They grow spinach in the desert with water vapor

Globally, it is estimated that close to 2 billion people, a quarter of the world’s population, lack access to drinking water, approximately 800 million do not have electricity and almost the same number have problems feeding themselves. Billions of people live in poverty in different parts of the planet and do not have the basic necessities to live from day to day.

“Many of them live in rural areas with arid or semi-arid climates,” explains Peng Wang, professor of environmental science and engineering at King Abdullah University of Science and Technology (KAUST). His latest work has succeeded in improving the food and water security of people living in regions with dry climates.

A solar panel, a special hydrogel and a jerrycan, these are the tools you have needed to grow spinach in the desert and, in addition, irrigate it with water vapor. “Our design makes water from air using clean energy that would have gone to waste, and is suitable for small-scale, decentralized farms in remote locations such as deserts and ocean islands,” notes Wang.

Access to drinking water is an adversity for 25% of the population, but the scarcity of water resources is increasingly a headache for certain regions. The lack of rain and periods of drought make it necessary to look for this liquid under the ground in wells and also by looking at the sky.

The study led by Wang states that atmospheric water may be “an important potential freshwater resource.” According to their calculations, they are estimated at approximately 12,900 billion tons in the form of vapor and drops. Cloud capture is one of the alternatives, “we offer” a low-cost and sustainable strategy, “says Wang in the journal ‘Cell Reports Physical Science’.

If the Canarian nets are used to irrigate trees in Gran Canaria, the solution of these scientists from Saudi Arabia has made it possible to grow spinach in the middle of the desert. Your formula? “We have used water extracted from the air and producing electricity,” she adds.

Spinach at 41ºC

Wang’s team planted 60 spinach seeds in a grow box in the middle of the desert. The test was carried out in the middle of June, where the maximum temperatures in Saudi Arabia reach 41ºC and the minimums are close to 30ºC. In addition, the rainfall regime is zero days in this month. A water and agricultural challenge, since spinach crops prefer rich and humid soils.

On this improvised orchard, scientists from the University of King Abdullah University of Science and Technology installed a system called WEC2P, consisting of a photovoltaic solar panel placed on a layer of hydrogel, which is mounted on a large metal box to condense and collect Water.

In previous research, Wang and his team managed to make solar panels sweat. The humidity increases at night and it is the moment of the capture. In recent years, researchers have devised materials that can absorb water vapor from the air and condense it into liquid water to cool solar panels and make them more efficient.

Now, scientists at the Saudi university have gone a step further. Thanks to a hydrogel with calcium chloride salt, the water vapor is trapped in the solution that condenses into droplets when the sun rises during the day.

The researchers used the waste heat from the solar panels when generating electricity to expel the absorbed water from the hydrogel. The metal box below collects the steam and condenses the gas into water. In addition, the hydrogel increases the efficiency of photovoltaic solar panels by up to 9% by absorbing heat and reducing the temperature of the panels.

Throughout the experiment, the solar panel, about the size of the top of a student’s desk, generated a total of 1,519 watt-hours of electricity, and 57 of the 60 water spinach seeds sprouted and grew normally. up to 18 centimeters. “In total, about 2 liters of water was condensed from the hydrogel over the two-week period,” notes Wang.

“Our goal is to create an integrated system of clean energy, water and food production, especially the water creation part of our design, which differentiates us from current agrophotovoltaics,” he reveals. However, to turn the proof-of-concept design into a real product, the team plans to create a better hydrogel that can absorb more water from the air.