How much power can we expect from rainfall?

TLDR, even though the tech is probably mature enough, the economics just aren’t there for private industry yet. It’s require major state-level funding to get it off the ground at this point, IMO. Very similar to how solar used to be.

First, tidal turbines are very specialized pieces of hardware (compared to wind turbines), that have to survive corrosive brine for a decade to pay for themselves. There are not many competing manufacturers, and they are expensive. The wires connecting them to land are also expensive, both in installation but especially in maintenance. So the up front and ongoing capital expenditures are relatively high, and there isn’t an economy of scale like there is for wind turbines and solar panels.

Second, there aren’t as many places that are well situated for tidal as you think. You need a basin of relatively shallow ocean, close to metropolitan power grids. There are only a handful of places like this in the world (around the UK, India, Australia), and developers would require a lot of work to get approval to develop this space, compared to solar or wind, where permit-seeking has relatively well-trodden path.

That would be fine, and we’d still be in business, but third, when you compare it to the opportunity cost of investing in a more traditional (or even “renewable”) power plant of a similar output, the story really falls apart. The ROI for the builder just isn’t there, and it makes way more sense to build solar or wind farms.

Some forward thinking governments are trying to help the ROI angle by providing subsidies on the generated electricity, but as a developer this is sketchy, because you still aren’t breaking even until 5-10 years, even with subsidies, and subsidies themselves can be politically fickle. When you combine this with the uncertainty attached to the turbines being relatively bespoke technology (compared to the commodity of wind turbines and solar panels), it makes sense why we haven’t seen more development here.

The way you get better at this is by doing it, a lot. Every time you read such an article, or some one relays such information to you, run the math through your head as much as you can. Make notes of the things you don’t know that prevent you from pushing the thinking further, and methodically learn about those. Don’t think of yourself in terms of particular labels - eg “I’m not much of a physics person” or “I’m a software guy” - your job is to understand the world, solve problems, answer questions.

It’s a constant effort and it’s not easy. It helps to surround yourself with others with the same drive. It helps to teach, as it forces you to constantly reassess the fundamentals, and the common mistakes beginners make (see Feynman’s writing on that topic).

The problem with these is terrible efficiency as you scale down, due to fluid dynamics and the added redundancy from having multiple small units rather than one large one. This is why generators are huge.