Solar Power

The first small scale bases on the Moon with either use solar power or nuclear power (or both).

Solar power can be thermal (e.g. Brayton Cycle or Stirling Cycle), or Photovoltaic.

Photovoltaic (PV) Solar cells have a low efficiency, mostly < 20%.

Soft landing hardware on to the Moon is very expensive, so weight is at a premium.

Until ISRU manufacturing is online, Solar Power Satellites (SPS) represent a more economic means of supplying large scale basebar power on the Moon in the early days.

SPS Rectennas are much lighter and more efficient (90%) than PV solar cells.

The distance from L1 to Luna is about the same as the distance from Earth to a geostationary satellite.

So one could put an SPS at lunar-L1 and beam microwaves from there to supply one or more rectennas on the Moon as a very efficient way to provide energy to a power hungry moon base.

The ideal site for the lunar rectenna would be in Sinus Medii at the Lunar 0-Longitude point on the Lunar Equator, in the middle of the side which faces the Earth.

1) Because it is directly below the L-1 point, 2) it is the closest point on the lunar surface to the L-1 point, 3) Because at that point the lunar surface is at right angles to the incoming microwave beam.

All these factors permit the smallest rectenna at that location.

Without making any modifications at all to that very SPS, it could easily be maneuvered from L1 to GEO to feed a terrestrial ground based rectenna. The antenna design for L-1 to Luna will work equally well from GEO to Earth