Subject: Re: Passive Solar home to be built in RI?

From: [email-masked] (Nick Pine)
Date: 11 Jun 1996 07:08:35 -0400

William R Stewart  <[email-masked]> wrote:
>NOMAD29 wrote:
>> I've just taken a job in RI and have decided to have a passive solar home
>> built.  I'm  Looking for a competent architect/solar engineer and builder
>> for the project.  any ideas??

It's a good idea to find an engineer to help.

>> Also I'm seriously concidering a large massonary heater system for the
>> house.  Any feelings pro or con??

Did you say you wanted a "solar" house? :-)

>I've selected a modular home built by Avis America, who participated with 
>DOE and Fully Independent Residential Solar Technology (FIRST) to design and
>build energy efficient homes that incorporate passive solar heating and
>photovoltaics.

Sounds good...

>See Solar Today Sept/Oct 1995.

That sort of house (house 1 below, essentially a Trombe wall house) is fairly
expensive and low-performance, as solar houses go, and needs a separate solar
water heating system. It gets off the mark in a house race, but quickly tires
in the backstretch, in partly cloudy climates, vs houses built with exactly
the same materials, or less expensive materials, in a different configuration.

>A builder in your area is EnerPro Engineering, Inc at 508.677.3533.
>The energy designer is Lyle Rawlings at 609.466.4495.

You might ask Lyle for the isolated gain, isolated store model :-)
 
Nick

They're off!

               Direct        Isolated      Isolated      Isolated
               gain,         gain,         gain and      store
Day            wall store    wall store    store         temp
 
 0             36 F          36 F          36 F          36 F
 1             51.625        51.625        51.625        51.625  
 2             62.06671      63.92594      64.2358       64.2358 
 3             69.04458      70            70            74.41387 
 4             70            70            70            83.32878 
 5             70            70            70            91.93831 
 6             70            70            70            100.2529 
 7             70            70            70            108.2827 
 8             70            70            70            116.0375 
 9             70            70            70            123.5266 
 10            70            70            70            130.7591 
 11            70            70            70            137.7439 
 12            70            70            70            144.4895 
 13            70            70            70            151.004 
 14            70            70            70            157.2953 
turn off the sun...
 15            58.72116      64.11539      70            150.1516 
 16            51.18385      59.24927      70            143.111 
 17            46.1469       55.22536      70            136.1719 
 18            42.78086      51.89789      70            129.3329 
 19            40.53144      49.14633      70            122.5925 
 20            39.02822      46.87101      70            115.9493 
 21            38.02367      44.98949      70            109.402 
 22            37.35235      43.43362      70            102.9491 
 23            36.90374      42.14703      70            96.58922 
 24            36.60394      41.08312      70            90.32111 
 25            36.4036       40.20335      70            84.14339 
 26            36.26971      39.47585      70            78.05479 
 27            36.18024      38.87426      70            72.054 
 28            36.12045      38.37679      66.13976      66.13976 
 29            36.08049      37.96542      60.92326      60.92326 
 30            36.05379      37.62525      56.60962      56.60962 

10 'a house race, among three 8' cube contenders, each having
20 '  R13 walls, one 8'x8' R2 window, and 4096 Btu/F of thermal mass.
30 '  House 1: a direct gain house with thermal mass in the walls.
40 '  House 2: an isolated gain house with thermal mass in the walls.
50 '  House 3: an isolated gain house with isolated thermal mass store.
60 OPEN "HROUT" FOR OUTPUT AS #1
70 PRINT#1,"They're off!"
80 PRINT#,
90 PRINT#1,"               Direct        Isolated      Isolated"
100 PRINT#1,"               gain, wall    gain, wall    gain and     store"
110 PRINT#1,"Day            store         store         store        temp"
120 PRINT#1,
130 'warmup over a long string of average Phila December days
140 RWIND=2'US R-value of window
150 RWALL=13'US R-value of walls
160 C=4096'thermal mass (Btu/F)
170 TA=36'average outdoor December temp in Phila (F)
180 SUNIN = 8*8*1000'average daily solar input (Btu)
190 TM1=36:TM2=36:TM3=36'initialize thermal mass temperatures
195 TLIM=36'initialize limiting temp
200 FOR DAY=1 TO 14'warmup over two weeks of average December days
205 FOR I=1 TO 10000:NEXT'delay loop
210 E1=24*(TM1-36)*64/RWIND+24*(TM1-36)*5*64/RWALL
220 TM1=TM1+(SUNIN-E1)/C'new thermal store temp
230 IF TM1>70 THEN TM1=70'overheating limit in sunny weather
240 E2=6*(TM2-36)*64/RWIND+18*(TM2-36)*64/RWALL+24*(TM2-36)*5*64/RWALL
250 TM2=TM2+(SUNIN-E2)/C
260 IF TM2>70 THEN TM2=70
270 E3=6*(TM3-36)*32/RWIND+18*(TM3-36)*32/RWALL
275 E3=E3+24*(TLIM-36)*(32+5*64)/RWALL
280 TM3=TM3+(SUNIN-E3)/C
285 IF TM3<70 THEN TLIM=TM3 ELSE TLIM=70
290 IF TM3>212 THEN TM3=212'water boils
295 PRINT#1, DAY,TM1,TM2,TLIM,TM3
310 NEXT DAY
340 'coming into the backstretch, a string of cloudy days
345 SUNIN=0'turn off the sun
346 PRINT#1,"turn off the sun..."
350 FOR DAY=15 TO 30'simulate two weeks of cloudy days
360 E1=24*(TM1-36)*64/RWIND+24*(TM1-36)*5*64/RWALL
370 TM1=TM1+(SUNIN-E1)/C
380 IF TM1>70 THEN TM1=70
390 E2=0*(TM2-36)*64/RWIND+24*(TM2-36)*64/RWALL+24*(TM2-36)*5*64/RWALL
400 TM2=TM2+(SUNIN-E2)/C
410 IF TM2>70 THEN TM2=70
430 E3=0*(TM3-36)*32/RWIND+24*(TM3-36)*32/RWALL
440 E3=E3+24*(TLIM-36)*(32+5*64)/RWALL
450 TM3=TM3+(SUNIN-E3)/C
455 IF TM3<70 THEN TLIM=TM3 ELSE TLIM=70
460 IF TM3>212 THEN TM3=212
470 PRINT#1,DAY,TM1,TM2,TLIM,TM3
480 NEXT DAY
500 CLOSE

---

From: William R Stewart <[email-masked]>
Date: Tue, 11 Jun 1996 20:34:49 -0400

> Did you say you wanted a "solar" house? :-)

A home can be passive solar AND have a fireplace.

> That sort of house (house 1 below, essentially a Trombe wall house)

It is not a Trombe wall house.

> is fairly
> water heating system.

You'll have to pardon our local eccentric, Nick Pine.  His ideas are the only
ones worth considering.  If you don't believe that, just ask him...

Nick provides a simple (but spaggetti) code exercise that somehow support
his thesis statements.  Note below how many temperatures 'magically' end 
up at 70 F.  The answer is buried in the 'code'.

> Day            wall store    wall store    store         temp

R13 walls are far below the R24 walls that are in the Avis home walls.
The R2 windows ignore the window shade insulation that would be used.

> 230 IF TM1>70 THEN TM1=70'overheating limit in sunny weather^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I've never heard of this rule before; where did you come up with this,
Nick?  The thermal store can be far above the ambient temperature of the
room.  This explains why you don't understand the concept of a masonry heater
fireplance.  Do you think that the thermal store is simply going to stop accepting
heat input?

Have you no shame?

> 260 IF TM2>70 THEN TM2=70
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
More bogus rules.

> 380 IF TM1>70 THEN TM1=70
^^^^^^^^^^^^^^^^^^^^^^^^^^^

More bogus rules.
 
> 410 IF TM2>70 THEN TM2=70
^^^^^^^^^^^^^^^^^^^^^^^^^^^

More number cooking

> 470 PRINT#1,DAY,TM1,TM2,TLIM,TM3

Back to the drawing board yet again, Nick.

Cheers,

Will Stewart

---

From: [email-masked] (Nick Pine)
Date: 12 Jun 1996 01:39:12 -0400

>> It's a good idea to find an engineer to help.

Or a physicist...

>A home can be passive solar AND have a fireplace.

Right... A friend of mine has a beautiful, seaworthy deep keel 28' Cape Dory
sailboat, with a small inboard diesel engine, federally-registered with the
merchant marine as an "oil screw," to reduce taxes and let him clear customs
more easily :-) Would you hang an outboard motor on your America's Cup boat?
 
>> >DOE...

>> Sounds good...

Did you say DOE? :-)

>It is not a Trombe wall house.

It's essentially a Trombe wall house, from a thermal point of view.
Direct gain, storage at close to room temp, ritual night insulation...
This has been around since 1881, with variations. It's time to do it better.

>> is fairly expensive and low-performance, as solar houses go, and needs a
>> separate solar water heating system.
 
>ones worth considering.  If you don't believe that, just ask him...
 
Norman Saunders, PE, Howard Reichmuth, PE, William Shurcliff, PhD,
William Beckman, PhD, John Duffie, PhD, and Steve Baer make a lot of
sense to me. I've talked with them all. Norman and Steve are American
Solar Energy Society Passive Solar Pioneers, and I've spent a few days 
talking over solar closets with each of them in person. I had the good
fortune to drive Norman from Boston to Lewiston, Maine in February, for 
the Maine Solar Energy Association's Sustainable Building Conference,
where Norman was one of the speakers at the session I moderated on
passive heating and cooling techniques. Norman is amazing. He's 80 years
old now, and he got into solar heating in 1944. At the moment, he's
helping design solar houses in Pennsylvania, California, and the UK.
Of course, he's no Will Stewart :-)

>his thesis statements.

Your CS degree is showing... :-) How many 3rd graders can understand C?
How many CS graduates are willing to understand simple physics, involving
ASHRAE-type R-value calculations?

>Note below how many temperatures 'magically' end up at 70 F.

This is the magic of temperature control by ventilation in the winter...
In houses with thermal stores with  no  insulation between the heat store
and the living space, like yours, you have to live inside the heat store.
So, during sunny weather, if you want to store heat for more cloudy days,
you have to live in a warmer house. How warm a house can you tolerate?
These houses work better if you are willing to let their indoor temps rise
to a high value in sunny times, and walk around in T-shirts and shorts in 
December. I picked 70 F as the upper limit for this sunny day house temp
limit. Perhaps I should have picked 80 F. Are you willing to live in a
house that is 80 F in December? The results don't change much.

>The answer is buried in the 'code'.

>> Day            wall store    wall store    store         temp
...

                      ^             ^                          ^
These are simple exponential decays |         So is this ------       
      well-known in heatflow                  But who cares, until it
                                              cools to 70 F?

>R13 walls are far below the R24 walls that are in the Avis home walls.

I suppose your house will be larger than an 8' cube too. This was just
an example of how the same materials can be arranged well or not so well,
>from  a solar performance point of view.

>The R2 windows ignore the window shade insulation that would be used.

True. That's house 2 above, if you cripple it slightly more.

>> 70 PRINT#1,"They're off!"
...

>I've never heard of this rule before; where did you come up with this, Nick?

That's my guess at how warm a house somebody might tolerate in sunny
winter weather. What's your limit, Will? Another issue for direct gain
houses is privacy, as Kurt Smith of Avis mentions. Or lack thereof, and
the interaction with house temperatures. One can only take off so much
clothing, with all those windows, especially near Washington, DC.

>The thermal store can be far above the ambient temperature of the room. 

A few degrees above, for a few minutes... Recall the half-hour time constant
for these water walls. We have discussed that before, but you didn't seem
to be listening. You are in a difficult psychological posture. Try this:
T(t) = 70 + (80-70)exp(-t/30), where t is in minutes.

>This explains why you don't understand the concept of a masonry heater
>fireplance.

I understand such fireplances, but what do they have to do with solar heating?

>Do you think that the thermal store is simply going to stop accepting
>heat input?

Is this a metaphysical or a physical question? The heat goes in one side
of those (opaque, window blocking?) water walls and out both sides, almost
immediately, heating the room air. This is similar to a person for whom 
ideas go in one ear and out the other. Mark Twain said perhaps such a person
should take out his brain and dance on it, to soften it up.
 
>Have you no shame?

I tell the truth, as I see it.

Cheers,

Nick

---

From: [email-masked] (Nick Pine)
Date: 12 Jun 1996 04:16:28 -0400

>R13 walls are far below the R24 walls that are in the Avis home walls.

OK. Let's change them all to R24.

>The R2 windows ignore the window shade insulation that would be used.

True. That's house 2, if you cripple it slightly more.

>What's your limit, Will?

Let's use 80 F as a house upper temp limit, disguised below as:

205 TU=80'upper temp limit for wall store houses (F)

John D. Muccigrosso <[email-masked]> wrote:
>[email-masked] wrote:

>| Nick provides a simple (but spaggetti) code exercise that somehow support
>| his thesis statements.  Note below how many temperatures 'magically' end 
>| up at 70 F.  The answer is buried in the 'code'.
>| 
>| >                Direct        Isolated      Isolated      Isolated
>| >                gain,         gain,         gain and      store
>| > Day            wall store    wall store    store         temp
>
>Hmmm, seems to me that the first 3 columns of temps are air temp, or at
>least living quarters temp including walls and stuff. The 70 degree limit
>would then be regulated by the homeowner who opens a window or closes a
>vent (or has some automatic (magic?) mechanism do this) so that the temp
>doesn't exceed 70.

Right. Or 80 F now, as below. BTW, a nice way to do winter ventilation
for a house might be to move open a hinged piece of foil-faced foamboard
with a $50 Honeywell damper actuator that uses 2 Watts when it is moving,
and 0 Watts when in a fixed position, connected to a cooling thermostat.
A less accurate and leakier way might be to use an automatic foundation vent
with some aluminum louvers that move with a bimetallic spring, such as
Leslie-Locke's FV-1B, which Home Depot sells for $11.83. Drill a hole in
the aluminum bracket covering the spiral spring and adjust the spring mount
with a screwdriver so the vent is open at 80 F, and mount it inside-out,
so the spring is exposed to house air.

>If the house gets above 70, that would be nice for those who like it hot,
>I guess, and would make the house cool down to an unacceptable temp more
>slowly, but probably wouldn't be desirable for most people.

Agreed. Here's the race again, with some NREL numbers for Providence, RI...

They're off!

               Direct        Isolated      Isolated     Isolated
               gain, wall    gain, wall    gain and     store
Day            store         store         store        temp
 
 0             33.8 F        33.8 F        33.8 F        33.8 F
 1             44.7025       44.7025       44.7025       44.7025 
 2   House 1   53.4434       54.97771      55.51239      55.51239 
 3   is a      59.8625       63.8481       65.32996      65.32996 
 4             64.57653      71.50574      70            74.24631 
 5   s         68.03838      78.11644      70 House 3    82.60956 
 6   l         70.58069      80            70 is always  90.72779 
 7   o         72.4477       80 The        70 the same.  98.60819 
 8   w         73.81877      80 ritual     70 A good     106.2577 
 9             74.82566      80 thermal    70 house for  113.6831 
 10  starter.  75.5651       80 curtains   70 reptiles?  120.891 
 11            76.10812      80 help       70            127.8877 
 12            76.5069       80 house      70            134.6794 
 13            76.79975      80 2.         70            141.2722 
 14            77.01482      80            70            147.6718 

House 1 one never quite makes it to 80 F, in 2 weeks of average December
weather. I would say house 2 is too hot, but chacun a son chaleur...
BTW, these are max temps for houses 1 and 2. They will be cooler at night,
vs house 3, which could be cooler at night, if it had a setback thermostat.

House 2 now has a fairly respectable RC time constant of 256 hours, and its
performance is not bad... House 1 is much poorer, with about 45 hours.
Will's Avis house might be about 53 hours, including the water walls,
with all the curtains drawn 24 hour a day, IF they work perfectly. 
How much do they cost, Will? And how do air leaks affect them?

Now let's turn off the sun again...

 15            65.27026      75.575        70            143.5775 
 16            56.64535<--   71.56485      70            139.5151 
 17  Houses    50.31143      67.93063      70   Look     135.4845 
 18  1 and 2   45.65995 too  64.63714      70   how      131.4854 
 19  get cold  42.24403 cold 61.65241      70   nicely   127.5176 
 20  very      39.73546      58.94749      70   house 3  123.5807 
 21  quickly   37.89323  --> 56.49616      70   rides    119.6746 
 22  since     36.54034      54.27465      70   out      115.799 
 23  their     35.54681      52.2614       70   almost   111.9537 
 24  thermal   34.81719      50.4369       70   3 weeks  108.1385 
 25  mass      34.28137      48.78343      70   of       104.353 
 26  was       33.88788      47.28499      70   cloudy   100.5971 
 27  never     33.59892      45.92702      70   weather  96.87059 
 28  very      33.3867       44.69636      70   tra la   93.17316 
 29  warm...   33.23086      43.58108      70   tra la   89.50462 
 30  And       33.11641      42.57035      70   ...      85.86474 
 31  house 1   33.03237      41.65438      70   :-)      82.25331 
 32  has that  32.97064      40.82428      70            78.67008 
 33  B I G     32.92532      40.072        70            75.11484 
 34  bare      32.89203      39.39025      70            71.58738 
 35  window.   32.86759      38.77242      68.08748      68.08748 

Looks like house 3 finishes 19 days ahead of the nearest contender,
if you call 68 F and 80 F comfortable interior temperatures.

10 'a house race, among three 8' cube contenders, each having
20 '  R24 walls, one 8'x8' R2 window, and 4096 Btu/F of thermal mass.
30 '  House 1: a direct gain house with thermal mass in the walls.
40 '  House 2: an isolated gain house with thermal mass in the walls.
50 '  House 3: an isolated gain house with isolated thermal mass store.
60 OPEN "HROUT" FOR OUTPUT AS #1
70 PRINT#1,
80 PRINT#1,"They're off!"
100 PRINT#1,"               Direct        Isolated      Isolated     Isolated"
110 PRINT#1,"               gain, wall    gain, wall    gain and     store"
120 PRINT#1,"Day            store         store         store        temp"
130 PRINT#1,
140 'warmup over a long string of average December days
150 RWIND=2'US R-value of window
160 RWALL=24'US R-value of walls
170 C=4096'thermal mass (Btu/F)
180 TA=32.8'average outdoor December temp in Providence, RI (F)
190 SUNIN=8*8*900*.92*.92'average daily solar input (Btu)
200 TM1=TA:TM2=TA:TM3=TA'initialize thermal mass temperatures
205 TU=80'upper temp limit for wall store houses (F)
210 TLIM=TA'initialize limiting temp for isolated store house
220 FOR DAY=1 TO 14'warmup over two weeks of average December days
240 E1=24*(TM1-TA)*64/RWIND+24*(TM1-TA)*5*64/RWALL
250 TM1=TM1+(SUNIN-E1)/C'calculate new thermal mass temp
260 IF TM1>TU THEN TM1=TU'ventilate house to limit indoor temp
270 E2=6*(TM2-TA)*64/RWIND+18*(TM2-TA)*64/RWALL+24*(TM2-TA)*5*64/RWALL
280 TM2=TM2+(SUNIN-E2)/C
290 IF TM2>TU THEN TM2=TU
300 E3=6*(TM3-TLIM)*32/RWIND+18*(TM3-TA)*32/RWALL'south wall loss
310 E3=E3+24*(TLIM-TA)*(32+5*64)/RWALL
320 TM3=TM3+(SUNIN-E3)/C
330 IF TM3<70 THEN TLIM=TM3 ELSE TLIM=70
340 IF TM3>212 THEN TM3=212'water boils
350 PRINT#1, DAY,TM1,TM2,TLIM,TM3
370 NEXT DAY
380 'coming into the backstretch, a string of cloudy days
390 SUNIN=0'turn off the sun
400 PRINT#1,"turn off the sun..."
410 FOR DAY=15 TO 35'simulate three weeks of cloudy days
430 E1=24*(TM1-TA)*64/RWIND+24*(TM1-TA)*5*64/RWALL
440 TM1=TM1+(SUNIN-E1)/C
450 E2=0*(TM2-TA)*64/RWIND+24*(TM2-TA)*64/RWALL+24*(TM2-TA)*5*64/RWALL
460 TM2=TM2+(SUNIN-E2)/C
470 E3=0*(TM3-TLIM)*32/RWIND+24*(TM3-TA)*32/RWALL'south wall loss
480 E3=E3+24*(TLIM-TA)*(32+5*64)/RWALL
490 TM3=TM3+(SUNIN-E3)/C
500 IF TM3<70 THEN TLIM=TM3 ELSE TLIM=70
520 PRINT#1,DAY,TM1,TM2,TLIM,TM3
540 NEXT DAY
550 CLOSE
 
Nick

---

From: William R Stewart <[email-masked]>
Date: Wed, 12 Jun 1996 22:19:09 -0400

[Followups to alt.solar.thermal, for the umpteenth time.  Nick wanders away and
we have to gently lead back to his cell^h^h^h^h room]

 
> more easily :-) Would you hang an outboard motor on your America's Cup boat?

So sailboats with motors are no longer sailboats?  I have to admit, you continue
to amaze me...  Bought any 12 watt rabbits, lately?

> >> >I've selected a modular home built by Avis America, who participated with

Are you hard of hearing?
 
> >> >See Solar Today Sept/Oct 1995.

A publication of the American Solar Engineering Society.

> Direct gain, storage at close to room temp,

By what measure?  Feel free to invent things right off the top of your head.

> ritual night insulation...

Go do so.

> sense to me.

I'll let them speak for themselves.  And a PE or PhD doesn't make a person a 
god, merely respectable, so stop worshipping.

> I've talked with them all. 

That doesn't make you a god, either.

> Your CS degree is showing... :-) How many 3rd graders can understand C?

Earth to Nick...

> ASHRAE-type R-value calculations?

Those who also have electro-mechanical engineering degrees.

> house that is 80 F in December? The results don't change much.

Not that your code can be trusted anyway.
 
> >> 230 IF TM1>70 THEN TM1=70'overheating limit in sunny weather

You make this assertion but fail to support it.
 
> clothing, with all those windows, especially near Washington, DC.

I wasn't planning on going nude where neighbors could see me.  The lots I'm
looking at are all over 5 acres.

You fail to realize that the thermal store can be much warmer than the ambient
room temperature.  Since the water wall will be painted (or papered) a light
color, most of the heat transfer will be from convection.  Do you understand how
to calculate convection?
 
> to be listening. 

You failed to supply a reasonable calculation.  A little bit of knowledge is
a dangerous thing.  Perhaps you should start another quiz so that you can 
pick up a few more formulas>.

>You are in a difficult psychological posture.

Quack, heal thyself.

> Try this:

Thermal mass, silly.  Do you think they are right at room temperature?
How do you think they can continue warming a room for up to 24 hours?
Perhaps you should learn something from one of those people you worship.
 
> immediately, heating the room air.

By what transfer mechanism, convection?  Please show me the calculation.  
You're in new and strange territory here, Nick.  Ohm's law only takes an 
EE so far in thermodynamics...

> This is similar to a person for whom

*THAT'S* what you've been up to; that explains everything....
 
> I tell the truth, as I see it.

The former is seldom, the latter, obvious.
 
Cheers,
 
Will Stewart

---

From: [email-masked] (John D. Muccigrosso)
Date: Wed, 12 Jun 1996 23:46:15 -0400

In article <[email-masked]>, [email-masked]
(Nick Pine) wrote:

| 180 TA=32.8'average outdoor December temp in Providence, RI (F)
| 190 SUNIN=8*8*900*.92*.92'average daily solar input (Btu)

| 380 'coming into the backstretch, a string of cloudy days

| 430 E1=24*(TM1-TA)*64/RWIND+24*(TM1-TA)*5*64/RWALL

Here's what I'm wondering. Shouldn't one really use not a string of avg
winter temp days, but a string of nasty, colder-than-usual, cloudy ones?
Say a week or two of a nasty arctic air mass stuck in your region.

-- 
John D. Muccigrosso                         Department of Classical Studies
[email-masked]                            University of Michigan

---

From: [email-masked] (Nick Pine)
Date: 13 Jun 1996 02:21:48 -0400

>| 190 SUNIN=8*8*900*.92*.92'average daily solar input (Btu)
                      ^-- these are for glazing transmission loss, BTW.

>| 430 E1=24*(TM1-TA)*64/RWIND+24*(TM1-TA)*5*64/RWALL
 
That's for a direct gain house. For an isolated gain house, eg one with
a low-thermal-mass sunspace, on a cloudy day we have lower loss:

>| 430 E1=24*(TM1-TA)*64/Rwall+24*(TM1-TA)*5*64/RWALL
                         ^^^^^--much higher

>Say a week or two of a nasty arctic air mass stuck in your region.

Sure. But this is a starting point. It seems to me that one can design a
good sunspace and solar closet house with just two numbers: the average
temp in the coldest month and the average amount of sun that falls on a
south wall. Successive refinements might be to look up the average daytime
high in that month, and use that number instead of the 24 hour average temp,
for the sunspace collection efficiency, to do a TMY2 simulation for the
house, using hourly NREL weather data for a typical meteorological year,
and to do a simulation using hourly weather data for the last 30 years,
>from  one of three $130 Sampson CD-ROMs available from [email-masked].
It seems to me that in many parts of the country, cold days are sunny...

Nick

---

From: [email-masked] (Nick Pine)
Date: 13 Jun 1996 03:33:14 -0400

William R Stewart  <[email-masked]> wrote:

>[Followups to alt.solar.thermal, for the umpteenth time...

Feeling uncomfortable, Will? :-)

>A publication of the American Solar Engineering Society.

My copy says "Published by The American Solar Energy Society."

>Those who also have electro-mechanical engineering degrees.

I have yet to see one... These calculations are just HVAC craftsmanship, not
"thermodynamics." (Is "electro-mechanical engineering" pinball machines? :-)

>color, most of the heat transfer will be from convection. Do you understand how

Sure. I just use an R-value of 2/3. I don't add anything for paint or paper.
Other people go on about Nusselt and Grashof numbers, but the results are
similar. R-values are actual physical measurements that include convection.

>> >The thermal store can be far above the ambient temperature of the room.

Not for long.

>>The heat goes in one side of those window-blocking water walls and out
>>both sides, almost immediately, heating the room air.

>By what transfer mechanism, convection?  Please show me the calculation.  

My NREL data book says about 1050 Btu/ft^2 would shine in your double-glazed
windows over a 6 hour winter day, of which they estimate 710 Btu/ft^2 would
get through the window, and shine on the water wall in your 70 F room, with
a still air film R-value of 2/3 for each side (see ASHRAE HOF, Fig 1, p 22.1),
heating it up to a temperature T, where 710 = 6(T-70)2/(2/3), so T = 109 F.
If the wall contains 4" of water, ie about 21 pounds per square foot of wall,
the RC time constant of the wall is about 2/3/2x21 = 7 hours. These walls
might keep your house warm for several hours, not just a half-hour...

If you close your curtains at 3 PM, and keep your solar house at 70 F all
night by burning wood, by 9 AM the next morning, the water walls might have
a temperature  

T(t) = 70 + (109-70)exp(-18/7) = 73 F.

If the next day is cloudy, and you leave your curtains closed, and keep
your solar house at 70 F by burning wood for the next 24 hours, the next
morning your water walls might have a temperature of 

T(t) = 70 + (109-70)exp(-42/7) = 70.1 F.
 
Suppose you didn't burn wood the first night. As I recall, your house had
an overall U value of about 150 Btu/hr-F. So over 18 night hours, at 30 F
outside, it would need about 18(70-36)150 = 92K Btu to stay warm. The 3300
lb of water walls and 1000 Btu/F (?) of house would need to cool 92K/4.3K 
= 21 degrees F to do that, so in the morning, your solar house and water
walls would have a temperature of about 70-21 = 49 F.

Over the next 24 hours, if it's 30 F outside, and you keep all of the thermal
curtains drawn all day, and they insulate as well as you say they will (who
makes these curtains, anyhow, and how much do they cost?) your house would
need less than 24(49-30)150 = 68K Btu to stay at 49 F, so after another day
your solar house and water walls would be at least 49 - 68K/4.3K = 33 F...

You could do these calculations in more detail, if you desired. 

The results wouldn't change much.

Nick

---

From: [email-masked] (John D. Muccigrosso)
Date: Thu, 13 Jun 1996 09:20:53 -0400

In article <[email-masked]>, [email-masked]
(Nick Pine) wrote:

| Successive refinements might be to look up the average daytime
| high in that month, and use that number instead of the 24 hour average temp,
| for the sunspace collection efficiency, to do a TMY2 simulation for the
| house, using hourly NREL weather data for a typical meteorological year,
| and to do a simulation using hourly weather data for the last 30 years,
| from one of three $130 Sampson CD-ROMs available from [email-masked].

Yeah, this is what I meant.

| It seems to me that in many parts of the country, cold days are sunny...

Right (having lived in MN where those cold Canadian air masses are often
cloudless), but you would build for a 30-yr (or 10-yr or some other
long-term) low, not for typical winter days, right? (Though avg days are
fine for a quick comparison of types.)

---

From: William R Stewart <[email-masked]>
Date: Thu, 13 Jun 1996 08:45:04 -0400

[followups to alt.solar.thermal for the umpteenth +1 time...]

> Feeling uncomfortable, Will? :-)

Trying to reduce the embarrassment you create for yourself...

> My copy says "Published by The American Solar Energy Society."

Do you have any problems with this organization, or are they all ignorant
and criminal, too?
 
> "thermodynamics." 

I wonder how many people in sci.engr.heat-vent-ac would consider you an
HVAC "craftsman"...  

Perhaps an understanding of thermodynamics should be your foundation for 
HVAC calculations, as is the normal in engineering schools.  Don't forget 
you are posting to sci.ENGR.heat-vent-ac.  You continue to strip away all 
of my followups to alt.solar.thermal, so you must suffer the consequent 
loss of face.  If you are trying to attract clients, this isn't a very good
approach.

> similar. R-values are actual physical measurements that include convection.

Convection equivalents are not so cut and dry.  Newton's law of cooling is;

qc = hc*A(Ts - Tf)

where 
  hc= average convection heat-transfer coefficient over the surface A
      in W/m2*K (Btu/hr*ft^2*F).  hc for air, free convection is 
      1-5 Btu/hr*ft^2*F 

  Ts= Surface temp
  Tf= Undisturbed fluid temperature

Because the thermal store wall will be resting on a perpendicular floor, and
will have a perpendicular table top extending 18 inches into the room, I will
assume an hc value of 1 for purposes of discussion.  The wall design is not 
completely set; one design I am looking at is 10'x2.5'x8", which is slightly 
different from 10'x4'x4".  This design would give a storage per wall at 
16.6 ft^3 X 7.48 gal/ft^3 X 8.33 lb/gal = 1041 Btu storage for each degree F 
delta T.  If they are exposed to 700 Btus/hr ft^2 solar insolation through
dual pane windows, then;

Each storage wall will receive 25 X 700 = 17500 Btus during the day.

With 4 walls, that translates to 17,500 x 4 = 70,000 Btus.

Of course each window group has an addition 50 ft^2 of window space that bypasses 
the thermal storage walls, so another 140,000 Btus will enter those windows.

Two more south window groups do not have thermal storage walls (will likely have
storage floors, such as slate or dark tile on concrete),
so 2 x 70 x 700 = 98,000 Btus additional input.

70K + 140K + 98K = ~310,000 Btus of solar insolation input on an average December day
(January and February are higher).

If we want to add in the thermal storage of other aspects of the house, such as
drywall and flooring, we will find that the thermal mass of the house is 
considerably more, though it is at, or close to, room ambient temperature. If the
room temperature is higher in the daytime, then this thermal mass will rise to
(almost) meet the ambient temperature high.  You calculated 4000 Btu/F for internal
secondary storage in an earlier post, so if the indoor daytime temperature is 75 F 
and the base winter room temperature is 65 F, then internal secondary storage is 
40,000 Btus.

If the Ts = 85 F and Tf = 75F (after a day of average sunlight in 
December), then;

qc = 1*50*(85-75) = 500 Btu/hr per storage wall

which, according to your calculation of my house design at 150 Btu/hr F 
(which you admit needs significant rework, I'll address this in another post),
would raise the room ambient temperature, conversely lowering the qc.

As the room and thermal storage walls starts to cool down to 
Ts = 73 and Ts =68 F, for example, then qc =  125 Btu/hr per storage wall

With 65 F being the base winter room temperature, the storage walls would 
still have 32000 Btus of energy left, not counting the wall, ceiling, and floor
thermal storage.

> might keep your house warm for several hours, not just a half-hour...

I'm glad to see that you admit you can be wrong.  Your understanding of 
convection still needs work, though, because we haven't even touched on Nusselt, 
Prandl, Reynolds, or Grashof.  You'll find fluid dynamics plays a large role 
in convection, free or forced.  Thermal conductivity physics only takes 
you so far in the real world.

Cheers,

Will Stewart

---

From: [email-masked] (paul milligan)
Date: 13 Jun 1996 21:18:50 GMT

In article <[email-masked]>,
   [email-masked] (John D. Muccigrosso) wrote:

~~>| from one of three $130 Sampson CD-ROMs available from [email-masked].

	Or http://www.ncdc.noaa.gov , their web site.

_________________________________________________________
No Disclaimer needed - This is my own PPP account, and my
employer doesn't care what I think anyway !  :-)
_________________________________________________________

The SEHVAC FAQ is at: http://www.elitesoft.com/sci.hvac/
My humble personal pages are at: http://www.webbuild.com/~pjm/index.html

---

From: [email-masked] (Nick Pine)
Date: 13 Jun 1996 18:30:04 -0400

>Do you have any problems with this organization, or are they all ignorant

They are good guys with their hearts in the right places, like yours, however,
we haven't seen many 100% solar houses like those of Norman Saunders, PE,
described in their pages lately. Bill Yanda and Steve Baer figure nicely
in their publications. Their technical journal is somewhat clogged with
academics, IMO.

>HVAC calculations, as is the normal in engineering schools.

Been there, done that. ASHRAE calcs are more useful and straightforward here.

>>>You fail to realize that the thermal store can be much warmer than the
>>>ambient room temperature. Since the water wall will be painted (or papered)
>>>a light color, most of the heat transfer will be from convection. 

BTW, I think the light color is irrelevant here, unless you are talking about
a shiny metallic surface. Dark colors are good for solar absorption, but IR
emission at eg 80 F is pretty much independent of color. Perhaps you believe
in painting radiators dark colors... I don't think that matters.

 
>qc = hc*A(Ts - Tf)

Right. Ohm's law for heatflow :-)

>      in W/m2*K (Btu/hr*ft^2*F).  hc for air, free convection is 

That's a U (=1/R) value, and it's hard to get below 1.5 in still air. It
increases if the air is moving to about U = 1.5 + V/5 for smooth surfaces,
U = 2 + V/2 for rougher ones like stucco, where V is in mph. See ASHRAE HOF
Fig 1, p 22.1. You might be able to get U < 1 if you make the water wall faces
shiny metal (U ~ 0.5 for upward heatflow, ~ 0.25 for sideways heatflow), but
that won't work for the side facing the sun, which will impose a lower limit
on the overall U-value of at least 1.5, unless it's a selective surface.
 
>  Tf= Undisturbed fluid temperature

Natch.

>assume an hc value of 1 for purposes of discussion.

1.5 is probably closer to the truth, especially since the floor and table top
will act as conductive fins. Gluing foil-faced foamboard to the non-south
surfaces would help...

>The wall design is not completely set; one design I am looking at is
>10'x2.5'x8", which is slightly different from 10'x4'x4".

OK.

>This design would give a storage per wall at 16.6 ft^3 X 7.48 gal/ft^3 X
>8.33 lb/gal = 1041 Btu storage for each degree F delta T.

OK.

>If they are exposed to 700 Btus/hr ft^2 solar insolation

That was 700 Btu/day-ft^2. Full sun is 311 Btu/hr-ft^2, max, on earth.
                 ^^^
>through dual pane windows, then;

>Each storage wall will receive 25 X 700 = 17500 Btus during the day.

Agreed, for a 25 ft^2 water wall face...

>With 4 walls, that translates to 17,500 x 4 = 70,000 Btus.
 
OK.

>Of course each window group has an addition 50 ft^2 of window space that
>bypasses the thermal storage walls, so another 140,000 Btus will enter
>those windows.

OK. But irrelevant.

>Two more south window groups do not have thermal storage walls (will
>likely have storage floors, such as slate or dark tile on concrete),

OK. But irrelevant.

>70K + 140K + 98K = ~310,000 Btus of solar insolation input on an average
>December day (January and February are higher).

OK. But irrelevant.

>considerably more, though it is at, or close to, room ambient temperature. 

That's what we will find, huh? :-) How much? Numbers please.

>If the room temperature is higher in the daytime, then this thermal mass
>will rise to (almost) meet the ambient temperature high.

Sure. Or higher, if it's in the sun, eg the floor.

>You calculated 4000 Btu/F for internal secondary storage in an earlier post,

That was a guess. Your house might have 4,000 ft^2 of 1/2" drywall with a
thermal mass of 0.5 Btu/F, ie 2,000 Btu/F. How much will your solar fireplace
weigh? That would add about 0.16 Btu/lb...

>so if the indoor daytime temperature is 75 F and the base winter room
>temperature is 65 F, then internal secondary storage is 40,000 Btus.

OK, go ahead, double that number, but that's still a drop in the bucket
compared to a typical day's energy need of 24(70-40)150 = 108K.

>If the Ts = 85 F and Tf = 75F (after a day of average sunlight in December),

Is Ts the water wall temp, and Tf the room and wall temp?

>qc = 1*50*(85-75) = 500 Btu/hr per storage wall

Let's see, you said above,

>qc = hc*A(Ts - Tf)

and you said you wanted to use hc = 1, altho 1.5 is a more reasonable min...
So where did the 50 come from? Oh, 2 sides to each water wall, each 25 ft^2.
I guess you'd want to add the perimeter area of 8"/12" x 25' = 17 ft^2, and
something for the floor and table fins? So I'd make this 1.5x67x(85-75) =
1,000 Btu/hr/wall, altho you seem to have pulled the 85 F out of a hat.
Perhaps you'd like to recalculate that 109 F with these new shapes.

>(which you admit needs significant rework, I'll address this in another post),

Perhaps you would like to recalculate that. It's your house.

>would raise the room ambient temperature, conversely lowering the qc.

Right. Until you are parading naked :-)
 
>Ts = 73 and Ts =68 F, for example, then qc =  125 Btu/hr per storage wall

What difference does that make? You might rework that too.

>still have 32000 Btus of energy left, not counting the wall, ceiling, and floor

OK. I get 33,312 Btu, using your numbers above.
But what's the point of this calculation, Will?

 
 
>I'm glad to see that you admit you can be wrong.

Sure. I miscalculated before. You are building a whole house wrong :-)

>Your understanding of convection still needs work, though, because we haven't
>even touched on Nusselt, Prandl, Reynolds, or Grashof. You'll find fluid
>dynamics plays a large role in convection, free or forced. Thermal
>conductivity physics only takes you so far in the real world.

R-values are sufficient here.

So let's see. Your new water walls have a thermal resistance of 2/3/67 ft^2
and a thermal mass of 1041 Btu/F, so their RC time constant is 10.35 hours,
and your house with the 4,000 Btu/F of inherent thermal mass and 150 Btu/F-hr
with all the curtains drawn has a time constant of 26.6 hours, so if I'm doing
this right, we might figure the RC time constant of your entire house with 
all those ritual curtains drawn as the RMS value sqrt(26.6^2+10.35^2)=28.5 hr.

Suppose we say the average temp of the thermal mass in your house is 80 F
to start with. Then when it's 30 F outside, with all the thermal curtains
drawn in the dark, 24 hours a day, the indoor house temp will be:

T(t) = 30 + (80-30) exp(-t/28.5)

80 F after 0 hours, 52 F after 24 hours, and 39 F after 48 hours.  
 
Still not a solar house by a long shot, I'd say. Altho it could be
dramatically improved by rearranging the same materials... 
 
Nick

---

From: [email-masked] (Nick Pine)
Date: 13 Jun 1996 21:15:37 -0400

I wrote:

>we might figure the RC time constant of your entire house with all those
>ritual curtains drawn as the RMS value sqrt(26.6^2+10.35^2)=28.5 hr.

On second thought, it's probably more accurate to calculate the steady-state
water wall temp and model the house as having a fixed hold time of a few hours
followed by an exponential cooling with a time constant of 8000/150 = 53 hours.

Still piss-poor solar performance...

Nick

---

From: [email-masked] (Nick Pine)
Date: 13 Jun 1996 13:46:11 -0400

>Yeah, this is what I meant.

OK...

>long-term) low, not for typical winter days, right?

Right, but... 

>(Though avg days are fine for a quick comparison of types.)

Yes, and for the more complete simulations I've run, I've noticed that
a house design based on daily averages works fine. It usually turns out
to be overkill. Simple simulations allow one to tweak the design a little,
to reduce the size of the required sunspace or thermal store, or decrease
the R-value of the walls or windows, or increase the allowable air
infiltration rate, vs. an average-day design. 

Nick