I found a video that I was trying to copy on a lot bigger scale, though I don't have the room to try and build it anyway.
I think the key word in the title is 'Micro.' If he's lucky he'll get a watt or two. Maybe he's hoping it 'works' like homoeopathy; the weaker the jet the more leccy it will generate.
I am sure a lot of well meaning experimenters have no concept of how much torque is needed to generate useful power at realistic speeds. They imagine the shaft should just spin freely as it does off-load. A jet sufficient to deliver even 1/2 hp would wrench that thing out of his hand and launch it across the garden.
Perhaps they imagine volts to be a measure of power.