Solar Space Heating Storage Tank Size [RE-wrenches]

Dana Orzel dana at solarwork.com
Sat Mar 6 10:09:01 PST 2004


Hey there Travis,

How about pouring a 4" to 6" Insulated slab with WIRSBO or eq. radiant heat
tube in the slab, viwalah - NO TANK REQUIRED. You are already pouring a slab
why not put it to work for you twice. Contact me off list or call to
discuss. This concept I call SDI - Solar Direct Injection PV pumped solar
heated water from a shw collector direct into the slab with a backup heat
source paralleled into the slab. I wish I could take credit for the concept
and origination but Bristol Stickney in NM is the man to whom I credit with
this.

Responsible Technologies for Responsible People.
Great Solar Works, Inc.
dana at solarwork.com - 970.626.5253
Ridgway, CO, USA

----- Original Message ----- 
From: "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
To: <RE-wrenches at topica.com>
Sent: Saturday, March 06, 2004 9:41 AM
Subject: Solar Space Heating Storage Tank Size [RE-wrenches]


> Hello All,
>
> I am designing a storage tank (atmospheric) for the radiant in floor
heating
> system for my new shop.  The office portion the shop will be constructed
of
> Insulated Concrete Forms (IFC's) with a concrete roof.  This will allow it
> to be also be used as storm shelter.  Three tornados missed us by less
than
> 5 miles last spring.
>
> These same forms will make a great tank as they are plenty strong and well
> insulated.  One wall of the storage tank can be shared with the office
> reducing the number of forms needed for the tank and the concrete pump
trunk
> will already be on site for the office walls.  I've had an engineer look
it
> over and he has given it his blessing to build a tank up to 8' tall!
>
> Of course I will have to line the tank, which is easy enough with EPDM.  A
> reasonably tight insulated lid will need to be constructed as well.
>
> I'll have 400 ft2 of liquid flat plates and a very efficient wood
> gasification boiler rated at 140,000 Btu's output.  Does 600 Btu's/ft2/per
> day sound right for the solar thermal array?  I'm thinking that is safe as
> here in Southwest Missouri our average winter daytime temps are reasonably
> mild.
>
> My main questions are the size and shape of the tank.  I can build the
tank
> in any size or shape (tall and skinny vs. short and wide for example).  In
> looking over some of my dated solar books, 2 gallons per sq ft seems to be
> the maximum ratio of thermal collector to storage.  I assume that "rule of
> thumb" was long before the widespread use of radiant in-floor heating.
> Since radiant in-floor requires lower temps than baseboards or forced air
is
> it acceptable (or required) to use a larger storage tank?
>
> I've built a very detailed spreadsheet that allows me to see how long it
> will take to "recharge" various sizes of tanks with the solar thermal
array
> and the wood boiler.  The most efficient operation of the boiler is to be
> fill it with wood then run wide open until the wood is gone.  If the tank
is
> not large enough then the boiler will shut down and smolder thus lowering
> the efficiency of the burn cycle.  The spreadsheet shows me that one
firing
> of the boiler will easily charge up to a 1500 gallon tank.  But this size
of
> tank amounts to nearly 4 ft2 of thermal per gallon of storage.  One idea
is
> to build a tall skinny tank.  I could place the solar heat exchanger
higher
> in the tank so it has less water to heat.  This is assuming that
> stratification will keep all that heated water up near the top.  Can
anyone
> confirm if this is a reasonable expectation?  The space heating tanks that
> I've seen are very short but that might have been for structural reasons.
>
> Does anyone have a source for the finned copper coils that were commonly
> used in these systems?  I'd rather use them than make my own coils.
>
> Any thought and suggestions are appreciated.  I'd be glad to share the
> spreadsheet and the system diagram should anyone want it.
>
> Thanks in advance!
>
> Travis Creswell
> Ozark Energy Services, Inc.
>
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