Researchers in China have built an off-grid, fast-cycling, sorption-based atmospheric water capture system. The system is powered by three PV modules and has been tested with four condensation methods, both indoors and outdoors.
A group of scientists from China’s Yunnan Normal University and Yunnan Provincial University have developed a PV-powered fast-cycling sorption-based atmospheric water harvesting (SAWH) system.
“To increase the usability and scalability of our previous system, an innovative photovoltaic (PV) powered fast cycling SAWH system is proposed for sustainable off-grid water harvesting,” the group explains. “A PV energy supply system is designed to meet the energy needs of continuous water harvesting: during the day, PV panels power electrical components directly, with excess energy stored in batteries; at night or when there is insufficient sunlight, the batteries discharge to maintain operation.”
SAWH (sorption-assisted water harvesting) is a technology that uses hydrophilic, hygroscopic materials to capture atmospheric moisture and recover water through desorption and condensation.
At the core of the SAWH unit are two pieces of commercially active carbon fiber felt (ACFF), stacked between electrodes and clamped to form a single adsorbent module. This module is placed in a closed structure consisting of an adsorption bed at the bottom and a condensation module at the top. The ACFF at the bottom captures moisture from the ambient air and serves as a resistor to generate heat for vapor release, while the top portion cools the vapor and condenses it into liquid water.
The SAWH housing is powered by two 300 W PV panels connected in parallel and two 12 V/200 Ah batteries connected in series. An auxiliary system, consisting of a 200 W PV panel and a 12 V/80 Ah battery, is also integrated and operates in three of the four condensation modes. In water cooling mode, a pump circulates water; with fan-assisted cooling, a fan is driven; and with semiconductor cooling, a semiconductor module is activated. The auxiliary system is not required in the fourth mode, natural convection.
The system was tested in both laboratory and outdoor environments using the four condensation modes. It was also evaluated under three adsorption timescales: Model 1 (9 h, 3 h, 3 h, 3 h), Model 2 (6 h, 3 h, 6 h, 3 h), and Model 3 (four equal intervals of 4.5 h). Outdoor testing took place in Kunming, southern China, between January and March 2025.
“The results showed that the fan-assisted condensation mode with water cooling was the most energy-efficient option, with a daily water production (DWP) of 0.96 kg water/kg ACFF/day and a specific energy consumption (SEC) of 2.59 kW·h/kg water,” the team reported. “The equal adsorption duration mode (4.5 hours x 4) showed the best overall performance, achieving a DWP of 0.50 kg water/kg ACFF/day and an SEC of 4.86 kW hour/kg water. This mode increased PV energy generation efficiency to 14.2%.”
Based on the optimized strategy for six days of outdoor use, the PV panels provided on-demand power with an efficiency of 15%–20%, and the power supply efficiency reached about 90%. “In addition, the system achieved an energy payback of 6.72 years and a life cycle CO₂ emissions reduction of 35.84 tonnes,” the group concluded.
The scientists presented the system in the study “A photovoltaic-driven fast-cycle sorption system for sustainable off-grid atmospheric water extraction”, published in Energy conversion and management.
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