I looked at this area a few decades ago and two approaches stood out as potential, though not stand out. 1) Roofs already collect a large surface area and funnel into a single point via roof guttering - so tapping the flow from the gutter run off would enable a viable volume of water turn a motor in the drain pipe as it descended and generate power. 2) Piezo electric generating from the roof, though was looking at a…
Most of the potential energy of rain is wasted as it falls through the sky. What you really want is a huge funnel held up by enormous hydrogen balloons that catches the rain directly from the cloud, and miles-long hose coming out of the bottom. Then you'll get some real bang for your buck!
Warm clouds full of evaporated water would hit it, be forced up into colder air, and release the water.
It would then run down the rockpile and freeze, but the ice would flow down to warmer air closer to the surface, where it would melt amd you could harness the energy of the aggregated raindrops as they flow back to the sea.
If “building the wall” is politically unfeasible due to liberal tears, you could find some drifting continent and get it to smash into another continent. Wait a while, and the continents smashing together will make the wall for you.
No need for balloons, just be patient.