in kilograms. That drum would weigh 2000 Newtons when full of water.

  3. Nice.

    At least that thing is much better than all that battery madness in unlimited cycles and constant readiness even after years in “discharged” state. Pity that it is not really useable for home appliances.

    Some rant:

    I hate all that rechargeable batteries for unreliability. It is very annoying to find your electric bike in garage at spring with completely dead battery because you just forgot to charge it in autumn before 6 months of cold winter. All that hand tools with batteries that dies if you forgot to charge them and didn’t use for some time. And the cost of new battery packs, of course. Especially taking in mind that most hand tools have unserviceable battery packs cases, that you have to crack with hammer and screwdriver and then fight with compound inside just to replace that silly 18650 elements. And absence of interchangeability between brands and even different models drive me wild. Anyway, it does not matter what brand to use – from top ones to cheap garbage, all of them ends in one way – batteries dead and new battery cost more than price of the tool when you bought it. I even thought about gas engine powered screwdriver drill. Finally I moved to corded drills-screwdrivers and other tools in past few years. No batteries – no problems at all. Even cord does not annoy me in comparison with batteries. Ready to go always and instantly. Even if there are blackout, it is just a few seconds to start gas generator. Batteries are definitely the worst technology ever. Slow recharge, temperature dependence, specific conditions for storage, highly limited cycles (500 cycles – it is insane low!) and no one manufacturer provide battery packs with easy 18650 cells replacement. something like exchanging AA batteries in oldschool devices.

    Interesting that fuel cells that definitely better than rechargeable batteries, at least in recharge speed and ease of empty storage, are still unavailable on the market. I ready to buy hand drill with fuel cell for any money, but nobody sells them. IDK if the problem in patented proton membranes or there is some conspiracy of battery manufacturers like one about incandenced bulbs, but there are no any sign of light in the dark tunnel of bothering battery madness.

    1. Yeah cuz it’s much much better to store gasoline in your garage. And nobody Ever forgets to fill up the can! And it’s much safer to climb that ladder if you are dragging a heavy outdoor grade extension cord with you.

      Not sure what you are complaining about anyway, my battery powered mower does the whole lawn on one charge with plenty to spare. My battery powered drill will easily break my arm with its ridiculous torque. Maybe you are remembering 20 years ago? Today batteries are great!

      1. > Yeah cuz it’s much much better to store gasoline in your garage

        Everybody store gasoline in garage without any problems for more than a century. In the car fuel tank. Don’t see much difference between car fuel tank and decent canister.

        > And nobody Ever forgets to fill up the can!

        It’s 10 minutes to get to gas station and return with canister filled with a lot of kWh of energy (10kWh per liter IIRC). You will spend a day to put same amount of energy into your batteries.

        > My battery powered drill will easily break my arm with its ridiculous torque.

        If battery is not dead and was charged properly. And ability to break your hand lasts ridiculously little time and you have to wait for charging again. Or you could pay (of course!) twice for two batteries, and charge one while other in work. But suddenly, for any battery charging current is lower than working current, so, if you really do some work, not just playing with your weekend hobby, you drain working battery faster than another one charges. And you don’t even notice the total absurd insanity of the whole situation with batteries.

    2. The industry I work in uses a lot of rechargable battery powered device and they are a PITA .

      Devices that use primary cells are much less troublesome. Batteries flat just pop in some new ones and off you go – rechargeable battery flat and it’s a couple of hours before the heat can be used again.

      Been tethered to the mains ain’t all that bad (but I do like the portability of my battery powered tools )

      1. > Been tethered to the mains ain’t all that bad

        For the hand tools I always replace default power cord with a longer one made from superflexible cable with rubber insulation. It even stays perfectly flexible at -20°C outside. Way more comfortable.

        > (but I do like the portability of my battery powered tools )

        I like the portability too, but want something more advanced than batteries as power source for hand tools. For now, battery drawbacks outweight the uncomfortability of power cord. Interesting, that many hand tool brands start to manufacture corded versions of their screwdrivers and other tools. I think they would not do that if there is no demand for corded versions. And that demand is a solid proof that there is really something wrong with batteries.

    3. Fuel cell don’t really scale down to power tool size yet from what I’ve seen of the tech – maybe one day but for now you would need something more suitcase size to deliver enough energy for a power tool.

      There really isn’t anything wrong with modern power tool batteries, seems like every reputable brand out there makes perfectly good, rather long lasting batteries with more than enough power for a long usage session in most cases. Sure if you really work them hard day in day out they won’t last anywhere near as long as a power cable, and you are going to want a few spare batteries for the tool, but they are convenient and functional enough now (though I mostly use Air tools – when you end up working outside in the UK you want tools that won’t mind getting rained on and its handy to be tethered to unlimited power with a tool that won’t ever overheat…)

  4. Didn’t HaD just have an article extolling the virtues and efficiency of high pressure hydraulics?

    So, instead of lifting a relatively small mass of water at low pressure, why not lift something heavy on hydraulic cylinders? Like, say, the whole house?

    What’s a house weigh? Mine’s pretty small, but is a lot of stone and brick and concrete. Excluding the foundation, it’s probably north of 30 tons. Say 1 m height is manageable without involving truly excessive plumbing and stair nightmares, so that’s 300 kJ. About a penny worth of electricity, or about 5 minutes of solar from a small array.

    Yeah, ok, dumb idea.

    Even if I use a back yard with 1000 tons of concrete (a house-size cube, about $50,000 worth here), it’s really tough to come up with a way to store more electrical energy than a kilobuck of batteries will.

    1. “it’s really tough to come up with a way to store more electrical energy than a kilobuck of batteries will.”
      Using water, it’s trivial to store heating or cooling at a cost far below that of using batteries for the task.

      1. But storing the energy in the form of low-grade heat is not storing electrical energy now, is it?

        From a purely Carnot perspective, cooling heat /cool at (say) 30 K temperature difference is only “worth” 30 K/300 K = 10% as much as storing it as electricity.

        In other words, to do a head:head comparison of storing electrical energy vs. thermal energy, consider how much it costs to store 1 GJ of heat energy (a few days of winter heating) vs. storing 100 MJ of electrical energy and using a heat pump when needed.

        1 GJ of heat will take 8 tons of water, and around 100 square feet of floor space (5% of a house, or maybe $10000 of space, plus around $5000 for the insulated tank, but let’s say the water is free)

        100 MJ of lead-acid batteries are only 1 ton, and occupy only 10 square feet of floor space, or $1000 of space. The cost of the batteries is roughly the same as the cost of the water tank.

  5. Rather do the same in an old, deep (> 10 m), digged (not drilled, but wide dia) well using a large weight and pulleys, but not by water and pump. The losses will be much smaller. Anyway the energy which can be stored by gravity using bulky equipments is negligible compared to modern batteries.

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