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a spencerator 28 feb 2005 a fridge can be a large winter load for an off-grid pv house... nrel says the average daily november temp in massena ny is 35.3 f, with an average daily min of 27.7. december has 20.2 f and an 11.7 min. january has 14.3 and 4.3. february has 16.5 and 6.5. march has 28.3 and a 19.1 f min. a 2'x2'x8' tall r20 34 f fridge in a 70 f room needs (70-34)80ft^2/r20 = 136 btu/h or 3456 btu/day of coolth, or 17,280 btu for 5 days, which might come from at least 17280/144 = 120 pounds of ice in an outdoor box, with a large water tray with a copper pipe in the freezer compartment, with free airflow to the fridge below and a liquid thermosyphoning loop to move coolth in from the box. can the loop stop working before it freezes the fridge contents? the ice box might be 2'x2'x8' tall, with a 55 gallon drum packed with 100 2 liter water bottles surrounded by an antifreeze solution thermosyphoning through an old 800 btu/h-f auto radiator above with an 8' chimney above. cold air might enter the radiator and flow out at the top of the chimney. with 800 btu/h-f of conductance from 32 f water to outdoor air at temp t, (32-t)800 = 3456 btu makes t = 32-3456/800 = 27.7 for 1-hour per day cooling and t = 32-3456/1600 = 29.8 for 2-hour cooling, and so on. the crude tmy2 (typical meteorological year) simulation below indicates that a fridge like this could work for 241 days (2/3) of a typical year in massena, from september 23 through may 22... nick this program makes a "fridge" prep file with the month, day, hour, and dry bulb temp... 10 screen 9:key off:cls 40 line (0,0)-(639,349),,b:xdf=.073:ydf=2.92 50 for tr= 20 to 40 step 10'temp ref lines 60 line (0,349-ydf*(tr+20))-(639,349-ydf*(tr+20)):next 70 open "94725.tm2" for input as #1'nrel tmy2 file name (massena) 80 open "fridge" for output as #2 90 line input#1,s$'read header 100 city$=mid$(s$,8,25) 110 lat=val(mid$(s$,40,2))+val(mid$(s$,43,2))/60 120 lon=val(mid$(s$,48,3))+val(mid$(s$,52,2))/60 130 print#2,city$,lat,lon 140 for h=1 to 8760'hour of year 150 line input#1,s$ 160 month=val(mid$(s$,4,2))'month of year (1-12) 170 day=val(mid$(s$,6,2))'day of month 180 hour=val(mid$(s$,8,2))-.5'hour of day 190 n=1+h/24'day of year (1 to 365) 200 tdb=val(mid$(s$,68,4))*.18+32'dry bulb temp (f) 230 pset(xdf*h,349-ydf*(tdb+20)) 470 print#2,month;day;hour;tdb 480 if day=1 and hour=.5 then line (xdf*h,349)-(xdf*h,345)'tick months 490 next h here's the start of the fridge file... massena ny 44.93334 74.85 1 1 .5 24.98 1 1 1.5 24.98 1 1 2.5 24.98 1 1 3.5 26.06 1 1 4.5 26.06 1 1 5.5 19.94 1 1 6.5 15.98 1 1 7.5 10.94 1 1 8.5 8.959999 1 1 9.5 6.979999 1 1 10.5 6.979999 1 1 11.5 6.079999 1 1 12.5 6.079999 1 1 13.5 6.079999 1 1 14.5 6.979999 1 1 15.5 6.979999 1 1 16.5 6.079999 1 1 17.5 1.939999 1 1 18.5 -2.020001 1 1 19.5 -2.920002 1 1 20.5 -4.000002 1 1 21.5 -4.000002 1 1 22.5 -.9400013 1 1 23.5 -.9400013 .... this program simulates a typical year... 10 screen 9:key off:cls 20 daystart=0'display start time (days) 30 ds=daystart*24'display start time (hours) 40 range=8760'display range (hours) 50 line (0,0)-(639,349),,b:xdf=640/range:ydf=2.69 60 for tr=-30 to 30 step 10'temp ref lines 70 line (0,349-ydf*(tr+30))-(639,349-ydf*(tr+30)):next 80 open "fridge" for input as #1:line input#1,h$ 90 for h=1 to 8760'hours of typical (tmy2) year 100 input#1,month,day,hour,tdb'read fridge file 110 if tdb |
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