Life's Good, but You Would Like to Know ...

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

jebatty

Minister of Fire
Jan 1, 2008
5,796
Northern MN
Looking for some teasers for the wood boiler experimenters and geeks. Your boiler room is good, really good, but you have a nagging question about something, you want to try something but not sure how, you're looking for some information about your system but puzzled over how to get it, or you just have a teaser that a boiler geek might be able to answer.

It's the dead of winter, very cold and snowy (at least in northern MN), and occasional loading of the gasser isn't providing enough stimulation. Even drinking beer and engaging in other (un)mentionable activities are beginning to reach their limit. Life's good, but you would like to know ...
 
... where can I find a residential sized, low temperature (180F), absorption chilller to run my air conditioning using my wood boiler (at a price I would pay). Arkla made one of these in the late 70's (a high temperature unit derated to 180F operation). They are like the propane refridgerators in RV's.
 
find the plans could build one, I am guessing the a low temp unit has some moving parts think they use a small pump to move the refrigerant.
 
Glad you asked. Being in the same situation, too much free time, I painted some boiler piping with flat black paint to get accurate IR temperature readings. This worked well.
I had been running with Tremovar bypass fully open. This is OK on start up with low water returns but last PM once things got heated up I found that the Tremovar was allowing water to continue to bypass. This in turn was allowing boiler to eventually reach high temp limit. I did turn Tremovar to about 1/2 closed and that helped keep the boiler from cycling / idling.
My plans: Tonight during start up I was going to re-adjust Tremovar to the most closed position but still allow for boiler protection.
Question ?
1) When I start to close the Tremovar bypass what is the low(est) temp that I'm looking for returning to boiler ?
2) If the boiler starts to kettle down low in it's belly, should I slowly open Tremovar to reduce kettling ? Boiler kettles just a bit on start up with Tremovar wide open.
Thank you.
 
1) When I start to close the Tremovar bypass what is the low(est) temp that I’m looking for returning to boiler ?

Last year I did some performance testing on Solo 40 btu output. I have 1-1/4" lines to and from the Termovar, with a 1-1/4" gate valve as the balancing valve. The gate valve allows for fairly precise setting. I also had a flowmeter installed which made calculation of btu output pretty easy to do. I determined btu output at various return water settings, and found that if boiler return could be maintained close to 160F when system return was less than 160F, then total btu output would be higher than if boiler return were at a lower temp. My theory is that hotter internal boiler water temp allows for higher production of wood gas in the firebox than if the firebox is surrounded by cooler water.

Since I moved and reinstalled my boiler system, I eliminated the flowmeter and installed a digital sensor panel meter to read the return temp on the boiler. I run my storage typically down to 100F, and occasionally into the 80's. Currently, more to reduce or eliminate mid-burn adjustments in the balancing valve as storage return rises during a burn, I set the balancing valve to a minimum of the high 140's, and then leave it alone until storage return gets above 150F (or leave it alone completely), but if I'm around during the burn I close down the balancing valve when storage return gets above 150F. Since the Termovar never closes completely, even at storage return of 150F boiler return will be higher.
 
i would like to know..........

Do I really need to scrub the turbs as clean as I do when I clean the tubes? Can't force myself not to, got it apart, why not scrub 'em clean? a simple question, thats all i have.

Note: i have the termovar loading valve (don't need the hand valve). pricey, but it seems to really do the mixing job well. Opens (or closes) i forget which, but it really brings the boiler up to temp quickly. I usually have 160ish+ water shipping to house and storage in 45 minutes. 60 minutes and i'm looking at 180 and climbing to 195/200. And these temps are on my piping 100ft from boiler. These figures are from a cold start up.
 
Hunderliggur said:
... where can I find a residential sized, low temperature (180F), absorption chilller to run my air conditioning using my wood boiler (at a price I would pay). Arkla made one of these in the late 70's (a high temperature unit derated to 180F operation). They are like the propane refridgerators in RV's.

You might try Solar Panels plus in VA. I know they were working with some manufacturers to get some of the smaller chillers in stock.

www.solarpanelsplus.com/solar-air-conditioning/

hr
 
if i ran my outside walkway/patio snow melt zone, approx. 780 sq feet thru my basement radiant zone, approx. 1600 sq feet would it melt moderate snow at 25* ambient temp? also without adding any heated water thru a flat plate. all the tubing spacing is around 8 inches. they would be tied together and antifreezed (basement/walkway). my thought is using the basement as a heat sink with the ability to isolate the walkways and heat the basement if i ever wanted to. i dont heat the basement now and it stays 65+*.
 
If I am allowed to think/ask big, how about a home-scaled/ home-built wood-fueled Fischer-Tropsch process to yield # 2 oil for vehicular fuel? :)
 
I took a look at http://www.solarpanelsplus.com/yazaki-solar-HVAC/ for absorption AC. I sent in a request for more information. It will be interesting to see if it can work for my loads with my boiler setup (and possibly solar). We cooled our house the last two years with about 20Kbtu of window AC. 30K would have been a little nicer. The smallest unit is 120KBtu cooling so derating 50% for lower water temp (165F versus 190.4F) would give me 60KBTU/h cooling. It is generally about 66% efficient, so I would need 90KBtu/hr to generate 60KBtu cooling. I am wondering what the price is though. I think I need to prepare some more wood!
 
2.beans said:
if i ran my outside walkway/patio snow melt zone, approx. 780 sq feet thru my basement radiant zone, approx. 1600 sq feet would it melt moderate snow at 25* ambient temp? also without adding any heated water thru a flat plate. all the tubing spacing is around 8 inches. they would be tied together and antifreezed (basement/walkway). my thought is using the basement as a heat sink with the ability to isolate the walkways and heat the basement if i ever wanted to. i dont heat the basement now and it stays 65+*.

Here is a start to that calculation.

At the least you want 100 btu/ sq. ft going into that slab to melt snow at a reasonable rate. So you need 78,000 BTU/hr. Insulation below and at the edge of an outdoor slab helps a bunch, I'll assume it is un-insulated.

1600 square feet of basement slab at 4" thick would be about 14 yards of concrete. 14 yards would weight around 56,000 lbs. So that is you heat storage, or boiler so to speak. Now calculate the specific heat of concrete and determine how cold you would pull that slab temperature down, that is the delta T you have to work with. To melt snow you need the slab surface just above 32F. 34- 36F works. Generally we supply 90- 110F fluid to a snowmelt slab to get the job done.

You only have 65F to start with, maybe. You'll get @ 2 btu/ square foot for every degree difference between the ambient temperature and the slab temperature. IF you could get the slab to 40F then 40- 25 ambient =15 X2= about 30 btu/ square foot output.

There is no free heat, it can not be created or destroyed only moved around. As you pull that basement slab down, hot goes to cold so energy will transfer from the heated space above down to that colder slabs, some from the ground below until it cools.

Or you could buy a bunch of mirrors to line the sides of the drive way and let the sun melt the snow
 
pybyr said:
If I am allowed to think/ask big, how about a home-scaled/ home-built wood-fueled Fischer-Tropsch process to yield # 2 oil for vehicular fuel? :)

I ponder the same question every day as I pass thru miles of dead trees on my daily commute. The next Bill Gates
will be the person that figures that out. Volvo makes a proprietary hybrid gasifier/digester for liquid fuel from wood. If
I understand their process unburned wood gas is pumped into a liquid which is then "fermented" into a liquid form...said to
convert at 75gal/ton.

My guess it will come down to the "disruptive innovation/incumbent technology" equation. There are over 100 semi loads
of wood chips per day going to waste in my area for the past 2 years..do the math...MM
 
Hunderliggur said:
I took a look at http://www.solarpanelsplus.com/yazaki-solar-HVAC/ for absorption AC. I sent in a request for more information. It will be interesting to see if it can work for my loads with my boiler setup (and possibly solar). We cooled our house the last two years with about 20Kbtu of window AC. 30K would have been a little nicer. The smallest unit is 120KBtu cooling so derating 50% for lower water temp (165F versus 190.4F) would give me 60KBTU/h cooling. It is generally about 66% efficient, so I would need 90KBtu/hr to generate 60KBtu cooling. I am wondering what the price is though. I think I need to prepare some more wood!

I really like that small PV powered AC system they show, for small loads like yours. Last I checked they were a bit too pricey, they do have a bit or R&D money tied up in that merger. Unless you are off grid and REALLY want ac.

I think most of those new mini split are inverter systems and actually run on low voltage DC. A clever "tinker" could build up a system like that from off the shelf components, possibly.

Cooling with power from the sun sounds more fun to me. Come March or April I've has a stomach full of the wood burning ritual.

Still storage will be the challenge, just as it is in the thermal heat side. Battery technology continues to improve but it is another expense and maintenance item.

hr
 
in hot water, i already tried this so im cheating a little bit (not all the mirrors). the walkways are insulated on the bottom not the sides. if i leave it running 24/7 the water temp never drops below 40*. so with that temp it melts off 1-3 inch snow amounts fairly well. i know it wont keep up with a big storm so i need to add some heat to it. now im trying different temps to figure out what will work without using boat loads of wood. i dont need the walkways spotless i just want it to go away on its own.
 
A "poor person's" semi-modulation control for the gasser is something that would make sense. Some of the old wood stoves had a (I assume) bi-metal control on the chimney damper to increase/decrease air based on the stove temp. Something like that, perhaps a little more sophisticated, to maintain pretty even stack temp? ... thinking that stack temp is also a pretty good measure of boiler output. Stack temp above X, slow down the draft; below X, increase the draft.
 
jebatty said:
A "poor person's" semi-modulation control for the gasser is something that would make sense. Some of the old wood stoves had a (I assume) bi-metal control on the chimney damper to increase/decrease air based on the stove temp. Something like that, perhaps a little more sophisticated, to maintain pretty even stack temp? ... thinking that stack temp is also a pretty good measure of boiler output. Stack temp above X, slow down the draft; below X, increase the draft.

For as long as gasification boilers with storage have been around you'd expect some sort of flue temperature control to be commonplace, but it seems like all conventional factory controls work with respect to boiler supply temperature, which is not what I'd want for heating storage.

I've jury-rigged a PID controller that bang-bangs between slow speed and high speed according to flue temperature setpoint, which works quite well surprisingly, and is fun to watch, but it's a bit of a kludge. Off-the-shelf you could use thermocouple, a NoFo controller, and a Nimbus speed control, but I'm holding off to see what else might do the trick.

But mechanical thermostatic damper would seem to be nearly ideal, I just can't find one that is adaptable yet.

Cheers --ewd
 
Some things I may never get to ...Or figure out they are not worth doing ...

Poor mans Phase change' use my food vacume sealer to bag up candle wax/parrafin and toss it in the tank keep it clear of the in/outs

Use the temperatures from my sensors and the manufacturers specs on my HX to calculate the flow rates and report/log them in my controller program.

Replace the boiler pump with a VS model controlled by the inlet outlet temp and my controller.

Use my tank and 50 Deg well water, Water/Air HX for AC
 
jebatty said:
A "poor person's" semi-modulation control for the gasser is something that would make sense. Some of the old wood stoves had a (I assume) bi-metal control on the chimney damper to increase/decrease air based on the stove temp. Something like that, perhaps a little more sophisticated, to maintain pretty even stack temp? ... thinking that stack temp is also a pretty good measure of boiler output. Stack temp above X, slow down the draft; below X, increase the draft.
thats funny you mentioned that, im working on that now! just trying to find the right stuff cheap in case it doesnt work. or if im not smart enough to make it work.
 
Status
Not open for further replies.