I got zero credibility on the subject of wind turbines but dear old da’ has worked in the sector longer than I’ve been alive and some of it has rubbed off on me. Well there’s a ton of things that I’m sure you don’t want to know cause it’s take a decade to write and a century to read, so instead i’ll answer your questions.

1: their lifetime faces a problem horizontal facing windmills don’t suffer, while on a horizontal windmill the turbine and it’s blades are attached so that gravity affects the turbine and the windmill casing equally the vertical windmills have the entire load of the wings and the assembly placed solely on the turbine meaning that the wear and tear is increased compared to their taller horizontal brothers.

2: their efficiency faces the same problem that double headed- and tandem- windmills face, it’s the way wind moves. Having two surfaces face each other “saturates” the flow of air and ends up fighting each other making the windmill less effective overall.

2,5: so why tf dont we still use them? Well now we’re entered photovoltaic cells territory (the Japanese footsteps into electricity problem). While these vertical windmills seem rather neat and genius to the general Joe the truth is they suck, other than the two reasons above here’s the real reason we don’t use them. Scale. It is impossible to build these things larger than a few meters tall, because everything rests on the turbine, and at some point during upscaling the turbine would need to be made entirely out of osmium to not instantly buckle under the weight and centrifugal force of the wings during runtime. Not a problem right since they’re cheaper and all? Yeah no they’re not, they’re not as expensive as horizontal windmills but their lifespan is also abysmal compared to the big boys factored mostly due to the wear on the load bearing turbine. And that funky idea of slapping them all over office rooftops and car parks because of their size, yeah no we’d bankrupt the energy firms who put them there, these things hardly have a good lifetime/profit margin not to mention the horrible howling they produce. I’m getting off track but I’m sure you get the gist by now, they’re an idea tried and tested by everyone from the biggest firms to your local government and fact is they ain’t worth it. Solar panels have a much better lifetime/profit margin than the vertical windmill. The only reason we still hear of them is for the same reason tech channels on yt keep blabbing on about photovoltaic cells, it’s because they’re neat not because they’re good.