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re: using well water as a storage medium
29 oct 1996
todd hoff wrote:
>does it make any sense to use well water as an energy
>storage medium rather than batteries? if we have enough
>water, and assuming the water can be reused, it would
>seem we could use the solar energy or wind to pump the
>water up a hill or something and recover the energy
>by flowing the water down.
curious how when people say "energy" around here, they so often mean
"electrical energy."
let's see... 1 hp is 746 watts, or 550 ft-lb/s, so a watt is about
1 foot-pound per second. a cubic foot of water falling 1'/s is about
50 watts, or holds 50 watt-seconds, or about 0.01 wh, if it can fall 1'.
so storing 1 wh requires about 100 ft^3 of water that can fall 1' or
10 ft^3 that can fall 10' or 5 ft^3 that can fall 20'. and we might
store 1 kwh by lifting 5,000 ft^3 of water 20'.
a frugal house consuming 500 kwh/month of electricity uses an average of
700 watts, ie 14 ft^3-ft/sec or 112 gallon-ft/sec or 6720 gpm-ft, eg 5 gpm
flowing down a 1,300 foot frictionless garden hose... this needs a bigger
hose, especially if someone turns on a toaster or a hair dryer, or both.
we might store a day's electrical energy consumption for a house, ie 17 kwh,
in a roof pond, by pumping 85,000 ft^3 of water up 20', eg an 85 ft deep roof
pond on top of a 32x32' house, with an extra water roof load of 3,000 tons,
ie 5,000 lb/ft^2, vs 50 lb/ft^2 for a plain old house.
we could store the same amount of solar energy as heat, in 3 plastic 55
gallon drums or 30 plastic 5 gallon drywall compound buckets (with lids)
full of 130 f water that can cool to 80 f. 55 gallon drums are about 3' tall
and 2' in diameter, and weigh about 15 pounds when empty. drywall buckets
have larger surface to volume ratios and they are easier to transport,
since they nest.
this artificial use of the sun seems more efficient than using the natural
solar process to evaporate water that falls as rain that runs down into a
lake with a dam and a generator, to heat houses electrically.
nick
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