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Forum Index : Windmills : Alternatives to batteries
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| RossW Guru  Joined: 25/02/2006 Location: AustraliaPosts: 495 |
I know this isn't really related to windmills specifically, but it's a universal problem from what I can see, and relates to all of us who are trying to go "green" and use renewable power. While we can make more and better wind generators, and PV is getting better (but still quite expensive), the one problem nobody seems to have come up with yet is that of storage of our power for use when WE want it. I've been thinking about it off and on for some time and would like to share thoughts - see if anyone has done this or got any thoughts to contribute. Batteries are an expensive part of our setups. They're heavy, they contain dangerous materials, they can form an explosion risk, the certainly can damage electronic circuits from the acidic vapours, they're relatively inefficient (take 1000 WH out of one and need to put about 1200 WH back in to recharge it), they have a limited life and they're expensive. Of course, batteries are required - PV rarely works when you need it, wind is there sometimes, but not always. My thoughts are related specifically to my application, they may not suit everyone here of course! I live on top of a hill. I don't have mains (grid) power, but I *DO* have town water. Ok, it's to the bottom corner of the property because thats the only place low enough to be fed by the town supply... but I have a 100,000 litre tank down there. We pump water from that tank up to another 100,000 litre tank at the house for domestic use and firefighting. This is a vertical distance of about 50 metres. I run the whole house off an inverter, so in the first instance, any renewable energy (PV, wind) can supply the inverter directly. This is more efficient as it "replaces" energy that would have come from the batteries and would then need to be replaced (with interest!) later. Any surplus power is used to charge the batteries, thus reducing the generator run-time. (I should point out, the generator runs on Propane - but it's not all bad - the "waste" heat from the generator provides heat for the house and domestic hot water, so until I can build/buy a decent heat-pump, the generator is a necessary evil). My idea was to use any "surplus" renewable energy to pump water from the bottom tank up to the top tank. By adding a micro-hydro turbine, I can let water run from the top tank to the bottom tank to produce power. I'd want to make darn sure there was always enough water in the top tank for domestic use and firefighting, so lets say only half of it could be used. 50,000 litre. If the fall to the bottom tank is 50m, lets say 30m to allow for dynamic head (friction losses), by my calculations, I'd need 2 litres per second to get 500 watts of electrical output (allowing for some losses), and that would last me 25,000 seconds or nearly 7 hours. Not great, but a reasonable start. If I reduce the flow rate, I reduce the friction losses and get more head pressure, so to some extent, I may be able to realize closer to 40 or even nearly 50m head. At 50m head, 1 litre/second is nearly 500W, but the tank would last now for over 12 hours. 500W is just about enough to cover my "base load". If the tank gets too low, the generator could still kick in, just like it does with a low battery - indeed, the tank *IS* my battery! I'd still need some battery capacity to handle those large transient loads - but instead of hellish-expensive 2V/1000AH cells, I could get by with some 6V/220AH trojans. I don't know the efficiency of water pumps to move water back up the hill - I guess if the overall efficiency is WAY less than batteries, its just not worth doing. But if it's even close then the fact it never needs replacing would have to be factored in. Anyone got any decent resources on this, or opinions, thoughts or experiences? Thanks, RossW |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Ross I have windmill to pump water out of the bore however bore pipe last two years due rusting way have not replace it 73 metres and l have looking some better way and found Australia design pump call www.theferipump.com might able help to sort thing out for you and l am still thinking about buying this pump as anyone has one let me know . regard Dwyer |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Shouldn't be a problem in my case, as the water is potable. Nice, clean, treated, drinking water. I'd expet that as we "draw off" water for domestic use, we'd "top up" with town water. That's a neat pump too. I've seen them before and never heard a bad thing about them. RossW |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5019 |
Hi Ross. I cant see any real reason you could't use water and gravity as a storage of energy. Batteries are small, easy to set up and well understood. But if you have the space and height, then a water storage system could work just as well. Harnessing the power would take a little clever design. I would imagine a adjustable water jet across a pelton wheel, flow adjusted to match the load. The system may only come online during times of peak usage, and normally the water flow is shut off. Thanks guys for the link to the Feri pump. Its something I've been looking for, what a fantastic idea. My jet pump is getting old and the Feri pump looks perfect as a replacement. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Everyone
At last l got my lathe running as two weeks ago l had to replace the motor which l brought from the wreckers for $330 corolla 4K as other motor didn't cost me a cent Newer motor run on generator 3Ph 415volts 10 Kva @ 3000 rpm and l am getting new camshaft From Crow camshaft that design give more torque at 3000 rpm At the moment running fine due lack of torque when the lathes come on Any way l have done some of the work on F & P stator and also got plan that l will be using rare magnet neodymium on the outside and inside the stator and l need 150 @ 25mmx12mmx4mm neodymium as l did look at E-bay and other webs site no-one there is none so anyone can tell me where l can find them ??? There is review of the stator .  |
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whirlybird Newbie  Joined: 08/02/2006 Location: Posts: 27 |
Hi Dwyer I may be able to help you with the magnets that you require These are non standard but i can have them made. Do you intend to use these in a F/P conversion ? reply in the first instance here regards whirlybird I am because I am.I am not always right but often I am. |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi whirlybird That would be great if you able to make them and will be use in a F&P conversion 150 @ 25mmx12mmx4mm neodymium and 25mmx8mmx4mm what about guass ??and is in gold plate or nickel plate and can you able to give me the cost ? and l am not to sure if will be 150 and l just work out now that 168 for larger size and 112 for smaller size Ok regard Dwyer
Dwyer the bushman |
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Chris Senior Member  Joined: 12/09/2005 Location: AustraliaPosts: 146 |
Thats actaully a pretty cool idea Ross. Instead of using batteries for the large transient loads, maybe buy some large capacitors? Ive seen some pretty big car audio ones >40Farad, the only problem is they are rated at 12v. Your system is probably higher voltage ey? |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Capacitors? Hmmmm.... IIRC 40 Farad is 40 amps for one second. A typical small car battery is about 35 amps for one HOUR. |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
I have an idea about using sealed Nickel-Metal Hydride from Wrecking Toyota Prius that product 273.6 volt DC and wonder if able to change to 240 volts AC by specialilty made invertor plus using F&P windmill to charge the batteries however l do not know how many amps putout ? so has anyone have thought about it ?? It worth a try or forget it ??
Dwyer the bushman |
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| Chris Senior Member Joined: 12/09/2005 Location: AustraliaPosts: 146 |
I would think the figure would be higher then that? Car audio systems draw huge amounts of power for quite a long time... This is what i got: W=V²*C/2 for the amount of energy in joules (watts). So W = 12 ² * 40 / 2 = 2880W So then use ohms law, I=P/V, so 2880/12 = 240A Plus a capactior can charge up alot faster then a battery can... It was just a thought anyway, was just throwing it out on the table  |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Caps are a nice idea, but alas they simpy don't hold enough energy. a few farads *might* be enough to kick the 'fridge off, but I can't see it going past that. My system is indeed a "nominal" 48V, so supercaps have a problem there for a start. My other issue is "large, short-term" loads. For example, it's lunch time. The missus decides to heat that leftover whatever. Pops it into the microwave and hits cook. Wham! 40 amps required. Ok, the genset can kick in, but that will take at least 10 seconds by the time the inverter decides the load is too high and/or the battery voltage is too low, calls for genset, which has to turn on the gas valve, check stuff, crank, wait for the engine to run, check oil pressure and so on, then kick the governor in and again check we have oil pressure, right RPM etc, operate the output contactor to apply power from the alternator to the inverter, which then has to synchronise to the incomming mains before it can transfer load..... It all takes precious time.... and I reckon those caps will have been dead long before all that can happen. No, as much as I hate it, I think I'm stuck with *SOME* batteries. But if I can get by with a small bank worth a thousand bucks, instead of a large traction battery costing ten grand or more.... RossW |
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