Water spinach from the desert: One solar panel, three functions

IAt night, the humidity in deserts often rises to 50 percent or more. A circumstance that can be used to obtain drinking water – and has inspired Peng Wang, Professor of Environmental Technology at the King Abdullah University of Science & Technology in Thuwal, Saudi Arabia, to do even more. His team has now presented a device called WEC2P (water-electricity-crop co-production system) that has three functions: it generates electricity with a solar module, drinking water, and it cultivates crops such as water spinach, which is popular in Asia.

Silicon-based solar modules generate less electricity the warmer they are. Wang and his team therefore place them on a hydrogel that binds water from the air at night. Then, when the sun shines, the solar cell transfers some of the heat to the hydrogel, allowing the water collected during the night to evaporate. It is collected in a tin box and condenses there. The temperature of the solar module is significantly reduced by this arrangement, so that it generates more electricity. The situation is similar with floating solar cells, which of course are out of the question for deserts.

Without cooling, solar modules heated up to 90 degrees Celsius in the same place. The gel drew so much energy from them that the average temperature dropped by up to 14 degrees. This in turn increased the electricity yield by up to ten percent.

In July 2021, the researchers sank 60 seeds into the ground in the shade below the device and germinated the water spinach with the water collected from the experimental setup. Within two weeks it reached a height of 25 centimeters and could be harvested. Only three seeds did not sprout.

“Our goal is an integrated system for the environmentally friendly production of electricity, water and food in arid regions,” says Wang. In a way, he creates oases in the desert. However, he is not yet satisfied with the yield. A device with an area of ​​30 x 60 centimeters produces 600 milliliters of water per day. This is enough to water the water spinach. For an effective drinking water supply, however, the gel still needs to be improved, says Wang. “Ensuring that everyone on earth has access to clean water and affordable clean electricity is part of the goals for the future set by the United Nations,” Wang said. “Our module can help with that.”

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