| Archive for Downsizer For an ethical approach to consumption |
| shadiya |
Batteries versus water for storage....The saga continues.... just as I'd got excited about battery banks and lights on the end of switches etc etc, in comes the wwoofer and starts muttering about environmental destruction and water being more efficient and clean blah blah. 'Why don't you pump the water to a reservoir and then you can release it when required?' says he, to which I didn't really have an answer (but I thought 'Why don't you bog off?' but I think that's because I'm not at my best before about eleven )
Of course, now that I think about it, I wonder whether it would work? The wind generator could pump water instead of charging batteries, we live on top of a hill and have space and could have a reservoir. He suggested using the pond we are planning on digging but I would have thought maybe not, quite disruptive having water being pumped in and out, but maybe a little system.... Anybody seen or heard anything that might be even vaguely relevant? |
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| vegplot |
It's quite a common scenario especially where the geography allows it without too much earth shifting.
Sizing is more critical as once you built your reservoir it's very expense to enlarge it if you find it's too small. It has less potential for environmental damage and you're also less reliant on external technologies such as batteries (although not impossible). There are loads of resources on hydro electricity available but much less so for pumped storage. If you want to see a large scale implementation come up our way and see Electric Mountain. |
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| RichardW |
If you are using elec to pump you will use about 4 units of power to pump up the hill for every unit of power you gain when releasing it down hill. It only works when you can use ultra cheap elec to pump & can sell at utra high prices. Thats what electric mountain does. They can buy the elec that would normally be dumped at night cos no one wants it at very low prices (think 1p per kwh or less) & sell it as peak / on demand elec at key points during the day at over the price most people pay for day elec (sounds odd that the grid will pay more than they charge but its cheaper than having the standard stations running idle all day just for a couple of mins worth of power to keep the htz steady).
If using a fuel to pump then its even worse as all engines are about 33% efficient (1/3 wasted 1/3 heat 1/3 provides power) aprox. Then add in pumping losses yada yada yada. Richard |
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| Mutton |
Electric mountain - I think that the pumps are also the turbines.
The design for water pumping wind turbines are very different to electricity ones. For water you want something slow with a lot of torque. Think the water pump turbines in westerns. You can find out quite a bit by googling on DIY turbines where that kind of design question is asked. Curiosity, as this is sort of the right thread. I've been watching all the rain tipping down and thinking "Ooh, how big a tank would I need to generate meaningful electricity". Old barn and cowshed up the hill from the house, gulley that drains to the river already at the bottom of the slope, so what if all the rain run off was collected in big tanks, then the overflow generates electricity, plus can do a release from the tanks. Suspect tanks could never be large enough - does anyone know. What is probably a how long is a piece of string question, as it will depend on fall, type of hydro turbine etc, but does anyone have a wet finger idea of what volume of water you need for 1kWh? |
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| vegplot |
Isn't the idea to pump water using electricty generated by the WT rather than directly? |
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| vegplot |
Power (Watts) =
flow of water (litres per sec) x Head of water (metres) x specific weight of water (kN/cubic metre = 9.81) To generate 1kW you'd need 102 litres per second, from a height of 1 metre or 1 litre per second from a height of 102 metres Do that for an hour for 1kWh Assume 50% efficiency so double the flow rate or height. |
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| Mutton |
That is the way round for electric mountain, but without cheap electricity it is expensive as others have said. Instead of converting from mechanical to electrical to pump up the water with all the losses, then using the mechanical directly should surely be more efficient. I hope. |
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| Mutton |
Thanks for the numbers vegplot, will convert to onsite and see what kind of tank I'd need. Too late at night to get the brain to do it now.
Having floated the idea, my gardener/shepherd part of my brain is saying "pouring water away like that - can't do it must keep it." So I guess that would be two sets of tanks, the second set to catch, with me walking the water back up hill to the greenhouse........... 
Really feel it should be possible to put a tiny archimedes screw in each of the downpipes on my house...... |
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| vegplot |
Ah, I see what you are driving at. Yes, very true if all you wanted to do is pump water. |
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| Mutton |
Yes - then you have a microhydro turbine for the electricity generation as the water comes thundering back down. (One hopes it thunders....) | ||||
| RichardW |
The elec mountain turbine / pump actually works as well as most pumps of that size. | ||||
| vegplot |
That would work if you were happy to have the wind turbine pumping water only and not generating electricity directly. |
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| Mutton |
Given the inefficiencies of the conversion and the unpredictability of the wind a wind powered pump would be my preferred way of "playing" - ideal world the water would be underground to reduce evaporation. Then you know how much potential electricity you have by the water level in the tank.
Just don't see a domestic wind turbine producing enough electricity to have sufficient surplus on very windy days to make building the water storage scheme worthwhile, once you look at buying the second water driven turbine and the pump to be run by the electric wind turbine to get the water up to the storage. Don't know how all that compares to batteries in terms of total storage and cost. Possibly more environmentally friendly depending on how much concrete in tank vs chemicals in batteries etc. What about hydrogen cells? Know very little about them except the basic principle. Anyone on here know the hazards, inefficiencies and life span. Any hazards in addition to the explosive nature of hydrogen - air mix? |
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| RichardW |
Stick with the open tank you will gain more from the rain than you will loose from evaporation. | ||||
| vegplot |
I don't have figures to hand but suspect hydrogen to be the more efficient option although there are problem with storing large volumes (compressing/cooling uses a great deal of energy) and you have to throw quite a lot of technology at it.
If the geography is in place then high torque pumped storage with turbine is probably the more efficient method but I'm not so pessimistic about using excess wind generated electricity in the right location. It's worth researching. |
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| RichardW |
I think if you are using wind then use a wind to pump directly.
With the current 5 to 1 price differential between day time power & E7 power. If you can get good efficiency (better than 5 to 1) then using night time mains to pump might be viable on a smaller scale. Got to be better than doing the same system with a battery & inverter as that system has lots of losses. |
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| jema |
Should you just concentrate on being happy that you have done something, someone will always have some better solution that involves a lot more work and expense. | ||||
| shadiya |
Well, of course, I haven't actually done anything yet but well done me anyway! 
Tom was suggesting a wind pump rather than creating electricity to pump water. I was interested once I got over my grumpiness because I saw this ages ago and wondered.... http://www.judyofthewoods.net/hydro.html I don't seem to have a physics brain so doing research into things like this takes me ages as I just can't seem to remember even the simplest things these days. Yesterday I had to ask a friend what the value of Pi was cos I'd forgotten. 
Bearing that in mind, and remembering that it's not nice to mock the afflicted, if the mini turbine thing that she's got wouldn't be in anyway suitable, try and say so nicely, even if you are thinking ' she knows nothing!'
It's a nice site though, well worth a look IMO. |
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| vegplot |
There's no reason why it shouldn't be suitable, but suitability is down to what you expect from the system and what the system can provide. Most hydro systems run continuously and therefore only a small turbine is required because the base load is low and peak loads are taken care of by batteries, much like a WT system. However, if the turbine needs to cope with peak loads then it needs to be much larger.
The most common scenario is for a grid connected hydro, where peak loads are handled by the grid. Hydro is excellent for this application. An awful lot will depend on your usage and how much capacity you have. |