Circulate glycol around a firebox, heating the glycol like an on-demand water-heater.

Am thinking to use an existing wood-stove, suited to wrap 3/8 copper tubing around the cylindrical (barrel type) firebox. Box is made of heavy 1/2 inch thick, 24-inch diameter pipeline pipe. I could enclose the stove except frontal access, in concrete blocks, lined with metal. That structure could be enclosed in an insulated wood frame, and steel roof. I'd use a metal chimney, and build the thing on one edge of my concrete slab. A pump would circulate glycol around the stove, and through a 50 gallon tank, also enclosed in the insulated structure. From the tank, I'd circulate heated glycol from the tank via PEX through lines under my 6' 1" basement 10x18 concrete. I'd try it on a solar budget using power stored in batteries, with input from my 1170-watt array.

All I need to purchase for this project is the concrete block, insulation, some lumber, the chimney, circulation pumps, and fittings. Fact that the 10x18 concrete basement is so small may make this viable.

Glycol circulates around firebox into 50-gallon tank. Then in a separate loop, from the tank through the PEX under my 10x18 basement. 3/8ths copper tubing wraps around the firebox absorbing as much heat from the fire as possible.

Of course, controls are needed, and if the system is closed, two safety valves must be installed. These things are readily available from a local store as replacement parts for outdoor wood boilers. Problem is to find an algorithm for control. Also, it may be advantageous to approach the problem WITHOUT the storage tank, looking at the transfer from a simpler perspective. Function of control may be to detect when firebox temperature drops, and to then moderate circulation, allowing more time for absorption. An adjustable indicator may alert when this condition warrants re-supplying the firebox.

Wood boilers contain about 200 gallons glycol-water mix. They sell for about $4,000. I'm looking to try this on a low budget. It may be possible to combine with a solar collector to heat the glycol-water mix.

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I checked yesterday, and found at one local store a pump rated at 1/30th HP. (747/30 = 24.9 WATTS) Control to moderate flow rate will save power, especially if a SOLAR COLLECTOR is used during the day. It may be possible to get by using less than 400 watts to circulate the glycol mix on a cold winter day. Algorithm to moderate flow, and provide an alert is much simpler without a storage tank. Typical use then is to maximize benefit of the fire, keeping a long-burning fire. System storage is in the basement concrete floor. Insulating the structure is key to surviving minus thirty-five in relative comfort. Perhaps the tank with safety could be used in flow series, instead of parallel, allowing safety release valves for that benefit. Also, the fluid level could be maintained with less frequent checking.

Without two pumps, the simpler system seems viable. It is an on-going project in conceptualizing, and planning stage.