Cristobal Cristo

Paul,

Designs with complicated channels were already criticized 90 years ago. Frequently it was empirical approach being passed from the master to the disciple without (or against) the physical justification of such a design. Professor Grum-Grzymajlo theory of free gas movements suggested using stratification chambers that are both more efficient (multiple channels affect the speed of gases) and also easier to build.
These heaters are efficient and probably clean enough, but rocket fireboxes are more efficient and cleaner and last but not least - scalable. Being not esoteric like some obscure designs, it's also easier to find solid information and advice help when building them.

D Nikolls wrote:The quickest method is certainly to buy a 12V car charger for your particular brand of power tools, if available. Some brands have one that handles 12-24V nominal input, others only 12v.. and some brands may have nothing to offer.

This is how I charge all my laptops, phones, hotspots and lights - dedicated car charges that can accept 24V - the voltage of my panels.
By talking about it (here, in reviews, everywhere) and supporting only the brands that have an option to use 12/24V eventually the other brands will catch up. I think it should be a standard - option for direct 12/24 VDC charging for all devices that use batteries.

Sheffield Pottery sells various firebricks - over 200 miles away from you. This is how far I have to drive to get quality product.

Tom,

Please share your approximate location so users will be more than happy to direct you to the closest suppliers in your area.

What does it mean "to have a supplier"? Also red "firebrick" will not really be a true firebrick, because of high iron oxide contents that is desired to be low (less than 2%) in refractory products.

Good findings Remy.
The exit temperature is rather too high.
Please work on insulation first and observe the results. If you will need help with the design of the actual heater you will find a lot of help here.

Remy,

I have plugged it to a more serious tool:

RemysHouse

I did not know exact location so I just clicked somewhere north of Firenze.
I have assumed the house perimeter to be 10x7 m and the exterior walls to be 40 cm. Room heights 2.6 m. I have used 18 C as desired inside temperature. Average heat loss 11.1 kW with the daily average of -1.8 C and max heat loss 19.3 kW if the outside was -14.7 C.
I can make corrections if needed.

In this case two 230 mm BBR heaters would provide 13 kW with two firings and it would raise to around 20 kW with more frequent fires in coldest winter days. The wood usage would be 21.6 kg * 4 = 86 kg/day so in 100 days it would amount to almost 9 tons. If you insulated the attic with 25 cm mineral wool, the values would drop to 9.2/15.9 kW.

Remy,

For the area have you used the area of exterior walls?
Are the exterior walls over a meter thick (42")?
Are the concrete or hollow blocks or bricks?
You put 35" for the ceiling thickness. Is it some conversion error? The same for the floor.
Please provide house dimensions: length, width and height, and I will play with it myself.

I can see the reason for the high heat loss. If I type the data with roof insulation of 250 mm roof for my house I'm getting 4.1 kW but if I remove the insulation it jumps to 32 kW. Other calculator that I'm using increases the heat loss two times with no insulation. If you provide the data I will plug it in and check.

These are good points. I just used another calculator and got around 5 kW. If Remy provides the input data we will see what could have gone wrong.

B Beeson,

For my adobe house with delta 20 C I'm getting 4 kW which is in the same ballpark as the results from other calculators I have used. I like this calculator, because it list a lot of masonry materials and any thickness can be selected so it's good for custom builds.
However if I add the floor with not precise "floor over unheated room" I'm getting 11 kW and I don't know if the calculator assumes that the "unheated room" under the floor has the same minimum temperature as the outside air (I selected 0 C). I have a slab on grade and the soil temperature at this depth would be around 10 C (50 F).
I agree that 31 kW is very high.

Remy,

Could you provide the input data that you have used for the calculator?