Engineers at UMass Amherst harvest clean energy from thin air
umass.edu
umass.edu
From the conclusion:
> Sustainable Air-gen technology holds promising prospects. Although a single sheet of Air-gen has a lower energy output (e.g., up to μW cm−2 level) than some existing harvesters (Table S2, Supporting Information), they may be vertically stacked to im- prove power without taking up additional footprint due to the diffusive nature of humidity. A preliminary study showed that an Air-gen device placed in an airgap of commeasurable size to device thickness (e.g., 20 μm) could retain electric output.[19] This leads to an estimated energy density of >1 kW m−3 in verti- cally integrated Air-gen (although this value is still subject to the available energy flow in the environment). Importantly, since air humidity is ubiquitous and continuous 24/7, Air-gen can be de- ployed almost anywhere for continuous energy harvesting, tran- scending the inherent intermittence of existing harvesters re- stricted to time or location (Table S2, Supporting Information). Air-gen offers flexibility in material choice (e.g., renewable pro- duction) and engineered form factors (e.g., environmental aes- thetics), making it a possible “greener” energy technology for the future.
Imo this is interesting, but I'd expect there should be diminishing returns to more layers of this in any one place - subject to airflow and current humidity at the least - there can only be so much charge on any particular set of water particles, and even if natural processes restore it they won't do so instantly.
The big question is, in a more optimized form of the device, whether the economics of such power generation are useful - how many $$ has to be spent to produce what sort of power output. It's an interesting proof of concept but without competitive economics for some use case, it is unlikely to see any notable adoption.
That’s what I thought as well, but they do talk about selection of materials to avoid wetting.
6 layers each 17 cm x 17 cm would be 4.9 mA @ 3 V which would be enough for quite a few of my current and planned projects, assuming no energy storage. With some kind of energy storage to store up the energy harvested when the microcontroller is sleeping it would be enough even for my projects that periodically send sensor readings by radio.