|
Seasonal storage in Ireland
QUESTION:Seasonal storage in Ireland
I've been looking into a large standalone circular water tank with
a draindown solar collection pond on top to store enough fall solar
heat to keep a house warm for a long cold very cloudy Irish winter.
The cylinder might be an 18' diameter x 18' tall low-cost ferrocement or
plastered-tire cistern, as used in Earthships--eg an 18' tall stack of flat
rings of recycled tires (18'OD x 14'ID) tied together and filled with peat
moss for insulation, with an outer cosmetic layer and a layer of wire mesh
and plaster inside the rings and a simple 15-strut wood geodesic cover
with twinwall polycarbonate faces...
Here's a more detailed calc for a tower with a simple equilateral pentagon
hat dome, with only 5 struts:
10 SCREEN 9:KEY OFF:PI=4*ATN(1)
20 GH=315'house conductance (Btu/h-F)
30 AW=300'south window area (ft^2)
40 FW=.5'window solar transmission fraction
50 ECON=300'indoor electrical energy use (kWh/mo)
60 EGAIN=3412*ECON/30'internal heat gain (Btu/day)
70 IDCYL=14'cylinder id (feet)
80 WCYL=2'cylinder wall thickness (feet)
90 HCYL=IDCYL+2*WCYL'cylinder height and OD (feet)
100 ACOV=PI*(IDCYL/2)^2'cover area (ft^2)
110 VCYL=ACOV*HCYL'cylinder volume (ft^3)
120 CCYL=62.33*VCYL'cylinder heat capacitance (Btu/F)
130 DCYL=IDCYL+WCYL'average cylinder diameter (feet)
140 AWALL=PI*DCYL*HCYL'average wall area (ft^2)
150 RWALL=3*12*WCYL'US R-value of wall (F-h-ft^2/Btu)
160 GWALL=AWALL/RWALL'cylinder wall conductance (Btu/h-F)
170 RCOV=30'US R-value of cover (F-h-ft^2/Btu)
180 GCOV=ACOV/RCOV'cover thermal conductance (Btu/h-F)
190 RDOME=2'US R-value of dome glazing (F-h-ft^2/Btu)
200 TDOME=.8'solar transmission of dome glazing
210 ADOME=PI*(HCYL/2)^2'dome surface (ft^2)
220 TW=170'initial water temp (F)
230 DATA 14.5,25,3597,12.8,20.2,2472,10.3,16.5,1607,6,12.6,849
240 DATA 6.2,13,469,5.1,13.1,689,4.6,14.7,1186,7,13.8,2199
250 FOR M=1 TO 8'Read August through March Energy Plus averages for Birr
260 READ TAVG,TMAX,IGLOH'metric temps and sun
270 TAVG=32+1.8*TAVG'24-hour average temp (F)
280 TMAX=32+1.8*TMAX'average daily max temp (F)
290 TDAY=(TAVG+TMAX)/2'est. daytime temp (F)
300 IGLOH=3.41*IGLOH/10.76'global sun on ground (Btu/ft^2-day)
310 HDAY=IGLOH/200'solar collection time (hours/day)
320 SGAIN=TDOME*ADOME*IGLOH-HDAY*(TW-TDAY)*ADOME/RDOME'net gain (Btu/day)
330 CLOSS=24*(TW-TAVG)*GWALL+(24-HDAY)*(TW-TAVG)*GCOV'net loss (Btu/day)
340 DHEAT=24*(65-TAVG)*GH'required house heat (Btu/day)
350 WGAIN=AW*FW*165/148*IGLOH'window solar gain (Btu/day)
360 SHEAT=DHEAT-WGAIN-EGAIN'required stored heat (Btu/day)
370 IF SHEAT<0 THEN SHEAT=0'no stored heat required
380 CGAIN=30*(SGAIN-CLOSS-SHEAT)'cylinder gain (Btu/month)
390 TW=TW+CGAIN/CCYL'new water temp (F)
400 IF TW>170 THEN TW=170'limit upper water temp
410 PRINT 600+M;"'";TAVG,IGLOH,SHEAT,TW
420 NEXT M
430 DTIRE=2'tire diameter (feet)
440 NTR=INT(PI*DCYL/DTIRE+.5)'approx number of tires per ring
450 HTIRE=.5'tire height (feet)
460 NR=INT(HCYL/HTIRE+.5)'approx number of rings
470 NT=NTR*NR'approx number of tires
480 PRINT 609;"'";NTR,NR,NT
490 THETA=36/180*PI'dome central half-angle (radians)
500 S=HCYL*SIN(THETA)'dome strut length (feet)
510 GH=S*COS(30/180*PI)'glazing height (feet)
520 GL=2.5*GH'total glazing length (feet)
530 GA=GH*GL'dome glazing area (ft^2)
540 DH=S*SQR(1-1/(2*TAN(THETA))^2)'dome height (feet)
550 PRINT 610;"'";S,DH
560 PRINT 611;"'";GH,GL,GA
outdoor horiz sun house heat stored water
month temp (F) (Btu/ft^2) (Btu/day) temp (F)
Aug 58.1 1139.942 0 170 | During these months
Sep 55.04 783.4127 0 170 | the house gets enough
Oct 50.54 509.2816 0 170 | heat through windows.
Nov 42.8 269.0604 88717.11 151.27
Dec 43.16 148.6329 106134.6 128.51
Jan 41.18 218.3541 109443.9 108.93
Feb 40.28 375.8606 89908.1 99.18
Mar 44.6 696.895 3562.5 115.61
tires per ring rings tires
25 36 900
dome strut dome height
10.58014 feet 7.676202 feet
dome glazing dome glazing dome glazing
height (feet) width (feet) area (ft^2)
9.162666 22.90667 209.8861
With 15 struts, we might increase the dome height to 7.67+10.58cos(30)
= 16.8 feet, which would make it more interesting for people.
Earthships plaster wire mesh inside their tire cisterns. As an alternative,
we might waterproof this one with 2 pieces of EPDM rubber, an 18' diameter
disk on the ground and an 18' tall x 44' perimeter skirt around the ID, over
several layers of welded wire fence, with a ring on the ground to join them.
ANSWER: Q: I've been looking into a large standalone circular water tank with
a draindown solar collection pond on top to store enough fall solar
heat to keep a house warm for a long cold very cloudy Irish winter.
A: I'm far from an expert in these things but wouldn't it be easier and
cheaper to build a very large solar collector and store a couple of
days worth of heat than a couple of months?
Q: The cylinder might be an 18' diameter x 18' tall low-cost ferrocement or
plastered-tire cistern, as used in Earthships--eg an 18' tall stack of flat
rings of recycled tires (18'OD x 14'ID) tied together and filled with peat
moss for insulation, with an outer cosmetic layer and a layer of wire mesh
and plaster inside the rings and a simple 15-strut wood geodesic cover
with twinwall polycarbonate faces...
A: Are you suggesting a water tank 14 feet in diameter and 18 feet
tall? Have you done any kind of engineering estimates on that
to see if it can be safely built out of old tires, wire mesh
and plaster as you suggest?
I think, if you must have a thermal cistern, that it would be
easier and cheaper to build if it was not as tall. It would
be even easier if it was built out of prefabricated components.
Say, a quonset hut style steel building insulated on the inside
with spray-on foam and containing one or more above ground
swimming pools.
|
|
|
|
