Electricity from thin air?

Carter Levy in this week's feature talks about a novel method of power generation

Carter Levy
2nd March 2020
New research into energy generation has revealed a novel way to generate electricity from the moisture found in the air.

Atmospheric moisture is almost everywhere, giving the moisture generator an advantage over other power generation methods which require specific environmental conditions such as “mechanical generators” and solar power. The device is detailed in an article published in Nature. Many of the moisture generators can be stacked on top of each other and may end up “outperforming solar cells” in power production per cubed metre.

The device consists of a biofilm layer, proteins taken from Geobacter sulfurreducens, that form nanowires. The top and bottom of the device are connected to electrodes; the top is open to air whilst the bottom is not. The moisture generator has been shown to generate a current for 20 hours before self-recharging for 5 hours. If many of these devices were connected some could be given time to recover whilst others generated electricity, giving a constant energy production.

Representation of the device with gold electrodes attached to a voltmeter
(Image drawn by Katie Tyley)

The theory on how the device generates power is still slightly vague in places. The current theory is that the biofilm’s porous nature causes more moisture to accumulate near the top of the biofilm than the base. In broad strokes, the water reacts and charged atoms are created which move from the exposed top to the unexposed base which attracts electrons which move through the circuit as the path of least resistance.

While the moisture generator was shown to yield the highest voltage at “a relative humidity of some 40–50%” it still generated a substantial voltage at a relative humidity as low as 20% ("comparable to a desert environment") and 100%. This ability is promising for the future applications of the device meaning that it can be used in a range of environments, even if it might be more efficient in some than others.

For large scale power generation many of the devices, which in this study had a surface area of about 25mm2, could be connected in series or parallel to increase the voltage or current respectively. Seventeen of the devices were connected in series to give a voltage of 10V. The device was shown to be still able to function after 2 months. However, creating the biofilm from proteins generated by whole cells on a large scale will have a large energy cost with current technology and the lifespan of the device over a longer period is not known.

This new development is an improvement on devices that used atmospheric moisture in the past and is an interesting area for research in the future. With the worlds power needs growing and the increasing unattractiveness of fossil fuels new developments such as this may become more and more important.

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