As a doctoral student at the Berlin University of Applied Sciences in cooperation with the Technical University of Berlin, you are researching atmospheric water harvesting (AWH) as part of the joint project “Sustainable Cities”? How exactly does this work?
Drinking water is a limited resource and is also very unevenly distributed. More than three billion people are affected by water scarcity, and this number will continue to rise due to the climate crisis. It is necessary to use every available source of water. The atmosphere contains large amounts of water vapor, which we perceive in the form of humidity and clouds.
An atmospheric water extractor draws in ambient air with the humidity it contains. Inside the device, the air flows through a material that absorbs the humidity it contains. Hydrophilic materials that absorb and store the water vapor like a sponge are particularly suitable for this purpose. This process is known as the absorption phase.
In order to extract the stored water, it must be removed from the material again, i.e. the sponge must be compressed in order to remain in the picture. The energy required for this can be covered by solar radiation. This is an advantage, as regions that suffer from water shortages generally have a high level of solar radiation. The heating of the material by solar energy leads to the release of the stored water. The resulting warm, moist air can condense in the course of the atmospheric water extractor, so that liquid water and dry air escape from the device. The desorption phase takes place during the day due to the required solar radiation, while the absorption phase takes place at night, creating a cycle.
What are the biggest challenges in atmospheric water extraction?
The choice of material for absorbing atmospheric moisture depends on many factors and is very decisive for the efficiency of the water extractor. I mentioned that hydrophilic materials are suitable, but that is only half the truth. The easier a material absorbs water, the more difficult it is to remove the water again. The perfect material is therefore location-dependent, depending on humidity, temperature and sunlight, to name a few key environmental factors. It should also be easy to produce, sustainable and at the same time cost-effective, which further narrows down the options.
Brandenburg is also affected by drought. Would it be conceivable to use this method of water extraction in the future for water supply in agriculture, for example?
Huge quantities of water are used in agriculture. A lot of water is converted in the atmosphere every day, more than we consume on earth every day as a human race, but I would hate to remove a large part of the water vapor from the atmosphere just to continue our current lifestyle regardless of the consequences.
I see extracting water from the atmosphere more as a piece of the puzzle to combat water scarcity, which is a complex problem and for which there is unfortunately no one-dimensional solution. Rather than for agriculture, I see an atmospheric water harvester on a balcony in apartments or in gardens of single-family homes to provide water for watering plants or sprinkling the lawn.
The interview was conducted in October 2024.
Picture: privat
