My goal was to achieve tent heating during night with burning time at least 3-4 hours, SAFE, and heating capacity of at least 2 kW for 4 cbm one wall tent. Fuel was main problem - collecting wood in forest or bring with fuel from home. High efficiency common burning fuel was to select : alcohol, diesel, wax, coal,etc. Liquid fuel -wax, with 2 kW/h was to expansive, so remain coal...barbecue-forge coal, pressed briquettes from black coal. Rated at 5,3kW /kg and replace 4 kg collected dry wood in forest. Not tree branches...
Starting data you can find here: https://hartley-botanic.com/guides/greenhouse-power-calculator-us/

And so, I start to construct the stove for this kind of fuel.

Step 1: Purchase...

In hard store I buy a stove pipe and cutting, and adding, riveting and welding.. and I got pipe with air oppening, bottom, firebox and one leg to be stacked in ground. It was prepared for initial test...

Step 2: First Burning Test

I stack stove in "ground" add 1/2 kg pc's barbecue pressed coal, and start fire. From 8:10 it burned and achieved temp. on outside pipe wall of 319 C, at outside temp of 12 C air. I ad a top holder and water start to boil in several minutes. Fire/amber distinguished at 9:15. Ash was as expected 5% of coal weight.

All this encourage me. to go further....

Step 3: Chimney Oven I.

Start to make a chimney oven ... plan and material was already here .. and all was ok - except the result. I add on my old camp wood stove this new chimney oven and test this in forest. It work perfect . bake an apple, but,.... oven build up a smoke sap, because insufficient smoke flow-draft inside oven. To tight.
Let try to correct this... with new approach.

Step 4: Chimney Oven II.

New visit to recycle waste yard, brought me new empty tin canisters and after few ours of work, a new form of oven was made - with bigger space for air/smoke draft-flow. I add later a shelf on oven top round side to accommodate cups for warming water, or drying purposes. etc. Total weight oven was 1,5 and pipe stove 1,4 kg. Two light packages in blue bags. Burning test on terrace brought perfect result:
1/2 kg pressed coal burn in amber form total 1h:45 min
In oven was 270C at full opening intake air and 160C at 1/4 opening. Success.

Step 5: Final Test in Winter and Winter Tarp...

Outside temp. was -4C to 0 C. and inside my winter tarp from +9C till +15C. Burning was perfect. I load at 8:50 one pressed briquette and 12 pcs barbecue briquettes and start fire from up, through small opening on pipe top- it amber burn till 11: 45 when I start a new load.
Snow was melted inside tarp under and around stove and my boots are in mud...
Baking bread was easy..making tee as well. Dinner was domestic bacon and bread.
Daily trial completed successfully.

See photo: Barbecue briquette and pressed coal briquette 1/2 kg

The 1/2 kg briquette last at slow amber burning over 1h 45 min editing about 1,5 kW energy.

Weight is not a problem for me because I go camping with my KP solo wheel. I do not carry load. I pull.

Overnight winter camp test follow - shall be done very soon (when snow come) and I hope with good results.
Sincerely,