Technology

I assume that this isn't going to be competitive against existing systems if you can connect to outside services. The use case they're talking about is where the user is isolated:

The device, developed by researchers at the University of Cambridge, could be useful in resource-limited or off-grid environments, since it works with any open water source and does not require any outside power.

I'd assume that, at scale, you're better-off with municipal water and power from a grid.

But if you have a couple houses together somewhere out in the boonies of a poor country, then it may not be worth running services out to you, and setting up local power generation can't really leverage economies of scale.

It sounds like they're doing distillation to purify the water. IIRC, distillation is not cost-effective compared to reverse osmosis (RO), and while they mention purity being a requirement in order to electrolyze the water into hydrogen, it sounds like RO and some related processes provides ample purity; you don't need to do distillation:

https://hydrogentechworld.com/water-treatment-for-green-hydrogen-what-you-need-to-know

But then you have a lot of complicated machinery, whereas this is simple.

I'd guess that it'd also make sense if you were extremely space-constrained on places to put solar cells, since they talk about using more of the spectrum (that is, they're using infrared or whatever to do distillation of the water). I think that it's uncommon to be bottlenecked on space to put solar panels, though. Maybe on a boat.