space stations vs terresterial colonies

> I think we might be talking at cross purposes. In a space furnace,

Ok, yes. Your furnaces won't need cooling vanes. But a lot of your
industrial processes will need electricity (or other forms of energy,
produced via electricity, even heat when there are volatiles in your
material), and I suspect that thermal will be a better way to generate
it on a large scale than photovoltaic.

> Besides mass is largely irrelevent. It doesn't really matter if a
refinery
> ends up weighing a million tons - as long as it's in a stable orbit,
doesn't
> need to go anywhere, and has plenty of customers.

You have to get it there, and mass is what's scarce in space. If you
can make a million-ton mirror, you could have made a thousand thousand-
ton mirrors instead. Another way mass is scarce is as propellant. To
get your mirror into the orbit where you want it, you have to use an
amount of propellant proportional to its mass.