[itake]

If the raindrops were caught with a funnel, so the actual surface area of the device is very small, but the funnel is large, would that improve the economics? Maybe add in a water tank + hydro power to capture more gravitational potential energy from the water,

[CPLX]

Catch them with a patch of ground and use a river as the funnel and you’re really on to something.

[zeropoint46]

Maybe you could like block the river just a bit to build up like a reservoir.

[dojomouse]

It wouldn’t help with kinetic energy harvesting from the raindrops as that would go into the funnel as heat.

It might provide a way to harvest the remaining gravitational potential energy of the rain (possible funnel being your roof and guttering) but the only upside is that you could concentrate the energy with something that’s already there (and hence harvest over a smaller area). The amount of energy (and hence value) available would be even lower - unless you had a really high roof.

This is also the reason I abandoned my high school scheme of hydro turbines at the bottom of downpipes.

As the comments below say - you need to be working at the scale of a few major geographic features as a funnel before it starts to get really interesting.

[LeonB]

Given the explanation above, it would need to be a funnel that is cheaper than paint. If the analysis above Is accurate (I can’t vouch for it either way) then it’s hard to imagine a material strong enough at such a low price point.

It’s possible too that the proposed mechanism is related to electrostatic charge in which case funnelling would probably interfere.