There are several ways to make an improvement, but essentially...

Build a second tower that stands in the sun, perhaps shading the first tower, paint it black, build heat exchanger vanes inside of it, and hook it to the output end of the wind turbines. As the sun heats the tower, thereby heating the air inside the tower, the hot air rising will suck the air out of the turbine, causing a faster, more powerful rate of air-flow through the turbine than with the downward pressure caused by the first tower alone.

The whole unit would be able to be made smaller and yet put out more power. Located in the right spot in Arizona - like next to, up the side of a mountain - construction costs could be minimized by attaching the towers to the mountain for reinforcement.

Of course, nobody does something like this for the fun of it. They do it for the money. Since they are using a mountain, why not erect a giant water-slide down the mountain, and use a chair-lift powered off the "twin towers" to take the people back up the mountain to the water slide. Think of all the money they could rake in if they did THIS!