Originally published 2017-11-28.
In 2017, Jawwad Patel, a 22-year-old engineering student from Hyderabad, India, showed off a small 3D-printed gadget he called the Dewdrop. Its promise was simple and appealing: draw in ordinary air, pull out the moisture and turn it into drinking water you can carry anywhere. Reports at the time said it could make close to two litres an hour.
The idea behind the Dewdrop is real. Machines that harvest water from the air, called atmospheric water generators, are sold and used around the world. But the output figures quoted for this particular prototype do not add up with the physics of condensing water from battery power. Below we look at how the device was meant to work, what the numbers really imply, how it compares with other water-from-air technology, and what part such machines can realistically play against water scarcity.
Jawwad Patel
What the Dewdrop is and how it was meant to work
According to Indian tech site TechStory, which interviewed Patel, the Dewdrop works in four steps. A fan draws air into the casing, a filter removes dust, a thermoelectric cooler chills a surface so that water vapour condenses on it, and the collected water is mineralised and stored. When the container is emptied, the cycle starts again.
The cooling relies on the Peltier effect: when an electric current passes through a junction of two different semiconductors, one side gets cold and the other gets hot. Reports also mentioned the related Thomson effect. Thermoelectric coolers have no moving parts apart from a fan, which makes them attractive for small, portable gadgets.
The specifications Patel shared were:
- weight: about 900 grams (roughly two pounds)
- body: 3D-printed
- power: a 12-volt, 6,000 mAh lithium-ion battery
- output: about 1.86 litres per hour, and at least 1.2 litres per hour in dry, desert-like air
- controls: an interface linked to humidity and temperature sensors
Jawwad Patel
Patel also said he was working on a second version with a solar panel and a choice of hot or cold water. We were not able to find later reports of a finished product.
A reality check on the output figures
The claimed output is where caution is needed. Turning water vapour into liquid water means removing its latent heat. For water, that is roughly 2,250 to 2,450 kilojoules per kilogram, depending on temperature. So condensing 1.86 litres requires taking away more than 4,000 kilojoules of heat, or about 1.2 kilowatt-hours, before counting any losses.
The battery listed for the Dewdrop stores 12 volts × 6 amp-hours, which is about 72 watt-hours, or 0.072 kilowatt-hours. That is less than one-fifteenth of the heat that must be removed for one hour's claimed output, even if the device were perfectly efficient.
And it would not be. Peltier coolers are known for low efficiency and high power use. A small thermoelectric unit would likely need well over one kilowatt-hour per litre once fans and losses are included. Large compressor-based generators do better, but they too need far more energy than a small battery can hold to make litres of water.
In other words, a small battery like this could realistically produce perhaps a few tens of millilitres, not litres, before running flat. The quoted figures came from the inventor and were never independently tested. They may refer to a different set-up, such as mains power, or may simply be wrong. Either way, they should not be taken as the performance of a pocket-sized, battery-powered device.
The inventor and the problem that inspired him
Patel told interviewers that his interest in water began on a visit to Latur, a town in the Marathwada region of Maharashtra. In 2016, after years of failed monsoons, the area's water shortage was so severe that drinking water had to be brought in by train. Seeing people struggle for something so basic convinced him to work on the problem.
Jawwad Patel
He described himself as a lifelong tinkerer who started experimenting with electronics at around 12 or 13, eventually building a small home laboratory with his parents' support. He named the late President A.P.J. Abdul Kalam, an aerospace scientist, as a role model, and said he hoped India would set up technology incubators where teenagers could experiment.
Water, energy and healthcare were the three fields he saw as most urgent for India. Rather than selling through private companies, he said he wanted to reach rural communities through government programmes. The users he had in mind ranged from hikers, mountaineers and desert travellers to poor households with no reliable supply.
How other water-from-air machines compare
The Dewdrop was not the first attempt at pulling water from the atmosphere. Most commercial atmospheric water generators work like a dehumidifier or air conditioner: a compressor circulates refrigerant through a cold coil, air is blown across it, and water condenses into a tank. Other designs use desiccants, materials that soak up moisture, which is then released with heat.
Two projects often mentioned alongside the Dewdrop are Fontus and Watergen. Fontus, from Austrian designer Kristof Retezar, was a solar-powered bottle concept with a small condenser for bicycle riders. Watergen, an Israeli company, builds refrigeration-based generators ranging from home units to large machines that it says can produce hundreds of litres a day, though they need a steady power supply.
Researchers are also testing materials such as metal-organic frameworks and engineered hydrogels that can capture water even in fairly dry air, sometimes using only sunlight to release it. These are promising but mostly still in laboratories or pilot projects.
Where water-from-air works, and where it struggles
Output depends heavily on the weather. Condensing machines work best in warm, humid air. As a rule of thumb, cooling-based devices perform poorly below about 18°C or below about 30 percent relative humidity, which is a problem in many dry regions that need water most.
Energy is the other limit. Because so much energy is needed per litre, the cost and carbon footprint depend on the power source. Generators run on fossil-fuel electricity can have a far larger footprint than seawater desalination. Powered by solar energy in humid places, they make much more sense, especially for remote clinics, disaster relief or small communities without pipes.
The water itself also needs care. Condensed water is naturally very low in minerals, which is why designs like the Dewdrop add minerals afterwards, and collection surfaces and tanks must be kept clean to avoid bacterial growth. Water from ordinary air conditioners and dehumidifiers is not safe to drink.
You can watch a short video about Patel's prototype below:
Can devices like this end water scarcity?
Water scarcity is huge in scale. Researchers estimate that about four billion people face severe water scarcity for at least one month a year, and close to two billion lack safely managed drinking water at home. A frequently quoted United Nations projection said 1.8 billion people would be living in areas of absolute water scarcity by 2025.
Most of that scarcity is driven by agriculture, growing cities, overpumped aquifers, pollution, climate change and weak infrastructure. Personal gadgets cannot fix those causes. The most effective responses remain better water management, fixing leaks, protecting groundwater, treating and reusing wastewater, and investing in safe supply.
Water-from-air technology can still help in specific places, especially humid areas with poor infrastructure or emergencies where pipes and wells fail. Young inventors like Patel play a valuable role in drawing attention to the problem and testing new ideas. The best response to their work is enthusiasm paired with careful testing, so that the solutions that reach people actually deliver what they promise.
Sources: TechStory: Jawwad Patel's Dewdrop; The Mind Unleashed (November 2017); Wikipedia: Atmospheric water generator; Wikipedia: Enthalpy of vaporization; Wikipedia: Water scarcity. Photos: Jawwad Patel.
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