Boiler and thermal batteries plan

[andyjim]

Hi all, just joining. First off, is there a search function so I can avoid asking questions already discussed? Maybe it's right in front of me and I'm not seeing it. But I'll go ahead and introduce my concern.
I built a certified food facility in an old (150 yrs) barn, encompassing about 1500 sq ft. It's well insulated (foot thick perimeter walls with an inch of spray foam to the outside, then filled with cellulose. Six inches of spray foam in one section. Anyway you get the idea. We've been heating with electric, the little radiant floor heaters on wheels. With the insulation we've gotten by okay but I want to go to a wood boiler system. I'm thinking gasification boiler with thermal batteries. I'm hoping that will enable me to run the burner full throttle for best efficiency, charge up the batteries and then shut down and draw heat from the batteries until time to fire up the boiler again, hopefully as much as 3-4 days in milder winter weather. I think this will save a ton of wood (and creosote) compared to throttling the fire (and killing the efficiency) when full demand isn't there.
So I welcome comments about this notion in general, but beyond that I'll put a couple of questions out.
Does anyone know of thermal batteries suitable for this application, in the U.S? Seems like Europe is miles ahead of us on this stuff.
If I'm figuring right, I think our peak demand may be less than 50k btuh, so I think the smallest boilers available will be more than adequate, and that's another reason I'm looking at battery storage. I'd had to severely throttle an oversized boiler (which it will be), and probably tar it up it in short order as well as waste a heck of a lot of wood. I'm also leaning to an indoor installation, though willing to consider outdoor.
So comments on what mfg and size of boiler might suit are also welcome. I want one with a track record; a builder who's confident enough of their product to slap a long warranty on it.
I'm glad I finally stumbled on Hearth.com. I've been thrashing all over looking for reliable information. I think I'll find it here.
In case it helps, I was an HVAC tech in my other life, and worked with boilers a fair amount (mostly nat. gas & propane), though I would never claim to be an expert.
I'm 75 now, and in some ways just getting started in life.
andyjim

 

[peakbagger]

I guess I would need a bit more info on what you refer to as "thermal batteries" Generally most wood boilers use water a thermal storage. The size of the thermal storage is directly related to the temperature of the water you can heat with. For an example, good old Slant Fin radiators are designed to put out usable heat between 140 and 180 F. Thermal Storage with water is generally limited to less than boiling temp if the tank is metal or less if it uses a PVC liner. So the thermal storage capacity is the peak storage temp lets assume 210 F so the useful thermal temperature difference is 210 - 140 or 70 F. If on the other hand you have radiant heating loops you may be able to heat with 90 F water so the thermal temperature difference is 210 - 90 or 120F. That means you have more usable storage the lower the temp you can heat with.

You are right, running a boiler at full load to heat up an insulated tank of water is far more efficient. The most efficient way to burn wood is with a gasifier but the trade off is gasifiers need dry seasoned wood to burn. Older style boilers are less efficient but can handle poorly dried wood. They can be prone to generate creosote but batch burning is usually going to reduce that.

New York state was paying a big rebate for wood gasifiers with thermal storage. They paid to have an online course on how to design these systems run by the guru of hydronic systems. Its free https://www.heatspring.com/courses/...ncy-biomass-boilers-sponsored-by-nyserda/faqs

 

[Tonty]

You have come to the right place for advice, but sometimes you need a thick skin. Some of it can be scathing. 😁
As far as searching, here is a screen shot from a phone browser. I have the magnifying glass circled with yellow, top right hand corner. Click on that and it should open a search bar.

I don’t want to scare you off, but if you want to do a modern wood gasser with storage, you are looking at quite a bit of money.
I have a Switzer wood boiler with built in thermal storage, and I love it. It’s only 600 gallons of storage, so I go 12-24 hours before recharging in the winter. It also heats my domestic hot water during th winter. Larger units would be longer between recharge. This is an indoor unit.

 

[andyjim]

Thanks peak bagger and Tonty.
As I suspected, finding the search button only required a bit more search. As to scathing, not sure I've seen any forum that was 100% free of scathing. I've got relatively thick skin when I need it, but sometimes I deserve a bit of scathing anyway.

Well, I don't have a place to put a big insulated water tank, and using the 13 gal/kw rule of thumb from the EKO manual I think I might require 600 gal per day of desired heat storage (I'd like 3-4 days, at least in mild winter weather). What I am wondering about is these new-fangled thermal batteries with phase change materials. Good as they're cracked up to be? Available in U.S.? Economical? Sensible?

Hmm, 90F for a radiant heating loop? Gosh, I don't think I've ever seen one run at much less than 140F. Can that really work? I also plan to heat the DHW with the boiler. Since I don't have wall space available for baseboard I am thinking of hanging radiant wall heaters at the junction of wall and ceiling, angled to radiate down into the space.
Wonder what guys here think of that, and know of good ones available in U.S.?

Hmm, I'm all awed and bright-eyed about gasifiers, but possibly should give more serious consideration to a less efficient but perhaps more forgiving (more reliable?) burner. Various people have warned me about the common wood-guzzling outdoor boilers though.

Garn, Switzer, EKO and I'm sure several others .... yikes, a lot to compare & ponder. Definitely want a keeper, preferably low maintenance, and not too many bells and whistles to fail. Do those specs rule out gasifiers?

I'll also mention that we have one fermenting room (for Kombucha) that we keep at 80F. That one requires some heat year round and will need a loop of its own, though it's a small room; unless there's a clever way I can send that water on to heat another space at a lower temp. But when the other space doesn't need heat that water will have to divert right back to the tank, not through another loop.

 

[Tonty]

Hmm, 90F for a radiant heating loop?

This is for radiant in-floor heat. Like pipes in a concrete floor. I run mine at 100 degrees, and have been told that you shouldn’t go over that due to potential for the concrete spalling.

 

[stoveliker]

Angling radiators down from ceiling height will require waaay hotter water imo.
I also think 3-4 days is not feasible.
And phase change materials will be out of your budget - and may require even larger volume than water because their specific heat is smaller than that of water (even if their weight will be larger making that a wash), because you likely need heat transport infrastructure to heat up a large volume of solid phase change material.

Water is your best bet to store water in this case imo.

 

[peakbagger]

Low emitter temps are not just floors, John Seigenthaler is finding the potentially lowest supply temps using radiant wall and ceilings.

 

[stoveliker]

I based my remark regarding temperatuers on that I see that radiant ceilings run at 175-185 F (80-85 C).
One example (out of many):
(broken link removed to http://www.twapanels.ca/faq.html)

I was (mistakenly; I can't see it online) thinking about 12' high ceilings (maybe the barn thing).
Looking at that here 70 C seems to be the minimum or above (depending on the surface area of the heaters):

 

[Bad LP]

Concrete spalls when the water turns to steam and explodes. 100 degrees is not close to steam.
In my direct experience with a gypcrete pour over TGI’s with insulation between the joists that a floor warmer than 115-120 is too hot. Even at -20 F below zero I run 110 degrees max with outdoor reset. Truthfully when the loop water is 90 my bathroom floor feels cool to the bare feet.
Higher temps are also not so great on wood floors if you have them.

Lastly, on a staple up RFH installation you will be running a higher overall loop water temp was my experience at work. The wood subfloor really doesn’t transfer the heat as well as concrete (for obvious reasons) but the area I was dealing with was also difficult.

 

[Bad LP]

Low emitter temps are not just floors, John Seigenthaler is finding the potentially lowest supply temps using radiant wall and ceilings.

I’m really looking at converting baseboard for radiant wall panels. I’m loving my CI radiator in one nearly all glass room and really need another or I will just run some CI baseboard on that wall.

 

[Tonty]

Concrete spalls when the water turns to steam and explodes. 100 degrees is not close to steam.

That would be one theory. However, concrete will also spall due to uneven expansion of materials. So if you rapidly introduce hot water, even below 212, it could spall due to the materials not heating up evenly at a slow rate.

 

[hedge wood]

andyjim First off Welcome to the forum. At 75 are you ready to take on cutting wood for the next bunch of years. Running these boilers is a life style. Back in 2009 when I put my Garn in I spent thirty grand back then on the system and I did all the work other than the spray foam. In my 60's the last two leaks I have had on my Garn I have considered very hard going back to propane. If the next time my Garn is leaking and would need replaced I sure wouldn't buy another Garn and I probably wouldn't buy another boiler. I might look at something used to get me down the road a little more.

 

[hobbyheater]

I'm 73 and when I no longer can get my own wood, I would consider buying wood.
First I have a very good wood splitter that can yard and lift large rounds onto the splitting table and four good saws that meet the size of the wood that I'm cutting.


I also have a very efficient downdraft boiler with 1,045 imp. gallons of storage , and an electric splitter for making kindling!



So there is still good reason to be able to heat with wood in your senior years!

 

[Bad LP]

That would be one theory. However, concrete will also spall due to uneven expansion of materials. So if you rapidly introduce hot water, even below 212, it could spall due to the materials not heating up evenly at a slow rate.

Not my experience with heat.

Freeze/thaw cycles absolutely.

 

[brenndatomu]

Hmm, I'm all awed and bright-eyed about gasifiers, but possibly should give more serious consideration to a less efficient but perhaps more forgiving (more reliable?) burner. Various people have warned me about the common wood-guzzling outdoor boilers though.

After having walked with my folks through a recent upgrade of their long term (20 yrs) smoke-dragon-wood-guzzling Central boiler (them more hesitantly than me) and now having 1 season experience with it, I can say for sure that the new gassers really are all they are cracked up to be...they bought a HeatMaster G10000 and cut their wood usage down by 50-60% (hard to tell exactly, because the CB used so much wood that it was really hard to keep track of it all...but a good estimate is 22 full cords per year(!)...this is for heating 2 farmhouses and 2 shops, one of them pretty large) You could probably get by with the much smaller G4000.
One of the things that I really like about the EPA 2020 HeatMaster design is they have full active air control due to using an O2 sensor...a design that many european boilers have been using for a while now already....makes for a very clean and efficient burn...oh, and they meet (and exceed) the efficiency standard to qualify for the 26% tax credit available this year too (might not apply for a business though?) I like making firewood as much or more than the next guy, but why have to make more than you really have to?

You mention the old school boilers possibly being more forgiving than the gassers...while that may be technically true, why would you ever want to burn wet wood? All it does is make you use more, and smoke up the neighborhood (although that part would not be as bad if you use storage) My brother (the main operator of the G10000) said he actually found their new G10k to not be terribly finicky...he was able to burn some pine and some marginal hardwoods with pretty good success...even more so than what the dealer told him to expect. They kinda pulled the trigger on this purchase at the last minute back in the fall, so he wasn't as prepared with proper fuel as he should have been (and will be this coming winter...they already have about 14-15 cords put up in the drying shed...should only need 10-12) so he was kinda forced to use what they had on hand and hope for the best...and it worked out.

Think about it like this...lets say you can load 100 lbs of wood (probably a reasonable load in a G4000...maybe even a bit on the large side) Now say the wood is 20% moisture content (20% is the highest that can really be considered "dry"...18% would be better) so at 20% MC, that 100 lbs of wood has 20 lbs of water in it...and at 8.345 lbs per gallon, that's almost 2.5 gallons of water!! Water is what firemen use to put fires OUT, right?!

 

[Jacon Construction]

I like the O2 sensor. That would enable you to get more flexibility with having to burn wood that could be higher in moisture then you realized??
22 cords wow!