An Allentown house
nicks...@ece.villanova.edu
an average 31.8 F December day with a 24.4 and 39.2 daily max and min
in Allentown, near the PA Renewable Energy Festival, 9/22-23/07,
http://www.paenergyfest.com, where I'll be talking about the system
below at 2:30 on Saturday and Nathan Hurst will talk about his Mazda
radiator solar heating experiments in Australia at 3:30 on Sunday.
Rich Komp (author of Practical Photovoltaics) will discuss energy-efficient
food storage at 3:30 on Saturday and new PV developments at 4:30 on Sunday.
We will all be exhibiting ourselves and a $35 1995 Mitsubishi 2.0 Eclipse
radiator at an "Ask the Engineer" table near Booth 24 in the exhibit area.
If a house is 65 F on average indoors (eg 70 F for 12 hours per day and
60 for the other 12) and a frugal 300 kWh/mo of indoor electrical use
provides 34K Btu of heat on an average day and a 4'x8'x3'-tall EPDM-lined
plywood heat storage tank on the ground containing 4x8x3x62.33 = 5984 pounds
of 140 F water warms the house using an 800 Btu/h-F radiator for 5 cloudy
days until it cools to Tmin and the house thermal conductance is G Btu/h-F
and we keep it 70 F on a 24.4 F morning, (Tmin-70)800 = (70-24.4)G makes
Tmin = 70+0.057G.
On an average day, we need 24(65-31.8)G-34K = 796.8G-34K Btu of heat energy.
If (140-Tmin)5984 = (140-(70+0.057G))5984 Btu = 5d(796.8-34K), G = 136 max,
and Tmin = 78 F, and the house needs 74.4K Btu/day of non-electrical heat.
A 1024 ft^2 house with a 640 ft^2 loft might look like this,
viewed in a fixed font:
.
. .
. .
. . 12'
8'. .
. 24' .
. . . . . . .
. .
8'. . . 8'
. .
. . .
..........................
32'
. . . . . . . . .
. . .
. . .
. . .
. . .
. . . 32'
. . .
. . .
. . .
. . .
. . . . . . . . .
If made entirely of Structural Insulated Panels (18 SIPs?) with R-value Rv
and 1024 ft^2 of ceiling and 2304 ft^2 of walls and no air leaks, G = 136
= 3328ft^2/Rv makes Rv = 24 ft^2-F-h/Btu min; 8" R32 SIPs make G = 104. With
good airsealing and 32 cfm of air leaks, we might have G = 136 Btu/h-F.
With 136 ft^2 of R30 walls and a 136/30 = 4.5 Btu/h-F conductance, the tank
would supply 24h(140-65)4.5 = 8K Btu of house heat on an average day, leaving
a need for 74.4K-8K = 66.4K Btu/day of solar air heat (line 150 in the calc
below.) Sunspace air keeps the house 70 F during collection time and stores
heat in the house mass (line 340) to keep it warm overnight as it cools from
70 F at dusk to 60 at dawn.
If 500 Btu/ft^2 of 250 Btu/ft^2 full sun arrives in 500/250 = 2 hours on
a 6-hour solar collection day and 300/(6h-2h) = 75 Btu/h-ft^2 arrives in
the other 4 hours, we can model AS ft^2 of $2/ft^2 Thermaglas Plus U0.58
twinwall polycarbonate "solar siding" with 80% solar transmission over
a 1 foot air gap over a dark south wall like this, viewed in a fixed font:
0.8x250AS = 200A Btu/h 1/(0.58A)
--- -------www---------- TSF
|---|-->|---------- TSF |
--- | - | 35+200A/(0.58A) = 380 F
| - ---
1/(0.58A) | - -
35 F----www----- |
-
TSF is a Thevenin equivalent (no load, stagnation) sunspace air temp in
full sun. With A = 192 ft^2 (line 170) and a 140 F auto radiator and
its 2 30 watt 1000 cfm 12 V fans to heat tank water:
RS TAF Q Btu/h
1/111 1/1000 | ---
-------www-------www-----*------|-->|---- 65 F
| --> | ---
| 380 F I | |
--- 4K Btu/h | | 1/800 140 F |
- v --www---------| |--|
| |
-
We can collect 8K Btu/h of tank heat in 2 hours of full sun if the sunspace
air temp TAF = 140 + 4K/800 = 145 F. At the same time, we can collect Q Btu/h
of warm sunspace air. With RSER = RS + 1/1000 = 1/100 and I = (380-145)/RSER
= 23.5K Btu/h (6.9 kW at $55K, for PV fans :-), Q = I-4K = 19.5K Btu/h.
In diffuse sun, we have:
0.8x75x192 = 11.5K Btu/h 1/111
--- -------www-------- TSD
|---|-->|---------- TSD |
--- | - | 35+60/0.58 = 138 F
| - ---
1/0.58 | - -
35 F----www----- |
-
And:
TAD
1/111 | 1/1000
-------www---------www----- 65 F
| ---->
| 138 F I
---
-
|
-
I = (138-65)/RSER = 7300 Btu/h. We collected 2Q = 39K Btu of the 66.4K/day
air heat in full sun. We can collect the rest in (66.4K-39K)/I = HDIFF < 4
hours, so 4 4'x12' sheets of twinwall suffices. We could verify this with
a simple simulation using NREL's Allentown TMY2 weather file with measured
hourly weather data for a Typical Meteorological Year.
20 TAVG=31.8'24-hour Dec temp in Allentown (F)
30 TMAX=39.2'average daily max (F)
40 TDAY=(TMAX+TAVG)/2'average daytime temp (F)
50 GSUN=800'south wall global sun (Btu/ft^2-day)
60 DSUN=300'south wall diffuse sun (")
70 FSUN=GSUN-DSUN'south wall full sun (")
80 HSUN=FSUN/250'full sun hours
90 HDAY=6'daytime hours
100 GHOUSE=136'house conductance (Btu/h-F)
110 HHOUSE=24*(65-TAVG)*GHOUSE'average day house heat (Btu)
120 UELEC=300'indoor electrical use (kWh/mo)
130 HELEC=3412*UELEC/30'electrical heat gain (Btu/day)
140 HTANK=8000'tank heat (Btu/day)
150 ESSA=HHOUSE-HELEC-HTANK'sunspace air energy (Btu/day)
160 PRINT HHOUSE,HELEC,HTANK,ESSA
170 A=4*4*12'sunspace glazing area (ft^2)
180 RS=1/(.58*A)'glazing resistance (F-h/Btu)
190 ISF=.8*250*A'full sunspace heatflow (Btu/h)
200 TSF=TDAY+ISF*RS'full sunspace equivalent temp (F)
210 CFM=1000'fan cfm
220 RSER=RS+1/CFM'sunspace series resistance
230 GRAD=800'radiator conductance (Btu/h-F)
240 TAF=140+HTANK/GRAD/HSUN'full sunspace air temp (F)
250 PRINT TSF,TAF,HSUN
260 FSSA=HSUN*(TSF-TAF)/RSER-HTANK'full sunspace air heating (Btu)
270 ISD=.8*A*DSUN/(HDAY-HSUN)'diff sunspace heatflow (Btu/h)
280 TSD=TDAY+ISD*RS'diffuse sunspace equivalent temp (F)
290 ICAP=(TSD-65)/RSER'house cap heatflow (Btu/h)
300 TAD=TSD-ICAP*RS'diff sunspace air temp (F)
310 HDIFF=(ESSA-FSSA)/ICAP'house heating hours)
320 PRINT TSD,TAD,HDIFF
330 HCOLL=HSUN+HDIFF'solar collection hours
340 ESTOR=ESSA-HCOLL*((70-TDAY)*GHOUSE-HTANK/24)'overnight heat (Btu)
350 HCAP=ESTOR/(70-60)'house heat capacity needed (Btu/F)
360 PRINT A,HCAP,HCOLL,HDAY
GHOUSE HELEC HTANK ESSA
Avg day electrical tank heat Warm air
heat (Btu) heat (Btu) (Btu) heat (Btu)
108364.8 34120 8000 66244.81
TSF TAF HSUN
Full sun Sunspace Full sun
eq temp (F) temp (F) hours
380.3276 145 2
TSD TAD HDIFF
Diff sun Sunspace House heat
eq temp (F) air temp (F) hours
138.9483 72.40973 3.65525
A HCAP HCOLL HDAY
Glazing House mass Collection daytime
area (ft^2) (Btu/F) hours hours
192 4159.546 5.655251 6
The radiator and its fan could be at the top of a vertical duct that returns
sunspace air to the lower sunspace without mixing with room air. On cloudy
days, pump water up through the radiator to warm the house. A pressurized
plastic pipe coil heat exchanger in the tank could heat water for showers,
with the help of a greywater heat exchanger.
Air might flow as below, conceptually, with a single fan and an upper
motorized sdamper hinged at the bottom (use Honeywell's 6161B1000 $50 2W
damper actuator or a $45 DC gearmotor from Grainger or a windshield wiper
motor with limit switches or a 12V damper from an auto heater) that opens
inwards up to 90 degrees (moving counterclockwise below) to block room
airflow when it is in the horizontal position:
top 2' top
---------------------------- -----------
a. r motor s. | | |
d. fa <--> d. | | adamper |
a. d a. | | |
m. <== ai m. 2' | | sdamper | 2'
p. a p. | | |
e. nt e. | | |
r. o r. s | | |
| r-.........-| u | |-----------| west
| 4' | n | | |
| | s | | |
| ^ | p | 20' | |
| | | a | | |
| room | c | s | |
| air | e | o | |
| | | u | |
.a .s | t | |
.d room sunspace .d ^ | h | |
.a air air .a | | | adamper |
.m ==> ==> .m | | |
.p .p | | sdamper |
.e .e | | |
.r .r | | |
---------------------------- -----------
12'
---------------------------- Drawing not to scale.
a| r s|s |
d| fa d|d |
a| d a|a |
m| <== ai top <== m|m 4' | 12' south
p| a p|p |
e| nt e|e |
r| o r|r |
---------r------------------
west
Modes:
1. To heat the tank, pull sunspace air through the radiator with its fan
and return it to the sunspace below, with the motorized sdamper horizontal.
A (redundant?) lower one-way lightweight plastic film convection sdamper
opens (to the right) over a vertical hardware cloth grate when the fan runs
and prevents reverse sunspace thermosyphoning at night.
2. To heat the house, pull room air through the radiator and out to the room
via the upper adamper. The upper and lower adampers should be heavy enough to
prevent room air thermosyphoning up through the vertical duct when room heat
is not required.
3. To do both, open the damper halfway, or give house heating priority.
Notes:
1. For more exact room temp control and less mass, add mass to the upper
24'x32' of the ceiling, with a ceiling fan and a room thermostat to keep
the house exactly 70 F when occupied and 60 when it's unoccupied. An open
wintertime door in place of the upper adamper can let sunspace air flow
into the room to heat the ceiling and return to the sunspace without mixing
with room air... 120 F ceiling mass can store 7 times more heat than 70 F
mass, with a shiny surface beneath to avoid room overheating by radiation.
2. Blowing room air through the lower adamper with a window fan could raise
efficiency and prolong the life of the radiator fans. Bearing guru Dave Pine
says auto radiator fan bearings last 3000-4000 hours (some last 7000 hours)
when he tests them at 225 F, and life doubles with every 10 C decrease, so
they might last 4000x2^((225-145)/1.8) = 87K hours at 145 :-)
Nick
Jeff
> NREL says 800 Btu/ft^2 of sun (300 diffuse) falls on a south wall on
> an average 31.8 F December day with a 24.4 and 39.2 daily max and min
> in Allentown, near the PA Renewable Energy Festival, 9/22-23/07,
> http://www.paenergyfest.com, where I'll be talking about the system
> below at 2:30 on Saturday and Nathan Hurst will talk about his Mazda
> radiator solar heating experiments in Australia at 3:30 on Sunday.
Nick, can you give us a summary of how this went? In particular I'd
like to hear something of the Mazda Radiator experiments. That 800
Btu/h-F radiator has me thinking about low temperature supplemental
heating, just 10F over ambient yields a whopping 16,000 BTUs/Hr. What
I'm thinking of is storing the higher temperature water from the better
collectors and using lower temp collectors to add heat while the sun
shines. I suppose that would be like heat pump heat, not warm to the
skin...
Jeff
nicks...@ece.villanova.edu
>> ... Nathan Hurst will talk about his Mazda radiator solar heating
>>experiments in Australia at 3:30 on Sunday.
>
> Nick, can you give us a summary of how this went?
Nicely :-) Nathan ran the 2 fans in series on our Mitsubishi radiator
directly from a 20 W PV panel during his talk.
>In particular I'd like to hear something of the Mazda Radiator experiments.
IIRC, he measured 972 W/C for the radiator, ie 1842 Btu/h-F.
>That 800 Btu/h-F radiator has me thinking about low temperature supplemental
>heating, just 10F over ambient yields a whopping 16,000 BTUs/Hr.
I was just estimating vs measuring 800 Btu/h-F. We could collect
800 Btu/h-F x 10 F = 8K Btu/h that way, no?
>What I'm thinking of is storing the higher temperature water from the better
>collectors and using lower temp collectors to add heat while the sun shines.
>I suppose that would be like heat pump heat, not warm to the skin...
Sounds interesting...
>> We will all be exhibiting ourselves and a $35 1995 Mitsubishi 2.0 Eclipse
>> radiator at an "Ask the Engineer" table near Booth 24 in the exhibit area.
One often-asked question was "What are you selling?" The answer was "nothing,"
which confused people :-) Exit interviews said ours was the most popular of
the 102 booths.
Nick
Jeff
> Jeff <dont_...@all.uk> wrote:
>
>
>>>... Nathan Hurst will talk about his Mazda radiator solar heating
>>>experiments in Australia at 3:30 on Sunday.
>>
>> Nick, can you give us a summary of how this went?
>
>
> Nicely :-) Nathan ran the 2 fans in series on our Mitsubishi radiator
> directly from a 20 W PV panel during his talk.
>
>
>>In particular I'd like to hear something of the Mazda Radiator experiments.
>
>
> IIRC, he measured 972 W/C for the radiator, ie 1842 Btu/h-F.
Is that with normal 12v running them? Or with the 20W panel feeding them
in series. Seems to me the lower power, quieter version is far more
desireable. At any rate, I'm thinking of using 3 in a zone system
(radiating, not collecting) and would only need around 200 BTU/h-f out
of each.
Some time ago I had thought of using a hybrid of Bill Kreamers design
but with a small radiator in each to transfer the heat to water. Now I'm
thinking that collecting detached sunspace (or maybe big fin) heat and
pumping it into the house is a better idea. Gary did a long run with
some of his collectors. I've got about a therm of air collector (7' *
24') and will be adding about a therm of water (6 - 2' * 10' collectors
after Mike in NZ). I think another therm would put me in good shape.
Also, is there any reason for choosing the Mazda radiators? Usually
radiators are all pretty easy to remove and at my local junkyard they
are the same price. The secret to taking out radiators is a knife to cut
the hoses.
>
>
>>That 800 Btu/h-F radiator has me thinking about low temperature supplemental
>>heating, just 10F over ambient yields a whopping 16,000 BTUs/Hr.
>
>
> I was just estimating vs measuring 800 Btu/h-F. We could collect
> 800 Btu/h-F x 10 F = 8K Btu/h that way, no?
Looks like my math is off!
>
>
>>What I'm thinking of is storing the higher temperature water from the better
>>collectors and using lower temp collectors to add heat while the sun shines.
>>I suppose that would be like heat pump heat, not warm to the skin...
>
>
> Sounds interesting...
>
>
>>>We will all be exhibiting ourselves and a $35 1995 Mitsubishi 2.0 Eclipse
>>>radiator at an "Ask the Engineer" table near Booth 24 in the exhibit area.
>
>
> One often-asked question was "What are you selling?" The answer was "nothing,"
> which confused people :-)
I can imagine!
Exit interviews said ours was the most popular of
> the 102 booths.
That's great!
We (in the US) are a long way behind most of the world in thinking
solar. It's all those decades of being consumption orientated.
Jeff
>
> Nick
>
nicks...@ece.villanova.edu
>>>... I'd like to hear something of the Mazda Radiator experiments.
>>
>> IIRC, he measured 972 W/C... ie 1842 Btu/h-F.
>
>Is that with normal 12v running them? Or with the 20W panel feeding them
>in series.
IIRC, he was using driving them with 60 watts total in a PWM circuit
vs 120 W full speed. Or maybe 16 watts... Each? This is a bit vague.
>Seems to me the lower power, quieter version is far more desireable.
Sure. Over some range, power is proportional to cfm^3.
>At any rate, I'm thinking of using 3 in a zone system (radiating,
>not collecting) and would only need around 200 BTU/h-f out of each.
That means moving about 200 cfm, with perfect heat exchangers.
If a fan uses 80 watts at 1000 cfm, it might use 80(200/1000)^3
= 0.64 W at 200. Probably more. Maybe not much more.
> Some time ago I had thought of using a hybrid of Bill Kreamers design
>but with a small radiator in each to transfer the heat to water. Now I'm
>thinking that collecting detached sunspace (or maybe big fin) heat and
>pumping it into the house is a better idea.
"Large format," vs lots of boxes.
>Gary did a long run with some of his collectors. I've got about a therm
>of air collector (7' * 24')
One therm per day?
>and will be adding about a therm of water (6 - 2' * 10' collectors
>after Mike in NZ). I think another therm would put me in good shape.
Collecting warm air and hot water at the same time can be more efficient
than collecting them separately. Give the water priority in full sun,
and take as much air as possible at the same time.
>... is there any reason for choosing the Mazda radiators?
I suppose that's what was in the local auto salvage yard.
>Usually radiators are all pretty easy to remove and at my local junkyard
>they are the same price.
I abandoned a dead '97 Ford Taurus after my mechanic said it would take me
3 days to remove its radiator. Remove the front bumper, then some large
structural metal pieces above and below the radiator, and so on. Toyotas
and other late model Japanese cars have 4 plastic posts... 2 drop into
holes below and 2 fit into plates above with 2 screws. Easy.
>The secret to taking out radiators is a knife to cut the hoses.
Leave longish pieces attached to help connect them to standard plumbing
and pick cars with manual transmissions and no AC, other things being equal.
> We (in the US) are a long way behind most of the world in thinking
>solar. It's all those decades of being consumption orientated.
We don't export lots of valuable goods or services nowadays. Movies,
intellectual property, high-tech medical devices. It helps to reduce
waste and use what we have, eg dead cars and the sun. People say our
only growing resource is trash.
Nick
nicks...@ece.villanova.edu
100% Solar House and Water Heating with Sunspaces, by Nick Pine
It is commonly believed that houses can't be more than about 50% solar heated.
This is true of direct gain "mass and glass" passive solar houses, since
the windows lose lots of heat at night and on cloudy days and we have to live
inside the "heat battery," so the mass can't be hot on an average day, so
it can't store much heat.
If cloudy days are like coin flips, a house that can store heat for 1 day can
be at most 50% solar heated; 2 days make 75% possible, 3 make 88% possible;
4 allow 94%, and 5 allow 97%. More than 5 becomes uneconomical. Designing
for 100% solar heating begins with the local weather...
National Renewable Energy Laboratory (NREL) data say December is
the worst-case month for solar heating in Allentown, when 800 Btu/ft^2
of sun (300 diffuse) falls on a south wall on an average 31.8 F day
with a 24.4 and 39.2 daily max and min.
We can use basic high-school physics (eg "Ohm's law for heatflow," like
Ohm's law with different units) and algebra to determine how much insulation
the house needs, based on constant internal energy gains and a easily-built
heat storage tank: if the house is 65 F on average indoors (eg 70 F for
12 hours per day and 60 for the other 12) and a frugal 300 kWh/mo of indoor
electrical use (vs an 800 kWh/mo US national average) provides 34K Btu
of heat on an average day and a 4'x8'x3'-tall plywood heat storage tank
on the ground (with a single 10'x14' piece of EPDM rubber roofing material
folded up like a Chinese take-out box as a liner) containing 4x8x3x62.33
= 5984 pounds of 140 F water warms the house using an 800 Btu/h-F radiator
for 5 cloudy days until it cools to Tmin and the house thermal conductance
is G Btu/h-F and we keep it 70 F on a 24.4 F morning, (Tmin-70)800
= (70-24.4)G makes Tmin = 70+0.057G.
On an average day, we need 24(65-31.8)G-34K = 796.8G-34K Btu of heat energy.
If (140-Tmin)5984 = (140-(70+0.057G))5984 Btu = 5d(796.8-34K), G = 136 max,
and Tmin = 78 F, and the house needs 74.4K Btu/day of non-electrical heat.
A 1024 ft^2 house with a 640 ft^2 loft might look like this, viewed in a
fixed font:
.
. .
. .
. . 12'
8'. .
. 24' . south -->
. . . . . . .
. .
8'. . . 8'
. .
. . .
...........................
32'
. . . . . . . . .
. . .
. . .
. . .
. top . .
. . . 32'
. view . .
. . .
. . .
. . .
. . . . . . . . .
If made entirely of Structural Insulated Panels (18 SIPs?) with R-value Rv
and 1024 ft^2 of ceiling and 2304 ft^2 of walls and no air leaks, G = 136
= 3328ft^2/Rv makes Rv = 24 ft^2-F-h/Btu min; 8" R32 SIPs make G = 104.
With good airsealing and 32 cfm of leaks, we might have G = 136.
With 136 ft^2 of R30 walls and G = 136/30 = 4.5 Btu/h-F, the tank would
supply 24h(140-65)4.5 = 8K Btu of house heat on an average day, leaving
a need for 74.4K-8K = 66.4K Btu/day of solar air heat (line 150 in the calc
below.) Sunspace air keeps the house 70 F during collection time and stores
overnight heat in the house mass (line 340), which cools to 60 at dawn.
If 500 Btu/ft^2 of 250 Btu/ft^2 full sun arrives in 500/250 = 2 hours on
a 6-hour collection day and 300/(6h-2h) = 75 Btu/h-ft^2 arrives in the other
4 hours, we can model A ft^2 of $2/ft^2 Thermaglas Plus U0.58 twinwall
polycarbonate "solar siding" with 80% solar transmission over a 1 foot
air gap over a dark south wall like this, viewed in a fixed font:
0.8x250AS = 200A Btu/h 1/(0.58A)
--- -------www---------- TSF
|---|-->|---------- TSF |
--- | - --- 35+200A/(0.58A) = 380 F
| - -
1/(0.58A) | - |
35 F----www----- -
TSF is a Thevenin equivalent (no load, stagnation) sunspace air temp in
full sun. With A = 192 ft^2 (line 170) and a 140 F auto radiator and its 2
30 watt 1000 cfm 12 V fans to heat tank water:
RS TAF Q Btu/h
1/111 1/1000 | ---
-------www-------www-----*------|-->|---- 65 F
| --> | ---
--- 380 F I | |
- 4K Btu/h | | 1/800 140 F |
| v --www---------| |--|
- |
We can collect 8K Btu/h of tank heat in 2 hours at sunspace air temp TAF
= 140 + 4K/800 = 145 F. At the same time, we can collect Q Btu/h of warm
sunspace air. With RSER = RS + 1/1000 = 1/100 and I = (380-145)/RSER
= 23.5K Btu/h (6.9 kW at $55K, for PV fans :-), Q = I-4K = 19.5K Btu/h.
In diffuse sun, we have:
0.8x75x192 = 11.5K Btu/h 1/111
--- -------www-------- TSD
|---|-->|---------- TSD |
--- | - | 35+60/0.58 = 138 F
| - ---
1/0.58 | - -
35 F----www----- |
-
And:
TAD
1/111 | 1/1000
-------www---------www----- 65 F
| ---->
--- 138 F I
-
|
-
I = (138-65)/RSER = 7300 Btu/h. We collected 2Q = 39K Btu of the 66.4K/day
air heat in full sun. We can collect the rest in (66.4K-39K)/I = HDIFF
< 4 hours, so 4 4'x12' sheets of twinwall suffice. We could verify this
Nathan ran a $35 '95 Mitsubishi radiator on a 20 watt PV panel during his
Festival talk, with the 2 fans in series. In Melbourne, he measured a Mazda
radiator conductance of 972 W/C (1842 Btu/h-F.) The radiator and its fan
could be at the top of a vertical duct that returns sunspace air to the lower
sunspace without mixing with room air. On cloudy days, we pump water up
through the radiator to warm the house. A $60 1"x300' 13-gallon pressurized
plastic pipe coil heat exchanger in the tank could heat water for showers,
with the help of a greywater heat exchanger, eg a plastic 55 gallon drum
with a filter to drip greywater through a 100' black plastic PE pipe with
a smaller 100' PE pipe inside it that thermosyphons pressurized warm water
up into a tank water heater, with a way to backflush the greywater path
from time to time. A non-toxic 0.5% sodium silicate solution (eg "ACI-100"
from D. W. Davies) could prevent corrosion of the aluminum radiator core.
Air might flow as in the diagram below, conceptually, with a room air fan
and an upper motorized damper (the sdamper in the figure below) hinged at
the bottom (use Honeywell's 6161B1000 $50 2W damper actuator or a $45 DC
gearmotor from Grainger or a windshield wiper motor with limit switches or
a 12V damper from an auto heater or a cordless drill) that opens inwards
up to 90 degrees (moving counterclockwise) to block room airflow in
the horizontal position:
top 2' top
---------------------------- -----------
a. r motor s. | | |
d. fa <--> d. | | adamper |
a. d a. | | |
m. <== ai m. 2' | | sdamper | 2'
p. a p. | | |
e. nt e. | | |
r. o r. s | | |
| r-.........-| u | |-----------| west
| 4' | n | | |
| | s | | |
| ^ | p | 20' | |
| | | a | | |
| room | c | s | |
| air | e | o | |
| | | u | |
r.a .s | t | |
o.d room sunspace .d ^ | h | |
o.a air air .a | | | adamper |
m.m ==> ==> .m | | |
f.p .p | | sdamper |
a.e .e | | |
n.r .r | | |
---------------------------- -----------
12'
---------------------------- Drawing not to scale.
a|a r s|s |
d|d fa d|d |
a|a d a|a |
m|m <== ai top <== m|m 4' | 12' south
p|p a p|p |
e|e nt e|e |
r|r o r|r |
---------r------------------
west
Modes:
1. To heat the tank, pull sunspace air through the radiator with its fan
and return it to the sunspace below, with the motorized sdamper horizontal.
A lower one-way lightweight plastic film convection sdamper opens (to
the right) over a vertical hardware cloth grate when the fan runs and
prevents reverse sunspace thermosyphoning at night.
2. To heat the house, push room air into the lower part of the duct with
the room fan (eg a $50 Lasko 2155A) and pull it through the radiator and
out to the room via the upper adamper. The upper and lower adampers should
be sloped vs vertical, and heavy enough to stop room air thermosyphoning
up through the vertical duct when room heat is not required.
3. To do both, open the damper halfway, or give house heating priority.
Notes:
1. For more exact room temp control and less mass, add mass to the upper
8'x32' of ceiling, with a slow ceiling fan and a room thermostat to keep
the house exactly 70 F when occupied and 60 when it's unoccupied. An open
wintertime door in place of the upper adamper can let sunspace air flow
into the room to heat the ceiling and return to the sunspace without mixing
with room air... 120 F ceiling mass can store 7 times more heat than 70 F
mass, with a shiny surface beneath to avoid room overheating by radiation.
2. My tribologist brother Dave says auto radiator electric fan bearings
last 3K-4K hours (some last 7K hours) when tested at 225 F. Life doubles
with every 10 C decrease, so they might last 4000x2^((225-145)/1.8) = 87K
hours at 145 (i.e. 10 years of continuous operation :-)
Nick
Jeff
> Jeff <dont_...@all.uk> wrote:
>
>
>>>>... I'd like to hear something of the Mazda Radiator experiments.
>>>
>>>IIRC, he measured 972 W/C... ie 1842 Btu/h-F.
>>
>>Is that with normal 12v running them? Or with the 20W panel feeding them
>>in series.
>
>
> IIRC, he was using driving them with 60 watts total in a PWM circuit
> vs 120 W full speed. Or maybe 16 watts... Each? This is a bit vague.
>
>
>>Seems to me the lower power, quieter version is far more desireable.
>
>
> Sure. Over some range, power is proportional to cfm^3.
>
>
>>At any rate, I'm thinking of using 3 in a zone system (radiating,
>>not collecting) and would only need around 200 BTU/h-f out of each.
>
>
> That means moving about 200 cfm, with perfect heat exchangers.
> If a fan uses 80 watts at 1000 cfm, it might use 80(200/1000)^3
> = 0.64 W at 200. Probably more. Maybe not much more.
>
>
>> Some time ago I had thought of using a hybrid of Bill Kreamers design
>>but with a small radiator in each to transfer the heat to water. Now I'm
>>thinking that collecting detached sunspace (or maybe big fin) heat and
>>pumping it into the house is a better idea.
>
>
> "Large format," vs lots of boxes.
>
>
>>Gary did a long run with some of his collectors. I've got about a therm
>>of air collector (7' * 24')
>
>
> One therm per day?
I think so. That's on the south facing wall of the house. It has an
additional 16" slanted top.
>
>
>>and will be adding about a therm of water (6 - 2' * 10' collectors
>>after Mike in NZ). I think another therm would put me in good shape.
>
>
> Collecting warm air and hot water at the same time can be more efficient
> than collecting them separately. Give the water priority in full sun,
> and take as much air as possible at the same time.
Different locations. The water collectors will be roof mounted south
facing at ~ 40 degrees. I think that's not bad for Atlanta.
I have a shed at the south end of the property that will be mostly in
open sun in the winter. There's maybe a 150 SF of south facing roof
there. If I solkoted (selective coating) galvanized roofing would I get
enough temperature rise as an unglazed trickle collector? I'm thinking
this would fall short, but am unsure. I think perhaps CPVC
tarred/siliconed in the V's of the roofing and some semi serpentine
plumbing may put me in the 100F water temp range that could be usefull.
It's not something I can calculate. Certainly would be much less on a
windy day!
I think this project will wait a year. And get more costly...
nicks...@ece.villanova.edu
>... If I solkoted (selective coating) galvanized roofing would I get
>enough temperature rise as an unglazed trickle collector?
I suspect the coating wouldn't keep its effectiveness long outdoors.
Nick
Jeff
I ran across this oldy but goody article of yours:
<URL: http://www.ece.villanova.edu/~nick/Solar_Heat.pdf />
What's the verdict on trickle collectors, I haven't heard you talk
about them for a while?
It seems the big disadvantage is the need for glass as glazing.
Cheers,
Jeff
>
> Nick
>
nicks...@ece.villanova.edu
> What's the verdict on trickle collectors, I haven't heard you talk
>about them for a while?
>
> It seems the big disadvantage is the need for glass as glazing.
That's one. I had thought polycarbonate might work before learning that
it won't last long in warm water vapor. Gary's looked into unglazed pool
trickle collectors at http://www.builditsolar.com. If we trickle down
water in a narrow channels that conduct heat in from nearby dry metal
surfaces, evaporation heat loss is less.
We might use an asphalt roof as a pool collector with a polyethylene cover
and something to hold it off the shingles to keep it from gluing itself to
the shingles when they are hot and dry in full sun, eg air inflation with
overhead straps to avoid wind fatigue.
Nick
Sundug
>
> read more ยป
Direct gain passive solar, properly designed can provide much more
than 50% of heating needs, I`ve been living in a direct gain home that
solar provides 90% of heaqting needs. Doug
91 award winning solar passive homes-
http://www.builditsolar.com/Projects/SolarHomes/91HomesBook/SolPasPlans91.htm
How to design and build a passive solar home that is energy efficient,
saves money, is easy on the planet, and is GREAT to live in.-
http://www.builditsolar.com/Projects/SolarHomes/solarhomes.htm
"I Did It" Sites and Stories
http://www.builditsolar.com/Projects/SolarHomes/ididitps.htm
"I love having a passive-solar house," she said. "It definitely makes
a
difference in the winter. "On cold, sunny days in the winter, the
furnace
doesn't even come on."
Albritton's house, like all of the houses in Solar Ridge, is angled to
harness
the energy of the sun in the winter. There are large overhangs
shielding the
floor-to-ceiling windows on the south side of the house from the
summer sun. In
the colder seasons, when the sun travels in a lower arc across the
sky, the
windows are in an ideal position to harness the sun's heat.
Robald said that passive solar is enough to heat his 2,200-square-foot
house on
the majority of winter days, with the furnace only coming on at
night.
In a 4,000-square-foot home Cox built in Solar Ridge, the highest
natural-gas
bill was $54.72 for the period from mid-December to mid-January. The
next
month, the bill dropped to $45.08.
Passive solar is still the "cornerstone of energy-efficient,
environmentally
friendly homes," Schroeder said.
http://www.earthtoys.com/emagazine.php?issue_number=07.02.01&article=ecological
Licensed master mechanic Gemma McKee says her new passive solar home
near Branson, Missouri, "sticks out like a sore thumb." In other
words, there hasn't been a glut of energy efficient construction going
on in her neighborhood. McKee's home is 3,570 square feet, one story
tall and designed to include a full range of creature comforts and
unusual design aesthetics. She can also heat and cool the whole space
for under $50 a month.
--------------------------------------------------------------------------------
http://www.eere.energy.gov/consumer/your_home/designing_remodeling/index.cfm/mytopic=10290
"Passive solar homes range from those heated almost entirely by the
sun to those with south-facing windows that provide some fraction of
the heating load.
The amount of passive solar (sometimes called the passive solar
fraction) depends on the area of glazing and the amount of thermal
mass. The glazing area determines how much solar heat can be
collected. And the amount of thermal mass determines how much of that
heat can be stored. It is possible to undersize the thermal mass,
which results in the house overheating. There is a diminishing return
on oversizing thermal mass, but excess mass will not hurt the
performance. The ideal ratio of thermal mass to glazing varies by
climate.
----------------------------------------------
The Hodges Passive Solar Home in Ames, Iowa
http://www.public.iastate.edu/~lhodges/house.htm
The Hodges Residence has proved extremely pleasant to live in, both in
winter and in other months. The direct gain system provides excellent
natural lighting to both levels, even on cloudy days. The temperature
fluctuations in the home are not large, because of the large amount of
thermal storage mass with a large surface area.
--------------------------------------------
http://www.nesea.org/buildings/passive.html
Thermal Mass is any material in the home that absorbs and stores heat.
Concrete, brick, tile and other masonry materials are the most common
choices for thermal mass in a passive solar home, these materials
absorb and release heat slowly and are easily and inexpensively
integrated into the house design. They are most effective when dark
colored and located in direct sunlight. The addition of thermal mass
allows saved solar energy to heat the house at night or on cloudy
days. The combination increases the performance and energy-saving
characteristics of the home, generally for only a modest cost
increase.
---------------------------------
The passive solar home: fed up with high energy bills? Make your house
into a solar collector!
http://findarticles.com/p/articles/mi_m0KWZ/is_4_3/ai_87703742
With the help of technology and experience, passive solar houses today
can enjoy the warmth and comfort of solar heat and still look and feel
just like home. In the our region, passive solar design usually means
using the sun to help heat the house, but it can also refer to passive
cooling strategies. For the purpose of this article, I have limited
what follows to what I consider to be the easiest and most cost-
effective means of passively heating a house: using living space as a
solar collector.
Jeff
> Jeff <dont_...@all.uk> wrote:
>
>
>> What's the verdict on trickle collectors, I haven't heard you talk
>>about them for a while?
>>
>> It seems the big disadvantage is the need for glass as glazing.
>
>
> That's one. I had thought polycarbonate might work before learning that
> it won't last long in warm water vapor. Gary's looked into unglazed pool
> trickle collectors at http://www.builditsolar.com. If we trickle down
> water in a narrow channels that conduct heat in from nearby dry metal
> surfaces, evaporation heat loss is less.
I haven't looked throug Gary's site for a while, I'll look into it. He
seems to be making every issue of Mother Earth News though!!!
>
> We might use an asphalt roof as a pool collector with a polyethylene cover
I did some experimenting with polyethylene last year and have come down
against it for a couple of reasons.
1) It is one of the few, if not the only glazing that is IR transparent.
You get much higher losses due to that.
2) It's hard to find really clear poly.
It seems to make a particularly poor glazing due to those. Shame
though, because it is so cheap!
I have some vinyl show curtain liner I may try... mostly becuase I
have it.... It's dead clear. The Dome book had some vinyl pllow domes in
it and they apparently did not age well. Anyone ever try Saran Wrap?
They make that in commercial widths.
Jeff
Jeff
nicks...@ece.villanova.edu
>Direct gain passive solar, properly designed can provide much more
>than 50% of heating needs...
Bullshit! :-)
Nick
Jeff
>
> I did some experimenting with polyethylene last year and have come down
> against it for a couple of reasons.
>
> 1) It is one of the few, if not the only glazing that is IR transparent.
> You get much higher losses due to that.
>
> 2) It's hard to find really clear poly.
>
> It seems to make a particularly poor glazing due to those. Shame
> though, because it is so cheap!
>
> I have some vinyl show curtain liner I may try... mostly becuase I
> have it.... It's dead clear. The Dome book had some vinyl pllow domes in
> it and they apparently did not age well. Anyone ever try Saran Wrap?
> They make that in commercial widths.
I did some looking up of PVDC saran and it appears that it would make
an excellent coatiing. Among it's properties are moisture impermiable
and wide corrosion resistance. It's widely used and has been used on
airplanes to protect against salt spray.
But then, if it isn't already available as a commercial coating for
lexan it doesn't do us a lot of good.
Perhaps just plain acrylic which is naturally UV resistant and is
widely used in aquariums. The limiting factor is the temperature limit.
I would think trickle collectors could slide under that. Surely this
must have been tried by someone.
Jeff
Jeff
> <snip>
>
>>
>> I did some experimenting with polyethylene last year and have come
>> down against it for a couple of reasons.
>>
>> 1) It is one of the few, if not the only glazing that is IR
>> transparent. You get much higher losses due to that.
>>
>> 2) It's hard to find really clear poly.
>>
>> It seems to make a particularly poor glazing due to those. Shame
>> though, because it is so cheap!
>>
>> I have some vinyl show curtain liner I may try... mostly becuase I
>> have it.... It's dead clear. The Dome book had some vinyl pllow domes
>> in it and they apparently did not age well. Anyone ever try Saran
>> Wrap? They make that in commercial widths.
>
>
> I did some looking up of PVDC saran
One more item for anyone think of rying saran wrap. It appears that it
is no longer made of Saran! DOW switched to polyethylene.
Jeff
nicks...@ece.villanova.edu
>returns sunspace air to the lower sunspace without mixing with room air.
Air might flow as below, with no room air fan, just the 2 radiator fans
in series and an upper motorized sdamper, hinged at the bottom, with
a windshield wiper motor with limit switches that opens inwards up to 90
degrees (moving counterclockwise) to block room airflow in the horizontal
position, like this, viewed in a fixed font:
top 2' top
---------------------------- -----------
| r motor s. | | |
| a <--> d. | | |
| fd a. | | |
| <== ai <== m. 2' | | sdamper | 2'
| na p. | | |
| st e. | | |
| o 2' r. s | | (sdamper) |
| r-........-| u | |-----------|
| | ^ | n | s | ^ | cool
| | | | s | o | | | room
| | cool room| p | u 20' | --- | air east
| | air inlet| a | t | | inlet
| ----------| c | h |-----------|
| | e | | |
| | | | |
. .s | | |
. sunspace .d | | |
. air .a ^ | | |
.<== warm room ==> .m | | | sdamper |
. air outlet .p | | | |
. .e | | |
. .r | | |
---------------------------- -----------
cool room 12'
air inlet
| Drawing not to scale.
v
----------------------------
| r top s|s |
| fa view d|d |
| d a|a |
| <== ai <== m|m 4' | 12' south
| a p|p |
| nt e|e |
| o r|r |
----------r------------------
west
Modes:
1. To heat the tank, pull sunspace air through the radiator with its fans
and return it to the sunspace below, with the motorized sdamper horizontal
and Grainger's 4PC93 pump on if the tank is less than 140 F and the sunspace
is warmer than the tank. A lower one-way lightweight vertical plastic film
convection sdamper opens over a hardware cloth grate when the fan runs and
prevents reverse sunspace thermosyphoning at night.
2. To heat the house, pull room air through the radiator and back into
the room via the lower room air grate, with the upper sdamper horizontal
and the pump off if the sunspace is warmer than the room, and the upper
sdamper vertical and the pump on if the sunspace is colder.
3. To do both, alternate modes 1 and 2, moving the damper slowly, with
full action in about 5 minutes at a 1% PWM duty cycle. At full speed,
our '97 Ford Taurus wiper motor opened a 1' damper with a 3" pulley in
about 3 seconds. We put a 10 ohm resistor in series to reduce coasting.
house tank sunspace
<70? <140? >70? >tank? | damper fans pump notes
--------------------------------------------------------------------------
0 0 - - | up off off default
0 1 1 1 | down on on heat tank
1 0 0 - | up on on heat house with tank
1 0 1 - | down on off heat house with sunspace
1 1 1 1 | down on on heat house and tank
The room air temp might be 70 F during the day and 60 at night, with
a setback thermostat. The damper motor circuit might look like this,
with the damper normally down:
+12 --------------------------------------
| |
- opens when up, - opens when down,
| to limit travel | to limit travel
| |
| |
x close to raise - open to raise
| |
| lower |
| <------ |
| ----- |
|--------------|motor|-------------|
| ----- |
| |
| |
- open to raise x close to raise
| |
| |
| |
|--------------------------------------
--
The damper might look like this, in a fixed font: / \
/|motor&|
/ |pulley|
/ \ /
/ | -- |
-----------------------------------------------------------------
| . / |
| . / o|
| . / \
| . / |-
| r . / |s| upper limit
| . / f| | roller leaf
F | . / e|s| switch
| a . / l|-
| . / t|
| . / |
| d . / (up) |
| . <== / | <-- sunspace
A | . / | air
| i . / |
| . / | ~2'
| . / h |
| a . / i |
| . / n |
N | . / g |
| t . | (down) strape |
| . ---------------------------------------- |
| .| 1/2" plywood | |
| o .|----------------------------------------| |
| .| | |
S | .| 2" foil-polyiso board | |
| r .| | |
| .|----------------------------------------| |
| .| 1/2" plywood | |
| . ---------------------------------------- |
| . |
| . ~~~~~~~~~~~felt weatherstripping~o~~~~~~~~|
---------------------------------------\---------------------
^ |s s|
| ---- lower limit
room air roller leaf switch
Nick
nicks...@ece.villanova.edu
>>returns sunspace air to the lower sunspace without mixing with room air.
>>On cloudy days, pump water up through the radiator to warm the house...
----------------------------
.a motor r motor . |
.d <--> a <--> . |
.a fd . | heat water with sunspace
.m <== ai <== . 2' |
.p na . |
.e st . s |
.r o 2' . u |
|.......---r--sdamper-| n | s
| | ^ | s | o
| v | | p | u
| room | a | t
| air | c | t
| | e | h
. .s |
. sunspace .d |
. air .a ^ |
. ==> .m | |
. .p | |
. .e |
. .r |
----------------------------
----------------------------
. motor r motor s. |
. <--> a <--> d. |
. fd a. | heat house with water
. <== ai <== m. 2' |
. na p. |
. st e. s |
. o 2' r. u |
|adamper---r--.......-| n | s
| ^ | s | o
| | | p | u
| room | a | t
| air | c | t
| | e | h
. .s |
. .d |
. .a ^ |
.==> cool room .m | |
. air inlet .p | |
. .p | |
. .e |
. .r |
----------------------------
----------------------------
. motor r motor . |
. <--> a <--> . |
. fd . | heat house and/or water
. <== ai <== . 2' | with sunspace
. na . |
. st . s |
. o 2' . u |
|adamper---r--sdamper-| n | s
| ^ | s | o
| | | p | u
| room | a | t
| air | c | t
| | e | h
. .s |
. sunspace .d |
. air .a ^ |
.==> cool room ==> .m | |
. air inlet .p | |
. .e |
. .r |
----------------------------
with this simple logic:
house tank sunspace upper upper
<70? <140? >70? >140?| sdamp adamp fans pump notes
-------------------------------------------------------------------------
0 0 - - | up up off off default
0 1 - 1 | down up on on heat tank
1 0 0 - | up down on on heat house with tank
1 0 1 - | down down on off heat house with sunspace
1 1 1 1 | down down on on heat house and tank
Nick
nicks...@ece.villanova.edu
>
> ----------------------------
> .a motor r motor . |
> .d <--> a <--> . |
> .a fd . | heat water with sunspace
> .m <== ai <== . 2' |
> .p na . |
> .e st . s |
> .r o 2' . u |
> |.......---r--sdamper-| n | s
> | | ^ | s | o
> | v | | p | u
> | room | a | t
> | air | c | t
> | | e | h
> . .s |
> . sunspace .d |
> . air .a ^ |
> . ==> .m | |
> . .p | |
> . .e |
> . .r |
> ----------------------------
>
>
>house tank sunspace upper upper
><70? <140? >70? >140?| sdamp adamp fans pump notes
>-------------------------------------------------------------------------
>0 0 - - | up up off off default
>0 1 - 1 | down up on on heat tank
>1 0 0 - | up down on on heat house with tank
>1 0 1 - | down down on off heat house with sunspace
>1 1 1 1 | down down on on heat house and tank
We could lower the sdamper with an SPDT thermostat and 2 power darlingtons
when the sunspace is warmer than 80 F, like this, viewed in a fixed font:
sw* (open if ss<80 F)
+12 -------|----------------------------
| |
| sw 1K |
---X------------www---| |
| |
limit - open when - open when
switches | fully up | fully down
| |
| down |
| ----> |
|------sdamper------|
| |
| |----------------www---|
| | |
/ 1K / c |
-----www--| sw --www--|p TIP120 |
| \ \ e |
| | | |
| - - |
| |
---------------------------------------------
And lower the adamper whenever the house needs heat, with a setback thermostat
(the setback stores overnight heat in the house thermal mass):
+12 ------------------------------------
| |
/ 1K / e
hw* --www--| hw --www--|n TIP125
\ \ c
| |
| |
- open when - open when
| fully up | fully down
| |
| down |
| ----> |
|------adamper------|
| |
| hw | hw*
|------www---| |----------------www---|
| | |
/ 1K / c |
-----www--| +12 ---X--www--|p TIP120 |
| \ close \ e |
| | for heat | |
| - - |
| |
---------------------------------------------
And run the 2 12V fans when the house needs heat or (the tank needs heat
and the radiator is warmer than the tank) using a differential thermostat:
hw --------------------------------------->|--------- fans in series---|
open if |
tank > 140F |
------------- +12 --X--------|--------->|-------- f
|differential |-------uuu--- |
| | 120V relay | |--- tank
| thermostat |------------- w
------------- w
w
|
-
The pump would run with the fans, except when the sunspace is warm and
tank water is not being heated, with a NOR gate and a 12V relay:
f ---www------------ 120V
| |
/ u |
hw* ---www-----|p u X
| \ e u |
tank ---www-- | | --- pump
- -
As an alternative, we could control the system with a $99 Eway PC and
a single motorized damper and 5 one-wire DS18B20 temperature probes,
which would allow automatic passive room heating with less damper
motion and lower-power pumping after the pipes are full.
Nick
nicks...@ece.villanova.edu
gains 34K Btu/day from 300 kWh of indoor electrical use plus 5K Btu of DHW
storage tank loss, with 6 hours per day of night ventilation, we need to
store 18h/24hx39K = 29K of coolth. If its thermal mass C warms from 65 F
in the morning to 75 by afternoon, (75-65)C = 29K makes C = 2.9K Btu/F.
A house with an inherent thermal mass of say, 2K Btu/F (1 Btu/F per board
foot of drywall, etc.), might include some basement mass for cooling, eg
900/55 = 16 4"x10' horizontal thinwall endcapped PVC water pipes tucked up
between first floor joists with a 3/4" hole on top and a #3 rubber stopper.
With more pipes or some uninsulated basement walls, we could store coolth
for a few warm days in a row.
>>>A radiator and its 2 12V fans could live at the top of a vertical duct
>>>that >>>returns sunspace air to the lower sunspace without mixing with
>>>room air, with 2 motorized dampers, fully-open or fully-closed...
In summertime, we could close the lower adamper and let outdoor air enter
the basement via a one-way window convection damper and exit via a summer
sunspace vent, like this, viewed in a fixed font:
------------------------------------------
| . motor r motor . .
| . <--> a <--> . . ==> (raise the upper damper to
| . fd . . stop natural airflow when
| . ==> ai ==> . 2' | the house temp drops
| . na . | to 65 F)
| . st . s |
| . o 2' . u |
| |--adamper-r--sdamper-| n | s
| | | s | o
| | | p | 20' u thermosyphoning night air
| | 2K Btu/F | a | t cools house and basement
| | house | c | t
| | mass | e | h
| a .s |
| d .d |
| a .a |
| m .m |
| ^ p .p .
| | e .e .
| | r .r .
|...........-------------.......---------------------
| 900 Btu/F | |
| basement . basement | |
| window mass | |
| damper . | |
| | |
| . . . . |
| |
| |
--------------------------------
During the day, we could run the radiator fans to cool the house with
basement air using a room temp thermostat and an occupancy sensor:
------------------------------------------
| . motor r motor s .
| . <--> a <--> d . ==>
| . fd a .
| . <== ai <== m 2' |
| . na p |
| . st e s |
| . o 2' r u |
| |--adamper-r--.......-| n | s
| | | s | o
| | | p | 20' u basement air cools house
| | 2K Btu/F | a | t during the day
| | house | c | t
| | mass | e | h
| a .s |
| d .d |
| a .a ^ |
| m .m | |
| | p ^ .p | .
| | e | .e . <== outdoor air cools sunspace
| v r | .r .
|...........-------------.......---------------------
| 900 Btu/F | |
| basement . basement | |
| window mass | |
| damper . | |
| | |
| . . . . | |
| ==> |
| |
--------------------------------
In 6 hours, 2 2'x3' vents with a 20' height difference and a 70-65 F avg
temp diff can move 6hx16.6x2'x3'sqrt(20')(70-65)^1.5 = 30K Btu/day.
Nick