Self-Filling Water Bottle For Your Bicycle

Solar-powered device converts moisture in the air into safe drinking water

Cycling is a good way to work up a thirst, but how do you ensure you always have some water to hand – even without a water source? The answer is Fontus, a self-filling water bottle designed by Kristof Retezar that collects the moisture contained in the air, condenses it and stores it as safe drinking water. Powered by solar cells, it can harvest up to 0.5 litres of water in an hour´s time – assuming you have the right climatic conditions.

Retezar conducted a series of experiments to try and identify the ideal conditions, materials and cooling systems for his water bottle. His high-tech laboratory also happened to be his bathroom, where he simulated different climatic conditions by modifying the air temperature and humidity.


The device works by cooling hot, humid air. It features a small cooler installed in its center called a Peltier Element. This cooler is divided in two, with each side isolated from the other. When powered by electricity, the upper side cools down and the bottom side gets hot. As air enters the bottom chamber at high-speed, it cools the hot side down. Moreover, when the air enters the upper chamber it is stopped by little walls perforated non-linearly, reducing its speed in order to give the air the needed time to lose its water molecules.


The designer explains the design process to the James Dyson Foundation:

After more than 30 experiments, I finally achieved a constant drop-flow of one drop of condensed water per minute. After developing a functioning inner system, I designed a compact and practical hull which can be easily attached to a bicycle, integrates the water bottle and can be comfortably handled.

Harvesting water from the air is a method that has been practiced for more than 2000 years in certain cultures of Asia and Central America. In his attempts to unlock roughly 13.000 km3 of freshwater trapped in the Earth’s atmosphere, Retezar aspires to help more than 2 billion people in over 40 countries where water scarcity is a real threat. In fact, water scarcity could be one of the most important resource issues to date. By 2030, 47% of the world´s population could be living in areas of high water stress.


So while Fontus might be perfect as a bicycle accessory on long tours, it’s also a clever way of acquiring freshwater in regions of the world where groundwater is scarce but air humidity is high.