DIY thermal storage

[Dman008]

Hi everyone,

Im looking to get a froling s3 turbo or possibly an effecta to replace my hs tarm 500. I'm having trouble finding a NYSERDA qualified installer near me in the lower Hudson Valley of Orange county NY, but fingers crossed because I need the incentives to afford it.

Do any of you have experience with or can point me in the direction of a resource on building your own hot water storage system rather than buying premade. What specifications must it have? How much do the heat exchangers cost? How many do I need? For DHW and baseboard.

Is this just a matter of finding 2x 500 gallon propane tanks and insulating them?

Thank you!
Danny

 

[maple1]

Specs? Most size to how long they want to go between burns, which depends mostly on your heat loss/load.

If you do pressurized, only one HX is needed - for DHW. Costs vary depending on size & usage - $200 area?

Most on here have done as you suggest. But when it comes right down to it there is some DIY 'at your own risk' element involved. So if you are talking incentives & state related programs you would need to do whatever they spec to meet their qualifications. If doing pressurized storage, that could mean ASME approved stuff which is $$$. In that case non-pressurized (not usually done with LP tanks but rather a lined box type tank) with additional HX for the heating side might be the alternative.

 

[peakbagger]

American Solartechnics will either sell you the entire tank or a liner and coils if you want to DIY a non pressurized tank. The tricky part with non pressurized tanks is that the only liner that holds up is a specialized PVC product. EPDM is not designed for long term elevated temperature submerged service.

Sizing is dependent on your boiler heat output and heating demand. One very important issue is what do you have for radiators?. If you have standard fin type radiators they were most likely sized for an oil furnace that runs between 150 and 180 F. The heat transfer drops off steeply if you go cooler. The storage tanks usable thermal capacity is the difference between how hot you can heat it (about 180 for non pressurized and possibly 210 very optimistically for pressurized) and the lowest temp your radiators will heat the house which is probably 140 in very cold conditions. If on the other hand you have radiant heat in the floors or walls, they can use heat down to around 85 deg F. 180 - 85 is lot better than 180 -140.

The amount of heat stored is the number of gallons multiplied by 8 lbs/gal multiplied by the temp difference. Next Is how days to you want between firing the boiler? I think most folks size the tank so they fire once per day in the coldest weather. You then need to know how much heat you need to heat the house. The right approach is a heat loss calculation but some folks wing it by tracking oil or gas usage over a couple of days. So if I assume the boiler is rated for 85000 btu/hr output and the house needs 200,000 btus over 24 hours that means you need to fire the boiler 2.3 hours and store 200,000 btus. Now divide by the delta T based on your radiation which may be 40 degrees for non pressurized storage and you get your minimum storage of 5000 pounds of water or 625 gallons. Note this is a very short from method as tanks stratify so that the highest temp at the top is definitely not the temp at the bottom so the overall delta T is lower. That is offset by I am using 24 hours of storage and really you only need about 21 as for three of those hours you are running the wood boiler. I have a small tight house, slant fin and 550 gallons of storage and I usually am pushing it in very cold weather to make it 24 hours. Very few folks ever complain they have too much storage but even with the American Solartechnics square design that takes up lot less room than propane tanks, its still a lot of space in basement. Note if you do put in really big storage and run it down for couple of days in order to recharge it you either need a high output boiler or 7 or 8 hours to charge it up.

For hot water I wait until my storage is up to temperature and then use the heat left in the boiler to heat up a "hot water maker" insulated hot water tank with a coil in it. I heat it up to as high as it will go which is close to 180 F and then have a high quality tempering valve fed on the cold side from my solar hot water system that acts as preheater in winter. By storing DHW very hot and using lukewarm solar hot water to temper it I can go 24 hours before I need to recharge it and don't need to worry about legionaries getting into my potable hot water. I ran like that for 10 years and finally hooked up a backup electric coil on my solar hot water tank as backup during shoulder seasons when I am not running the wood boiler as often but my solar hot water is not hot enough

By the way the state of NY paid probably the #1 hydronic heating expert to set up a course on Biomass Heating. https://www.heatspring.com/courses/...ficiency-biomass-boilers-sponsored-by-nyserda. If you search around I think there is also a slide show made by the same teacher John Siegenthaler. He is big advocate of actually designing an overall system instead of guessing which is what many folks do. I haven't taken this specific course but took a longer more detailed hydronics course from the same person.

 

[Woodman1]

Maple and Peakbagger did a good job of explaining storage and how it works. My only thing to reiterate is to know your homes average hourly btu and water temperature requirements and size appropriately. It will mean the difference between being a slave to your boiler or loving your system. My house is pretty tight considering it's size and the amount of windows I have. It averages 25,000 btu heat loss on an average winter day. I can heat with water down to 110 degrees. With a 1000 gallons of storage and a 60 kw boiler, one fire for 5-6 hours gets me 24 hours.

 

[Chris Hoskin]

Advanced Radiant Design in Stone Ridge, NY

 

[Dman008]

Advanced Radiant Design in Stone Ridge, NY

Thank you. I reached out to John there, but he told me that I was outside of his service area.

 

[salecker]

At -40C we burn for about 10 hrs
At -20C we burn for about 5 hrs
Now at spring temps we burn for about 2 1/2 hours
1000 gallons sprayfoamed storage

 

[Dman008]

At -40C we burn for about 10 hrs
At -20C we burn for about 5 hrs
Now at spring temps we burn for about 2 1/2 hours
1000 gallons sprayfoamed storage

Did you build the storage yourself? Do you have the plans by chance? Or would you be willing to provide a brief over view?

Thank you!

 

[salecker]

Did you build the storage yourself? Do you have the plans by chance? Or would you be willing to provide a brief over view?

Thank you!

Yes i built it myself,two 500 gal propane tanks and a bunch scrap steel to mount them.Built them on a skid,insulated then slid into place. The only thing that cost any money was the insulation.

 

[huffdawg]