Carbon negative space heating for small to medium sized greenhouses and other spaces eg. Tiny house, small dwelling etc.
Carbon negative space heating for small to medium sized greenhouses and other spaces eg. Tiny house, small dwelling etc.

I was inspired by the thermal storage idea from:

- molten salt 

Used widely in earlier Concentrated Solar Power plants (my first flirtation with thermal energy)


- water

- graphite

- sand


- gravel


I thought to myself, why not biochar? So I set off on my journey...


How could it work?
- Sunshine hits the reflectors then heats up biochar in a galvanised tank section

-water in the soft/annealed copper water pipes is heated by the biochar then circulated to heaters/radiators in a greenhouse/other space for heat exchange and space heating (for cooler nights) and cooler water recirculated back to the biochar thermal energy storage for reheating - basically, a hydronic heating system.


The main weakness would be multiple successive cloudy days however the thermal energy storage duration in the biochar needs to be tested - maybe the biochar will store enough heat for hot water after sunshine followed by a few cloudy days? This can be tested using my new TASi TA612C thermocouple thermometer with a couple of stainless K type thermocouples.

The 'Boulder Biochar Barrel(s)' (with charcrete surrounding the barrels inside the greenhouse) or even external TLUD boilers (both technologies producing biochar) connected to the hydronics system, could be used as a backup system if the water temperature is too low for adequate heating.
- there might be a small electric USB inline fish tank/other pump needed per unit which could all run off the same power bank connected to a small solar panel for charging during the day.

-the heaters can be turned on or off with a valve and circular dial


Alternatively, photovoltaic/thermal (PV/T, PVT) panel(s) could be used to power a greenhouse and provide hot water for hydronics.

Or, panels (with prinatable semi-transparent perovskite solar cells (ST-PSC), copper pipe and biochar) could be used instead of water tank sections and the biochar would be finely milled, increasing the surface area for solar absorption and storage and reducing the amount of biochar used in the unit compared to the water tank system. The motivation in the above Indian research was partly to use cogeneration heat from the PVs for hot water while also increasing the PV efficiency. In the system below, heat cogen would presumably not be much of an issue for the ST-PSC but the PVT panel would still use solar light and heat in one efficient system.

Maybe hemp (waste) as a 'Phase Change Material' (PCM) could be used, instead of Water Hyacinth, as feedstock for the biochar which can be grown in many parts of the world and could be used as a standard for research. Kelp and bamboo waste would be good options too. PEG could possibly be combined with biochar instead of Alumina powder (used in the Indian PVT prototype) or something organic or something with 'green chemistry'...


Could be combined with Atmospheric Water Harvesting (AWH) machines (powered from the PVs on the unit eg.Powerpanels OR see the diagram at the end of the page) or standalone panels eg. possibly without the water mineralisation. There's a possibility for unpowered biochar-based hydrogels for AWH but the water yields would be predictably less than the powered machines. It's also possible to design and build a DIY AWH machine using 3D metal printing (eg. when the price of office printers go down, such as the 'Studio System 2' by Desktop Metal), off-the-shelf components, activated biochar for post-water filtration etc....if you're interested please get in touch.


Photovoltaic thermal (PVT) panel with semi-transparent Perovskite solar cells (ST-PSC), copper pipes and biochar for electricity and hot water
Photovoltaic thermal (PVT) panel with semi-transparent Perovskite solar cells (ST-PSC), copper pipes and biochar for electricity and hot water

The panels could be deeper for more biochar and solar thermal storage for longer duration, similar to the galv tank idea for 'biochar hydronics'. The weight would be greater than the above design so would need to be ground mounted. No.8 304 stainless reflectors could also be added to the panel, as with the galv tank idea, which could help concentrate more light and heat on the panel.

SpaceBox V2 with hopefully correct plumbing
SpaceBox V2 with hopefully correct plumbing

I called the main box with PVs and Copper pipe the 'SpaceBox' referring to space heating, where I originally got my idea using biochar for solar thermal mass and space itself - adaptations of this mainframe could possibly be some useful tech on Mars and beyond. The most exciting aspect of this research area to me is diving deep into the solar thermal storage properties of biochar. Matching the right feedstock composite (which may not even be needed - biochar alone might suffice) with particle size and volume of biochar needs to be discovered for this system. I should also mention that the SpaceBox would need to be ground mounted due to it's hypothetical high weight. The design is for a stationary energy situation - not a mobile situation as with the 'PowerPanel'. The SpaceBox would need to be built on site - at least for V1, anyway. Though there is the possibility of bags of biochar/biochar composite imported to the place of installation but I prefer the KTE used on site for biochar production which can be used in other systems, technologies or value adds. It's also possible that biochar wouldn't need to be milled since there would be air pockets formed between unmilled biochar particles (with an enormous surface area at the nanoscale for heat exchange) that could store/trap heat. Biochar also has insulation properties - which is why I did not add insulation to the SpaceBox.


I found a couple of websites in Oz where you can buy reclaimed/salvaged hydronic panels/radiators.


The AWH machine (off-the-shelf eg.TSUNAMI-T50) would be powered from the ST-PSCs as with the 'Space', for whatever it's being used for eg. In a 'Greenerhouse' (see the page above) for fans and LEDs. A backup power bank/extra solar panels could be handy in case of days with low solar insolation - if the budget and access permits. The extra panels and power bank could also be useful for field adventures.


How to fabricate the SpaceBox? It could be fabricated with a printed ST-PSC film (off-site) adhered to a super strong and low CO2 emissions 'Lionglass' backing panel (stability, transparency, insulation and weather protection), a biochar kiln eg.Kon-Tiki 'Essential' at the installation site for biochar, assembly of the box steel (3mm HW350) on site with laser cut panels (using a tab and slot system, similar to that used in the Flat-Tiki 'Carbon' V3 biochar kiln), laser cut 304 'No.8' 1.5mm mirror finish stainless reflector panels, everything else assembled with off-the-shelf components.


It would be great if it could be kept 'Open Source' as it's a potential IP nightmare and if it works well, can help People and Planet.


If cash and access ain't a problem, then maybe a heat pump hydronics system (with propane refrigerant and a reverse valve for cooling or heating) powered from the N facing (Southern hemisphere) or S facing (Northern hemisphere) aspect of a greenhouse built from the ST-PSC printed films adhered to Lionglass panels (or ClearVue panels if the cost and performance adds up but I'm not sure if they are hailstone proof which I would bet the Lionglass is). The panels could also power LEDs and small water pumps if needed.


For something more commercial, AWH could be integrated with a heat pump also for off-grid potable ?cold and hot water aka both water moisture and heat could be recovered simultaneously from the atmosphere which could be a very efficient use of electricity. Some waste water, possibly acidic, is produced with a Sanden heat pump for hot water - but, the volumes would need to be larger. Biomimicry could be used, based on the Namib desert beetle back, to fabricate a C-based material wrapped around the condenser tubes. The possibilities are endless.

Anyone interested please contact me on the 'Contact' page.

The SpaceBox is a trans-disciplinary modular mainframe research idea. Below are some of the key areas of research, I believe, for this emerging field:


Solar energy

  • photovoltaics
  • thermal absorption
  • thermal storage and conversion


  • water quality
  • water scarcity
  • Atmospheric Water Harvesting (AWH)




  • hemp, bamboo, kelp etc.
  • biochar
    • thermal absorption
      • ticks the box - tested successfully for solar steam generation
    • thermal storage and conversion
      • ticks the box, possibly as a composite with PEG (off-the-shelf but fossil-derived)
    • thermal conductivity
      • a mix of opinions which could determine how deep the heat will penetrate the biochar in the SpaceBox
    • heat exchange
      • high surface area which should tick the box according to Prof Walter Grestle
      • particle size I predict will be a major determinant eg.air pockets for heat traps
    • insulation
      • ticks the box


  • HW350 weathering steel
  • Stainless steel eg.316
  • Copper (pipe)


Thermal carrier fluid

  • water
  • oil



  • propane
  • CO2
  • ?


  • space heating
  • hydronic heating
  • heat pumps
  • plumbing
  • electricity/power
  • Insulation
  • greenhouses
  • tiny houses
  • small dwellings





Anisotropic hemp‑stem‑derived biochar supported phase change materials with efficient solar‑thermal energy conversion and storage
Anisotropic hemp‑stem‑derived biochar su
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Semitransparent Perovskite Solar Cells for Building Integrated Photovoltaics: Recent Advances
Semitransparent Perovskite Solar Cells f
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