Combined domestic hot water and house heating system

[Lloyd]

Sorry just one more link...I'm done
http://www.tsl.uu.se/UHDSG/Popular/Peat.pdf

Other uses:
Peat has also been used as an isolation material for construction due to the low thermal conductivity. Iceland, Ireland and many other places suffer from lack of major forests and had to use other construction materials. Peat was then used as an isolating layer between the outer wall and the inner wall or as covering material on the roof.

Here is a link http://www.pws.gov.nt.ca/pdf/GEP/13-Insulation-Apr04.pdf to a gov study on northern pipeline insulation issues....which may be a good resource for all insulation ideas.


http://www.vdh.virginia.gov/EnvironmentalHealth/Onsite/Regulations/FormsDocs/Documents/Eco-PureTypicalDesigns.pdf It could also be combined to create a water purifier.

http://www.eco-purewastewatersystems.com/septicpumptanks.html Eco Pure Poly Septic Tanks

Methods of Insulation http://www.freepatentsonline.com/6105335.html

Peat Moss Insulating Panels http://www.kompass.com/guide/extraction-industries/peat-moss/GSENWW51010102_C11140.html

Thanks,

Lloyd

[mbryner]

Lloyd,

Well, I'm learning new things about peat.  Peat may be a great insulation material, but how would you use it around a wooden storage tank like most of the guys here are interested in?   It would make the wood rot and be wet all the time.   Also, it wouldn't work in my situation because if I do place a septic tank under the foundation of my house, the building dept will want it surrounded by non-compactable material, i.e. gravel, sand.

Anyway, I was all excited about this septic tank heat storage idea, thinking we had a novel concept.   Then I found another guy on the net who did it 30 years ago:

http://yarchive.net/ac/solar_heat.html

Still, it's pretty cool.

Marcus

[mbryner]

OK, I feel stupid.  I'm finding more and more stuff about using septic tanks for heat storage online:

http://hearth.com/econtent/index.php/forums/viewthread/17752/P0/

[mike90045]

When peat is kept dry and fluffy, it's insulative.  If damp, it rots, composts, decays.  Hay bale houses do the same.   If you want insulation, keep it dry < 20% moisture, otherwise it will decay.  You may get a little warmth from it's decay, but you then start loosing insulation that must be replaced. Same from the methane, too much work to try to get methane from your peat insulation, then you have to clean up the mess, and replace it.

[Lloyd]

When peat is kept dry and fluffy, it's insulative.  If damp, it rots, composts, decays.  Hay bale houses do the same.   If you want insulation, keep it dry < 20% moisture, otherwise it will decay.  You may get a little warmth from it's decay, but you then start loosing insulation that must be replaced. Same from the methane, too much work to try to get methane from your peat insulation, then you have to clean up the mess, and replace it.

Mike,

You are for getting the anaerobic process, natural peat bogs are a direct result of being water saturated, which creates the oxygen starvation.

Lloyd,

Well, I'm learning new things about peat.  Peat may be a great insulation material, but how would you use it around a wooden storage tank like most of the guys here are interested in?   It would make the wood rot and be wet all the time.   Also, it wouldn't work in my situation because if I do place a septic tank under the foundation of my house, the building dept will want it surrounded by non-compactable material, i.e. gravel, sand.

Anyway, I was all excited about this septic tank heat storage idea, thinking we had a novel concept.   Then I found another guy on the net who did it 30 years ago:

http://yarchive.net/ac/solar_heat.html

Still, it's pretty cool.

Marcus

Marqus,

I think that the ply tanks are going to suffer rot in a very short time, the liner will trap the moisture. The only sure way to slow the rot will be to use pressure treated lumber and plywood.

All insulation material are subject to water take up and will eventually loose their insulating values...yes even the various of foam boards, especially if they will be used in the tank.

It might be possible to excavate a 2-3 foot  around the septic tank and back fill that with peat.

Lloyd

[Lloyd]

Marcus,

When I built my cabinet shop, the Old Swed who poured the slab put about 1 1/2 foot of  highly compacted peat down, then a layer of 6 inch crushed rock, then a 5' reinforced concrete slab, the floor stayed at near room temperature, and was warmer than room temp in the morning before the shop heater came on. After 20 years the slab has not failed, and shows absolutely no signs of hydrostatic pressure cracking.

Lloyd

[BruceM]

Where do you get Peat for cheap?  I've never seen anything but very expensive bagged Canadian Spaghnum (sp?) peat moss here in AZ. It would make foam look cheap.

Foam board also works well under a slab, so it's also only a matter of cost and risk. Foam between slab edge and stem wall is also very important, thermally.

I don't suppose there is any data available on R value for peat moss at various compressions/density?

[Lloyd]

Hi Bruce,

My shop is a pole building, so no stem wall.

In Seattle at Home Crapo the good Canadian Peat goes for about $6.00 per bail...don't know the weight, but it is highly compressed, and the bail is about 36 x 18/20" square.

Which is way cheaper than insulation at the same store.

A good garden/farm store will likely sell it by the yard or truck load.

Lloyd

[BruceM]

I'm still trying to find some R-value info for peat moss.  Any suggested links? 

[Lloyd]

Hi Bruce,

I'll have a look....Quick search turned this up, certainly worth looking at.


http://www.perlite.com/faqs.htm
Q. What about Perlite's insulation uses?
A. Perlite's R-value is nearly 3.0 per inch at 6-lbs./cu. ft. density. It registers 0,0,0 on ASTM's E-84 fire tests for flame spread, fuel contribution and smoke density. Water resistant, silicone treated Perlite is poured directly from the bag into cmu block and cavity walls. UL Design U905 shows that a 2-hour fire rated 8", 10" or 12" concrete block wall improves to 4-hours when cells are filled with water resistant Perlite insulation.

or this

http://seanmichaelbutler.wordpress.com/2009/01/05/your-home-is-garbage/
A Bioblock with a one-foot thick EPS or peat moss core, on the other hand, achieves an R-value of 40.


http://www2.niles-hs.k12.il.us/jacnau/IJAS/Best%20in%20Category%20Winners%2706.htm
29. Which Filling Gets Top Billing?

Purpose

            The exhibitors are attempting to determine which of four selected materials, when used as fill in a burlap sack, performs best at stopping the passage of water.

Procedure

            The exhibitors assembled a controlled water flow device and filled burlap sacks with each of the four selected materials: sand, soybeans, diaper material and peat moss.  Using their controlled water flow device, the exhibitors tested the performance of each material in stopping the passage of water.  These tests produced substantial, reliable data from which to determine the efficacy of the fill materials in stopping water flow.

Conclusion

The exhibitors concluded with reasonable confidence that peat moss blocked the highest volume of water, followed by, in order, sand, diaper material and soybeans.  Peat moss was the most effective at stopping the passage of water.  The exhibitors noted, however, that the peat mossÕ lack of measurable weight would be a problem in actually substituting peat moss for sand in any burlap sack barrier, as pressure would have to be applied to keep the bags in place.  The exhibitors expect that a combination of sand and peat moss could provide both an improved fill material for any burlap sack barrier and a more environmentally-friendly option.

[Lloyd]

Bruce,

A definitive answer.


On the other hand, some tests carried
out by the National Research Council some years ago on a material
marketed as peat moss indicated a "k" value of 0.29 when placed
at 3.2 Ib./cu. ft. density.
http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/tn/tn222.pdf

[Ronmar]

When I build my large heat storage tank I will depend on the heat stratification of the stationary hot water for additional efficiency.

Ditto.

ronmar, how would a flatplate heat exchanger work in a large tank?   Don't they have to have a counter-current set-up of transfer fluid and fluid to be transferred to?

Same as a copper coil would in a large tank.   Pump hot water thru a coil at the bottom of a tank of water, and the tank water that gets heated by the coil rises to be replaced by cooler water.  Add or subtract energy to/from the tank and you will have fluid movement.  Stop moving energy and the water will mostly stop and stratify.  I say mostly because you will always be removing/loosing energy.  

Since the flat plates thermosiphon so well, a vertically oriented flat plate heatex at the bottom of a tank, with the primary "loop" fed with a hot supply and cold return pipe, would induce thermosiphon flow in it's secondary "loop". A chimney pipe on the upper outlet of the secondary side would assist this flow and deliver the warmed water to the top of the tank.  This would also allow you to setup counter flow which would be more efficient and which is not really possible with a free coil in or at the bottom of a tank(see attached drawing).  This would be way easier to service than the coil in tank, cost less than the copper coil material for a given surface area, and be more efficient IMO.

Turbulence is your friend in heat transfer.  A coil in tank heats up, and the surrounding water absorbs this heat.  Since there is nothing really there to channel the water, it dosn't readilly move away due to eddy currents and friction.  As the warmed water slowly flows around the pipe it builds up laminar flow.  So you get a really warm layer right against the pipe skin, kind of like the water layer in a wet suit.  This warm water against the pipe, effectively lowers your Delta T which slows heat transfer.  It takes time for the heat to move thru this layer to dissipate into the surrounding water.  So you either need to pump your supply water slower to allow more time for heat transfer, or add additional surface area(copper) to compensate for ths fact.  The same thing is also happening on the inside of your copper pipe where the pumped fluid builds up a laminar layer against the skin of the pipe which insulates the warmer center flow from the cooler pipe skin.  Most of the Wort Chiller builders reccomend running a piece or two of bare copper wire(there is that "C" word again) inside the pipe to cause turbulence and help break up laminar flow.  The opposed herringbone pattern of the flat plate heat exchangers makes laminar flow all but impossible even at very slow flow rates.  That is the real key to their efficiency.

I believe this same configuration could be used for domestic water pre-heat.  Just put the heatex at the top in the warmest water.  As long as the water at the top of the tank is warmer than the feed water, it should cool the water which will flow downward thru the heatex secondary, same as the cooled water falls in a thermosiphon radiator...   My personal plan will have a little twist on this scheme with a pump that is controlled by a thermostatic switch set just a little higher than the electric element controller is.  As the water tank temp falls, this pump will draw cool water from the bottom of the domestic hot water tank and pump it thru the heatex to maintain domestic tank temp instead of the electric element cycling on.

[BruceM]

Thanks Lloyd, alas I'm not able to convert that to a US R value for comparison. A K value is the same as the newer U value, I think.   R= 1/U if it was in US units, but I'm not sure to get it to an R value per inch thickness.  It does seem like an interesting material for some applications.

[mbryner]

Ronmar:

That's an interesting idea.  All the flatplate exchangers on e-bay are pretty expensive though....   Where were you going to get them?

[Ronmar]

Some of the industrial flat plate exchangers are pretty expensive.  The one I am using is a brazed variety, stainless plates, brazed together with copper in an oven.  Search "brazed flat plate heat exchanger" on ebay  and you will see a lot of these smaller units engineered for domestic heating and lighter industrial applications.  I bought the one I use on my 6/1 from a wood fired boiler vendor for under $100 delivered.  5"x12", 10 plate, about 600 sq/in.  It quite easilly takes 195F engine coolant and delivers 120F domestic water, transfering about 18,000 btu/hr at full engine load...  www.flatplate.com has an online calculator to help you choose an appropriate sized heatex for your application.