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NOT the underwater pressure tank energy storage
project (which stores air)
Friends of mine run a farm using a total of 750 kw (100
hp) water-pumps (10 pumps, approximately 75 kw
each), working around the clock, typically at 20
Atmospheres, and pumping water to the fields 24
hours
a day,
for about 7 months a year, to a total of 6M
cubic
meters annually (the last number I'm not sure of).
This is standard for many similar farms of that size,
and probably the same for areas around the world
with dry
periods during the year, such as North Africa, the
Middle East and many of the landlocked states in the
US.
They pay for extremely low cost electricity at off-
peak
hours and it has been seriously calculated that gravity
energy storage would pay off well. But, luckily for the
wildlife's sake, they lack the permission to create a
water reservoir on the tree covered mountains
nearby.
So:
A system of many water balloons in a set of containers
in
a warehouse, hold stacked pressure-tank balloons,
digitally controlled (a digital pressure measuring
device
can cost less than 1 cent), each balloon is filled under
pressure, bottom to top, and emptied top to bottom.
The system returns the water under pressure during
peak hours.
The water had to pumped up to ground level in any
case, and, hopefully, only a small amount of energy
will
be lost to heat. Costing much less than the extremely
expensive and complex pressure and heat retrieval
systems needed with air or gas compression.
Your friends may want to consider this
http://www.youtube....watch?v=Sddb0Khx0yA
if power is the only price pressure. [4whom, Nov 29 2012]
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//24 hours a day, for about 7 months a year, to a total of 6M cubic meters annually (the last number I'm not sure of).// |
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If that figure is trustable, I make it you would need 6,000,000 * 12/7 / 365 = 28180 cubic meters per day.
That's equivalent to a cube approx. 30.4 metres to a side. Is it a big farm? |
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The basis that your plan seems to be that you can run the pumps part-time the whole year round, so saving on pumping capacity. As far as I can see, this has two main potential draw-backs:
1) The pumps may well not be easy to turn on and off. The stop-start cycle may reduce their mean time between failures.
2) At the start of the irrigation period you will need to have storage for 6,000,000 * 5/12 = 2,500,000 cubic metres of water. This volume is equivalent to a cube approx. 135.7 metres to a side ... quite large to store with your proposed relatively technological method. |
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Its a collective farm, therefore quite large, in Israeli
terms. |
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A Texan farmer visited Israel. The Israeli proudly
showed him his farm: See det line of trees zerr, end
de
brrokne traktore on de road, zerr? All dees eez mine!
The Texan says: Well, it takes me a good two days to
get from one saad of maa property t'the other saad of
it! The Israeli is silent for a minute and says: Yes. We
used to hev broken car like det. |
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I only store for peak hours - 6 hours a day. Digital
control makes it quite easy, including balloon failure
and maintenance when empty, and the whole thing
shouldn't cost too much. A large warehouse would do
the job. |
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//I only store for peak hours - 6 hours a day.// |
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In that case - why store the water at all? You'd need to increase the pumping capacity either way.
(In fact you'd need less additional power to use the water directly; loss to friction and back-pressure will be lower.) |
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Have they considered an old-fashioned water tower? Or a new-fashioned one (they come in a variety of sizes and take up far less ground space than a lake). |
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So the energy-storage medium here is actually the rubber of the balloons? The water is just a handy way to distribute the pressure around, right? This is equivalent to stretching elastic bands? |
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Or am I missing something, and is the weight of the water somehow the primary storage medium? Are the balloons just bags under no tension? |
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Because giant water balloons capable of storing energy in their stretchiness sound quite expensive. Non-stretchy bags that just hold water sound like needless tank liners. |
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I've seen giant water bags used as emergency water tanks, but they had maybe six feet of pressure head, and took up a lot of ground area. And were very expensive---making them out of stretchy rubber would cost many times more. |
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I can't see why not to use a water tank. |
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Why not switch the plants off during the day? |
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I store at night when off-peak electricity is at least
1/9th the price of the 6 hour peak price. |
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I use the elasticity to achieve the desired pressure.
Yes the energy-storage medium is the "rubber" of the
balloons, which are under tension. The water is both
the pressure distributor and what will be used for the
fields, pumped at night time from a well. The space
they take is limited by the containers they are sitting
in (so the tension is mostly "UP DOWN") |
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Custom made balloons at a commercial quantity are
not expensive. Even pressure tank balloons. |
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A water tower will need special permits, will not give
the desired pressure, and in any case is impractical
for such a large amount of water. And, in all
practicality, a warehouse filled this way, is in fact a
water tower. Except that the water on the top is
leaning on more water lower below. |
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//Why not switch the plants off during the day?//
You can almost literally do that with CAM plants,
such as cactuses. They can happily take up all their
water and carbon dioxide at night. |
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Is there a problem with simply irrigating at night (as
[Loris] suggested)? Can the soil not hold 6 hours
worth of water? |
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Nope. This farm works around the clock. They also have
livestock, a dairy farm, a winery and more. And as I
wrote, there are many many places around the world
with a similar need. |
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//NOT the underwater pressure tank energy storage project (which stores air)// |
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How about the underground pressure tank energy storage project (which stores water pressurized by air) ? Might be worth the waste heat: Hydraulics 101 with real hydra. |
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Or, if there's such a thing as a temperature sensitive dessicant, put an inch of that on the fields, water it at night when it's cool and the substance soaks up water, then during the day the heat causes it to unhydrate into the soil. |
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Meanwhile //1/9 the price//, seriously ? Sounds like an opportunity for battery farms. Or something sneaky and Escheresque with the water-gas reaction. |
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Pressure generated by tension of the balloon would be inverse cube, in a perfect world. You would get far less than that in the real world, and even less so as you scale up. Far better to store electrical potential energy as per link above. |
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