Experimental Shop Heat (the plan)

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Well as many of you know, I have been researching a "massively crazy idea". A thread I started on this very sub-forum that you can find easily and read. In a nut shell I want to use the heat of a compost pile to heat my house and shop.

Well I have done a lot of online research and I found out, this is not only possible, but a lot of people are doing it. Well okay maybe not a lot, but some are doing it.

Well this is my plan. In order to test the system this winter, I want to do a trial run and see how it works. I have a small, but well insulated shop that would be awesome if it was heated 24/7, but costs keep me from doing that. My plan is to try using a compost pile to heat that shop. This will allow me to keep costs to a minimum, and yet see if this is even close to feasable.

So I am going to take haybales and form a square 2 haybales wide, by three haybales long, by two haybales deep. About 6 feet, by 10 feet, by three feet deep. The haybales will help insulate the pile from the cold outside, and help promote decomposition. I will then fill this pile with wood chips (slow decomposition) haylage and corn silage (both fast decomposition) as I own a farm and can get this stuff easily. In the end I will cover the pile up with insulated Styrofoam to keep the heat in.

As I build the pile up, I will add some black dirt to get the system going, and place black plastic pipe in coils all through the grassy/ corn matter. I will then bring these two pipes into my shop and run one through a circulator, and also through a car radiator. I will then put a box fan behind the radiator to blow the heat into my shop.

This is a very basic system I know, but I think I can get a good idea if this system will work. Everything will be manualy controlled. No expensive timers, switches or meters. If it gets too hot, I will stop the flow of water by shutting off the pump. If I need more heat, I will turn it on. If nothing else I am out a few bucks and still have a non-heated shop 24/7.

Any thoughts on my experimental heating system as explained?
 
I'd like to say "Go Get em Travis! :wave:"

One thing I'll point out, if it even sort of works, it will work a LOT better in an inslab setting, as the exchange of heat from the circulator and radiator will be much less efficient.

Good luck, take pictures! :D
 
make sure you have a positive seal between the box fan and the radiator...duct tape will work for a trial. otherwise the air will do the path of least resistance thing.
 
I think it's going to work just fine. As Tod said ... make sure you get optimum (but not necessarily maximum) air flow thru' the rad for maximum heat transfer and also make sure your piping is well insulated so that you don't lose too much heat as the warm fluid travels from the heat source pile to the rad.

My "economy of operation" thought about this small experiment is that even if all you get is a shop that is warm enough 24/7 so that tools don't rust and warm enough 24/7 so that a bit of extra heat application is all that's needed to get you to working temperature, then you've succeeded massively. To my way of thinking, that "paying for itself" temperature is something just above freezing 24/7 without adding extra heat

Please keep us posted?

cheers eh?
 
An Alternative Plan

My father came up with an alternative plan. Maybe something that is a bit easier and cheaper to build. Its interesting because for experimental reasons, it might make for a good heater test.

His plan was instead of running water through black plastic pipe, use a blower to push air through 4 inch diameter sewer pipe (the kind without holes). In his way of thinking, it would be quicker and easier to have several coils in the pile of compost and then pump that heated air into my shop directly. The infeed end would be in my shop for a cold air return.

This would simplify things greatly as I am not dealing with the thermal dynamics of water. Just warming air.

My initial thoughts were it would be hard to push air through a pipe that has so many coils and turns in it, but my father disagrees. He thinks that once the air inside the pipe gets heated, thermal convection air currents will help push the air into the shop. He thinks a small blower would be enough to do what I need.

Which idea do you think is best? I really am swaying towards my dad's idea as it is very easy and cheap to do.

Sorry about going back and forth on this thing, but I am just thinking aloud and trying to get some input and thoughts from other people. I have always said, "No one person here is smarter than all of us put together".
 
Power Generation: really thinking outside the box

Please take a look at this page, and then scroll down just a bit to the animation of the Stirling Displacement Engine. I keep looking at that animation and keep thinking..

http://auto.howstuffworks.com/stirling-engine2.htm

Would it be possible to use my unique geography here in Maine to power a small 2 horsepower Stirling Engine?

For those that are not familiar with a Stirling Engine, its a engine designed in 1819 for powering pumps. Its different in that it produces power by heat transfer and an external source. It's neat because cow chips can create heat to power it, just like ice can. Its the difference in temp that makes it run. The greater the temp difference, the faster it rotates.

Anyway, I was thinking that by using the heat of my compost pile from below, and the cold from Maine winters from above (or an ice house in the summer), I could power a 2 hp engine. I happen to have a small 1000 kw generator that could easily be hooked up to a small Stirling Engine. That way I could use all the wiring that has gone into this small gen set and I would only have to worry about powering it. Again this would be another easy, small scale test bed. I am not looking to go off the grid here, but I think it would be cool to add what would be 10% of my total house load just but letting some grass clipping rot. (it takes 10 kw to power a home roughly)

After looking at the animation, what do you guys think? Am I way off base here or is the theory sound?
 
on the air in a pipe idea......it`ll really depend on how many cfm you push through the pipe as to how much heat is actually transfered to the air...the ol` convection vs conduction arguement.....if air is the carrier of choice many small diameter pipes would be much more efficient..(fluid too)....with air it`ll loose its thermal mass much more quickly than a liquid.......i ain`t no engineer but most thermal transfer systems rely on fluid to do the heat transfer probably for a reason....
 
Travis,

This is not may area of specialization, but I believe you should consider the efficiency of the difference between water and air and the ability to transfer heat. I know that when trying to remove heat from a data center, it is much more efficient to use water than air. I have heard 3 to 4 times more efficient for water than air. Here is a link to a web page that goes into the science behind this. It also has a table that talks about the specific heat capacities of common materials.

http://en.wikipedia.org/wiki/Heat_capacity#Heat_capacity

It is also why solar collectors, engine cooling systems, etc. tend to use water and not air cooling.

As a result of this, I would consider water before I would try to use air.
 
I'd think the fluid transfer is the way to go also. Think of thermal mass. Fluid has more mass that air, thus will hold the temp longer. If you want to experiment, do some of each. Maybe increase your "field" by another bale and try both. But I'd also think that the fluid transfer would be easier to insulate from the pile to the shop than the 4" air line. And I agree with Robert that you don't want the pile too close to the shop. We've had an incedent here locally this summer where the wood chips placed on a playground caught fire. There is a web cam covering the playground for security, and they don't think anyone or anything caused it. They think it was the decomposition combined with no wind that it just caught fire.
Which ever method, how will you insulate the pipe to get it toward the shop?
The other thought I had was with the radiator. As well as sealing the blower to the radiator, also put some "blinders" on the front to direct the air away so it doesn't just wrap around back to the fan.
Hey I just thought of something that just may be wild and crazy enough for you! :wave: Let the air pipe be convection instead of forced air and house the water pipe. The heated air then becomes the insulator, and could transfer some more heat to the fluid. You'd just have to have a couple wyes in the field with caps drilled out for the fluid pipe to enter and be sealed off so the air stayed "clean". Let the air pipe rise on an angle to the shop, then drop down to the radiator. The inlet for the air pipe back to the field could be on the ground level, and the fluid return could run to in and enter. You could see if the air pipe added any heat by feeling the air coming out of it in the shop. It would be close enough to the back of the fan that the fan would pick it up and distribute it to the shop too. 2 experiments in 1!!:D Jim.
 
That is a cool idea Jim and I might try it. In fact I will try it if I get the chance to do all this. Time seems to be my enemy right now. Boy is ever getting cold here. I started shingling this morning and the first three layers of my shingle bundles were froze together. I had to take a hammer and lightly bust up the first layer of shingles in the bundles before I could get started. That only means one thing, the temp was below 32º!!:eek:

I was looking for something else today but happened to go into our family shop. Its kind of a put-anything-here-of-somewhat-value kind of place. Anyway I spotted one of those old steam radiators. About 18 inches square, plumbed for fittings of 1½ inches and with a fan and shroud all built into one. You have all seen them, like Modine or whatever that hangs from the ceilings. That would make for the perfect radiator assuming the fan still works.

Your idea is intriguing, a two-for-one kind of deal. I would definitely try it. As for the gen-set idea, too radical eh?
 
Sorry, Travis. I focused on the other idea, and didn't even think about the genset one. I don't know anthing about that type of engine, and didn't have time to educate myself on it. If it will provide free power, then yes I'd try it. Maybe it only provides power for the fans on the radiator(s) and a few lights, but it's power that you don't have to pay for, and that's a good thing! Anxious to see how it all unfolds! Jim.
 
Travis, to get any kind of a decent trial using warm/hot water, you will need a different kind of radiator, because the radiators that were built to use steam will be nearly useless with only warm water. An economical way to do it though would be to go down to a HVAC dealer, or a scrap metal yard and get the "A" frame radiator out of an OLD central HVAC unit they have replaced. It will be made using copper tubing with aluminum fins and will transfer MUCH more heat by blowing air across it than that Steam radiator. The other thing you will need to do is to use a very low speed on the fan so it doesn't Over cool the radiator before more warm water comes through. The other thing that will help is to find a small, inline LOW volume circulating pump, (like they use in home plumbing to circulate warm water in a loop system in some homes to keep hot water available at all the hot water faucets without having to run all the cold water out before the hot water shows up at the faucett). This inline pump will SLOWLY circulate the water through your system and make it much more effective.
 
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That's kind of cool Tod. I browsed through it and hit a few links but did not get a chance to digest it too much. Anyway, I was thinking today...

(hey when you are a machinist you get plenty of chances to put your mind to use on anything other than the job you are doing)

...that it would be pretty neat to design a solar wood kiln that could also help heat your home/ shop or domestic hot water needs. If you are going to spend good money on glazing materials and using your time to build something, why not see if you could dry wood and heat things????

I like to concept even if it is not feasible!

At work I have a co-worker that is very interested in helping me design and build a Stirling Engine. Just a model at first and then maybe something bigger. Together we are dreaming up a design that can utilize the heat from a compost pile and Maine's cold winters to produce electricity. We are getting some ideas geared down so that it just might work!!

We have scuttled the gen-set idea for now and are thinking of hooking up an 12 volt alternator system to the flywheel (a necessity for Stirling Engines). That would either charge a deep cycle battery, or power the fan/ circulating pump directly.

Another idea my co-worker came up with was an ice house. His idea was that by placing a separate in ground root-cellar type ice house fairly close to the compost pile, I could run two sets of pex lines. One to heat my house with the compost pile, and another to cool my house in the summer by circulating water through the ice in the ice house. The ice would obviously insulated by the ground and copius amounts of sawdust. Between the sawmills we have, and having plenty of ponds on my property, I could gather up the sawdust and blocks of ice I would need in the winter. Of course this all sounds great, but I live in Maine so the three days a year we hit the 90 degree mark might mean more work than it is worth. :)
 
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