Hybrid Car – More Fun with Less Gas

External stacked plate HE -vs- in tank

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Posted by v8z on March 18, 2011, 2:31 pm
 
I'm planning on installing a closed loop, gycol filled solar thermal system
sometime this season.  The panels will be located on a shade roof on the
south side of the house that is part of the passive solar design.  That roof
give me room to mount three thermal panels, one PV to power the pumps &
controller, and makes for a direct route above the ICF wall, through the
sill, parrallel with the joists to the DHW tank at the center of the
basement.

I have most of the components decided upon and some already purchased:
3 - AET  AE-24 panels
1 - 30watt PV panel brand TBD
1 - ( possibly 2, see below) Laing D5 solar pumps
1- Eagle D2 PV powered pump controller
air vent, expansion tank, epdm pipe insulation, etc.

What I haven't been able to decide upon is storage and heat transfer.  The
house is only a year old and has an extremely efficient 50 gal Rheem
power-vent NG DHW tank.  I'm figuring the system should have add'l 60 - 80
gall of storage capacity.  What I can't decide between, based on research
I've already done, is whether to go with an in tank heat exchanger like the
one made by Rheem ($$$$$$$$$), or use a well insulated electric tank with
the elements removed and an external stacked plate exchanger like shown here
http://www.solartubs.com/solar-water-tank.html

I would use a second pump to circulate water through the HE and back to the
storage tank, instead of relying on convection.

Any experiences, thoughts, observations, etc. from this group?



Posted by Steven Shantz on March 21, 2011, 8:41 pm
 
I have an external brazed plate (50 plates) HX on my system, and I
love it!  I cannot see many advantages in an internal coil HX other
than ease of connection.  The cost of the electric heater tank + the
HX is way less than an internal coil tank, and if the HX ever gives
out, it can easily be replaced.  Not so with an internal coil!  I am
very satisfied with this arrangement.

Steve



Posted by v8z on March 22, 2011, 1:27 pm
 Steve,

Some add'l questions:
Do you have your HX insulated?  If so, how?  I was thinking of making a box
out of 1" PU rigid insulation then foil wrapping?
Do you have a circ pump on the tank side of the HX?

TIA,
v8z

I have an external brazed plate (50 plates) HX on my system, and I
love it!  I cannot see many advantages in an internal coil HX other
than ease of connection.  The cost of the electric heater tank + the
HX is way less than an internal coil tank, and if the HX ever gives
out, it can easily be replaced.  Not so with an internal coil!  I am
very satisfied with this arrangement.

Steve



Posted by Steven Shantz on March 23, 2011, 8:50 pm
 Yes, I've insulated my HX exactly as you have described.  I have a
very small ELSid pump on the tank side of the HX, powered by a small
PV panel. They glycol loop has its own 20 Watt ELSid pump, with
another small PV panel. It is most excellent!   When the sun shines,
the pumps run.  No other controls.



Posted by v8z on March 24, 2011, 1:47 pm
 Thanks for the info!

Yes, I've insulated my HX exactly as you have described.  I have a
very small ELSid pump on the tank side of the HX, powered by a small
PV panel. They glycol loop has its own 20 Watt ELSid pump, with
another small PV panel. It is most excellent!   When the sun shines,
the pumps run.  No other controls.



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