I’m all in favor of far-reaching, ambitious projects like the colonization of Mars and stuff, but covering the Moon with mirrors to increase the chances of aliens seeing us? I’m more than a little skeptical. Aside from the very idea being totally insane, it’s a ridiculous notion that it would help aliens find us. Any alien race that has the power to contact or visit us almost certainly has the power to find us without us flashing prime numbers at them via the Moon.
The secondary benefit of collecting solar energy and beaming it back to Earth is kind of weak too. First, the amount of energy created would be relatively small. Second, have you seen how much dust there is on the moon? And how many meteoroids hit the sucker? The solar array would be down before you could charge up your cell 
phone.
On the Moon, readers, scientists like this have their pants pulled down and they are spanked with moon rocks.