Aquaponics Digest - Wed 05/16/01
Message 1: Re: heat loss
from "Adriana Gutierrez"
Message 2: Re: heat loss
from Ronald Polka
Message 3: Re: heat loss
from Jim Joyner
Message 4: Re: heat loss
from "bennett"
Message 5: new farmer
from van jones
Message 6: Re: heat loss
from Jim Joyner
Message 7: Re: new farmer
from "KenHale"
Message 8: newish member
from "TheStraits"
Message 9: Re: heat loss
from dreadlox 'at' cwjamaica.com
| Message 1
Subject: Re: heat loss
From: "Adriana Gutierrez"
Date: Wed, 16 May 2001 02:26:12 -0500
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I just received this month's issue of Practical Hydroponics and =
Greenhouses. It has an ind-depth article on a variety of heating =
options. One other excellent source of information on a wide range of =
information, including greenhouses is Growing and Selling Fresh Cut =
Herbs, by Sandie Shores (!). It covers every aspect of growing, =
marketing, packaging, regulaotry, structures, pest control in an =
extremely comprehensive manner. Even though she is an in-ground grower =
I recommend this book to everybody, even those of us who have already =
climbed the front end of the learning curve. It is a must-have for =
specialty produce growers. Since she grew in Rochester, Minnesota, =
heating of greenhouses is a serious subject. She has made some of the =
mistakes members on this list have made and gives alternatives.
Adriana
If you can figure out a so-called "Hydronic" approach to heating =
your
system, that would be advisable over air heat alone
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I just received this month's issue of =
Practical=20
Hydroponics and Greenhouses. It has an ind-depth article on a =
variety of=20
heating options. One other excellent source of information on a =
wide range=20
of information, including greenhouses is Growing and Selling Fresh Cut =
Herbs, by=20
Sandie Shores (!). It covers every aspect of growing, marketing,=20
packaging, regulaotry, structures, pest control in an extremely =
comprehensive=20
manner. Even though she is an in-ground grower I recommend this =
book to=20
everybody, even those of us who have already climbed the front end of =
the=20
learning curve. It is a must-have for specialty produce =
growers. =20
Since she grew in Rochester, Minnesota, heating of greenhouses is a =
serious=20
subject. She has made some of the mistakes members on this list =
have made=20
and gives alternatives.
Adriana
If you can figure out a so-called =
"Hydronic"=20
approach to heating your
system, that would be advisable over air =
heat=20
alone
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| Message 2
Subject: Re: heat loss
From: Ronald Polka
Date: Wed, 16 May 2001 09:46:46 -0600
At 06:37 PM 5/15/2001 -0500, you wrote:
>Hi all,
>
>I'm building a masonry wood stove (kind of a cut down Russian) for my
>20x20 greenhouse and I want to make sure it will provide enough back up
>heat. Double glass, for my greenhouse, would require about 8k to 12k btus
>per hour with an inside/outside temp differential of 45 degrees (f). Does
>anyone know or have a feel for the relative heat loss from double plastic,
>air inflated green house compared to a double glazing of glass?
>
>I'm also interested to know your experience with plastic "air pillow"
>green houses.
>
>Thanks,
>
>Jim
Jim
The heat transmission coefficient U-value of double glazed glass
is about the same as that of inflated double polyethylene, commonly listed
as 0.70 Btu/hr ft2 deg F as given by the National Greenhouse Manufacturers
Association Standards for Heat Loss in Greenhouse Structures. Another
source, ASHRAE HVAC Systems and Applications Handbook lists double glass
as 0.5 Btu/hr ft2 deg F and double poly as 0.8 Btu/hr ft2 deg F. So you can
see there is some discrepancy between these two sources. However this value
usually does not reflect radiant losses or infiltration losses. These
should be addressed separately. A glass house will have low radiant losses
but higher infiltration losses, the magnitude depending upon construction
practices. A double poly house will have very low infiltration losses but
relatively higher radiant losses, dependant on the optical characteristics
of the particular type of poly used. These two heat loss mechanisms will
balance each other out to some degree when comparing the two types of
glazing but nonetheless contribute to the overall heat loss of the
structure. For a small system such as yours sizing to the nth degree is
difficult. Generally heating systems are sized up to provide a measure of
safety.
Do you feel confident that you can achieve adequate temperature
control within the greenhouse with a wood stove, or would you operate it to
meet a baseline load and use some other automated heater to provide heat
during peak loading hours, such as before dawn when we are all sound
asleep. By the way what is an "air pillow" greenhouse.
Ron Polka
Southwest Technology Development Institute
New Mexico State University
Box 30001, Dept 3SOL
Las Cruces, NM 88003
rpolka 'at' nmsu.edu
| Message 3
Subject: Re: heat loss
From: Jim Joyner
Date: Wed, 16 May 2001 13:38:30 -0500
Ron, thanks for the information and ideas. My "Solar Greenhouse
Book" says double glazed glass has a U value of .37. If that were
doubled I think I could still squeeze by. I'm still assuming that the
double poly ("air pillow", see below) has heat losses similar
to double glazed glass, and I'm hoping it's less.
Do you feel confident that you can achieve
adequate temperature control within the greenhouse with a wood
stove
Yes
or would you operate it to meet a baseline
load and use some other automated heater to provide heat during peak
loading hours, such as before dawn when we are all sound asleep.
Well, that's not a bad idea. I hadn't thought of doing that. I could
probably do peak supplemental heating with not very much expense -- and
sleep better.
I've used these masonry stoves before (not in a green house, though).
Heat output is fairly constant for 6 to 8 hours, and btus out are
somewhat related to the amount of wood put in. Now, if there were a 65 -
70 degree differential, I'd probably have to be up feeding the fire a
time or two -- but that shouldn't happen very often here.
Another reason I like the masonry stove is that the fuel is essentially
free for the hauling. There are 30 chair shops in my county. The shops
will give away the scraps gladly -- if not, they burn them anyway.
There's almost no pollution regardless what kind of wood it burns. The
stove is 90 to 95% efficient which means one pound of wood will give me
net about 8000 btus. Twenty pounds of wood should just about take care of
the worst night I could have, I think. Don't let me oversell or over
simplify these stoves, though, they take a little getting used to. But
the lack of fuel cost makes it worth while to me.
By the way what is an "air pillow"
greenhouse?
I saw the term used here (correct me if I'm wrong, someone). I think it's
what I mean by forcing air between two layers of poly over a frame. A lot
of my Mennonite neighbors use them, but they don't have a name for them.
They claim their heating bills are cut more than half compared to a
single sheet -- not very scientific but I suspect it's close. They claim
also that they have less wind damage because the plastic is always
taut.
Again, Thanks.
Jim
| Message 4
Subject: Re: heat loss
From: "bennett"
Date: Wed, 16 May 2001 14:46:10 -0400
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I've used these masonry stoves before (not in a green house, =
though). Heat output is fairly constant=20
=20
Could you please explain just what a masonry stove is? I'm =
considering installing a wood heater in my greenhouse-to-be. :-)
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I've=20
used these masonry stoves before (not in a green house, though). =
Heat output=20
is fairly constant
Could=20
you please explain just what a masonry stove is? I'm =
considering=20
installing a wood heater in my greenhouse-to-be. =
:-)
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| Message 5
Subject: new farmer
From: van jones
Date: Wed, 16 May 2001 14:32:32 -0500
Hello All, I am new to the aquaponic way of life. I am very
interested in organic farming (aquaponics), and I'm still in
the research phase. I do, however, plan to get into the greenhouse
business. I realize that some farming practices and also some crops
are better than others. I would like to ask a few of questions
of this group. What would be the best and most cost efficient way to
get started, which crop would be most lucrative, and lastly-
what would I do with all that tilapia when they reached maturity?
I live in northeast Arkansas about 60 miles from Memphis, Tn.
and I don't know, yet, if there is a market for this fish there.
Any and all comments and information would be greatly appreciated.
Thank You All,
Sincerely,
Van Jones
| Message 6
Subject: Re: heat loss
From: Jim Joyner
Date: Wed, 16 May 2001 15:04:09 -0500
At 02:46 PM 5/16/01 -0400, you wrote:
>>I've used these masonry stoves before (not in a green house, though).
>>Heat output is fairly constant
>>
>>Could you please explain just what a masonry stove is? I'm considering
>>installing a wood heater in my greenhouse-to-be. :-)
Bennett,
You can probably find pictures on the net under Russian or masonry stoves.
You may even be able to find plans.
Typically, it's a stove made of brick. There is a inside made of fire brick
with a skin of regular brick on the outside. Usually there is a burn box at
the bottom, there are baffles or a serpentine exhaust meant to capture heat
in its mass. There are open stoves with a hearth, the ones I build are
closed, i.e., when the burn is down to red coals, burn box and exhaust are
closed.
When a burn is done, it's done as hot and fast as possible -- this makes it
clean and the mass makes it efficient. There is never any creosote. The
only danger is if you had cracks in the stove and the fire was not down to
red coals before closing up the stove, it might yield carbon monoxide.
The burn takes about 45 minutes or so before heat is yielded. You never
have to worry about someone falling against or touching the stove because
skin temps rarely get above 120 deg. Doing this to transfer heat to water
storage is a whole nuther thing that I know nothing about . . . yet.
Also, I haven't found anything that would tell me how big a stove will
yield what in terms of btus, so I just have to guess. The model I'm
building was adequate for a 1500 foot house.
Didn't I get that term "air pillow" from you? Am I right in assuming it's
what I said it was?
Jim
| Message 7
Subject: Re: new farmer
From: "KenHale"
Date: Wed, 16 May 2001 16:19:39 -0500
Van you need to know who is going to buy your fish before you ever start
unless your just going to grow a few for your own enjoyment. Ken
----- Original Message -----
From: "van jones"
To: "s&s aquaponics"
Sent: Wednesday, May 16, 2001 2:32 PM
Subject: new farmer
> Hello All, I am new to the aquaponic way of life. I am very
> interested in organic farming (aquaponics), and I'm still in
> the research phase. I do, however, plan to get into the greenhouse
> business. I realize that some farming practices and also some crops
> are better than others. I would like to ask a few of questions
> of this group. What would be the best and most cost efficient way to
> get started, which crop would be most lucrative, and lastly-
> what would I do with all that tilapia when they reached maturity?
> I live in northeast Arkansas about 60 miles from Memphis, Tn.
> and I don't know, yet, if there is a market for this fish there.
> Any and all comments and information would be greatly appreciated.
> Thank You All,
> Sincerely,
> Van Jones
>
| Message 8
Subject: newish member
From: "TheStraits"
Date: Wed, 16 May 2001 18:56:28 -0500
Okay Hi everyone,
I've been 'listening' to the list for a while (mid-march) and thought I'd
jump on the new member band wagon
I'm Dave Strait & and I live in Buffalo Minnesota, a small
community about 30 miles west of Minneapolis. I'm
interested in aquaponics & in growing food for my
family. I've also enjoyed the off topics, sterling engines
and all.
I'm currently working on my little greenhouse, a 16x30
attached to our house via the walk out basement. Once
that is done, I'll start on the 'big house', a 30x96. Short
summer, long to do list.
Great list, please keep it up
Thanks,
Dave
| Message 9
Subject: Re: heat loss
From: dreadlox 'at' cwjamaica.com
Date: Wed, 16 May 2001 20:56:08 -0700
To all interested in stoves
. you could join the stoves group at
www.crest.org look under forums
.those guys are into building the
"perfect" stove and a re also a great resource should you ask your
techie questions there.
Mike
JAMAICA.
Jim Joyner wrote:
>
> At 02:46 PM 5/16/01 -0400, you wrote:
> >>I've used these masonry stoves before (not in a green house, though).
> >>Heat output is fairly constant
> >>
|
