So I finally bought the Rocket Mass Heaters book from http://www.rocketstoves.com/
and read it. Holy smokes people have put a lot of effort and thought into these things.
John Sizemore wrote:Problems with water would be construction cost. The materials would need to be welded in place and of higher strength.
Moisture. Hot water equals vapor and unless your tank was covered your home would become s steam room.
Calcium builds up in the water tank.
Legionnaire’s disease. It is a problem in hot tubs and other water bearing indoor locations. You would have a petri dish in the center of your home.
I can't argue with you there. The costs/difficulty of construction will go up depending on the configuration and one's scrounging ability.
To avoid indoor moisture buildup the water storage will need to be vented to the exterior in some manner. There may be other options. I haven't researched this one yet.
If calcium/mineral precipitation will be a problem I'm assuming distilled water can be used.
Legionnaire’s disease is a valid concern. I'm not sold on the idea of using a large volume of water which eventually ends up at the hot water heater as being wise. If not much hot water is being used and the water is held at the wrong temperature for too long prior to hitting the water heater a lot of bacteria growth can occur.
140º F will kill the Legionnaire’s bacteria. I suppose one needs to be aware and take the temperature of the water thermal mass above that on a regular basis. I have done no research to see what other options there are.
Dale Hodgins wrote:I think it would be important to ensure that the water is not allowed to cool the effluent before complete combustion is achieved. Wood stoves with water jackets are prone to creosote buildup if unburned hydrocarbons go up the chimney. The heat riser and several feet of pipe may need to be far hotter than a water jacket would allow.
Definitely the water will have to rob the heat after the heat riser to avoid the problems you’ve mentioned.
Dale Hodgins wrote:It would be a shame to have a giant water tank like this for thermal storage only. Water could be drawn off to heat a hot tub and for regular domestic uses.
It seems the Legionnaire’s risk will preclude the drawing off of water unless the 140º F can be maintained. If one desires to pre-heat the hot water heater feed I think coils robbing heat from the rocket mass heater water mass will be more prudent. The challenge will be preventing bacterial growth in the rocket mass heater water mass which, theoretically, one will not be contacting on a regular basis anyway.
That said 140º F may not be that hard to maintain for an extended period depending on how large an area one is trying to heat.
In this thread, https://permies.com/t/12344/stoves/Rocket-Powered-Sterling-Engine-water
Dale has proposed the coupling of a Stirling engine powered generator with the RMH to produce electricity (along with other mechanical needs such as water pumping and clothes washing) while using water thermal mass as the coolant for the Stirling engine. After much consideration it seems to me that in order to most effectively use water as the thermal battery for a RMH the water needs to be located at floor level. In other words, if I understand how a thermo siphon works, if one if going to use a passive means to heat the water thermal mass the thermo siphon is doable but only if the tank is located higher than the heat source. Am I understanding this correctly? This would not allow the water thermal mass to be located in a cob bench unless the RMH was sunk below floor level significantly. Dropping the RMH below floor level may have it’s usefulness as can be seen in this thread: https://permies.com/t/5937/stoves/rocket-mass-floor-heater-finally
. But can one really heat below the floor and a water thermal mass located in a bench on the floor? I suppose it’s a function of how long the burn is.
It seems to me that in order to realistically use water as the primary thermal mass one needs the ability to move water around on an active basis utilizing steam, a steam powered engine/pump or a Stirling engine powered pump. In other words to really utilize water’s heat storing/transferring ability well the ability to circulate the water though various connected by piping water storage vessels and through the heat exchanger piping either next to or inside of the RMH barrel becomes necessary. I am continuing to research what is the quietest and most simple method to actively circulate the water without steam.
1) Is anyone familiar with a passive design for circulating water which works with the water tank and heat exchanger being at the same level? For all I know there is a simple method of passively circulating the water and I’m not bright enough to see it.
2) What is a simple, quiet pump design which can utilize Stirling engine principles to actively circulate the water?
3) Is there another mechanical, quiet, simple design which can utilize the heat generated by the RMH to pump the water?
Thanks for your input.