Usually I'd ask this kind of stuff at the tamrielvault/skyrimblog but it seems to be down for now and I can't play Skyrim to test it ;-;

Anyways, secret of arcana allows concentration spells to be cast at no cost even when it expires, as long as you keep casting.

Does anyone know if this works with lightning storm? If so, we have a very powerful trick we could use to clear a whole dungeon at no magicka cost. Slap on zahkriisos and shock perks and no one will claim destruction is underpowered.