Solar Space Heating Storage Tank Size [RE-wrenches]
Dean T. Newberry
deant at dcn.org
Sun Mar 7 19:07:16 PST 2004
<x-flowed>
Hi y'All
There are a couple of ways to transfer more energy from a heat exchanger
in a tank.
The first is to move the water in the tank Grunfoss makes a vertical
axis special pump for this. Use a relay to slave it to circulation
demand on the loop side of the heat exchanger, you only need to stir the
tank when exchanging heat in or out. .
RBI sells replacement boiler pipes, copper fin tube in various sizes.
The copper fin tube is what Heat Transfer Products uses in it's tanks to
promote heat exchange.
I'll see if I can find the formulas for calculating the heat exchange
given a delta T, heat exchange area and rate of flow on each side of the
heat exchanger.
Since you are going to pump both sides of the heat exchanger it might be
cheaper and easier to control with a flat plate heat exchanger.
cul deant
Jay Peltz, Peltz Power wrote:
>Hi Tom,
>
>Its what I have as well, but I recommend using at least 2 x that length. I
>find that I cannot get enough heat into the heat exh from the surrounding
>water.
>
>I've thought of two ways to deal with this 1. more heat exhanger, to get
>more heat out of the water quicker. 2. using a pump to move the water
>just a bit. ( althought haven't figured out a good way to control the pump)
>
>jay
>
>Peltz Power
>----- Original Message -----
>From: "Tom Simko" <tom at skylinesolar.com>
>To: <RE-wrenches at topica.com>
>Sent: Saturday, March 06, 2004 8:20 PM
>Subject: Re: Solar Space Heating Storage Tank Size [RE-wrenches]
>
>
>
>
>>Travis,
>> As to the heat exchangers, its pretty hard to beat a roll of type K
>>
>>
>copper
>
>
>>for cost effectiveness and ease of installation. I threw a 60' roll of
>>
>>
>3/4"
>
>
>>K into my 500 gallon storage tank about 20 years ago, and its still
>>
>>
>working
>
>
>>fine, (glycol loop now serving 6 4x8 Heliodynes). I also augment the
>>
>>
>thermal
>
>
>>array with a wood fired boiler (my own design) if needed. A finned
>>exchanger would be the way to go if room was a factor,but you'll have
>>
>>
>plenty
>
>
>>of course in the size tank you're considering.
>> The ICE blocks should make a dandy storage tank, just make sure you dowel
>>the floor slab with rebar to lock the walls into place, and more foam
>>
>>
>sheet,
>
>
>>especially on the bottom sure wouldn't hurt, more is better in this case.
>>I'd suggest a 1,000 gal tank max, 750 minimum.
>>
>>Tom Simko
>>Skyline Solar
>>Idaho
>>
>>
>>on 3/6/04 9:41 AM, Travis Creswell, Ozark Solar at ozsolar at ipa.net wrote:
>>
>>
>>
>>>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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>>>
>>>
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--
* Cooperative Community Energy* *Dean T. Newberry*
430 D Street, Davis CA, 95616
Tel: 530 758-6064
Fax: 530 758-3684
Email: deant at dcn.org
Web: CCEnergy.com
Talbott Solar <http://www.dcn.davis.ca.us/go/deant/>
Contr. Lic. # B-667908
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