How to control multiple fans (fan speed and power)

Hello.

I would like to connect multiple fans to arduino, then control each fan's speed and power.
There are manual, digital fans..
I can imagine controlling fan speed with power currents, but can it works? How can I control fan speed for digital fans?
Also, Dyson fan.. is this controllable with arduino?

Second,
Is there a solution of wind distribution for covering 15x10ft. other than using a fan?
I want the air comes from the floor, how do you think about using wind pipes with air holes and wind machine?

thank you.