alt.energy.renewable

On Sep 20, 11:43 am, nicksans...@ wrote:
> NREL says 800 Btu/ft^2 of sun (300 diffuse) falls on a south wall on
> an average F December day with a and daily max and min
> in Allentown, near the PA Renewable Energy Festival, 9/22-23/07, , 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 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 = 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 F morning, (Tmin-70)800 = (70- )G makes
> Tmin = 70+ .
>
> On an average day, we need 24(65- )G-34K = Btu of heat energy.
> If (140-Tmin)5984 = (140-(70+ ))5984 Btu = 5d( ), G = 136 max,
> and Tmin = 78 F, and the house needs 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 = Btu/h-F conductance, the tank
> would supply 24h(140-65) = 8K Btu of house heat on an average day, leaving
> a need for -8K = 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
> 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:
>
> = 200A Btu/h 1/( )
> --- -------www---------- TSF
> |---|-->|---------- TSF |
> --- | - | 35+200A/( ) = 380 F
> | - ---
> 1/( ) | - -
> 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
> = Btu/h ( kW at $55K, for PV fans :-), Q = I-4K = Btu/h.
>
> In diffuse sun, we have:
>
> = Btu/h 1/111
> --- -------www-------- TSD
> |---|-->|---------- TSD |
> --- | - | 35+60/ = 138 F
> | - ---
> 1/ | - -
> 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 /day
> air heat in full sun. We can collect the rest in ( -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= '24-hour Dec temp in Allentown (F)
> 30 TMAX= '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)
> 34120 8000
>
> TSF TAF HSUN
> Full sun Sunspace Full sun
> eq temp (F) temp (F) hours
> 145 2
>
> TSD TAD HDIFF
> Diff sun Sunspace House heat
> eq temp (F) air temp (F) hours
>
>
> A HCAP HCOLL HDAY
> Glazing House mass Collection daytime
> area (ft^2) (Btu/F) hours hours
> 192 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)/ ) = 87K hours at 145 :-)
>
> Nick

Is there a question somewhere in this, besides who cares?

JK