Innovative air-to-water tech using liquid desiccant makes affordable, renewable water

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Innovative air-to-water tech using liquid desiccant makes affordable, renewable water

Mega Indian cities like Bengaluru have been staring at the looming threat of a potential Day Zero for some time now. The mismanagement of water resources in the city is so severe that lakes and tanks — historical structures once essential for meeting the city’s water needs — are now polluted and frothing with toxic waste. Meanwhile, groundwater resources are depleting at an alarming rate.

The situation is further compounded by the climate emergency. Scientist T.V. Ramachandra, coordinator of the Energy and Wetlands Research Group at the Indian Institute of Science (IISc), explains that the city’s water scarcity is due to “a depleting groundwater table and lower yield in the (river) Cauvery catchment.” He adds, “The climate emergency is aggravated by the loss of native species and forest cover resulting from deforestation.”

Bengaluru is not alone in this predicament. Other cities around the world, such as Cape Town in South Africa, Mexico City, and Istanbul in Turkey, are also grappling with severe water stress.

Atmospheric water gets bottled at Uravu Labs in Bengaluru. The innovative atmospheric water generator uses a liquid desiccant to absorb moisture from air. Image by Abhishek N. Chinnappa for Mongabay.

According to the 2018 Composite Water Management Index (CWMI) report released by NITI Aayog, 600 million Indians face high to extreme water stress and about two lakh people die every year due to inadequate access to safe water. The report predicts worsening of the crisis and by 2030, the country’s water demand is projected to be twice the available supply, implying severe water scarcity for hundreds of millions of people and a potential 6% loss in the country’s GDP.

A growing consensus exists among water experts that the solution to the escalating global water crisis may lie in harnessing renewable water resources.

Air to water technology

“There is an atmospheric river around us,” says Bengaluru-based engineer Swapnil Shrivastav, who co-founded Uravu Labs, a pioneering startup that generates water from air. He refers to atmospheric water or humidity that can be captured and bottled. According to Shrivastav, there is an average of two billion litres of water in the 100 metres of Bengaluru’s air column at any given time, a figure he calculates based on the city’s absolute humidity average.

Could harnessing this water potentially address the city’s drinking water crisis?

According to a report by the Bengaluru-based think tank WellLabs, the city’s freshwater demand is 2,632 MLD (million litres per day). Currently, nearly 50% of this demand is met through groundwater. The remaining 1,460 MLD is sourced from river Cauvery, located about 100 km away, making it one of the most expensive waters made available in a city in terms of its energy consumption—an estimated Rs 3 crore per day.

Additionally, the city administration is advancing the controversial Yettinahole water project, which aims to lift 24.01 TMC of water from the Yettinahole stream in the Western Ghats, 274 km away. In an open letter to the Chief Minister of Karnataka, several city scientists, including T.V. Ramachandra, have highlighted the potential environmental and economic consequences of the project.

The source of Uravu

At Uravu Labs located at Kadagrahara in Hennur, air moisture is absorbed using a liquid desiccant and then processed through a desorption method to convert it into water. This water is purified and enriched with essential minerals and bottled for consumption. The name “Uravu” means source (of water) in Malayalam and relationship in Tamil, which aptly reflects the venture’s goal of preserving our connection with water.

Water pots lined up to be filled at the street tap in Tamil Nadu. Image by McKay Savage via Wikimedia Commons (CC BY 2.0).

Generating water from the atmosphere is not a new concept. Various organisations worldwide, both large and small, have been employing this technology. Where Uravu Labs differs from other companies is in their use of a liquid desiccant instead of the more popular condensation technology. In condensation technology, used in air conditioners, air is cooled to reach its dew point, causing water vapour to condense. The resulting water is then collected and subjected to a purification process for consumption.

According to Uravu Labs, using liquid desiccant technology is both more affordable and efficient, currently producing over 4,000 litres per day. This technology performs consistently across varying humidity levels, whereas condensation technology depends heavily on the relative humidity (RH) of the area. “In coastal regions like Chennai, condensation technology works well, but in drier areas like Bengaluru, its output is significantly lower compared to our technology,” Shrivastav explains.

Additionally, the power consumption of condensation technology is, on average, 50% higher than that of Uravu Labs’ technology, depending on the relative humidity. Using grid electricity, Uravu Labs’ system consumes an average of 300-400 Wh/L across 30%-100% RH conditions. In contrast, condensation-based technology consumes 300-400 Wh/L at 80% RH or higher; 500-600 Wh/L at 60-80% RH; and more than 800 Wh/L at RH below 60%. “The energy required for absorption in liquid desiccant technology is only about 20% of the total energy used. Desorption requires heat energy. Currently, we are using electricity due to logistical constraints, but if we can switch to solar or waste heat, power consumption can be further reduced,” he adds.

From science lab to startup

Uravu’s origins can be traced back to an international student competition in 2012, where two of the three founders, Swapnil Shrivastav and Venkatesh Raja, both architecture and design students and classmates at the National Institute of Technology, Calicut (Kozhikode), focused on extracting water from air using condensation technology. The competition, titled “Imagine the Future of Water and City,” prompted them to explore water availability in Kochi and uncover gaps in piped water supply and infrastructure. “Overall in India,” says Shrivastav, “we have almost 80% dependence on groundwater supply,” which they deemed unsustainable. Inspired by Star Wars and its depiction of an air-to-water (moisture vaporator) device, Shrivastav, a big fan of the series, and Raja decided to develop the idea further.

One of the founders of Uravu Labs, Swapnil Shrivastav says that though the initial motive behind creating the new air-to-water technology was to provide a solution to the water crisis in the country, Uravu needs to first focus on scaling up production to make the water both affordable and accessible to rural poor. Image by Abhishek N. Chinnappa for Mongabay.

Initially using condensation technology for prototypes, they faced challenges such as high power consumption and over dependence on humidity. Solid desiccants, such as silica gel, seemed like a promising alternative. After being selected as one of the top five global finalists and winning $50,000 at the Water Abundance XPrize in 2018, they decided to pursue the technology full-time. Mechanical engineer Govinda Balaji, who joined as the third founder, brought his creative expertise to the venture.

A significant milestone for Uravu was the shift from the solid desiccant to a liquid desiccant, specifically calcium chloride, sourced from an external company in Maharashtra. The adoption of this economically viable liquid desiccant proved crucial, as it is “low-cost, performs better, and can be scaled up more rapidly.” Uravu has since scaled up production from five litres per day in 2019 to 4,000 litres per day, currently.

Better technology, wider application

“We are targeting industrial applications and have developed a production roadmap to achieve output ranging from 50,000 to 500,000 litres per day,” Shrivastav says. While their goal is to reach rural markets where water availability and quality are poor, they recognise that this is feasible only by scaling up production to lower the cost of water.

The subsequent CWMI report in 2019 highlights the projected increase in industrial water demand in the country, which is estimated to quadruple between 2005 and 2030. The report states, “Water shortages in the country can hamper industrial operations and other economic activity, and lead to muted economic growth. Industrial activity accounts for about 30% of GDP contribution at the national level and holds significant importance in India’s economy.”

However, associate professor Deepak Swami from the School of Civil & Environmental Engineering at IIT Mandi expresses concerns about the scalability of air-to-water generators. He notes that these technologies cannot produce enough water to address the global or urban water crises. “The performance of these systems depends on various factors such as humidity and temperature, and there is also the risk of drawing water from polluted air in urban areas,” he points out.

Prickly price point

Currently, the cost of water production for Uravu Labs is Rs 3-4 per litre, with a goal to reduce this to Re 1 or less per litre. Uravu serves around 50 hospitality clients, primarily premium hotels and restaurants in Bengaluru, who sell the water at Rs 90-150 per litre. The water is produced at the lab and sold to companies in glass bottles to ensure end-to-end sustainability.

Water shortages can hamper industrial operations and other economic activity, and lead to muted economic growth. Image by Bharu snapzzz via Wikimedia Commons (CC BY-SA 4.0).

Ashwathy Inns, which operates three restaurants in Bengaluru, has been purchasing Uravu water for the past eight months. General Manager Rakesh Gurung highlights three key reasons for their choice: the youthful entrepreneurship behind Uravu Labs, the local business aspect, and the novel, sustainable concept. The packaging in glass bottles and the buy-back practice for the bottles were also appealing.

“With the city facing severe water stress, Uravu water was a welcome alternative,” Gurung notes. They purchase the water at Rs 35 per litre and use it solely for drinking, while continuing to rely on distilled RO water for cooking and other needs. Gurung adds that although they preferred Uravu water for other purposes due to the water wastage associated with RO plants, the high cost remains a significant barrier.

The Royal Orchid Hotels have also been drawn to Uravu water because of its sustainability features. Anand H.N., the corporate marketing head of the hotel chain, explains, “Choosing Uravu water was a deliberate part of our broader sustainability initiatives in the city.” Initially, some clients found the glass bottles inconvenient, and the hotel’s sustainability goals had to be explained. However, the concept gained popularity faster than expected. The hotel chain is now considering extending this practice to their hotels across the country.

Expanding the reach

Uravu Labs is also making inroads into other areas like hydroponics and vertical agriculture in Dubai where they are setting up operations. They are also exploring opportunities with industries such as distilleries, pharmaceutical companies, and green hydrogen producers, where the water can be used directly without fortification.

Despite its cost-effectiveness and availability, few companies use liquid desiccants in their technology, as it is more complex and time-consuming, says Shrivastav. While setting up a condensation device takes only 30 days, the liquid desiccant technology took three years to develop.

Shrivastav explains that Uravu’s technology is evaluated in terms of absolute humidity rather than relative humidity. Absolute humidity (expressed as grams of water vapour per cubic metre volume of air) is a measure of the actual amount of water vapour (moisture) in the air. On the other hand, relative humidity (expressed as a percent) measures water vapour, but relative to the temperature of the air.

Uravu developed a device using liquid desiccant that is compact enough to fit in a shipping container and can be stacked to reduce footprint. Image by Abhishek N. Chinnappa for Mongabay.

“A place may be very humid but too cold. For example, if you go to a Nordic country, humidity will be 90% but temperature may go as low as five degrees celsius. That means there is less water to extract from the air. In Delhi, there is 30% humidity on an average with high temperature. There is more water to extract under such conditions,” explains Shrivastav.

He also highlights that Uravu’s technology is distinctive in its ability to utilise five types of energy sources—solar, solar thermal, biomass, industrial waste heat, and grid electricity—for its operations. The company is, right now, dependent on hydropower. They began with solar power but couldn’t use it at the current facility due to operational issues.

How pure is the water?

For a technology addressing such a fundamental need, purity is crucial. Given concerns about air pollution, the purity of atmospheric water naturally comes into question.

Shrivastav explains that the desiccant used in their system has an affinity only for water particles, so larger particulate matter like PM 10 is not absorbed. Additionally, filters are employed to remove PM 2.5, dust, NOx, and other contaminants. “In polluted areas, the operational cost increases because filters need to be replaced more frequently, but the quality of the water remains unaffected,” he says.

At the desorption stage, where temperatures exceed 60 degrees Celsius, all remaining contaminants are eliminated. The water is then fortified with essential minerals, as well as zinc and copper, before being bottled in premium glass containers.

 

Attached link

https://india.mongabay.com/2024/08/innovative-air-to-water-tech-using-liquid-desiccant-makes-affordable-renewable-water

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