You have a fundamental misunderstanding about solar power: they don't generate heat, they consume solar radiation (which reduces heat, much like a body of water).

They do generate heat, not reduce it. From the lay literature, the efficiency of solar panels is 12-20%, while the theoretical limit is just over 30%. New advancements may beat those numbers. Maybe the glass panels act as insulators, but the heat is radiated back somewhere. Also, bodies of water and suspended particles absorb light and are heated by it; water doesn't reduce heat.