archdruid gets it wrong!!!

[Nathan Hurst]

I wrote a lovely comment correcting the misconceptions on
http://thearchdruidreport.blogspot.com/ this week. I explained
patiently about film dampers, about trombe wall failings, how to model
performance using 'typical year weather data', the problem with
concrete in the living room and how to take his ideas and make a cheap
and workable system. Oh, and that he should read builditsolar.com.

And blogger ate my post. I will have words to them on monday. But in
the meantime I can't be bothered retyping it all and thus hand the
baton to the sunspace group.

njh

[Don Hull]

I am a ground source heat pump contractor. You may be interested to know that a well designed passive solar home should have a cooling demand of about one ton. This can be installed for under $10,000.00. Take your fed. tax credit and PECO incentives and your looking at under $7000.00. Throw in a desuperheater and a heat pump hot water heater and you are still under $9000.00. Duct work not included.

 

Don Hull

Ground Source HVAC

610 306 6245

--
Donald Hull
Geothermal Specialist
Ground Source HVAC
610-306-6245
groundso...@gmail.com
www.groundsourcehvac.com
Call When You're Serious About Saving Energy

[CJE]

That seems like a pretty definite statement. By what means, other than the reduction in square area, do you get the summer heat gain to less than 12,000 BTU's per hour?

How big is "a well designed solar house"? And what state/country is it located in?

stephen
-----------

[nick pine]

Nathan Hurst <n...@njhurst.com> wrote:

> I wrote a lovely comment correcting the misconceptions onhttp://thearchdruidreport.blogspot.com/this week. I explained

> patiently about film dampers, about trombe wall failings, how to model performance using 'typical year weather data',

Terri and I just got started on modeling houses in Excel with 8760
lines of hourly TMY3 weather data. Seems doable.

> concrete in the living room and how to take his ideas and make a cheap
> and workable system. Oh, and that he should read builditsolar.com.
>
> And blogger ate my post. I will have words to them on monday. But in
> the meantime I can't be bothered retyping it all and thus hand the
> baton to the sunspace group.

You don't have a "sent items" folder? You would spend your whole life
correcting
ignorance, vs plowing ahead? Allez en avant, et les foies vous
viendront.

Don Hull wrote:

> I am a ground source heat pump contractor. You may be interested to know that a well designed passive solar home should have a cooling demand of about one ton. This can be installed for under $10,000.00. Take your fed. tax credit and PECO incentives and your looking at under $7000.00. Throw in a desuperheater and a heat pump hot water heater and you are still under $9000.00. Duct work not included.

Off-topic blatent commercialism is worse than ignorance, Don. Your
days in this group may be numbered.

CJE <cjec...@verizon.net> wrote:

> That seems like a pretty definite statement.  By what means, other than the reduction in square area, do you get the summer heat gain to less than 12,000 BTU's per hour?
>
> How big is "a well designed solar house"?  And what state/country is it located in?

Good questions. Solar heating fractions of passive mass and glass
houses near Phila rarely exceed 50%, no matter how well designed.
A house with a low-mass sunspace and lots of thermal mass inside
insulation and airtightness can do 90% or more.

My TMY2 simulations say smart night ventilation can make brick row
houses in Phila comfortable (T<80 F and w<0.012) for all but 2 weeks
in a typical year (ceiling fan times), without gas-passing or
steenkeeng tax credits. Warm air rises. Turn on a fan or open a 2-watt
damper when outdoor air is cooler than indoor air on an average 76.7 F
July day with a 67.2 night min and outdoor humidity ratio w = 0.0133
pounds of water vapor per pound of dry air.

Nick

[nick pine]

> Warm air rises. Turn on a fan or open a 2-watt damper when outdoor air is cooler than indoor air on an average 76.7 F July day with a 67.2 night min...

An 80 F house with 2 A ft^2 windows with a 24' height difference and a
plastic film damper could lose 12K Btu/h if it's 67.2 F outdoors and A
= 12K/(16.6sqrt(24)(80-67.2)^1.5) = 3.2 ft^2, with a $1 investment and
an infinite COP.

Nick

[Nathan Hurst]

On Sat, Apr 09, 2011 at 05:35:50AM -0700, nick pine wrote:
> Nathan Hurst <n...@njhurst.com> wrote:
>
> > I wrote a lovely comment correcting the misconceptions onhttp://thearchdruidreport.blogspot.com/this week. I explained
> > patiently about film dampers, about trombe wall failings, how to model performance using 'typical year weather data',
>
> Terri and I just got started on modeling houses in Excel with 8760
> lines of hourly TMY3 weather data. Seems doable.

Certainly, although harder to maintain I would expect.

> > concrete in the living room and how to take his ideas and make a cheap
> > and workable system. Oh, and that he should read builditsolar.com.
> >
> > And blogger ate my post. I will have words to them on monday. But in
> > the meantime I can't be bothered retyping it all and thus hand the
> > baton to the sunspace group.
>
> You don't have a "sent items" folder?

Not for blog comments.

> You would spend your whole life correcting ignorance, vs plowing
> ahead? Allez en avant, et les foies vous viendront.

Ha! You can talk! I thought it was mildly worthwhile as
thearchdruidreport has a few thousand readers who are interested in
solar heating. Better payoff than arguing on usenet :)

njh

[nick pine]

> Ha!  You can talk!  I thought it was mildly worthwhile as
> thearchdruidreport has a few thousand readers who are interested in
> solar heating.  Better payoff than arguing on usenet :)

OKOK. I attempted to add the following Archdruid comment. Dunno if it
worked...

>In most areas, given a decent southern exposure, a house designed for passive solar heating, and adequately insulated and weatherized to make best use of it, requires little or no heating other than what the sun provides.

But cloudy days are like coin flips. A house that can only store
enough heat for 1 cloudy day can be at most 50% solar-heated... 2 days
make 75% possible... 5 days are like flipping 5 tails in a row with a
3% probability and a possible 97% solar heating fraction. Mass and
glass "direct loss" passive solar houses with windows on living spaces
lose lots of heat on cloudy days. TAPs and low-mass sunspaces lose
little.

>A TAP is a wide, flat box with glass on the front, insulation on the sides and back, and a sheet of metal running parallel to the glass, with a couple of inches of air space between metal and glass.

This is more efficient and cost-effective with corrugated
polycarbonate glazing vs glass and dark window screen vs metal. Cool
house passes into the space between the screen and the glazing and
only gets heated as it rises and passes from south to north through
the glazing. THe back wall of the box is an insulated house wall. See
http://www.builditsolar.com/Projects/SpaceHeating/SolarBarn.pdf

>The downside is that the heat goes away as soon as the sun does, and at night, the thermosiphon effect can work in reverse – hot air gets sucked in the top, flows over the chilly metal, and emerges as an icy breeze at floor level. Thus a TAP needs valves to cut off the air flow when the sun goes away;

Note the passive one-way plastic film damper at the top of the diagram
on page 32 above.

>To balance the quick but unsteady heat of a TAP system, you need another system that soaks up heat whenever the sun is out, and distributes it to the house in a steadier manner throughout the day and night. The key to getting this effect is thermal mass... most passive solar systems use plenty of thermal mass to soak up the sun’s heat in the daytime, and radiate it all night.

But if we live inside the heat battery, the mass can't be very hot, so
it can't store much heat, compared to a tank full of hot water. And
living space mass near windows loses lots of heat back out through the
windows on cloudy days.

>What’s a trombe wall? Basically, it’s a wall-sized TAP with thermal mass rather than a metal sheet inside the glass...

EXTREMELY inefficient, since it loses lots of heat back out through
the glazing at night. Much better to put the mass inside the house, on
the other side of an insulated low-mass wall.

>The next step up from the trombe wall, and one of the most widely used and thoroughly tested of the passive solar retrofit technologies, is the attached solar greenhouse. You build this onto the south or southeast face of your house, sealing it up tight so that air doesn’t leak in or out, and put a trombe wall between the greenhouse and the rest of the house;

Nice, without the Trombe wall.

>Quite a few experiments were made with active solar space heating – that is, systems that collect heat from the sun and then pump it somewhere else. It can be done, but because of the diffuse nature of solar heat, the efficiencies are low, and you very quickly end up using (and losing) more energy in the process than you gain by it.

This one collects at least 30 times more energy than it uses:
http://www.builditsolar.com/Projects/Sunspace/LowCostHtStorageNathan.pdf

Nick

[Don Hull]

Keep gain down by using something like attic radiant film as movable radiant insulation. Open it in the night and close in the day. In the winter reverse.

 

d.

[Gary Burk]

Don Hull mentions using both a ground source heat pump and a heat pump water heater.  What's the economics of operating a heat pump water heater

to extract heat supplied by the space heating ground source pump?   Unlike a de-superheater, which uses heat that is "almost" free,  this seems like a lot of expensive

hardware to replace an admittedly expensive-to-operate but cheap and simple resistance heater.    Of course during warm weather, the  heat pump water heater

has access to ambient heat.    

The house I now live in has used ground source heat pumps since I built it in 1987.  Both pumps feed from always 53.5F well water.  The main unit, a 49,000 BTU Water Furnace has now run for 23 years without servicing, and remains quiet and efficient.  ( I do flush it yearly with "Iron-Out" ).  The 12,000 BTU Water Furnace auxiliary unit, a more modern design with a rotary compressor, has been an expensive

pain, now being on its 3rd compressor and 2nd evaporator heat exchanger.  Warranties paid for some, but not all of that hassle.

GaryB

---

Date: Sun, 10 Apr 2011 08:19:45 -0400
Subject: Re: archdruid gets it wrong!!!
From: groundso...@gmail.com
To: suns...@googlegroups.com

[CJE]

When you calculate your operating costs do you include pumping costs?

And it is still the same well pump from 1987?

If you have fairly specific use-timing hot water use, and control the resistance water heater with a timer, the operating costs do not seem to be high. I would find it hard to believe it cost effective to produce hot water with a heat pump system. Of course I have been wrong before and would enjoy that being shown to me. <g>

Can you list the details of the failures with the newest WF heat pump?

stephen
----------

On Apr 10, 2011, at 8:42 AM, Gary Burk wrote:

Don Hull mentions using both a ground source heat pump and a heat pump water heater. What's the economics of operating a heat pump water heater
to extract heat supplied by the space heating ground source pump? Unlike a de-superheater, which uses heat that is "almost" free, this seems like a lot of expensive
hardware to replace an admittedly expensive-to-operate but cheap and simple resistance heater. Of course during warm weather, the heat pump water heater
has access to ambient heat.

The house I now live in has used ground source heat pumps since I built it in 1987. Both pumps feed from always 53.5F well water. The main unit, a 49,000 BTU Water Furnace has now run for 23 years without servicing, and remains quiet and efficient. ( I do flush it yearly with "Iron-Out" ). The 12,000 BTU Water Furnace auxiliary unit, a more modern design with a rotary compressor, has been an expensive
pain, now being on its 3rd compressor and 2nd evaporator heat exchanger. Warranties paid for some, but not all of that hassle.

GaryB

Date: Sun, 10 Apr 2011 08:19:45 -0400

[nick pine]

Once again, heat pumps are off-topic in this group.

The next person to mention one is outta here.

Nick

[Gary Burk]

CJE,

     Good point!.  I have not included pumping costs, which are significant.  Further, I've replaced the downhole submersible well pump at 15 years and the 120 gallon "Well-XTroll" pressure tank at 18 years.

When we built in 1987, our  5 acres were is an outlying suburban/rural area.  There was commercial water available at a steep price.  We do use that for domestic purposes, but use the well for a heating/cooling source and irrigation purposes of lawn,  vegetable garden and fruit orchard.  In retrospect, I would have saved had I dig a second well for re-injection of the water from the

heat pump and chillers, since the water falling down that pipe would lift the water in the supply pipe.  But, finances were strained and I have a creek flowing 50 feet from the house, so I just dump the heat pump water there.  That creek drains into the same river that the water table I'm tapping does, and even when pumping 25 gals/minute for irrigation, I can't drop the head in the well.

Our newer 12,000 BTU Water Furnace was installed when we built a "4 season" add-on glass room in the woods.   Even though we used pretty good thermal windows, the 500 square foot room with three glass walls is not thermally efficient, so it needs lots of coolling in the summer and heating in the winter.  The 53F well water supplies almost free cooling most of the time in the summer.  If it's over 90 outside, or when we have lots of people here, the compressors do kick in to supplement cooling.  We've never been able to overwhelm this AC, even on one 100F day when we had a large pool party with kids constantly running in and out, the system holds our summer setpoint of 75F.    In the winter, the house setpoint is 73F and the heatpump balance point is at about 3F.  Below that temperature a bank of 15KW resistance heaters join in, 5KW for each 2F below the setpoint.

The newer Water Furnace lost its compressor after 1 year.  It was replaced on warranty without problems.  However, that new compressor failed in its 4th year and Water Furnace would not cover it.  I believe it was $2K or so, I've forgotten.  Three years later the heat exchanger started leaking water - another $2000!   Since then it's been OK  (knock on simulated wood grained formica.)

GaryB
 

> Subject: Gary - Re: archdruid gets it wrong!!!
> From: cje...@verizon.net
> Date: Sun, 10 Apr 2011 10:43:45 -0400
> To: suns...@googlegroups.com

[CJE]

I'm sorry.

I either didn't know that or had forgotten it.

What is the reason for the ban on the device which I now refuse to mention?

stephen
-----------

[Terri E. Booth]

Bravo, Nathan! (hee hee)

[Don Hull]

The heat pump hot water heater dehumidifies as it heats the water. Think of it as ofsetting the refrigerator which is doing the opposit. We use a preheat tank with the desuperheater and then send to water to the HPHW heater at about 95%. So there isn't a lot required of the heat pump in the water heater.

 

Don Hull

[nick pine]

Don Hull <groundsourceh...@gmail.com> wrote:

> The heat pump...

Gary Burk and Don Hull are no longer allowed to post here, altho they
can appeal.

Meanwhilst, my comments haven't shown up on the Archdruid blog yet.

Maybe he's away from his PC and falling behind in comment moderation.

Nick

[CJE]

In their defense Nick: their comments were made before your ban could have been read by them.

Although; being in sequential order; their comments did appear after the ban was posted.

stephen
-----------

[nick pine]

CJE <cjec...@verizon.net> wrote:

> In their defense Nick:  their comments were made before your ban could have been read by them.  

OK. They can post again.

Nick

[Gary Burk]

I don't think I'll post again.   It's not important and I find Nick's attitude annoying.

In any case,  Good Luck to all and I may follow along on the Yahoo groups.

Regards,

     GaryB

> Date: Tue, 12 Apr 2011 04:34:29 -0700

> Subject: Re: archdruid gets it wrong!!!

> From: ni...@early.com
> To: suns...@googlegroups.com

[Don Hull]

What would be the definitive book on passive solar?

 

Don Hull

[CJE]

I kind of like Nick's work but I don't know if he has a book available.

Although; his calculations and writing styles do very often lose me. <g>

stephen
----------

[nick pine]

Don Hull wrote:

> What would be the definitive book on passive solar?

I don't know of a good current book. I use basic high-school physics,
eg Ohm's law for heatflow. My back of the envelope solar house heating
designs start by finding the worst-case month with TMY2 monthly
average data, the one with the least Btu/DD, eg an average 30 F
January day in Phila with 1000 Btu/ft^2 of sun per day on a south wall
and 1000/(65-30) = 29 Btu/DD.

Then I figure cloudy days are like coin flips, so a house that can
store enough heat for 1 cloudy day can be at most 50% solar heated,
with 75% for 2 days... and 97% for 5 days. If a house cools from 70 to
60 F over 5 30 F cloudy days, RC = -5x24/ln((60-30)/(70-30)) = 417
hours. Direct gain doesn't do well... an 8' R32 cube with an 8'x8' R4
window with 50% solar transmission and a G = 26 Btu/h-F conductance
needs C = RCxG = 417x26 = 10.8K Btu/F, eg 2168 8"x8"x16" hollow
concrete blocks inside, 2.5X the cube volume, which doesn't leave much
room for people.

With another R32 wall behind the window, G = 12 on cloudy days,
approximately, with a mere 1001 blocks. If the blocks are under the
ceiling with foil beneath, as in the Barra system, they can be warmer
than 70 F and store more heat. If 8'x8' of R2 air heater glazing with
80% solar transmission collects 0.8x1000x64ft^2 = 51.2K Btu/day =
6h(T-30)64/R2 during the day + 18h(70-30)64/R32 at night + 24h(T-30)64/
R32 for the ceiling + 24h(70-30)4x64ft^2/R32 for the other 4 walls,
then the ceiling mass temp T = 205 F. If it's only 130 because of
radiation loss through the glazing and it can keep the cube 70 F when
it's 80 F and its average temperature is (130+80)/2 = 105 over 5
cloudy days when it loses 120h(105-30)64/R2 = 18K Btu through the
ceiling while the lower part of the cube loses 120h(70-30)5x64/R32 =
48K and 18K+48K = (130-80)C, C = 1320 Btu/F, only 264 blocks or 21.2
ft^3 of water in 4" trays under the ceiling, or a 2.77' 130 F water
cube.

Line 460 below uses thermosyphoning sunspace air with an old empirical
chimney rule: cfm = 16.6Asqrt(HdT), with Btu/h = cfmxdT,
approximately. The warmstore below is a 2'x3'x4' 140 F max water tank
heated and cooled by a 1000 Btu/h-F car radiator with its 2 12V fans,
which use 20 watts in series.

Nick

10 PI=4*ATN(1)
20 CLS:SCREEN 9:LINE (0,0)-(639,349),,B
30 TMIN=-20: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
90 AWWIND=36*60/144'west window area (ft^2)
100 GWWIND=AWWIND/4'west window conductance (Btu/h-F)
110 AWWALL=72-AWWIND'net west wall area (ft^2)
120 GWWALL=GWWIND+AWWALL/33'total west wall conductance (Btu/h-F)
130 GNWALL=90/28'north wall conductance (Btu/h-F)
140 GEWALL=72/28+0/(28+19)'east wall conductance (Btu/h-F)
150 GSWALL=90/33'south wall conductance (Btu/h-F)
160 GCEIL=72/33'ceiling conductance--6"FG + 2"board (Btu/h-F)
170 GH=GWWALL+GNWALL+GEWALL+GSWALL+GCEIL'cube conductance (Btu/h-F)
180 CH=800'cube capacitance--16 9'x4" ceiling pipes (Btu/F)
190 AHA=2*46.5*93/144'air heater area (ft^2)
200 AVA=.5'air heater vent area (ft^2)
210 AVH=(93-4)/12'vent height difference (ft)
220 KT=16.6*SQR(AVH)'thermosyphoning air constant
230 CW=2*3*4*62.33'warm store capacitance (Btu/F)
240 RCFM=1000'radiator fan cfm
250 RAH=2/AHA'air heater equivalent resistance
260 TW=110'initial warm store temp (F)
270 TH=70'initial cube temp
280 TAMIN=100'initialize min outdoor temp (F)
290 FOR YEAR=1 TO 2
300 AHMIN=1000'min cube temp (F)
310 EE=0'initialize electrical energy use (kWh)
320 OPEN "cutyear" FOR INPUT AS #1:LINE INPUT#1,H$
330 FOR H=1 TO 8760'TMY2 hours
340 INPUT#1,MONTH,DAY,HOUR,TA,WIND,TDP,SH,SS,SW,SN,SE
350 IH=(TH-TA)*GH'cube heat loss (Btu/h)
360 TH=TH-IH/CH'new cube temp
370 TTA=TA+2*.8*SS'Thevenin equivalent air heater temp (F)
380 IF HOUR>6 AND HOUR<22 THEN TT=70 ELSE TT=60
390 QHEAT=(TT-TH)*CH'cube heating need
400 IF QHEAT<0 THEN QHEAT=0:GOTO 570'cube needs no heat. Charge warm
store?
410 IF TTA<TH GOTO 500'no ss heat available. Warm cube with warmstore?
420 IF TTA-QHEAT*RAH-TH<0 GOTO 450'partial sunspace heating
430 KTH=QHEAT/(TTA-QHEAT*RAH-TH)^1.5'Kth for full sunspace heating
440 IF KTH<KT THEN TH=TT:GOTO 570'full sunspace heating
450 IAL=0
460 IA=(TTA-TH-(IAL/KT)^(2/3))/RAH'partial sunspace heating (Btu/h)
470 IF ABS(IA-IAL)>1 AND IA>0 THEN IAL=IA:GOTO 460'iterate
480 TH=TH+IA/CH
490 QHEAT=(TT-TH)*CH
500 AWARM=(TW-TH)*CW'available warmstore heat
510 IF AWARM<0 THEN GOTO 570'no warmstore heat available
520 IF QHEAT<AWARM THEN TH=TT:SHEAT=QHEAT:GOTO 540'full target heating
530 TH=TH+AWARM/CH:SHEAT=AWARM'partial target heating
540 TW=TW-SHEAT/CW'new warmstore temp (F)
550 IF MONTH<>12 AND MONTH<>1 GOTO 570
560 EE=EE+.12*SHEAT/(TW-TH)/1000'energy used for pump and fan (kWh)
570 IF TTA-QHEAT*RAH<TW GOTO 640'no heat available for warmstore
580 QWARM=(140-TW)*CW'warmstore heating need (Btu)
590 IF QWARM<0 GOTO 640'warmstore needs no heat
600 IW=(TTA-QHEAT*RAH-TW)/(RAH+1/RCFM)'warmstore charging (Btu/h)
610 IF IW<QWARM THEN TW=TW+IW/CW ELSE TW=140'new warmstore temp
620 IF MONTH<>12 AND MONTH<>1 GOTO 640
630 IF QWARM<IW THEN EE=EE+.12*QWARM/IW ELSE EE=EE+.12'pump+fan energy
640 IF TH<AHMIN THEN AHMIN=TH'min cube temp (F)
650 IF H>HE OR YEAR=1 GOTO 730
660 X=(H-HS)*XSF'horizontal screen coordinate
670 PSET(X,349-V*(TA-TMIN))'plot ambient temp
680 IF TA<TAMIN THEN TAMIN=TA
690 'PSET(X,349-V*(SS/4-TMIN))'plot south sun
700 PSET(X,349-V*(TH-TMIN))'plot cube temp
710 'PSET(X,349-V*(TW-TMIN))'plot warm temp
720 IF DAY=1 AND HOUR=.5 THEN LINE (X,349)-(X,345)'mark months
730 NEXT H
740 CLOSE #1
750 NEXT YEAR
760 PA=1000*EE/2/30/24'average winter fan+pump power (watts)
770 PRINT "2000'";CH,,AHA,GH,TAMIN
780 PRINT "2010'";CW,TW,AHMIN,PA

800 60.0625 16.17208 -20.92
1495.92 138.2261 60 19.96858

Here's a 55-line program that converts a TMY2 file's global and
diffuse horizontal and direct normal radiation numbers into
Btu/h-ft^2 numbers on the ground and ESWN walls:

10 SCREEN 9:KEY OFF:CLS:PI=4*ATN(1)
15 LINE (0,0)-(639,349),,B
20 TMAX=100'max display temp (F)
40 XDF=640/8760:YDF=350/TMAX
50 FOR TR= 0 TO TMAX STEP 20'temp ref lines
60 LINE (0,349-YDF*(TR))-(639,349-YDF*(TR)):NEXT
70 OPEN "13739.tm2" FOR INPUT AS #1'NREL TMY2 file name (Phila)
80 OPEN "ecayear" 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)
210 TDP=VAL(MID$(S$,74,4))*.18+32'dew point temp (F)
220 PSET(XDF*H,349-YDF*(TDB))
230 IF DAY=1 AND HOUR=.5 THEN LINE (XDF*H,349)-(XDF*H,345)'tick months
240 WIND=VAL(MID$(S$,96,3))*.22371'wind velocity (mph)
250 IGLOH=VAL(MID$(S$,18,4))*.317'global horizontal radiation (Btu/
ft^2)
260 PRINT#2,MONTH;DAY;HOUR;TDB;WIND;TDP;IGLOH;
270 IDIF=VAL(MID$(S$,30,4))*.317'diffuse horizontal radiation (Btu/
ft^2)
280 IDIR=VAL(MID$(S$,24,4))*.317'direct normal radiation (Btu/ft^2)
290 L=PI*LAT/180'Phila latitude (radians)
300 T=HOUR'solar time (EST)
310 X=-SIN(PI*23.45/180)*COS(2*PI*(N+10)/365.25)
320 D=ATN(X/SQR(-X*X+1))'sin^-1(x) = declination (radians)
330 W=2*PI*(T-12)/24'hour angle (radians)
340 X=COS(L)*COS(D)*COS(W)+SIN(L)*SIN(D)
350 THETAS=-ATN(X/SQR(-X*X+1))+PI/2'cos^-1(x) = sun zenith angle
(radians)
360 X=COS(D)*SIN(W)/SIN(THETAS)
370 IF X^2 >=1 THEN PHIS=-1.570796327#:GOTO 390
380 PHIS=ATN(X/SQR(-X*X+1))'sin^-1(x) = sun azimuth angle (radians)
390 FOR PHIPD=0 TO 180 STEP 90'azimuth angle of plane (degrees)
400 PHIP=PI*PHIPD/180
410 X=SIN(THETAS)*COS(PHIS-PHIP)
420 THETAI=-ATN(X/SQR(-X*X+1))+PI/2'incidence angle to surface
(radians)
430 IF THETAI>=PI/2 THEN THETAI=PI/2
440 RHOG=.2'ground reflectance
450 IGLOP=IDIR*COS(THETAI)+IDIF/2+IGLOH*RHOG/2'radiation on surface
(Btu/ft^2)
460 PRINT#2,IGLOP;
470 'IF PHIPD = 0 THEN PSET(XDF*H,349-IGLOP)
480 NEXT PHIPD
490 PHIP=PI*270/180
500 X=SIN(THETAS)*COS(PHIS-PHIP)
510 THETAI=-ATN(X/SQR(-X*X+1))+PI/2'incidence angle to surface
(radians)
520 IF THETAI>=PI/2 THEN THETAI=PI/2
530 IGLOP=IDIR*COS(THETAI)+IDIF/2+IGLOH*RHOG/2'radiation on surface
Btu/ft^2)
540 PRINT#2,IGLOP
550 NEXT H

Nick

[Nathan Hurst]

On Tue, Apr 12, 2011 at 01:40:07PM -0400, Don Hull wrote:
> What would be the definitive book on passive solar?

Yes, a great question. The Maine solar primer (rich komp et al) is a
good summary of technical stuff (but is a little dated).

njh