From Lab Materials to Continuous AWH Devices: Scalable Paper-Based Water Harvesting
- Amin Mojiri
- 6 hours ago
- 4 min read
Original Authors: Yanhua Guan, Dexi Tang, Xiaoting Yu, Haibo Liu, Peng Chen, Jingfeng Wang, Lin Dai, Wenshuai Chen, Chenyu Li, Chuanling Si
Original paper is accessible at: https://doi.org/10.1002/aenm.70889
Why scalability is the missing link in AWH
Atmospheric water harvesting (AWH) is often presented as a promising solution for water scarcity because the atmosphere contains nearly 13,000 km³ of water vapor. However, many advanced AWH materials remain limited to laboratory-scale demonstrations.
Materials such as MOFs, COFs, hydrogels, and salt-based composites can show impressive water uptake, but practical deployment requires more than high adsorption capacity. A real-world AWH system must also deliver:
fast adsorption/desorption kinetics
low energy demand
low material cost
scalable manufacturing
continuous water production
This paper directly targets one of the biggest gaps in the field: how to move from high-performance materials to scalable, productive AWH devices.
A paper-based sorbent made by industrial processes
The core innovation is a functional atmospheric water harvesting paper, referred to as P/LiCl paper, produced using an industrial papermaking platform.
The paper is composed of:
cellulose fibers as the structural network
chloride-doped polypyrrole (PPy-Cl) for photothermal conversion and moisture affinity
LiCl as the hygroscopic salt
A key advantage is scalability: unlike many lab-made sorbents, this material can be fabricated using established papermaking processes and customized into different shapes and sizes.
Why paper architecture matters
The P/LiCl paper has a thin, porous structure with a thickness of approximately 100 µm, a porosity of 70.27%, and an average pore size of 70.85 µm.
This structure is important because it creates:
short water transport pathways
rapid vapor diffusion
fast heating and cooling
efficient moisture adsorption and release
Compared with bulk gels or thick sorbents, the paper format sacrifices some equilibrium uptake capacity but gains much faster cycling. This is a major advantage for continuous AWH systems.
Fast adsorption and desorption kinetics
The optimized P/LiCl paper shows rapid moisture capture across dry to humid conditions.
At 30% RH, the paper reaches 80% of its saturated water uptake in only 14 minutes. At 60% RH, it reaches 80% saturation in about 18 minutes.
Its moisture adsorption capacity reaches:
0.16 kg water/kg paper at 30% RH
0.36 kg water/kg paper at 60% RH
The adsorption rate at 30% RH is reported as:
0.53 kg water/kg paper/h
Although this uptake is lower than some high-capacity hydrogels or MOFs, the fast kinetics make the paper highly suitable for rapid-cycle and continuous operation.
Solar-driven desorption with minimal electricity
The PPy-Cl component provides strong photothermal conversion. Under one-sun irradiation, the P/LiCl paper rapidly heats from room temperature to about 60°C within 1 minute and reaches around 70°C after 2 minutes.
During desorption at 65°C, the paper releases most of the captured water within 20 minutes:
99% release after adsorption at 30% RH
95% release after adsorption at 60% RH
97% release after adsorption at 90% RH
The maximum desorption rate reaches:
2.3 kg water/kg paper/h
This rapid desorption allows the system to avoid conventional electric heating, with sunlight providing the energy-intensive regeneration step.
The real breakthrough: continuous crawler-type AWH
Most AWH devices operate intermittently: the sorbent adsorbs water, then the same chamber switches to desorption. This creates downtime and reduces productivity, especially for fast sorbents.
To solve this, the authors designed a crawler-type water harvester that enables synchronous and uninterrupted adsorption–desorption.
In this system:
the lower section adsorbs water from ambient air
the upper enclosed chamber receives sunlight and desorbs water
vapor condenses on collection surfaces
the paper continuously rotates between adsorption and desorption zones
This is a major device-level innovation because it turns a fast sorbent into a continuous water production platform.
Device design and operating conditions
The crawler-type harvester has:
5.5 L volume
3.26 kg weight
0.096 m² footprint
crawler length of 84 cm
crawler width of 10 cm
optimized crawler speed of 2.52 m/h
The device uses very little external electricity. The motor and fan require about:
3.0 × 10⁻⁵ kWh/day in one section of the paper
and the broader device discussion reports auxiliary consumption around 0.03 kWh/day
The desorption step itself is powered by solar irradiation, making the system highly suitable for off-grid and resource-limited regions.
Field performance over 15 days
The device was tested outdoors for 15 days under non-rainy conditions, with:
temperature: 15.4–21.7°C
relative humidity: 15–65.8% RH
more than 500 adsorption–desorption cycles
The system achieved:
5.3–15.3 g/day water production from a 0.096 m² device
13.3 g water/m² device/h
3.83 kg water/kg paper/day
This performance highlights that continuous system design can compensate for moderate single-cycle uptake by increasing cycle frequency and reducing downtime.
Water quality and material stability
The collected atmospheric water complied with WHO drinking water requirements. Importantly, the measured Li⁺ concentration was below:
0.003 ppm
equivalent to 2.9 µg/L
This low Li⁺ concentration suggests effective retention of LiCl within the paper matrix and reduces concerns about salt leakage into collected water.
The paper also maintained stable pore structure and LiCl loading after multiple cycles, supporting its potential for repeated operation.
Cost and practical deployment
The authors estimate the current harvester cost at approximately:
$49.71, including the P/LiCl paper
Because the sorbent is produced through established papermaking methods, costs could decrease further through industrial-grade raw materials, injection molding, and rapid papermaking technologies.
This makes the approach especially interesting for decentralized and low-cost atmospheric water production.
Key insights
Scalability is as important as adsorption capacity
Industrial papermaking provides a realistic manufacturing pathway
Thin paper architecture enables very fast adsorption/desorption
Continuous crawler operation eliminates downtime
Solar-driven desorption reduces electricity demand
Field testing over 15 days strengthens practical relevance
Water quality meets WHO standards with very low Li⁺ release
Takeaway
This work shifts the AWH discussion from “how much water can a material hold?” to a more practical question:
How fast, continuously, and affordably can a system produce water?
By combining scalable paper manufacturing, fast photothermal sorption, and a continuous crawler-type device, this study offers a practical pathway toward low-cost and deployable atmospheric water harvesting systems.
