Objective
- An affordable DIY 'Atmospheric Water Harvesting' (AWH) kit
    - material absorbs water->desorbs->condenses->collects, using solar energy with no external power source other than the Sun

-Components could include a TLUD (passive and forced air modes eg. Permastove Burner (see 'Permastove Kitchen' page), Dome, Funnel, Heat shield, Collector and a kg of Sodium Alginate
- A rooftop AWH panel or ground based rig for mobile application eg. the Source 'Hydropanel' but much cheaper and DIY
- organic components for the hydrogel matrix (or something else), eg.

Experimental
    - Sodium alginate fine powder, mixed together with:

  •   biochar from a Kon-Tiki biochar kiln then 'activated' eg.steam (which can be partly done with top quenching in a KTE) then biochar finely milled to a powder
  •   biochar from a high temperature TLUD eg. 'Permastove Burner' with a 5V USB centrifugal fan at the same level as the bottom air holes (which can be covered with duct tape if necessary) in the base connected to a reverse power bank on a smartphone with a big battery/power bank - switched on), or, say, a '1G Toucan' with an 'Airbase' (see file attachment below); both using dry (<15% moisture content) thin bamboo pieces, wood or rice husk pellets then biochar finely milled to a powder
  • Increased Oxygen->Higher temperatures of pyrolysis->larger surface area->increased water binding sites->increased water adsorption (+ lower biochar yield). I'm not sure that the lower biochar yield really matters since the AWH systems could be on the household scale and once built, the hydrogel should last for a long time ?years - but, again, this would need to be field tested. Please fact check if you're interested and you'll be amazed what's out there on the Internet. Try using keywords like 'Activated Carbon', 'Activated biochar', 'biochar water adsorption', 'atmospheric water harvesting porous Carbon', 'pyrolysis temperature effect on water adsorption' et al

- 3D printed microalgae bioplastic components (box or dome)
- multiple cycles/day (ideally)
- high water yield/cycle
- high water yield/m2 or per kg
    - 4L/day (men need 3.7L/day, women need less)
- operates at low relative humidity (RH)
    - operates in arid and semi-arid environments
    - could operate on Mars
- can do both Biochar water filtration eg.removes 'Forever chemicals' and AWH

AWH Companies
20k for 400L/day plus larger units - awesome but exxy
https://genesissystems.com/wc-100-watercube
https://www.spoutwater.com/
'The Source' 'Hydropanel', developed by Zero Mass Water (awesome)
https://www.source.co/how-hydropanels-work/
'Drupps Concept'
'Wedew' - biochar, electricity and water
'Kara Pure' AUD5.5k, 10L/day, mineralised, alkaline pH

The 1G Toucan and Airbase for high adsorption biochar
How_to_make_high_and_low_adsorption_bioc
Adobe Acrobat Document 487.3 KB

Here are some design concepts

My fourth attempt of building a solar still and collector mainframe - just need to test the hydrogel proposed
My fourth attempt of building a solar still and collector mainframe - just need to test the hydrogel proposed

Another interesting modification could be passive 'Green Hydrogen' production using a biochar supported catalyst (BCSC), a photocatalyst, in the water for converting water into Hydrogen and Oxygen with sunlight.

The above design could be a modular and scalable system for semi-arid and arid areas. There could be, say, for a small settlement, 4 K-T's for biochar production,  ? for 'Atmospheric Water Harvesting' (AWH) and ? for 'Green Hydrogen' production, depending on the water, sanitation, building, growing system and electricity needs.

 

For the AWH, there would need to be a source of Sodium Alginate powder (still to be tested), a small-scale method to produce 'Activated Biochar' after pyrolysis of biochar produced in the Kon-Tiki kiln. The AWH module has a lot of potential - or, at least the material does and could be a cheaper option than the Hydropanel in a DIY rooftop or land-based mounted panel system.

 

For the 'Green Hydrogen', a cheap and clean method of producing a biochar photocatalyst (a BCSC), preferably with local resources. Access to fuel cells, Hydrogen-powered transport/machinery or even standalone/stationary charging of e-motorcycles with Ceramic/C based Solid State Batteries.

 

There would also need to be tech that could separate the H2 from the O2 and collect and store the H2, maybe pumped directly into H2 canisters (using an 'Activated Carbon' storage medium) that can be plugged into a modular and stationary fuel cell system for electricity. But - handling H2 can be a risky business (WHS) - maybe stick with mesoporous C printed PV panels and SSBs eg.Lithium-Air in a standalone system would be a better idea.

 

It may all sound ridiculous but I imagine there could be a variety of combinations to suit local needs around this theme. On a more serious note, there's nothing ridiculous about water and energy scarcity. Whether it's human-controlled scarcity or a real physical scarcity, access to affordable potable water and clean energy are essential for survival and quality of life, eg. water and energy are harvested ideally at the local household, village, community, refugee camp (war &/climate, other) scales et al

Research

Super hygroscopic polymer films (see article)
https://www.chemistryworld.com/features/atmospheric-water-harvesting/4011929.article

HYDROGELS
Main Criteria
- specific water production per day per unit collector area (SWP)
- specific energy consumption per unit mass water production (SEC)
- recovery ratio of the feed air (RR).

Physics
- thermoresponsiveness
- cycles/day
- cycling stability
- RH
- absorbency/desorbence
- C porosity
- Wide-band

Box design
- acrylic
- insulation
- could use a pyrex (borosilicate glass) 3L mixing bowl (no ribbing); clear salad bowl ($10, plastic, 25cm diameter, but ridged, probably on the outside) - purchased from Big W

Additions to hydrogel
Chemistry
- could use the new SmartDope lab to search for optimised nanoparticles
-  zwitterionic moieties and thermoresponsive moieties.
- MOFs
- nanoparticles
- salts
- porous C eg.biomass->biochar

Hydrogel candidates
- Sodium alginate is a natural polysaccharide extracted from brown algae (and kelp bc). Also known as a 'natural polymer'. It consists of two linked anionic monomers, β-d-mannuronic acid (M) and α-l-guluronic acid (G) residues.
- can buy 1kg powder for around $100 eg. Prosthetic grade, gelling agent, health supplement
- acacia gum/gum arabic (and acacia bc)
- or combine the two (see research paper)

General research

https://www.pnas.org/doi/10.1073/pnas.2308969120
- Temperature-sensitive polymers
- thermoresponsive polymers
- molecularly confined hydration in thermoresponsive hydrogels by employing a bifunctional polymeric network composed of hygroscopic zwitterionic moieties and thermoresponsive moieties.

https://www.sciencedirect.com/science/article/abs/pii/S2211285519309620
-Improving atmospheric water production yield: Enabling multiple water harvesting cycles with nano sorbent

https://pubs.acs.org/doi/abs/10.1021/acsmaterialslett.9b00315
-alginate & binary salts
-ideal dessicant characteristics: high water sorption capacity, low desorption temperature, wide light spectrum absorption, ease to scale up, and low cost.

https://www.sciencedirect.com/science/article/abs/pii/S2213343722021200
-Humidity capture and solar-driven water collection behaviors of alginate-g-PNIPAm-based hydrogel

https://pubs.rsc.org/en/content/articlelanding/2021/EE/D1EE01723C
-Ultrahigh solar-driven atmospheric water production enabled by scalable rapid-cycling water harvester with vertically aligned nanocomposite sorbent

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202211267
-Sorbents for Atmospheric Water Harvesting: From Design Principles to Applications

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874879/
-Statistical Modelling of Temperature and Moisture Uptake of Biochars Exposed to Selected Relative Humidity of Air

Biochar and AWH
Search "biochar atmospheric water harvesting"
Porous Carbon eg.biochar
- very high water holding capacity (WHC)
- black, which absorbs heat->high evaporation
- no specific testing of biochar for AWH in the research - just some passing references to Carbon Nano Tubes (CNT) and Graphene Oxide (GO). Activated Carbon/biochar could also be a goer (see the Tropical Island research). This could be green pastures for biochar AWH research!

Desirable properties of functional materials:
affinity to moisture, which affects the
adsorption capacity of material; rich in polar oxygen-containing
functional groups, which enables the material to capture water
molecules from air through hydrogen bonding and provides the
dissociated ions during hydration; specific surface area, which
determines the number of adsorption sites available on sorbents;
pore features including pore size, distribution, and connectivity,
which affects the kinetics of adsorption/desorption, speed of mass
exchange, and the adsorption capacity; and thermal/electrical
conductivity, which facilitates heat exchange, charge transfer, and
the adsorption/desorption of water molecular

Activated C/biochar could be a winner!!

LI: does Biochar have thermoresponsive properties? Eg. Could it adsorb water from hot/cold air? It's a black nanosponge - might work?
HYP: the high surface area of biochar could be used for passive continuous solar AWH
HYP: biochar and MOFs both have massive surface area
LI: can biochar adsorb water from the atmosphere? YES
LI: what are the ideal surface characteristics of biochar for water absorption?
MOFs 'box in a box' experiment (see link above) - could use one of my spare solar panels and a fan OR experiment with the pyramid solar oven
OR as a 'dessicant' eg.hydrogels or 'composite sorbent' eg Carbon-Lithium chloride
**Are there ways to treat Biochar to enable AWH?**
Plants can only be used once but Biochar could theoretically be used many times over.
HYP: fine Biochar powder could be modded and turned into a hydrogel with a 'gelling agent'**
Eg. Gelatin, sodium alginate, tapioca, vanillin, other organic substrate? Clay?

NOTES

MOFs - water collects/adsorbs inside the MOF and is released. A powder is used
Biochar - water adsorbs between the particles, not inside the matrix
LI: could water adsorb between biochar particles in a thin layer of biochar powder then release it with solar radiation and collected?
Yes. The biochar could also be soaked with non-potable water and even seawater. The water holding capacity (WHC) Of biochar can hold up to 10 times it weight in water (more than Sphagnum moss!
A valve in the lid that could be opened at night (for AWH) and closed during the day (no water vapor loss) would be perfect!!
OR the lid could be removed at night for dew collection when the RH is higher

https://www.nature.com/articles/s41565-022-01135-y
-High-yield solar-driven atmospheric water harvesting of metal–organic-framework-derived nanoporous carbon with fast-diffusion water channels
- Abstract
Solar-driven, sorption-based atmospheric water harvesting (AWH) offers a cost-effective solution to freshwater scarcity in arid areas. Creating AWH devices capable of performing multiple adsorption–desorption cycles per day is crucial for increasing water production rates matching human water requirements. However, achieving rapid-cycling AWH in passive harvesters has been challenging due to sorbents’ slow water adsorption–desorption dynamics. Here we report an MOF-derived nanoporous carbon, a sorbent endowed with fast sorption kinetics and excellent photothermal properties, for high-yield AWH. The optimized structure (40% adsorption sites and ~1.0 nm pore size) has superior sorption kinetics due to the minimized diffusion resistance. Moreover, the carbonaceous sorbent exhibits fast desorption kinetics enabled by efficient solar-thermal heating and high thermal conductivity. A rapid-cycling water harvester based on nanoporous carbon derived from metal–organic frameworks can produce 0.18 L kgcarbon−1 h−1 of water at 30% relative humidity under one-sun illumination. The proposed design strategy is helpful to develop high-yield, solar-driven AWH for advanced freshwater-generation systems.

https://www.sciencedirect.com/science/article/abs/pii/S0045653522003435?via%3Dihub
-High surface area acid-treated biochar from pomegranate husk for 2,4-dichlorophenol adsorption from aqueous solution

Relative Humidity

Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air.

https://en.wikipedia.org/wiki/Humidity#Relative_humidity

 

Pyrex
Pyrex® is borosilicate glass which differs from other glass types as it possesses unique properties of high resistance to chemical exposure, thermal expansion and thermal shock. This has advantages in laboratory uses, a key one being where glassware is directly heated, in beakers, test tubes or flasks.
Search 'UV performance of pyrex'

 

An adapted AWH mainframe sitting on a 100L stainless stockpot lid, with 40cm wide 304 baking tray with biochar (and some water for initial testing) and a 450mm acrylic dome on top for condensation and collection
An adapted AWH mainframe sitting on a 100L stainless stockpot lid, with 40cm wide 304 baking tray with biochar (and some water for initial testing) and a 450mm acrylic dome on top for condensation and collection
I think I fluked it. Those large water droplets are right where I need them after they fall into a cavity in the lid ribbing.
I think I fluked it. Those large water droplets are right where I need them after they fall into a cavity in the lid ribbing.
AWH system with reflector...ready to start testing hydrogels
AWH system with reflector...ready to start testing hydrogels