Thunderf00t
1 HN recommender · recommended in 4 months, 2021–2022
16:52 · 1.1M views · May 8, 2016
Thunderf00t debunks the Fontus self-filling water bottle, arguing that pulling meaningful amounts of water from air with a small solar-powered device is thermodynamically impractical.
Cited in atmospheric water harvesting threads as a debunking of products that promise drinking water from thin air.
4 comments from Hacker News
Check out Thunderf00t's videos cricising solar water collectors, e.g.: - [LINK] - Zero Mass Water: BUSTED! "Honestly, it drives me crazy how many people have reinvented the dehumidifier, put a solar panel on it, and the media has danced around like theyve just saved the world!" - this video - Self-filling water bottle: BUSTED! " The fact that its thermodynamically impossible seem to stop 'science communicators' from promoting this. The fact that its a really dumb, and not particularly inventive idea didnt stop the 'science communicators' from promoting this. Kinda depressing really. " Problems include: - it's much cheaper to bring in a tanker of water from somewhere else, than for the electricity to do this. - It's a dehumidifier; in places where the air is wet, it rains, and you don't need it. In places where you need it, you need it because there's not much water, so it doesn't work well. - It's going to be prone to growing bacteria; warm and moist. - It needs a vast volume of air; when water becomes steam it expands 1000x. Which means to go the other way you need at least 1000 litres of steam dragged through for a litre of water. Air can be around 4% water says Britannica.com, so 20,000 litres of humid air for a litre of water if it's perfectly efficient. Thunderf00t's estimate is 50,000 litres of air for 1 litre of water; And the air needs to be cooled. That needs big fans and lots of power (air is heavy to move).
Wow, I was under the impression that atmospheric water harvesting (AWH) was extremely inefficient. I don't have any numbers but things like [1][2] seem to indicate that AWH is currently not very useful. The paper doesn't seem to (if I read it correctly) actually address this directly, instead it talks about how much energy is needed to extract water at different relative humidity levels and factors in the potential energy generated through solar panels. It also looks at the usefulness of this process given factors such as existing access to clean water (or lack thereof) and population. I didn't looking beyond the 'Methods' section, I hope I didn't miss anything here. [1]: this video and/or [LINK] (talk about same silly product) [2]: [LINK]
I was initially afraid this was going to be a solar self-filling water bottle KS. [0] So, it's basically a porous mirror of the tried-and-true emergency solar water collector design. It seems legitimately legit. I wonder if an extremely dark material (nanotube appliqué[1]) on a porous material would be able to process water faster? The trillion dollar question is: How much material do you need to generate enough fresh water for an average human? And, can it be made more durable than a diaper? 0. this video 1. [LINK]
Nope, there's no magic or free lunch. It depends heavily on local conditions which might not always be suitable. Thunderf00t has debunked a bunch of other enterprises doing water from the air: [LINK] this video [LINK] [LINK] etc