"sun's heat" is correct and usable in written English.
You could use it in a descriptive sentence like: "The sun's heat was so intense that I felt like I was being baked alive."
That's because unlike nitrogen or oxygen, carbon dioxide molecules absorb the Sun's heat rays even though they let light rays pass through, like a greenhouse.
It deflects the sun's heat and ultimately increases fuel efficiency.
I feel the sun's heat all over me".
Others waited for the sun's heat to abate before venturing to hunt in the forest.
The plastic magnifies the sun's heat, sterilizing the top few inches of soil.
They were once part of a comet's tail, shed under the influence of the sun's heat.
When soot from those fires settles over the ice, it captures the sun's heat.
They store the sun's heat at the tropics and deliver it to northern and southern seas.
It is a season of gnat-killing nights and afternoons when the sun's heat is becoming elusive.
The latest data suggest that ISON may have split apart under the stress of the sun's heat and gravity.
e., not steel frames covered with masonry--are known to be considerably bent by the sun's heat.
