the next wave in solar

 http://www.iht.com/articles/2008/09/24/technology/solar.php

 

Assuming the thief's are not educated:
http://www.tamperproof.com/tamper-resistant-screws.cfm

And if they are:
http://www.tamperproof.com/categories/breakaway-nuts-non-removable.html
( of course service is another issue )

Just make it not worth the effort to remove them.
Just one or two nuts can sap the enthusiasm out of them.

Cheers

 @registered.motzarella.org:


Don't you just thread on two nuts tightly against each other and then use
them?

 

That sounds like a lock nut, nuts back-to-back. We are talk about
anti-vandal nuts, that cannot be removed.

Cheers

 @registered.motzarella.org:


removable.html

Check the breakaway link