Energy-free PV Cooler and Water Harvester


Passive cooling system to enhance photovoltaic panel performance, by absorbing water vapor at night and desorbing it in sunlight. Harvested water can also be used for drinking, irrigation and panel cleaning.

  • Energy-free PV Cooler and Water Harvester
Research completion
Commercialisation opportunities
Technology licensing agreement
Problem addressed

Commercial Photovoltaics (PV) can only convert ~15% of sunlight into electricity, with the rest wasted as heat. The resulting high PV temperatures decrease the efficiency, shorten the lifetime, and cause fire risks, thus should be suppressed. These dilemmas call for innovation to address PV thermal management in a high-flux, energy-free, and water-free way.

  • This invention provides high-flux passive cooling for the thermal management of PV via a moisture desorption-absorption process without energy consumption.
  • It desorbs water vapor under sunlight, dissipating waste heat from PV to ambient. It absorbs moisture from the ambient at night, recovering sorbent material for the next-day cooling.
  • The desorbed vapor can be condensed for drinking, irrigating, and PV cleaning. This invention can promote the development of efficient, reliable, and versatile solar power technologies.
Key impact
  • High flux cooling via moisture desorption and evaporation
  • Energy-free and self-recovery
  • High water yield
  • Low-cost raw material and facile fabrication
  • 48th International Exhibition of Inventions Geneva (IEIG) - Gold Medal
  • PV plant thermal management
  • Remote and off-grid area energy and water production
  • Support farming and forestry in the arid area


  • Patent No. 63/323,483 (USA) IDF 1127
  • Patent No. 18/183,184 (USA)
City University of Hong Kong (CityU)

As one of the fastest growing universities in the world over the past decade, City University of Hong Kong (CityU) is recognised as a hub for innovation in research and professional education. CityU identifies solutions to critical global challenges by extending the frontiers of knowledge both within and beyond existing research paradigms.

The University’s highly qualified academics are drawn from all over the world, not only bringing a wealth of research and professional experience to the teaching programmes, but also contributing to the knowledge and technology advancement.