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Potential of Atmospheric Water Harvesting
Context:
Recently, University of Utah researchers have developed a pioneering compact, rapid-cycling, fuel-fired atmospheric water harvesting (AWH) device that extracts water from dry air using adsorbent materials and heat.
More on News:
- Earth’s atmosphere contains enough water to fill Utah’s Great Salt Lake 800 times, presenting a vast potential resource for clean drinking water.
- Researchers have developed a compact, rapid-cycling, fuel-fired AWH device designed to improve efficiency and practicality.
- The device uses adsorbent materials, specifically metal-organic frameworks (MOFs), to extract water from non-humid air.
- MOFs, likened to Lego blocks, can be customised to adsorb water vapour selectively.
- Current atmospheric water harvesting (AWH) technologies face limitations in size, cost, and efficiency, making them less practical for widespread use.
Mechanism of the Device:
- The prototype uses aluminium fumarate arranged in panels to capture water as air is drawn through.
- Water molecules adhere to the material’s surface, which is reversible and allows for efficient water collection. The material’s surface area is extremely high, equivalent to two football fields, enabling significant water capture.
- The prototype achieves 5 litres of water per day per kilogram of adsorbent material.
- The second step of the process involves precipitating water into liquid form by applying heat from a standard Army camping stove.
- The device is efficient because the water collection process is exothermic, meaning it releases heat as it collects water, simplifying the condensation process.
Advantages over Existing Solutions:
- Uses energy-dense fuels, suitable for arid conditions, not limited to daytime or reliant on batteries.
- Effective for water harvesting in conditions where conventional methods, like refrigeration, fall short.
- Addresses water scarcity issues impacting 4 billion people, worsened by climate change, population growth, and pollution.
- Conventional sources are limited to rainfall, rivers, and lakes, with access issues in undeveloped and landlocked areas.
Atmospheric Water Harvesting (AWH)
- AWH is the process of capturing and collecting water present in the air as vapour or tiny droplets.
- There are about 13 trillion litres of water in the atmosphere at any time.
- Recognized for providing potable water, particularly in areas with scarce liquid water or unreliable infrastructure.
- How AWH Works?:
- Dew Harvesting: Condensation relies on the process where water vapour turns into liquid droplets when exposed to a cooler surface.
- It replicates natural dew formation by cooling warm, humid air to below the dew point, causing water vapour to condense into droplets for collection.
- Sorbent Systems: Adsorption refers to the adhesion of molecules to a solid surface, while absorption involves the penetration of molecules into a substance.
- In sorbent systems, materials such as silica gel, hydrogels, and MOFs capture water vapour from humid air through adsorption.
- Saturated sorbent materials undergo regeneration through heating or pressure reduction to release the captured water vapour.
- The condensed water vapour is then collected, treated, and made suitable for various uses.
- Dew Harvesting: Condensation relies on the process where water vapour turns into liquid droplets when exposed to a cooler surface.
- Types of AWH Systems:
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- Active Systems: It requires electricity or other high-grade power.
- Examples: Air-conditioning systems and thermoelectric coolers.
- Passive Systems: It uses natural or sustainable power with no energy demand. Examples: Fog and dew collection on large-area panels.
- Active Systems: It requires electricity or other high-grade power.
There are four main methods for extracting water from the atmosphere:
- Fog nets: Physical nets are set up in humid environments to collect water in the air.
- Dew plates: Using temperature differences to encourage water to condense on metal plates.
- Sorbents: Chemicals are used to absorb water from the air, and then the material is heated to extract the water.
- Membranes: Using vapour-selective membranes that extract water as air passes over them.