New cooling system works by gravity rather than electricity

Its abundance of sunshine and massive investments in solar cell technology have positioned Saudi Arabia well in its transition to becoming a leading exporter of renewable energy. Indeed, solar energy today represents more than 80% of the Kingdom’s green energy capacity. However, these cells bring a twisted irony, because their operation exposes them to the risk of overheating. Cooling systems are therefore necessary, but many rely on electricity.

An international research team led by KAUST Professor Qiaoqiang Gan has designed a potential solution. Their device requires no electricity because it extracts water from the air using only gravity and relies on cheap, readily available materials.

In addition to keeping solar cells and other semiconductor technologies cool, water can be reused for irrigation, washing, cooling the buildings on which the solar cells are placed, and other applications.

Scientists estimate that the atmosphere contains six times more water than all the fresh water in rivers combined. “This water can be collected through atmospheric water harvesting technologies,” says Gan.

Although these technologies work reasonably well, in arid environments like that of Saudi Arabia, they require electricity to harvest practical amounts of water. This demand risks dissuading the adoption of solar cells in rural areas of the Kingdom, where electricity infrastructure is expensive.

One reason for low efficiency is that water adheres to the surface of the harvesting device. Professor Dan Daniel and Shakeel Ahmad, a postdoctoral researcher in Gan’s group, found that by adding a lubricating coating made from a mixture of commercial polymer and silicone oil, they could collect more water by pressing solely on gravity.

“A common challenge in atmospheric water collection systems is that water droplets tend to get stuck on the surface (of the device), requiring active condensate collection. Our coating effectively removed the blockage, allowing for true passive collection of water-entrained water,” explains Ahmad. “As this system runs entirely on passive radiative cooling, it consumes no electricity.”

The solution is based on earlier technology developed by Gan, which he describes as a “double-sided vertical architecture.” This system was originally designed to reflect thermal heat back into the sky to keep the solar cells cool, but not to capture the water produced.

The new device was tested six times over the course of a year under natural conditions in the town of Thuwal, about 100 km north of Jeddah, and could almost double the water collection rate compared to alternative technologies. collection of atmospheric water.

Alongside Gan and Daniel, KAUST Associate Professor Gyorgy Szekely contributed to the study published in Advanced materials.

Besides the efficiency of water harvesting, Daniel is also excited about the economic benefits of adopting it.

“The system does not consume electricity, resulting in energy savings. Additionally, it does not depend on any mechanical parts like compressors or fans, reducing maintenance compared to traditional systems, which results in additional savings,” he said.