Photovoltaic　(PV)　power　generation,　which　converts　sunlight　into　electricity,　stands　as　a　pivotal　mode　of　solar　energy　utilization.　The　thermal　effect　poses　a　significant　challenge　for　all　types　of　PV　panels　under　real　operating　conditions,　as　it　diminishes　both　the　photovoltaic　conversion　efficiency　and　the　lifespan　of　the　PV　panels.　This　paper　presents　a　novel　passive　cooling　approach　for　silicon-based　photovoltaic　panels,　employing　night-time　hygroscopic　hydrogel　adsorption,　daytime　desorption,　and　subsequent　water　evaporation　for　cooling.　Both　laboratory　and　outdoor　experiments　were　conducted　to　validate　this　strategy.　Experimental　results　reveal　that　under　simulated　laboratory　light　of　1　kW　m-　2,　the　hydrogel　cooling　layer　delivers　an　average　cooling　power　of　288.2　W　m-　2.　It　lowers　the　PV　panel　temperature　by　9.9　degrees　C　and　enhances　both　the　maximum　power　and　effi-ciency　at　equilibrium　by　5.92%　and　5.93%,　respectively.　Outdoor　experiments　in　Beijing,　China,　during　summer　demonstrated　that　this　method　reduced　the　average　daytime　temperature　of　the　PV　plate　by　7.1　degrees　C　and　increased　the　average　maximum　power　by　5.21%.　The　hydrogel　layer＇s　high　hygroscopicity　enables　it　to　support　passive　cooling　effectively　all　day.　Passive　cooling　strategies　for　PV　panels,　leveraging　the　atmospheric　water　harvesting　cycle,　face　fewer　application　constraints.　They　offer　the　potential　to　increase　power　generation　and　reduce　CO2　emissions　from　PV　plants　both　now　and　in　the　future.