Woodstove to water heat (big fish tank?)

bennelson · 11-23-10, 05:07 PM

OK, crazy idea. Just throwing it out there.

I have a little wood stove. I love it. However, it is NOT good for a steady heat, especially unattended, and STORING that heat for any amount of time.

Water is a fairly good material to use for storing heat. It's cheap (nearly free!) flexible, moveable, has all sorts of good qualities.

The trouble with water is that it takes up a good amount of space.
I don't have a lot of space. I don't have room to add 55-gallons drums in my living room.

What I do have is a 210 gallon freshwater aquarium.

It happens to have goldfish in it.

It's not heated. I think that electric heat for something like fish is a waste. (Keep in mind these are just pretty carp, and they don't care about their water being cold. If you keep a small tropical fish tank and run a heater all day and it's you one love in life - GOD BLESS YOU!)

SOOOOOO....... What about the potential of using 210 gallons (roughly 1700 lbs) as an absorber of heat from the woodstove?

The aquarium is about 6' long, 30" high, and 24" deep. I would imagine that it would just slowly radiate heat out to the room.

How would the fish feel about it?
I image that goldfish wouldn't mind 80 degree (F) water. Any fish experts here? Being cold-blooded, their metabolism would increase. They would eat more, be more active, grow bigger, and have a shorter life span?

The aquarium is about 10 feet from the woostove. The sofa is between the two. I could run insulated pipes under/behind the sofa to the aquarium. Maybe just a coil of cover pipe poking down under the water of the fish tank as a heat exchanger?

A small pump would push water through the pipes to woodstove, where it would be heated, then back to the aquarium, where the cooler fish tank water would absorb the heat.

Heat builds up in the aquarium, making the water hotter than room air temperature. Late at night and early morning (when the fire is out) the heat from the aquarium would radiate out into room space.

The aquarium already has a thermometer on it to monitor temperature. I could probably figure out a way to automate it, based on temperature, but to start with, just watching the thermometer and modulating how much heat goes into the system should be OK.

What other things do I need to think about. Obviously, I don't want to boil the fish...
Somewhere in here I need pressure relief. That could be taken care of simply by having an additional, open-topped vessel that would allow pressure to escape. (Kinda like in a drain-back system.)

Your thoughts?

Daox · 11-23-10, 06:12 PM

Crazy idea! I also like it.

It would be useful to calculate min/max temperatures of the tank and see how many btus you actually be able to capture and compare that to how much your house uses on an average day. This could give you a rough idea of how much heating you could actually get out of it.

As for the system itself, why even have a heat exchanger? Why not just plumb it direct?

bennelson · 11-23-10, 10:49 PM

Quote:

Originally Posted by Daox

Crazy idea! I also like it.

uld actually get out of it.

As for the system itself, why even have a heat exchanger? Why not just plumb it direct?

Fish are dirty.
I wouldn't want to get gunk in the plumbing.
A current from heated water going into the tank would likely stir things up a bit.

Clev · 11-24-10, 04:04 AM

I don't think it's the temperature that's the problem for the fish; it's the continual change in temperature.

bennelson · 11-24-10, 08:48 AM

I was wondering about that as well.

I will have to do some BTU calculations. Hmmm. Actually, I will have to learn HOW to do BTU calculations....

AC_Hacker · 11-24-10, 04:54 PM

Quote:

Originally Posted by bennelson

...Keep in mind these are just pretty carp, and they don't care about their water being cold...

If you're going to extract heat from your wood stove using a pipe loop and then pump the heated water into your fish tank, you will likely cook your fish, unless you have an automatic temp sensor that can shut things down quickly when the water gets too warm.

And, since electronics are subject to failure, here's something to make a potential disaster into something wonderful:

Easy Carp Chowder

Ingredients

2 pounds carp
1 cup chopped celery
1/3 cup butter
1/3 cup flour
I cup chopped onions
1 1/2cups lima beans
1 1/2cups corn nuggets
2 tbs. thyme
1 tsp. MSG
salt and pepper
1 quart heavy Cream
1 tsp. garlic powder

Directions
Cook the carp in a microwave and take off the skin. Mix the butter and flour. Then, simmer carp, vegetables, thyme, salt and pepper slowly in cream until thickened.

* * *

-AC_Hacker

bennelson · 11-24-10, 05:26 PM

I love it!

That recipe sounds fantastic! Nice photo too!

AC_Hacker · 11-24-10, 07:38 PM

...but kidding aside, have you considered Phase Change Materials?

I spent months searching out information on PCM.

This link was the most valuable one I came across:

Reversible phase change compositions of calcium chloride hexahydrate with potassium chloride

Regards,

-AC_Hacker

bennelson · 11-24-10, 07:56 PM

Phase change materials are very interesting.

However, I am trying to simply make best use of what I already have, and in limited space.

Hard to beat all the good qualities of water; cheap, easily available, easy clean-up, etc. etc.

Also, my goldfish can't swim in phase change materials.

I DO have another aquarium. That one is ONLY 40 gallons. If I did the heat calculations, and found that using the 210 gallon aquarium was the greatest thing ever for heat storage, I could just switch over to only using the 40 gallon to actually house fish. The 210 gallon would then only be a huge heat storage tank, but would look nice in a livingroom (unlike a large pile of steel drums and pipes..)

That way, it would be heat storage, but camoflaged. If I did that, I would then do a simple open loop into the aquarium.

Tim, can you help me with those BTU calculations?

AC_Hacker · 11-25-10, 01:42 AM

Quote:

Originally Posted by bennelson

Also, my goldfish can't swim in phase change materials.

I completely understand about the gold fish...

But if you had the 210 gal tank of water (1680 lb). and you let it absorb heat from your stove until it got to 85 degrees, then let it cool to 75 degrees, it would release 16,800 BTUs of heat.

On the other hand if you had the same 210 gal tank filled with calcium chloride PCM, and let it absorb heat from your stove until it got to 85 degrees, then let it cool to 75 degrees, it would release over 178,860 BTUs of heat.

Pretty big difference...

-AC_Hacker

11-23-10, 05:07 PM	#1
bennelson Home-Wrecker Join Date: Sep 2008 Location: SE Wisconsin Posts: 546 Thanks: 3 Thanked 165 Times in 96 Posts	Woodstove to water heat (big fish tank?) OK, crazy idea. Just throwing it out there. I have a little wood stove. I love it. However, it is NOT good for a steady heat, especially unattended, and STORING that heat for any amount of time. Water is a fairly good material to use for storing heat. It's cheap (nearly free!) flexible, moveable, has all sorts of good qualities. The trouble with water is that it takes up a good amount of space. I don't have a lot of space. I don't have room to add 55-gallons drums in my living room. What I do have is a 210 gallon freshwater aquarium. It happens to have goldfish in it. It's not heated. I think that electric heat for something like fish is a waste. (Keep in mind these are just pretty carp, and they don't care about their water being cold. If you keep a small tropical fish tank and run a heater all day and it's you one love in life - GOD BLESS YOU!) SOOOOOO....... What about the potential of using 210 gallons (roughly 1700 lbs) as an absorber of heat from the woodstove? The aquarium is about 6' long, 30" high, and 24" deep. I would imagine that it would just slowly radiate heat out to the room. How would the fish feel about it? I image that goldfish wouldn't mind 80 degree (F) water. Any fish experts here? Being cold-blooded, their metabolism would increase. They would eat more, be more active, grow bigger, and have a shorter life span? The aquarium is about 10 feet from the woostove. The sofa is between the two. I could run insulated pipes under/behind the sofa to the aquarium. Maybe just a coil of cover pipe poking down under the water of the fish tank as a heat exchanger? A small pump would push water through the pipes to woodstove, where it would be heated, then back to the aquarium, where the cooler fish tank water would absorb the heat. Heat builds up in the aquarium, making the water hotter than room air temperature. Late at night and early morning (when the fire is out) the heat from the aquarium would radiate out into room space. The aquarium already has a thermometer on it to monitor temperature. I could probably figure out a way to automate it, based on temperature, but to start with, just watching the thermometer and modulating how much heat goes into the system should be OK. What other things do I need to think about. Obviously, I don't want to boil the fish... Somewhere in here I need pressure relief. That could be taken care of simply by having an additional, open-topped vessel that would allow pressure to escape. (Kinda like in a drain-back system.) Your thoughts? __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-23-10, 06:12 PM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Crazy idea! I also like it. It would be useful to calculate min/max temperatures of the tank and see how many btus you actually be able to capture and compare that to how much your house uses on an average day. This could give you a rough idea of how much heating you could actually get out of it. As for the system itself, why even have a heat exchanger? Why not just plumb it direct? __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-24-10, 08:48 AM	#5
bennelson Home-Wrecker Join Date: Sep 2008 Location: SE Wisconsin Posts: 546 Thanks: 3 Thanked 165 Times in 96 Posts	I was wondering about that as well. I will have to do some BTU calculations. Hmmm. Actually, I will have to learn HOW to do BTU calculations.... __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-24-10, 05:26 PM	#7
bennelson Home-Wrecker Join Date: Sep 2008 Location: SE Wisconsin Posts: 546 Thanks: 3 Thanked 165 Times in 96 Posts	I love it! That recipe sounds fantastic! Nice photo too! __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-24-10, 07:38 PM	#8
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 724 Times in 534 Posts	Pcm ...but kidding aside, have you considered Phase Change Materials? I spent months searching out information on PCM. This link was the most valuable one I came across: Reversible phase change compositions of calcium chloride hexahydrate with potassium chloride Regards, -AC_Hacker

11-24-10, 04:04 AM	#4
Clev Wannabe greenie Join Date: Sep 2008 Location: Crestline, CA Posts: 74 Thanks: 1 Thanked 1 Time in 1 Post	I don't think it's the temperature that's the problem for the fish; it's the continual change in temperature.

11-24-10, 07:56 PM	#9
bennelson Home-Wrecker Join Date: Sep 2008 Location: SE Wisconsin Posts: 546 Thanks: 3 Thanked 165 Times in 96 Posts	Phase change materials are very interesting. However, I am trying to simply make best use of what I already have, and in limited space. Hard to beat all the good qualities of water; cheap, easily available, easy clean-up, etc. etc. Also, my goldfish can't swim in phase change materials. I DO have another aquarium. That one is ONLY 40 gallons. If I did the heat calculations, and found that using the 210 gallon aquarium was the greatest thing ever for heat storage, I could just switch over to only using the 40 gallon to actually house fish. The 210 gallon would then only be a huge heat storage tank, but would look nice in a livingroom (unlike a large pile of steel drums and pipes..) That way, it would be heat storage, but camoflaged. If I did that, I would then do a simple open loop into the aquarium. Tim, can you help me with those BTU calculations? __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.