The question is the frontal airspace as swept area. For a VAWT of one mile diameter with blades of 1/8 mile height (see the document I attached above), the swept area is one rectangle of 1 mile x 1/8 mile. But as such a diameter corresponds roughly to the distance of two rows in a HAWT farm in such a way that the second row is not too penalized by the wind shadow of the first row. The same for a VAWT when the diameter is huge. So the rectangle is roughly multiplied by two.
Knowing the coefficient of power of a VAWT is about 0.35-0.4 against 0.45-0.5 for a HAWT whatever the dimensions, you can calculate how many 15 MW HAWT you have to implement in order to achieve the power of a VAWT of one mile x 0.125 mile (and almost 2 times). Then you have to calculate the spacing requirement due to all wind direction possibility. The land use will be far higher.
I think @Massimo has well studied carousels of any dimensions, until GW range. I only propose replacing kites with vertical blades. Carousels could scale in any dimensions, not HAWT because of the tower, and the weight of the generator in altitude.