# Re: Best Starting method

Posted by nicksanspam on October 1, 2005, 6:15 pm

Au contraire. You might make an air heater with an inexpensive sunspace or
polycarbonate "solar shingles" over a south house wall for space heating
with a 1-2 year payback.

Or supply close to 100% of the hot water needs for a family of 4 all year
with a simple solar pond water heater like this, with a 4'x8' polyethylene-
lined tank under a greenhouse with 6'x8' of 6 mil PE or 4'x12' of 0.020"
flat polycarbonate film for the south wall and 6 mil PE for the north, with
whitewash or reflective Mylar under the north. The south wall might have
a 6' slant height. The north might be roughly parabolic, like this:

.           -
.   .
6'.      .
.  |      .    h
.           .
.    |        .
.................. -
|  d            |
|               | 3'
|               |
-------------------
4'
---------------
|               |
|               |
|               |
|               |
|               |
|               |
|               |
|               |  8'
|               |
|               |
|               |
|               |
|               |
|               |
|               |
---------------

10 DATA 60,1020,1160,100,2410,440
15 W=4'box width (feet)
20 D0.45001#/12'south wall to ridge distance (feet)
30 H=SQR(6^2-D^2)'ridge height above water level (feet)
40 PRINT D,H
50 FOR CASE = 1 TO 2'January and July in Phoenix
60 READ TD,HSUN,SSUN'daytime temp (F), horiz and south sun (Btu/ft^2-day)
70 EIN=.9^3*D*HSUN'direct sun from above (Btu/wft^2-day)
90 SUNHOURS=6*CASE'solar collection hours
100 EOUT=SUNHOURS*(140-TD)*W/2'daily heat loss from top (Btu/wft^2-day)
110 DHWHEAT=8*(EIN-EOUT)'daily hot water production (Btu)
120 DB=3'depth of box (feet)
140 QB*W*8*62.33*(140-110)'heat stored on average day (Btu)
150 RB 'R-value of db'xw'x8' box
160 AB=2*(W+8)*DB+2*W*8'box area (ft^2)
170 GB/RB'box thermal conductance (Btu/h-F)
180 LB\$*(125-TD)*GB'box heat loss on cloudy day (Btu)
200 ND=QB/(LB+DHWL)'cloudy day storage (days)
210 PRINT CASE,DHWHEAT,LB,ND
220 NEXT

d             h

2.537501      5.437011 feet

daily         daily         numbe of
month         output        loss          cloudy days

January       40518.5 Btu   10608 Btu     4.420568
July          40541.5       4080          5.267324

During the day, a \$ 10 watt fountain pump would move tank water over
a 4'x8' layer of EPDM rubber over a 2" horizontal polyiso board cover,
and the water would drain back at night. Cold pressurized house water
would enter a \$0 1"x300' coil of PE pipe under the cover and emerge to
enter the cold input of a conventional water heater inside the house,
which would do nothing most of the year. The materials cost would likely
be less than \$00. See more details at http://builditsolar.com .

Nick

Posted by Derek Broughton on October 2, 2005, 3:22 pm

nicksanspam@ece.villanova.edu wrote:

Even so, it _is_ cheaper to conserve the power you're already using than to
retrofit methods to utilize solar energy to an existing house (even with
Nick's cheap solutions).  otoh, if you're building a house from the ground
up, it's cheap (ie, same cost as standard building practice) to build in
passive solar heating
--
derek

Posted by Solar Flare on October 3, 2005, 9:19 pm
A second heating system is never as cheap as one.

nicksanspam@ece.villanova.edu wrote:

Even so, it _is_ cheaper to conserve the power you're already using than to
retrofit methods to utilize solar energy to an existing house (even with
Nick's cheap solutions).  otoh, if you're building a house from the ground
up, it's cheap (ie, same cost as standard building practice) to build in
passive solar heating
--
derek