[Greenbuilding] An annotated St. Louis TMY2 simulation

Tue Jan 18 11:09:05 CST 2011

If you want send me an email off line and I will send you the chapter in my textbook. 
All of this is available in basic physics and engineering texts but is not often summarized nicely. 

Sent from my BlackBerry®

-----Original Message-----
From: Johannes Martinez <johannes.martinez at gmail.com>
Sender: greenbuilding-bounces at lists.bioenergylists.org
Date: Tue, 18 Jan 2011 10:17:13 
To: Green Building<greenbuilding at lists.bioenergylists.org>
Reply-To: Green Building <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] An annotated St. Louis TMY2 simulation

Hi Nick, i wonder if there's a reason you didn't include losses through
the floor, is that usually negligible?  I don't seem to remember any
well insulated floors where i've lived in canada. 

Do you have a helpful resource for all the formulas you use, or do you
just have them all memorized?

I'm looking to build a 3d house construction and simulator in lisp.  Not
having to google for everything would be a godsend.  Most useful would
be if there's a free database of construction materials and their
properties.

I could cull some from your code, but my eyes start to go wonky after
staring at basic for a while, too many repressed memories of typing in
increasingly more difficult to comprend, obfuscated basic code until it
evolved into reams of hexadecimal...you know you've gone to far when you
can start recognizing opcodes.

Thanks,
Johannes

On Tue, 2011-01-18 at 09:06 -0500, nick pine wrote:
> Here's a basic simulation for a 40'x60' house with 96 ft^2 of U0.25
> windows and R30 walls and an R40 ceiling using NREL's TMY2 hourly
> weather data file for a Typical Meteorological Year in St. Louis.
> 
> The first few lines set up the screen to allow
> displaying hourly temperatures during the year.
> 
> 20 CLS:SCREEN 9:LINE (0,0)-(639,349),,B
> 30 TMIN=0:TMAX=140:V=350/(TMAX-TMIN)'vertical scaling
> 40 FOR TR=0 TO TMAX STEP 20'plot temp ref lines
> 50 LINE (0,349-V*(TR-TMIN))-(639,349-V*(TR-TMIN)):NEXT
> 60 DS=0:DE=365'start and end display days
> 70 HS=24*DS:HE=24*DE'start and end display hours
> 80 XSF=640/(HE-HS)'horizontal scaling factor
> 
> The next few lines describe the house, thermally-speaking.
> 
> 90 L=60'house length (ft)
> 100 W=40'house width (ft)
> 110 AWIND=96'window area (ft^2)
> 120 UWIND=.25'window U-value (Btu/h-F-ft^2)
> 130 GWIND=AWIND*UWIND'window conductance (Btu/h-F)
> 140 AWALL=8*2*(L+W)-AWIND'wall area (ft^2)
> 150 RWALL=30'wall R-value (h-F-ft^2/Btu)
> 160 GWALL=AWALL/RWALL'wall conductance (Btu/h-F)
> 170 RCEIL=40'ceiling R-value
> 180 GCEIL=L*W/RCEIL'ceiling conductance (Btu/h-F)
> 190 GH=GWIND+GWALL+GCEIL'house conductance (Btu/h-F)
> 200 CH=7000'inherent house capacitance (Btu/F)
> 
> An 8'x48' patch of solar siding and a 1075 gallon tank
> can provide 100% of the house heat in a typical year:
> 
> 210 AHA=384'air heater area (ft^2)
> 220 CW=1075*8.33'warm store capacitance (Btu/F)
> 230 CFM=1000'fan cfm
> 240 RAH=2/AHA+1/CFM'air heater equivalent resistance
> 250 TW=110'initial warm store temp (F)
> 260 TH=70'initial house temp
> 270 TAMIN=100'initialize min outdoor temp (F)
> 280 FOR YEAR=1 TO 2
> 290 AHMIN=1000'min house temp (F)
> 300 NCD=-1'initialize # Nov cloudy days
> 310 OPEN "stlyear" FOR INPUT AS #1:LINE INPUT#1,H$
> 320 FOR H=1 TO 8760'TMY2 hours
> 
> Here's a fundamental simulation step: read the hourly
> outdoor temp and find the house heat loss and adjust
> the house temperature, based on its heat loss and
> thermal mass: IdeltaT = CdeltaV, in electrical terms...
> 
> 330 INPUT#1,MONTH,DAY,HOUR,TA,WIND,TDP,SH,SS,SW,SN,SE
> 340 IH=(TH-TA)*GH'house heat loss (Btu/h)
> 350 TH=TH-IH/CH'new house temp
> 360 TTA=TA+2*.8*SS'Thevenin equivalent air heater temp (F)
> 
> A night setback allows the inherent house mass to store
> overnight heat from solar-warmed air. Without the setback
> the house could not store any heat, so the tank and its
> water heater would have to be larger.
> 
> 370 IF HOUR<6 OR HOUR>22 THEN TT=60 ELSE TT=70'target temp
> 380 QHEAT=(TT-TH)*CH'house heating need
> 390 IF QHEAT<0 THEN QHEAT=0:GOTO 510'house needs no heat. Charge 
> store?
> 400 IF TTA<TH GOTO 460'no ss heat available. Warm house with store?
> 410 IF TTA-QHEAT*RAH-TH<0 GOTO 430'partial sunspace heating
> 420 TH=TT:GOTO 510'full sunspace heating
> 430 IA=(TTA-TH)/RAH'partial sunspace heating (Btu/h)
> 440 TH=TH+IA/CH'new house temp
> 450 QHEAT=(TT-TH)*CH'heat required to reach target temp
> 460 AWARM=(TW-TH)*CW'available warmstore heat
> 470 IF AWARM<0 THEN GOTO 510'no warmstore heat available
> 480 IF QHEAT<AWARM THEN TH=TT:SHEAT=QHEAT:GOTO 500'full target heating
> 490 TH=TH+AWARM/CH:SHEAT=AWARM'partial target heating
> 500 TW=TW-SHEAT/CW'new warmstore temp (F)
> 510 IF TTA-QHEAT*RAH<TW GOTO 560'no heat available for warmstore
> 520 QWARM=(140-TW)*CW'warmstore heating need (Btu)
> 530 IF QWARM<0 GOTO 560'warmstore needs no heat
> 540 IW=(TTA-QHEAT*RAH-TW)/RAH'warmstore charging (Btu/h)
> 550 IF IW<QWARM THEN TW=TW+IW/CW ELSE TW=140'new warmstore temp
> 560 IF TH<AHMIN THEN AHMIN=TH'min house temp (F)
> 570 IF H>HE OR YEAR=1 GOTO 690
> 
> Defining a cloudy day as "one with less than 50% of average sun,"
> ie less than 510 Btu/ft^2, this St. Louis TMY2 file contained
> 11 cloudy days in November of 1979...
> 
> 580 IF MONTH<>11 GOTO 620
> 590 IF DAY=LDAY THEN ST=ST+SS:GOTO 620'accumulate daily solar energy
> 600 LDAY=DAY:STT=ST:ST=0
> 610 IF STT<510 THEN NCD=NCD+1'count November cloudy days
> 620 X=(H-HS)*XSF'horizontal screen coordinate
> 630 PSET(X,349-V*(TA-TMIN))'plot ambient temp
> 640 IF TA<TAMIN THEN TAMIN=TA
> 650 'PSET(X,349-V*(SS/4-TMIN))'plot south sun
> 660 PSET(X,349-V*(TH-TMIN))'plot house temp
> 670 'PSET(X,349-V*(TW-TMIN))'plot warm temp
> 680 IF DAY=1 AND HOUR=.5 THEN LINE (X,349)-(X,345)'mark months
> 690 NEXT H
> 700 CLOSE #1
> 710 NEXT YEAR
> 720 PRINT "2000'";CH,AHA,GH,TAMIN
> 730 PRINT "2010'";CW,TW,AHMIN,NCD
> 
> 7000     384           134.1333     -4.000127E-02
> 8954.75                109.2637      60            11
> 
> This simple simulation can be refined further with heat gain
> from indoor electrical use, direct solar gain from windows,
> slab heat loss, ventilation heat loss, and DHW preheating
> with a pressurized plastic pipe coil in the tank.
> 
> Nick 
> 
> 
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