PV-powered sorption system for atmospheric water harvesting

<p class="p1"><span class="s1">Researchers in China have built an off-grid rapid-cycling sorption-based atmospheric water harvesting system. Powered by three PV modules, the system was tested with four condensation methods indoor and outdoor.</span></p><p>A group of scientists from China’s<a href="https://www.pv-magazine.com/2024/04/15/photovoltaics-for-cold-storage/" rel="noopener" target="_blank"> Yunnan Normal University</a> and Yunnan Provincial University has developed a PV-powered rapid-cycling sorption-based atmospheric water harvesting (SAWH) system.</p>
<p>“To enhance the practicality and scalability of our previous system, an innovative photovoltaic (PV)-powered rapid-cycling SAWH system is proposed for sustainable off-grid water harvesting,” the group explained. “A PV energy supply system was designed to meet the energy requirements of continuous water harvesting: during daylight hours, PV panels power electrical components directly, with excess energy stored in batteries; at night or under insufficient sunlight, batteries discharge to maintain operation.”</p>
<p>SAWH (sorption-assisted water harvesting) is a technology that uses hydrophilic, hygroscopic materials to capture atmospheric moisture and recover water through desorption and condensation.</p>
<p>At the core of the SAWH unit are two pieces of commercial activated carbon fiber felt (ACFF) stacked between electrodes and clamped to form a single adsorbent module. This module is placed inside an enclosed structure consisting of an adsorption bed at the bottom and a condensation module on top. The ACFF at the bottom captures moisture from ambient air and serves as a resistor to generate heat for vapor release, while the top section cools and condenses the vapor into liquid water.</p>
<p>The SAWH enclosure is powered by two 300 W PV panels connected in parallel and two 12 V/200 Ah batteries connected in series. An auxiliary system, comprising 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; in fan-assisted cooling, a fan is powered; and in semiconductor refrigeration, a semiconductor module is activated. The auxiliary system is not required in the fourth mode, natural convection.</p>
<p>The system was tested in both laboratory and outdoor environments using the four condensation modes. It was also evaluated under three adsorption time schedules: 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.</p>
<p>“Results showed that the fan-assisted water-cooling condensation mode was the most energy-efficient option, maintaining 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 h × 4) exhibited the best overall performance, achieving a DWP of 0.50 kg water/kg ACFF/day and an SEC of 4.86 kW·h/kg water. This mode increased PV power generation efficiency to 14.2%.”</p>
<p>Based on the optimized strategy for six days of outdoor operation, the PV panels provided on-demand power with an efficiency of 15%–20%, and the power supply efficiency reached approximately 90%. “Additionally, the system achieved an energy payback time of 6.72 years and a lifecycle CO₂ emissions reduction of 35.84 tons,” the group concluded.</p>
<p>The scientists presented the system in the study “<a href="https://www.sciencedirect.com/science/article/pii/S0196890425011008" rel="noopener" target="_blank">A photovoltaic-powered rapid-cycling sorption system for sustainable off-grid atmospheric water harvesting</a>,” published in <em>Energy Conversion and Management</em>.</p>