Heat storage unit cost estimate and is it worth it?

[rcollman]

Hi,
Anybody got some paper napkin estimates about how much might cost (US$, New England) to put in a low pressure water tank. I am thinking about something over 500 gals. I got no basement. Two options are outside or I steal some space from a nearby guest bedroom. And I am worried about 2 - 4 tons of weight on that floor . Thinking about next year and something that my forced hot water system can utilize without a heat exchanger, so no pond-in-a-box.

I just don't think it is worth it for the Fall and Spring storage of heat. Why not a flat out measured fuel load burn every morning, with the coffee? How much does it really increase the efficiency? I can see one efficiency is from not trying to reheat the 1,000 pound dry mass of my boiler every morning, but on the other hand, a good percentage of that is heat storage.

That you don't have to light as many fires, I get. But this is about saving money and payback of an investment to me. My wife might have other ideas

Thanks in advance Chris

 

[carbon neutral]

I am allotting $600 for my 1200 gallon heat storage tank. I think that is a very do able budget. I am using a pond in a box as you call it, the heat exchanger that puts heat into the tank will be the same as what pulls it back out to my forced air furnace. I set up a spread sheet and have been keeping track of my costs on that so I will re-post when I am done and everything works when that will be I do not know yet?
I have heard that effieicency goes up by 40% and I have also heard from nofossil that in his experience it hasn't helped his effiency at all. I think the payback would be in the ability to more easily utilize wood heat in the shoulder seasons and the increased boiler life that you should get by using heat storage.

 

[Bad Wolf]

Clarkharms, Send me a PMl. I made a 1200 tank and spent around $600 total. I've got swimming pool sheet metal sides that I used and a bunch of insulation for sale!! I'm in S.E. CT as well if you'd like to see my set up.

 

[Nofossil]

Some folks have been able to find used propane tanks in the 500 gallon range for very reasonable prices. I'll agree that storage doesn't necessarily buy you a lot of efficiency improvement IF you're burning short hot fires without storage. What it buys you is comfort and convenience. My EKO needs to burn an average of 7 hours per day. With storage, I can choose when to schedule that burn, at my convenience. The house temperature stays pretty constant unless I get lazy and skip a day when I shouldn't.

 

[BrownianHeatingTech]

Cost will vary dramatically based upon where you get your tank(s), what sort of controls you use, how much of what you have needs to be modified, etc.

Somewhere between $1k and $10k, I would say.

Joe

 

[Tree farmer]

I'm in my first heating season with an Eko 25 with no storage. The plan is to run the season and see how much wood I consume, personally I would rather put the $$ into a backup generator and shoulder season heat (napolean insert). A friend of mine did a complete revamp of his heating removing oil, adding gas munchkin and an eko 25 with storage. The 25 is not hooked up yet but is near completion and I am anxious to hear his reviews. I load mine in the morning before work and a few splits when I get home (only 3 or 4) and then full load around 9 just before I hit the sack. The thing goes forever and my wife has not had to touch it yet (the way I like it) we are a balmy 72 and washing clothes with hot water every day. To me I have a hard time justifying the added cost at this point plus the extra space it will take up and I would only do pressurized storage. I estimated around $2000 plus for pressurized storage, copper ain't cheap.

 

[carbon neutral]

"Something that my forced hot water system can utilize without a heat exchanger, so no pond-in-a-box."

I am not sure why you think you would need a seperate heat exchanger for a "pond in the box" for forced hot water? Why not just use the heat exchanger you have to load the heat storage to unload to your zones once it is loaded?

 

[WoodNotOil]

I would say that a spare bedroom is out of the question without some serious reinforcement in the floor. Do you have a garage it could go in? I like the sound of the sheetmetal ones clarkharms made. Smee made one as well for very little money. I made mine out of cement. (see my page in my signature) Insulation is a big expense in these tanks and putting it outside or in an unheated space requires more insulation. Pressure tanks allow higher temp, have no hx necessary, but do require large expansion tanks. Both types of storage work, just different sizes and approaches to it.

I burned in the mornings for a few weeks this summer to tide me over till' my tank was finished for DHW. (I ran out of oil and couldn't afford more!) It worked, but used many times the amount of wood compared to using the tank. I would say it was about a 5-1 ratio. I was expending enough heat to charge the tank for 1 week each day and a half that way. It also gunked up the firebox and flue, not to mention water temp was very inconsistent. I would not recommend it.

 

[BrownianHeatingTech]

"Something that my forced hot water system can utilize without a heat exchanger, so no pond-in-a-box."

I am not sure why you think you would need a seperate heat exchanger for a "pond in the box" for forced hot water? Why not just use the heat exchanger you have to load the heat storage to unload to your zones once it is loaded?

I think he's saying he wants no heat exchanger at all.

Joe