Deserts may be dry, but that’s not to say there are no moisture particles in the air. The relative humidity in the region revolves around 40%, but Wang says it’s closer to 80% at night. As a result, the hydrogel material typically absorbs water vapour during the evening and at night.

Water In Saudi Arabian Desert

Like most conventional solar panels, 10-20% of the solar energy they absorb is converted to electricity. The remaining 80-90% is converted to heat. The hydrogel material—think of it as a layer of jelly attached to the backside of the solar panel—plays a dual role. First, it can cool the solar panel so it doesn’t overheat. Second, it can absorb water vapour from the air because of the calcium chloride, which can absorb more than its weight in moisture. The hydrogel itself swells and locks that moisture into the material so it doesn’t spill.

How The Prototype Works

In Saudi Arabia, some 50 miles north of Jeddah, 57 seeds sprouted into healthy, seven-inch-tall water spinach leaves by harvesting water out of thin air.Like all conventional crops, spinach needs water to grow. But, in this case, the spinach sprouted thanks to a solar-powered system that pulled vapour from the air and condensed it into two litres of water. Now published in the journal <a href="https://www.cell.com/cell-reports-physical-science/fulltext/S2666-3864(22)00048-0">Cell Reports Physical Science</a>, the results of the experiment suggest that small farms in remote, arid regions can grow their own crops without a water supply.

Growing Spinach In A Desert

The prototype used during the experiment consists of three main components: a small-scale photovoltaic panel, a composite material made of hydrogel (a high-tech version of the hydrogel used in bandages to re-hydrate wounds), calcium chloride (the kind of salt we use to de-ice roads), plus a metal container that acts as a condensation chamber.

The Desert Crop Experiment

By the morning, the material is saturated with moisture, so when the sun hits the solar panels, and the heat from the solar panels comes into contact with the material, it turns the moisture into vapour and drives it out of the hydrogel layer. The metal box below then collects the vapour and condenses it into water.  None of these steps consumes the electricity generated by the solar panel, meaning that if the system gets scaled up, the electricity produced by the panels could be fed directly into the grid, and the heat produced by the panels could be used to grow crops.

Overnight Result

There are many steps before the system can be commercialized.The scientists need to find industrial collaborators who can manufacture the system cost-effectively it could be used in off-grid communities around the world. For a single household living in the mountain, or a very small community living in the middle of nowhere, this system can really help get those very basic human needs.

The Bottom Line

The results suggest that small farms in remote, arid regions can grow crops without a water supply.
