[Greenbuilding] refrigerators (again) and the use of outside air

[Nick Pine]

molasses at speakeasy.net cites:

http://www.blog.thesietch.org/2007/05/31/an-obviously-good-idea-save-money-save-energy-freeaire/

... $5K seems like a lot to retrofit a walk-in cooler with no coolth 
storage.

Using NREL's TMY2 ("Typical Meteorological Year") hourly
weather data file for Philadelphia, one of 239 US cities listed at

http://rredc.nrel.gov/solar/old_data/nsrdb/tmy2/

10 OPEN "tmycool" FOR INPUT AS #1
30 FOR H=1 TO 8760'read ambient temperature every hour for a year
40 LINE INPUT#1, S$'input a line from the TMY2 file
50 TEMP=VAL(MID$(S$,27,4))'ambient temp (F)
60 ATEMPT=ATEMPT+TEMP'accumulate average yearly temperature
70 IF TEMP < 32 THEN FDHT=FDHT+32-TEMP'accumulate freezing degree-hours
80 IF TEMP > 32 THEN MDHT=MDHT+TEMP-32'accumulate melting degree-hours
90 NEXT H
100 PRINT "average yearly temperature:";ATEMPT/8760
110 PRINT "freezing-degree days:";FDHT/24
120 PRINT "melting-degree days:";MDHT/24
130 CLOSE 1

average yearly temperature: 53.62591 F,
freezing-degree days: 339.4584, and
melting-degree days: 8232.917,

like heating and cooling degree days (F) for 32 F houses. The number of
"freezing degree days" (FDD) is the number of days with an outdoor temp
Ta less than freezing, times (32-Ta).

More FDDs make icemaking easier. If 144 Btu can freeze a pound of
water at 32 F and an outdoor surface has a still airfilm conductance of
2 Btu/h-F-ft^2 and a cubic foot of water weighs 62.33 pounds, we can
freeze an ice layer 339x24hx2/(144x62.33) = 1.8' thick on a specially-
designed icemaking pond in Phila, or maybe 3.6' thick, if outdoor air
can also flow under the pond.

More MDDs make icehouses bigger. An L' cube inside R40 insulation
can store 8976L^3 Btu. A yearly gain of 24hx8233x6L^2/R40 Btu
in Phila over a year makes the minimal L = 3.3'.

We might make an 8'x8'x4' thick 256 ft^3 water wall inside an 8'x8'x10'
ID outdoor walk-in cooler with welded-wire mesh and 2x4 shelves under
plastic film 55 gallon drum liners, like Anna Edey used for solar heat
storage in her Cape Cod Solviva greenhouse.

A 256ft^3/1.8' = 142 ft^2 roofpond might freeze the wall, eg a 10'x14'x1"
thermosyphoning saltwater pond under IR-transparent polyethylene film.
Winter winds and night sky radiation would cool the pond more, as would
evaporation, without the poly film to keep it clean. We might increase
the saltwater-wall conductance with some 4" vertical thinwall saltwater
PVC pipes going down through the wall.

This might provide 6'x8'x8' = 384 ft^3 of year-round useful refrigerated
space inside the box, like 20 home fridges. Is it time for neighborhood
icehouses yet? Filled with beer for apres-lawn-mowing-male-bonding?
And what will we do about lawns, after the oil runs out?

Nick