Do we have enough surplus energy for this manufacturing proposed?
The energy requirement looks to be the heating of the source material and then the cooling of the fiber. So to produce the amounts at the rates being discussed by MIS, it should not take much power in a % value of that available on ISS or even on a more power constrained BA330 module. These are small NAROO (no assembly required on orbit) rack mount boxes that are doing the work not some large built up system. To produce from 6 to 14 km of fiber a 2 kg block of source material is what is being brought to a melting point. It takes ~20Mj to melt the 2 kg block and that is equivelent to just ~6 kwh. Meaning to also cool it would require 12kwh to produce the entire fiber from the source block. If the unit only pulls 200w it would take ~60hours (2 1/2 days) to produce the complete fiber.
So the amount of power used by these boxes is almost trivial to the other power requirements of the ISS or other space-station such as a BA330.
A BTW that 6km of fiber at $300/m let alone the $3000/m price is worth $1.8M. At $3,000/m it is worth $18M.