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147 points rbanffy | 1 comments | | HN request time: 0.214s | source
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blueflow ◴[] No.42726585[source]
Take that ammonium, burn it, have heat, power a steam engine, infinite energy?

Where does that energy come from? 1st law of thermodynamics?

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pjc50 ◴[] No.42727208[source]
This is under-explained, isn't it? The reaction has to be endothermic, so it must be taking in ambient heat. Would be useful if someone dug up the actual paper rather than the press release.

One aspect of these miracle solutions to watch out for: the catalyst is often very expensive and has a finite lifespan.

Edit: actual paper https://www.science.org/doi/full/10.1126/sciadv.ads4443

Edit: got to the bit in the paper where they describe the process; "contact electrification". This appears to be an electrostatic phenomenon like tribocharging (the old "rub a balloon on your hair" trick). Water droplets hitting the catalyst generates enough potential at the surface to trigger a reaction. So I suppose the energy input is actually in the spray+pump of the experiment, or wind in the outdoor example.

The resulting output is extremely dilute. Raising the concentration is likely to consume more energy for generating an actually useful output.

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blueflow ◴[] No.42727345[source]
There is the smoking gun:

> resulting in ammonia concentrations ranging from 25 to 120 μM in 1 hour

Not usable as fuel. You'd need to separate the ammonium from the water using a energy intensive process (cooking or such).

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NortySpock ◴[] No.42728467[source]
At that point in the presentation, I'd probably sarcastically ask if they were accidentally measuring how many dogs mark their territory in a 100 foot radius of the device, per hour, via their collector.
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1. amluto ◴[] No.42728709[source]
They did attempt to control for the ammonia concentration in the collected water without their catalyst. But they did not try to calculate the equilibrium concentration of ammonia in water exposed to the atmosphere.