Desiccant-based water harvesting from Air
Science & Technology
28th Jul, 2023
Recently, a Bengaluru-based deep-tech start-up has found a technique to harvest water from air entirely powered by renewable energy.
What is this new Product?
- The product is based on ‘desiccants’.
- This contains a salt solution of calcium chloride. It allowed to scale up production to 20-30 litres of water per day.
- The product is significant to reimagine the water infrastructure by reducing dependence on conventional water sources such as groundwater.
As per the observations, for coastal areas like Chennai and Calicut, where the relative humidity is usually 80-90 per cent on average, optimum water production can be done at lower energy.
How water extraction can be done from air?
- Conventional technologies that harvest water from the air are roughly based on an air conditioning device.
- Basically, the air conditioner cools the air by condensing the moisture present in the atmosphere and then forms water.
- But the new technology is power-hungry and is highly dependent on the relative humidity of the place.
‘Science’ behind the Technique:
- Desiccants are materials that attract and absorb moisture from the surrounding air. The common example of a desiccant is silica gel.
- It can absorb moisture from the air when exposed.
- And heating this material to about 70-80°C releases the moisture in an almost steam-like form, which can be condensed to form fresh water.
How does the equipment make drinkable water?
- First, when air enters the unit, the absorber air filters remove some dust particles.
- Second, the liquid desiccant has an affinity only for water vapor and no other pollutants.
- Third, microbial life dies when the material is heated to over 70°C. The water becomes pure and distilled, with no minerals, heavy metals, or microbial life.
- To make it drinkable, the water is passed through an ultrafiltration membrane.
- The ultrafiltration stage removes any particles that might have entered after the water gets collected; no water gets wasted at this stage.
- At last, it is passed through an ultraviolet disinfection chamber to add an extra layer of safety and minerals (minerals are primarily added in the form of a powder).