‘Harvesting water from air can help reimagine water infrastructure for humanity this century’

Uravu Labs, a Bengaluru-based deep-tech startup, harvests water from air entirely powered by renewable energy. Their technology is based on desiccants, which are materials that attract and absorb moisture from the surrounding air.

Swapnil Shrivastav, the founder of the start-up, hopes to reimagine the water infrastructure by reducing dependence on conventional water sources such as groundwater. Down To Earth spoke with Shrivastav to find out more about the technology. Edited excerpts from the conversation:

 

Rohini Krishnamurthy (RK): How is your product different from other players in this space?

Swapnil Shrivastav (SS): Conventional technologies that harvest water from the air are roughly based on an air conditioning device. If you run your air conditioner for many hours, you’ll see some water droplets coming out of it. So basically, the air conditioner cools the air by condensing the moisture present in the atmosphere and then forms water. But this technology is power-hungry and is highly dependent on the relative humidity of the place.

For coastal areas like Chennai and Calicut, where the relative humidity is usually 80-90 per cent on average, which is very high. In these places, we can have optimum water production at lower energy.

But in cities like Bangalore and Delhi, the power consumption will increase by almost two or three to four times, respectively. So the operating cost to produce a litre of water goes anywhere from Rs 5-15 per litre.

So, we started working toward a different technology, which uses a desiccant — a class of materials that can absorb moisture from the air.

A very common example of a desiccant is silica gel, which you can find while buying a pair of footwear or electronics. When you pass air over it, it absorbs moisture from the air. 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.

We also wanted to make it fully sustainable and pair this with solar energy. Later, we realised that silica gel also has some limitations while trying to scale up the prototype we built in 2018. It hardly made two-three litres of water per day.

So in 2021, we decided to shift to a liquid desiccant system: A salt solution of calcium chloride. It allowed us to scale up production to 20-30 litres per day. Now we have expanded it further and are able to produce up to 3,000 litres per day.

Across the world, over 190 companies use conventional technology and only four or five companies use the desiccant-based technology. There are a lot of new advances. Desiccants are currently at a nascent stage — very similar to electric vehicles, which were in a budding stage 10-20 years ago. It needed a long time and curve to understand the technology and make it mature. 

RK: What makes calcium chloride an ideal material?

SS: In silica gel-based technology, both the absorber and desorber (material that releases moisture) were in the same chamber. Since silica gel is a solid material, it can’t move around. So, we had to bring air into it. Once the gel saturates and absorbs the moisture, it has to be heated.

This created a lot of engineering problems when we wanted to scale it up. We had to redo the whole architecture in terms of airflow, heat transfer and heat exchanger. However, with the liquid desiccant, we can have the absorber and desorber in separate chambers. The liquid desiccant first absorbs the moisture. Once saturated, the solution is pumped into a desorber, where we heat it and release the moisture.

This decoupling enables you to independently scale them up. So it was much easier from the engineering side as well. On the other hand, silica gel is energy-intensive. It requires to be heated at around 85-90°C, whereas calcium chloride requires only 65-70°C.

RK: How much electricity does the equipment consume?

SS: We are energy agnostic and are not limited to just using electricity as our input. We can use various other forms like waste heat from industrial boilers or chimneys. Biomass can also be used to power the equipment.

Conventional air conditioning technology consumes around 350-450 watt-hours per litre if the humidity is around 80-90 per cent. Those numbers are almost similar in the case of our technology.

In Bengaluru, where the average humidity is 60 per cent, the power consumption for conventional technology will almost double to more than 800-900 watt-hour per litre. But in our case, it will almost remain the same, around 300-350 watts-hour per litre.

The amount of desiccant we use to absorb the moisture can be modulated based on the location. For example, in a place with high humidity like Chennai, you need only x litres of desiccant. But in Bangalore, you will need 2x the amount of desiccant. So you will get the same amount of water from the system with the same energy consumption but at a slightly higher machine cost. 

RK: Does the equipment purify water?

SS: First, when air enters the unit, the absorber air filters remove some dust particles. Second, the liquid desiccant has an affinity only for water vapour and not other pollutants. Third, microbial life dies when we heat the material to over 70°C. So the water you get is pure and distilled, with no minerals, heavy metals, or microbial life. To make it drinkable, we pass the water 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. Then, we pass it through an ultraviolet disinfection chamber to add an extra layer of safety and minerals. So these minerals are primarily added in the form of a powder. 

RK: What is the size of the equipment? Are you targeting households as well?

SS: We have decided not to make it a household equipment. We are going more towards commercial, industrial applications. The current unit, which produces 3,000 litres per day, occupies almost a footprint of two shipping containers. One shipping container is almost 40 feet by eight feet. 

This equipment is not fully ready to be deployed at a customer site at the moment. So currently, we will have a centralised facility. And along with that, we are integrating a bottling facility.

So all the water we produce is sent to an automated bottling facility, where we use only glass packaging, which can be 500 millilitres (ml), 750 ml or 1 litre. We fill the water, add the minerals, seal the bottles, do a quality check and then distribute it to hotels and restaurants.

We also have a reverse logistics model, where we collect the glass bottle back and reuse them. These high-quality bottles can be reused 60-80 times.

RK: How much does a bottle cost?

SS: I can’t tell you the price of a bottle we sell, but our restaurant partners are selling at anywhere from Rs 80-120 for a 750ml bottle. And some customers, like the Leela Hotel, are providing it as complimentary.

We are also looking at industries. We already have a pilot unit with Budweiser, which is installed in their office space. It can make 5-50 litres per day. We will scale it up next year.

As long as we keep scaling up and reducing the cost of water per litre, new market opportunities will keep unlocking. So the cost of producing one litre of water is around Rs 5-6 per litre. We hope to bring it down to Rs 1-3 per litre. We are also planning to reach rural communities as well.

Our long-term vision is to reimagine the water infrastructure for humanity for this century. This is going to be a 30-50 year-long journey.

Subscribe to Daily Newsletter :

SUPPORT US

We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.