Post by Solomon on Feb 22, 2021 14:06:42 GMT -8
I've been thinking for quite some time about water storage for rocket stoves.
The main reason is because earth and stone have such low specific heat capacity vs water.
Water is 4182 J/kgC That's 4.1 kilojoules to raise one kg of water one degree C.
Here I am trying to put a load of granite (790) in my bench. Though to be fair, granite is much more dense than water, so you can fit more of it in the same space. Granite is 2.75 more dense than water whereas water has 5.2 times the heat capacity. Which means for the same volume, water performs about twice as well as granite for storing heat.
Sandy clay (lets call it "cob") is even better than granite at 1381 though it is around half the density of granite. Still puts it around half as good as water for storing heat.
So thinking of materials available to me and technological possibilities, it seems to me the best engineered solution for making heat from wood and storing it, to slowly be radiated into a home is a water heating rocket stove with a large partially insulated unpressurized tank nearby.
Now we've seen the Dutch guy who built the water heating batch rocket:
His rocket stove heats a large tank in another room with a pump to move the water.
Imagine a large tank sitting next to this, or somehow worked into the wall (Trombe Wall) or as part of the decor or masonry in the house, all thermosiphon fed and variably insulated to control heat output and storage time. I'm thinking of flat wall shaped tanks made of simple sheet metal. Maybe a bench that's actually a tank rather than made of cob.
Obviously this is beyond the skills of most of us. But I would wager not beyond the capabilities of those of us willing to learn a couple new skills. Me for instance, I need to learn to tig weld stainless steel. That's the only skill I lack for this project.
This also massively increases the thermal mass of the home providing summer benefits as well as winter.
The downside of course is the cost. Those stainless steel heat exchangers are not cheap to make. Parts need to be laser or water jet cut. And stainless is just expensive off the bat.
Anyway, this is the direction I'm thinking in. What do you think?
The main reason is because earth and stone have such low specific heat capacity vs water.
Water is 4182 J/kgC That's 4.1 kilojoules to raise one kg of water one degree C.
Here I am trying to put a load of granite (790) in my bench. Though to be fair, granite is much more dense than water, so you can fit more of it in the same space. Granite is 2.75 more dense than water whereas water has 5.2 times the heat capacity. Which means for the same volume, water performs about twice as well as granite for storing heat.
Sandy clay (lets call it "cob") is even better than granite at 1381 though it is around half the density of granite. Still puts it around half as good as water for storing heat.
So thinking of materials available to me and technological possibilities, it seems to me the best engineered solution for making heat from wood and storing it, to slowly be radiated into a home is a water heating rocket stove with a large partially insulated unpressurized tank nearby.
Now we've seen the Dutch guy who built the water heating batch rocket:
His rocket stove heats a large tank in another room with a pump to move the water.
Imagine a large tank sitting next to this, or somehow worked into the wall (Trombe Wall) or as part of the decor or masonry in the house, all thermosiphon fed and variably insulated to control heat output and storage time. I'm thinking of flat wall shaped tanks made of simple sheet metal. Maybe a bench that's actually a tank rather than made of cob.
Obviously this is beyond the skills of most of us. But I would wager not beyond the capabilities of those of us willing to learn a couple new skills. Me for instance, I need to learn to tig weld stainless steel. That's the only skill I lack for this project.
This also massively increases the thermal mass of the home providing summer benefits as well as winter.
The downside of course is the cost. Those stainless steel heat exchangers are not cheap to make. Parts need to be laser or water jet cut. And stainless is just expensive off the bat.
Anyway, this is the direction I'm thinking in. What do you think?