Desert solar power boost and water generator

Saudi Arabia has a lot of sun and a lot of space, so it can grow solar power quite well, but not food: it’s a dry, hot desert. But now that might be about to change: researchers have been testing a system in Jeddah that extracts water from the arid air of the desert and uses it to grow crops in a greenhouse and cool their solar panels so they work better. It hinges on a special material that works a bit like a sponge. This soaks up water from damp, cool air at night. Then, during the day, waste heat from photovoltaic - or PV - electricity generating solar panels drives off the water again, keeping the panels cooler so they work 10% more efficiently. Piped into the greenhouse, the water can then enable you to grow food, even in a desert. The same technology could also help thirsty counties like Cambridgeshire, predicted to face much drier summers in future through the effects of climate change. The technology is the brainchild of researcher Peng Wang…

Peng - The essence of getting water is to have a special material. That material can harvest individual water molecules from the air and this happens typically in the evening or at night, when the temperature is low and the humidity is high. During the daytime, the heat coming from the PV drives the water to evaporate out of this material. Then you have the cooling because evaporation takes heat away. This reduces the PV temperature, and then lets the PV give us more electricity.

Chris - Is the material that's doing the soaking up of the water at night time from the air separate from the panel and you send heat from the panel to that material to drive the water off? Or is it intrinsically within the panel material?

Peng - In our design, we have our material stuck on the backside of the PV panel. This way the heat can naturally flow into the material and drive the water evaporation.

Chris - In essence we've got a system that's storing water at night time, which it's soaking up from the cooler night time air, the system that's capturing heat during the day is passing that heat into this water reservoir, driving the water off, cooling itself in the process, and you are capturing the water, which you can then send to a system that will use that water to grow food.

Peng - Precisely.

Chris - How much water are you able to get out of the system?

Peng - For our experiment, we were able to produce about 1 litre per day, per square meter. We still believe there's a lot of room for further improvement.

Chris - If you talk to your plant science colleagues, do they think this is a viable option?

Peng - Many people believe so because, in Saudi Arabia, there's no river and this technology gets water from nowhere. It does not rely on conventional water sources to produce water, therefore with a small amount of water being produced by this system, if you can utilise this very pressure water for a beneficial purpose to meet very basic human demand, that would be great.