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re: parabolic energy storage.
4 sep 2000
graham cowan wrote:
>cnmcdee@my-deja.com wrote:
>> has anyone experimented with parabolic energy storage?
maybe you mean "parabolic solar heat collection."
>how many watts of heating load did you treat the house as?
good question. a typical(?) 20 c house with 150w/c of thermal
conductance needs 24h(20c-(-1c))150w/c = 75.6 kwh (258k btu)
of heat on an average -1 c day where i live near philadelphia.
>> if you used a 9ft reflective dish tracking the sun, focusing
>> its energy on a hollow copper block with a glycol/water fluid
>> flowing through it, that you should be able to met about 50%
>> to 70% of a houses heat energy need.
a 9 foot (5.9 m^2) dish with a 90% reflector and no heat loss at all
would collect 0.9x2.7kwh/m^2x5.9m^2 = 14.4 kwh of direct beam sun on
an average january day, according to nrel data, ie about 19% of that
typical house heating need.
a 10m reflective solar trough attic with a 5 m peak (33'x16' tall)
might provide 0.8x2.3x10x5 = 92 kwh, closer to the daily heat need.
>> a large resevoir tank i estimated would have to be used, and
>> this resevoir tank would have to be heavily insulated, and
>> hold about 500+ gallons or so.
a 500 gallon 200 f tank cooling to 80 f would store 500x8(200-80)
= 480k btu, enough for 1.9 cloudy days in a row; 5 days is better.
(sun only shines about 50% of the time where i live, so the chance of
1.9 cloudy days in a row is about 0.5^1.9 = 0.27, vs a 0.5^5 = 0.03
probability of 5 cloudy days in a row.) those large cheap ($400)
poly 1500 gallon tanks can only stand 120 f, so you might use
5dx258k/(1500x8(120-80)) = 3 of them.
nick
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