Sadly, It doesn't work. I did an amazingly in-depth research into the metagame, and built around 20 Sunny Day teams. The simple fact is, they don't work. The reason for this, isn't neccassarily lack of Permanent sun, but of the current pool of Pokémon who can abuse it. A Sunny Day team in this meta, needs to win in about 12 turns. Otherwise, you're screwed. Despite this, I will try and rate you're team.
Switch Bronzong to Heatproof, and it becomes a Heatran Counter. Nobody, and I mean NOBODY uses ground moves on Bronzong, unless they surprisingly do pitiful damage with a Fire Blast. If the sun is up, null what I just said (FireBlast outside of sun=~40%)
Solar Beam is the worst move possible in this Metagame. Here's how the typical play would work out.
[insert Pokémon here used Sunny Day]
I switch to Tyranitar now, while you begin Solar Beam.
Now your Solar Beam is weaker, and I get a free turn. Also, while Heatran is awesome considering your Fire Weaknesses, he's so common in the meta, there are a plethora of counters to him, and as such, will be taken out early. (He's on one out of every four teams). Again, Solar Beam hurts his performance, as his biggest counter is Tyranitar. Don't you dare get rid of Exeggutor. He's your saving grace. Ditch Solar Beam, iirc he gets Flamethrower+Sun. If you need Stab, go with Leaf Storm. He'll be forced out quickly anyway.
Dugtrio doesn't do anything to gengar. Gengar knows about Sucker Punch, and will switch out. Levitate>Arena Trap.