Extracting water from the desert air, USA

USA

last update:

2 years ago

#water generation

Problems

Water scarcity

Water scarcity in the United States has predominantly been a Western issue, most severely impacting the Southwestern region. The Southwest region is home to 60 million people and has a population that’s growing 30% faster than the rest of the United States. 

Since 2000, the region has experienced a historic drought, which has led to a 19% average decrease in the flow of the Colorado River, the region’s main water source. At least one-third of this loss is attributed to increased temperatures. According to the National Climate Assessment, the Southwest region is expected to see a temperature increase of 2.5°F to 5.5°F by 2041-2070, meaning water scarcity in the Southwest is likely to get worse.

While water scarcity has historically been a Western issue, it is spreading further east and is increasingly becoming a problem the whole nation must address. A 2013 survey from the Government Accountability Office found that 40 of 50 state water managers expected to see freshwater shortages in their states, given average conditions. With population shifts and climate change, these shortages could become even more severe.

Solutions

condensing water out of air using only sunlight for energy

Author: One Step Green

In a humid climate, water is harvested using a fog harvester (or similar) or condensation. But in climates where relative humidity (RH) is low, notably lower than 40%, bringing down the air temperature below the freezing point is mandatory, making it impractical and energy-consuming.

MIT scientists have invented a water harvester that uses only sunlight to pull water out of the air under desert conditions, using a “metal-organic framework” (MOF) powdered material developed at the University of California, Berkeley (UC Berkeley).

The water harvesting cycle is assisted with an absorbent MOF-303 to overcome this. The Water Harvesting Cycle (WHC) comprises a capture and collecting cycle.

In the capture cycle, the desert air is captured with the saturation of MOF at night. During the day, the air inside is heated and humidified, releasing the captured air. Due to the convection property, the hot and humid air is transported to the condenser that cools it below its dew point, yielding water. The collecting cycle is when the condensed water is released and collected.

Metal-organic framework (MOF) is a super absorbent that easily absorbs and releases water when heated. The first water-absorbing MOF, MOF-801, was founded by Yaghi, a UC Berkeley professor of chemistry, along with his UC Berkeley colleagues.

The new and upgraded MOF, MOF-303, is based on aluminum, while the MOF-801, used in the water harvester prototype, was based on zirconium. The new MOF has many advantages, like more productivity, holding 30% more water than MOF-801, and adsorbing and releasing water faster.

This model can work in regions with extreme water scarcity and no power source, as it uses solar energy. The key material used in the framework is a powder called Metal-Organic Framework, MOF-303, spread across the framework that absorbs the water molecules.

The framework is kept for the absorption process at night as the water content in the atmosphere is high. The MOF similarly adsorbs the water molecules as a sponge absorbs and holds water. During the daytime, when the framework gets heated due to the sun, the material releases water molecules that can be collected as liquid water. Solar panels and batteries power the harvester.

MIT tests show that 1 kilogram (2.2 pounds) of MOF could collect about 2.8 litres (three quarts) of fresh water per day from very dry air with a humidity of just 20 percent. That is more than enough drinking water for one person in a day.

Source: https://onestepgreen.com/water-harvester-by-uc-berkeley/

Gallery

Water Harvester at the university of Berkeley

A water harvester designed and built at MIT condenses water from air.

UC Berkeley postdoctoral fellow Mathieu Prévot displays water collected by the harvester (foreground) in the Mojave Desert.

Timelines

2019

In their latest version of the water harvester, the researchers claim that the water harvester can generate 1.3 liters of water per day by using 1 kg of the microporous aluminum-based metal-organic framework, MOF-303, considering that relative humidity is more than 32%. The goal is to harvest sufficient water that can benefit many people.

2018

The scientist successfully tested their new prototype in the Arizona desert in 2018, which was able to harvest water from dry air and that too by using solar energy.

2017

Some scientists from the University of California, Berkeley, demonstrated how a MOF ( Metal-organic Framework) can absorb water from dry air.

2014

UC Berkeley team led by chemist Omar Yaghi, PhD, synthesized a porous MOF — a combination of zirconium metal and adipic acid — that was able to bind water vapour. He suggested to Evelyn Wang, Ph.D., a mechanical engineer at MIT, that they join forces to turn the MOF into a water-collecting system.