@ what I assume is the laser.
For tips, look in to turbo smooth or meshsmooth that will reduce the polycount because it allows
you to work 8 sided cylinders but when rendered that cylinder will look like it had 80 sides.
You do however need to pay attention to the edges but for that I've attached an image:
Which I believe gives a good idea how turbo smooth and edges work together
To ad to Valkyrie's comment check these links:
Radioisotope thermoelectric generator - Wikipedia, the free encyclopedia CTV.ca | New plastic can better convert solar energy
The effect used in the first link could, I think at least, be applied to your ships own waste heat and maybe even the exhaust.
The second link speaks for itself I think.