Navigator Stove

 

 I've seen, sold, used, designed and built many different stoves over the years. The Navigator Stove 'Backpacker' in my mind is one of the best I've ever used.

 

Here are some pros

  • No patents or patents pending. This 'Navigator Stove' design is an adaptation for a grinder and steel tube based on the Top-Lit UpDraft (TLUD) mainframe design principles which are completely 'Open source' to use
  • Cost-effective
  • 'Green' 'Carbon negative' (produces biochar) multi-biomass fuel stove suitable for biomass pellets eg.wood and environmental biomass fuel
  • Clean emissions (Needs emission testing at 'Aprovecho Research Center' to confirm) and smokeless fire (Biomass fuels with 15% or lower moisture content are easier to burn)
  • Made from durable, high quality 304 stainless steel
  • Weld-free/no weld fabrication. Easy tube grinding with 2D laser cut pot stand (cross piece) with optional grinded pot stand
  • Depending on fuel restrictions eg.National Parks, which should be followed, possibly no more ethanol, butane, propane, white fuels eg.Shellite, petrol, diesel, kerosene etc. 
  • No pressurised and single use gas canisters or pressurised fuels for mutli-fuel stoves
  • If used for an outdoor kitchen it's an alternative to LPG and natural gas/'unnatural methane' (which produces harmful benzene emissions during combustion)
  • A great option if no electricity is available as the stove is unpowered with no electronics to potentially fail
  • If there is electricity available but not 'Green' eg. a fossil-powered grid, or reliable eg. brown outs or black outs, the stove is an alternative to electric stove tops. Could be used as a backup stove just in case or if you just like 'Carbon negative' outdoor cooking at home or away!
  • Easy to operate
  • Solid state operation (no moving parts)
  • Modular: Tube, cross piece (2)), optional 6" heat and wind shield. Billy lifters/pliers/C clamp are essential. For an outdoor kitchen I recommend using the oven tray/saucepan quench system.
  • Suitable for a range of cooking accessories eg. 2L billy, frypan, saucepan, Kadhai wok (+inverted wok ring) etc.
  • No maintenance
  • Can be 'quenched' with water or soil. No need to carry fuel across borders - just a trowel (handy for bush bogs too)

Here are some cons

  • No air->Oxygen->flame->heat control during a burn. If this is an issue and you can afford and access one, then the 'FabStove' could be a good option (too large and heavy for trekking though could be suitable for a car or permanent base camp/guest house, which could also use the 5" 'Navigator V1' for, eg. yak dung, cow dung etc. integrated into an existing stove top)
  • Probably not suitable (or allowed in more regulated Countries) for indoor use
  • Probably too heavy for 'Alpining' (plus there's the fuel access and the stove and fuel weight problem at higher altitudes - Gravity's a bitch for weight)
  • Potentially no access to and/or finance for tools, materials and electricity for manufacturing

Additional Technical Specifications

  • 2L billy with a 28-37m water boiling time (time after lighting the fire) using wood pellets (ambient temperature dependent)
  • 1h-1h11m burn time using wood pellets (ambient temperature dependent)
  • Maximum fuel volume and dims similar to the Permastove V4 which has been extensively and successfully tested
  • Stove weight 944g
  • Stove volume 1.62 litres
  • 98% biochar recovery ('Carbon negative') using wood pellets
  • Maximum fuel cost per burn: 15kg (bag of wood pellets)/0.64 (max wood pellet weight)=23.4 burns so at $19.95 per bag, $1.17 per burn

 

Overall, the 'Navigator Stove' could be a success in the future for many use case scenarios, such as outdoor kitchens for primary or backup use, and in Australia and many other Countries where there are various camping and trekking options!

Design
- 5 x 20mm tube sections off 1m for 5 stoves
- 2 rows of primary air slots at base
- 1 row of secondary air slots 140mm above base (enough volume below for a range of feedstocks and burn times)
- 4 equidistant notches eg. 3mm x 4mm on top (for stable pot stand/cross piece placement)

-pot stand (cross piece recommended)

*if a lighter stove with less volume is needed, the fuel volume can be reduced (with shorter burn time). Basically, the stove can be shrunk by keeping everything above the secondary air slots identical (to maintain an effective UpDraft) and decreasing the height of the secondary air slots eg.140mm->90mm, for an overall stove height of 150mm

 

Materials
- 1m length of 4" 304 1.6mm stainless exhaust tube

 I should mention here that the 1m lengths of exhaust should be considered for prototyping, small production runs and not mass production. Also, the high quality grade of 304 exhaust tube is probably overreach for wood pellets but not for some environmental fuels.

- Pot stand: 2D laser cut 304 2.5mm cross piece (see dxf for CAD software eg.LibreCAD, below) or optional grinded pot stand off sheet metal eg.304 2.5mm

Cross piece design, 2D laser cut, 2 parts per Navigator V2 TLUD stove off 2.5mm 304 stainless steel
Cross piece.dxf
Text Document 18.7 KB

Tools
- small grinder eg.100mm (disc is 2.5mm thick)

-2D laser cutter

Personal Protective Equipment (PPE)
- goggles
- face mask/respirator (if available)
- helmet with face shield
- gloves
- cotton clothing

Build

-cut off tube sections with small grinder
- grind the primary and secondary slots and 4 top notches (for a pot stand/cross piece) with a small grinder

-pot stand: 2D laser cut cross piece OR grinded off sheet

 

Operation

-position the stove in the centre of a thick oven tray or thick bottomed saucepan on a flat surface

-fill the stove with fuel eg.wood pellets, rice husk pellets, bamboo, sticks etc. up to desired level to a maximum height of 10mm below the secondary air slots

-add 5 equally spaced blobs of firelighter gel (or 3 cotton wool buds soaked in kerosene)

-position the pot stand (cross piece) guided by the 4 notches

-light the stove from the top with a wooden skewer lit at one end (or a BBQ lighter)

-position the cooking accessory eg.2L billy, on top of the cross piece after 5 minutes

-ready to run without adding any additional fuel during the burn

 

At the end of the burn:

 

-flame goes out and usually smoke follows

-put on some leather gardening gloves (and keep them on until the water quench or soil quench has been performed)

-remove the cooking accessory

1-Water quench (if enough water is available). Add water from above the top of the stove eg.watering can, for initial quench of biochar pellets until oven tray/saucepan/pot water level is above the primary air slots (mind the steam)

-remove the pot stand (cross piece) with billy lifters/pliers/C clamp

-lift the stove vertically eg. 20cm above the oven tray/saucepan, with billy lifters/pliers/C clamp, and the biochar will fall out the bottom (may need to use a stick to push out the biochar)

-using a stick, stir the biochar into the water and there will then be a complete quench

-wait 10 minutes then, wearing leather gloves, empty the oven tray/saucepan/pot into a bucket eg. a 20L stainless one,  then it will be ready for the next burn

 

OR

2-Soil 'quench'. Next to the stove, dig some soil and make a pile before the burn.

-remove the pot stand (cross piece) with billy lifters/pliers/C clamp

-fill up the air space between the heat and wind shield and stove plus the air space inside the stove, above the biochar, with soil

-Leave for 10 minutes

-lift the stove vertically with billy lifters/pliers/C clamp until all the biochar and soil has fallen out the bottom (may need to use a stick to push out the biochar and soil)

-mix the biochar in with the soil inside the shield space

-remove the shield with billy lifters/pliers/C clamp

-add the biochar and soil mix back into the soil hole, next to the stove - the climate and microbes will love it!)

 

END

 

Navigator Stove testing

OK, guys. I don't think I can improve the 'Navigator Stove' at this point. With a burn time of around 1 hour for wood pellets and 98% biochar recovery, I think this design strikes a good balance between DIY manufacturing, available steel, available and affordable fuel, stove weight, stove volume and a near or complete flame cap (ideal for fuel efficiency in an Oxygen limited environment for high quality biochar).

The 4th burn

- slight cross breeze
- wood pellets
- 5m startup
- 2L billy boiling time: at 33m
- burn time:1h4m
- Biochar recovery: 98%

The 5th burn

 -no wind, 9 degrees Celsius ambient temperature
- wood pellets
- 5m startup
- 2L billy boiling time: at 37m
- burn time:1h11m
- Biochar recovery: 98%

The 9th burn

- heat and wind shield
- tatonka cookware
- wood pellets
- ambient temperature: 13 degrees Celsius
- 5m startup
- 2L boiling time: 44m
- the lid controls boiling and simmering
- burn time:1h22m
- Biochar recovery: 95%

The 10th burn

 - tatonka cookware
- Scanpan 16cm saucepan (6.4mm thick base) for quench system
- wood pellets, 2cm below secondary air slots
- ambient temperature: 13 degrees Celsius, RH 73% ('Wunderground' app), no breeze
- 5m startup
- 2L boiling time: 28m
- the lid controls boiling and simmering
- burn time:1h3m
- Biochar recovery: 98%

Fuel

As you can see, wood pellets have a relatively low volumetric and gravimetric energy density compared to other liquid and compressed fuels. But - in most cases produced from sawdust - a 'waste' stream from sawmills, which may or may not use sustainable forestry practices eg.FSC certified. Safer handling too than most other fuels. May need to research your pellets. In Australia, it's an emerging fuel source with a small number of options for Australian produced, affordable and large bags eg.15kg. Balancing all this, get the wood pellets that are also closest to you for the smallest logistics C footprint.

 

Alternatively, if you're in it for the long haul and can access locally produced sawdust or rice husk (or Cyanobacteria on Mars), you might consider buying a small and electrically compatible pelletiser machine that can process your biomass feedstock waste. Most of the pelletisers are from China. Not sure about their reliability. Plus there is postage cost, dubious warranties and potential customer service issues. Can be expensive but over time possibly save you money if all the ducks line up and depending on how much pellet fuel you are consuming. Bags of pellets, produced by your pelletiser, could also be locally bartered or sold.

 

More information about clean stoves can be found here, with some great info under 'Publications'.

http://aprovecho.org/resources/