[larkeith]

The IKAROS sail (launched 2010) is 196 m^2, using aluminum as a reflector (about 90% efficiency). With regards to transferring a lens to orbit, that is a self-solving problem - a large lens or mirror can both be used as a solar sail, potentially even hauling additional mass to Mars orbit.

Mars receives 593 W/m^2 flux, so each IKAROS-sized reflector could produce about 100 KW of energy. Given the expected difficulty of large scale terraforming and colonization efforts, it seems the cost of, say, the equivalent of 10,000 IKAROS-sized mirrors (~1 GW, comparable to a large nuclear plant) would be relatively minor.

Whether that would be more cost effective than shipping an equivalently powerful reactor or other generator is questionable - it will presumably depend on our lifting capacities.