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This topic contains 15 replies, has 13 voices, and was last updated by  Darrel Raynor 4 years, 3 months ago.

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    Has anyone got practical experience in pumping water up hill using abundent solar energy and running it back down through a small turbine at night?
    Thanks heaps


    Henry J

    Not personally, but I would have assumed the costs involved would make it more profitable to sell it back to the the grid (unless you have a turbine etc already)




    You should do it! And let us know what you find out 🙂




    It would probably pump better with a windmill into a water tank than a solar pump (If you have the space to do this.)

    Each option is pricey.



    Thanks for the replys.
    Yeah I think I’ll give it a go. Grid power is too far away and I have no desire to play their game anyway. The creek is low in the valley so wind is not regular and gusting. A ram pump will work for over 6 months of the year but for the rest solar is abundant cause when te creeks not flowing well the sun is out in force. I’ve got a few cheap ($20) 12v diaphram pump that can pump up to 1mpa in small volumes 4l/m which I want to set up for the water supply on the top of the ridge at least 100m elevation above the creek and use 3 of them to get the water up that high. Then I’ll use the same pipe to run water back down through a home made turbine on a car alternator. Try this out as a test run and if it has potential put some bigger pumps with bigger solar panels and more storage up high. I don’t mind even > 50% loss if I can avoid the expensive and consumable batteries which I’m replacing. I’m thinking I might need a small deep cycle as a power buffer and some voltage switch to start the water flow and alternator when the voltage of that battery drops low. Enjoy.


    Henry J

    Good luck with your mill. Other ideas to store energy could be heat in bricks or running a compressor with a tank. You can run a suprising amount of tools on compressed air. I looked into it more when Bill Mollison says about building a trompe (an air compressing device with no moving parts on a river) in one of his videos.



    You could use a solar to pump water up hill then run it down through a turbine to get some energy for however long the water lasts or you could perhaps use the solar to directly charge 12volt batteries that are then used to power a site. Another method to get water up hill may be focused sunlight on a copper pipe. This causes water to boil and the steam rises then use a still type device to cool the water at the other end so it drips into the catchment area. I suspect both the methods I suggest here will cost less than a solar panel or wind turbine and be more efficient in that the processes are shorter..

    This video shows how heat can be used to cause water to pump quite quickly http://www.youtube.com/watch?v=rrGMidc_P7s hope it gives you some ideas



    Would be better using a diesel pump/motor unit that has been modded for biofuel or some such (or a Stirling, whatever you got handy). Problem to this is that it encourages water usage to get sufficient charge/running time=empty water tanks. Fit an alternator/turbine to your outlet by all means but only use it as a battery top-up.



    Hi Paul,

    When building my own system i first wanted to go off-grid. So i implemented a battery bank, charge controller, inverter, panels and so on. The panels were super expensive so I started small. I refitted lights superefficient appliances and so on as every watt saved was a watt not needing to be captured… I had to buy many panels as the batts just weren’t being charged. Eventually i reached a plateau and i decided to get a small gridfeed inverter to dump excess charge back in the grid. I then had a bank failure and as i rewired the system to run partially off the grid (i live in the city) i noticed that i was feeding the grid way more kwh than when i had the batts on line. I did soe calculations and figured that the battery bank is a rather nefficient beast and for every kwh pulled out much more has to be fed in. The net result for me was to use the grid as a battery bank as this setup is way more efficient whilst I am in town. Your water pump setup is one such battery and I am pondering about the efficiency of such a setup. If you haea surplus of power above your daily needs by all means put it to use but other than this I think the generation and pumping losses would make it a poor/inefficient battery. You would really need to put on many extra panels just to get sufficient water up hill to still give you meaningful power levels when generating.

    Keep thinking tho because somehow we need to get power happening at night.

    I was looking into fuel cells as little units were becoming available at local electronic store. The added bonus is that they can be used as generators by adding fuel. Ie add alcohol or methane and away they go…. Should be quite efficient.. I’ve yet to see actual numbers. Another thing I was thinking that by fermenting your food wastes prior to composting and return to earth we may be ave to either get methane or alcohol either can be used a fuel in a fuelcell or an appropriately adapted generator. What are your thoughts?



    Hi again.

    I was researching for some numbers on the inefficiency of lead acid batteries (in solar systems) – see my earlier post above, and found this piece of text which confirms my findings…
    The Lead Acid battery is not 100% efficient at storing electricity – you will never get out as much as you put in when charging. Overall, an efficiency level of 85% is often assumed.
    The efficiency will depend on a number of factors including the rate of charging or discharging. The higher the rate of charge or discharge, the lower the efficiency.
    The state of charge of the battery will also affect charge efficiency. With the battery at half charge or less, the charge efficiency may be over 90%, dropping to nearer 60% when the battery is above 80% charged.
    However it has been found that if a battery is only partially charged, efficiency may be reduced with each charge. If this situation persists (the batteries never reaching full charge), the life of the battery may be reduced.

    The reason I’m explaining this further is that as in the case of lead acid batts, your proposed pumping project will also have some. The pump wont be 100% efficient, each elbow/joint/metre of water pipe will introduce friction and thus increase the overall inefficiency. It would be useful to know as a start how much power do you expect to use during times of low or no solar generation? Say from 8pm to 7am? In my case this was very little – bit of lighting and refrigeration. I solved the refrigeration by adding 10litres of water into the integrated freezer cabinet to form a cold bank – a battery of sorts and using a timer to switch off the power to it during the night. Works great as a vego the freezer compartment was empty anyway…. The I used rechargeable batteries in my laptop and desklamp, bedside lamps etc to provide local power. I plan to introduce a small wind turbine to provide a few hundred watts during the night. Given that my needs are minimal this may just be enough with only occasional fallback to batteries in appliances. Back to you, once you know how much you will need you can work backwards from the specs of water turbines to see how much water you will have to store in the upper reservoir. Then work out how long you will have to run your pump to push the water up there given that you only have 6-7 hours of solar power. This will give you a ballpark figure of how many kilowatts the pump takes times the hours it will need to run to “recharge” the system to be ready for use the next evening. This is very simple and I hope it makes sense.

    On the other hand, you could just give it a go and may find that despite it all because the purchase price and the labour by you it is still a good setup. At the very least it will be a great learning experience so you can’t loose really.



    Hi, I’m new here. After reading this thread, I am surprised that no one mentioned using the stored water (after running it through a turbine) for irrigation. The added benefit of using the water for growing crops could easily offset inefficiencies in your system and help tip the C/B ratio.


    Colten Jackson

    Really interesting thread! It bums me out sometimes to see so much focus being placed on batteries and solar cells (photovoltaics) being praised as the answer to out problems – the mining for rare earth metals, lithium etc is incredibly destructive! I’ve seen solar heating applications, but never heard the idea to use the solar heat directly to move water uphill via a still. Sounds like that has some potential!




    I wanted to pose a slight alteration or perhaps collaboration. Why not create a small catchment (swale) up hill where you speak and have it drain into the turbine and alternator set up (water wheel) like you said. Maybe a small pump up the hill or the still idea would be ideal.

    A friend of mine was using what he called “rain jets” which seemed to be rain catchers with a unique orifice using the weight of the collected water to force the water out in a small and powerful stream. Through this, he was able to catch a lot of water and essentially shoot it up hill which stocked the reservoir which kept the water wheel turning …Gears turning?


    Paul, Very interested in this thread. My land has a fairly large and swift creek running alongside. Close proximity to my fruit trees but would require about 10 feet of lift. I have been toying with the idea of RAM pump vs solar. Your point about each as the primary source about half of the year is well taken. Currently I end up dragging buckets up and down the hill about 6 times to get the job done. Trees are on a mild slope which I think is desirable but as you state a fairly low lying area which is concerning regarding freeze. I like the idea of rings around the base of the tree and on a timer. Im waiting to hear what approach you take and how it goes. Im not trained as a technical person but solar makes sense to me because the times of most drought and heat correspond with the sun in full force. Also, after fruiting and throughout the winter, Im thinking the need for water is greatly reduced. Ill be listening closeby. Cheers. Regina from Virginia



    One alternative to look at would be supercapacitors. These have been getting cheaper and more efficient over the last few years and the trend is likely to continue; I am not sure whether they are a good choice yet, but at some point they will be. It is possible to include one on the chip for a solar cell which gives a very simple storage system.

    Another would be to use a compressed air tank as storage. Some tools can run directly off air, e.g. many garages have these. For other things, run an air turbine to generate electricity.

    If a major use of electric power is air conditioning, it may be more efficient to just use the solar power to run a heat pump into some sort of large heat reservoir and let the reservoir cool your space. For heating, you might do something similar or pump solar heat into the reservoir.

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