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re: solar storage tank design
26 mar 1997
tvoivozhd wrote:
>...don't even think about a wooden tank.
plywood tanks lined with epdm rubber have been used for off-peak storage in
electric resistance house heating systems for years. sven tjernagel of stss
(477 woodcrest drive, mechanicsburg, pa 17055, usa) started making something
like tallish prefabricated steel circular swimming pools lined with epdm and
foam when ul wouldn't approve site-built plywood tanks. (sven built hundreds
of 10x20' solar collectors out of epdm rubber bladders as well.)
>go to the local library and have the librarian get on interlibrary
>loan the two ken kern (deceased) books on "owner-built home" and
>"owner-built homestead". much cheaper, much better, much easier...
perhaps not, for a 1000 gallon tank inside an existing garage.
>...think about using a phase-change material like glauber's salt...
from what i've read, glauber's salts get tired of changing phase after a few
hundred cycles, and have to be mechanically stirred up, or something, to help
them keep working. corrosion, cost and getting enough thermal mass surface
area for charging with solar-warmed air without lots of electrical power for
fans and blowers can also be problems. and i've read that phase change waxes
catch fire, and often need to be stored outdoors, building-code-wise...
>...i've forgotten the math, but phase-change materials occupy a lot smaller
>space than liquids---l/l0th?, l/20th?----and size of installation translates
>directly to cost.
how about water phase change in a lithium chloride solution? cypress-foote
mineral sells licl for about $4/pound, and it can absorb 12x its weight in
water, at 1000 btu/lb vs about 50 btu/lb for sensible water heat storage, so
100 lb might store 1 million btu for a cloudy week, in a house with lots of
internal thermal mass and external insulation, which can keep itself warm
with a low-thermal-mass sunspace for 24 hours over an average winter day,
with an average amount of sun. put a solar still in the sunspace, store
concentrated licl in 2 uninsulated plastic 55 gallon drums in the house, and
let the licl somehow absorb water from a damp basement floor or an indoor lawn
as it evaporates with ground-coupled heat on a cloudy day?
then again, an all-masonry house with exterior insulation can have an rc time
constant of several weeks (and 1/3 the fire insurance rate), so all it needs
is a low-thermal-mass sunspace with lots of glazing, which gets cold at night.
who needs more thermal storage?
nick
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