[weby]

A realistic solar panel module would likely provide much less than 1 power point at Earth distance.

Current panels provide up to 300 W/kg, thus that SM +10 ship module of 500 tons would provide about 150 mega watts at TL 8, thus you would need about 6 modules to provide the estimated 1 GW for 1 power point.

But there is a large margin of error on that 1GW, thus any range between about 3 (allow firing of a high efficiency (50%) energy weapon once every 20 second turn) and 120 modules(allow a 25% efficient weapon be fired every second) would make sense.

At higher TLs the structural weight might decrease and efficiency might increase, allowing that 1 module to finally give one power point at about TL 12 as armor at that point is 4 2/3 times as protective. (Or if the panels and weapons get very high efficiency, maybe at TL 11 or 10^)


But yes, solar mirrors would definitely increase the effect of solar panels at earth distance until the panel gets too hot. That depends a lot on the cooling you have and the exact composition of your panel. (and cooling uses mass, lowering the area you get for the same mass). I do not know the exact numbers but solar cell efficiency does go down with raised temperature. (The cells I have go down about 10% between having a surface temperature of 25 centigrade to 45 centigrade at same illumination level according to their data sheet)

In fact many experimental(and few real installations) of solar cells have solar mirrors "built in" to increase the illumination level.

Conclusion:
So in game terms I would likely not allow solar mirrors as such to increase the efficiency a great deal, as the likely technologies getting anything close to the energy indicated by "1 power point" would need to have things like reflectors as part of the design. And the design would likely be optimized to work at a given energy level. (and even then you likely need the several modules indicated above at earth distance). If you use simpler panel structures you fall further and further behind from that "power point"

I would however allow things like rigging extra reflectors to compensate for being further away from the sun than the design specs for the complex panels.

As for retractable: Yes, you could build panels to be be retractable, however that tends to increase the mass(thus you would get even less energy/mass unit)

TLDR; You need a lot more mass than spaceships solar panels likely and reflectors are likely already part of advanced space based solar panel arrays.