Preliminary quantification of the available solar power near the lunar South Pole

Abstract

The lunar South Pole is an area of great interest for human bases and for the mining of water from the nearby permanently shadowed regions (PSRs) that remain below 110 K at all times. To provide power for these activities, only solar and nuclear fission are currently feasible options. Solar power is nearly continuously available from vertically deployed solar panels from some quite restricted high illumination regions (HIRs) close to the PSRs. One factor in determining the choice between solar and nuclear power sources is an assessment of the total solar power available. If solar power is found to be inadequate, even in a best-case scenario, for the demands of a base or, more challenging, of mining, then nuclear fission will become the only option. Local topography means that the amount of solar power available from the HIRs depends in a non-trivial way on the height of the solar panels deployed. Here we use average illumination maps for a range of heights above the local topography from 2 m to 20 m (for near-term deployment) and up to 2 km (for long-term consideration) to determine the total solar power that is potentially available from the HIRs as a function of time of lunar day. Overshadowing of highly illuminated areas by solar panels placed in sunward locations (at a given time of day) limits the total power to significantly smaller values than the highly illuminated area would suggest. The answers depend on the percentage illumination demanded by the application. We find that for near-term realizable vertical solar panels (up to 20 m), the upper limit to the time-averaged power available is ∼55–63 MW at >70% illumination, reducing to ∼6 MW at >90% illumination. This is sufficient to power thermal mining requirements at a rate of 1600–2450 tonnes/year of water. For the more distant future, for towers up to 2 km in height, a maximum time-averaged power of order 22,000 MW at >70% illumination could be realizable and ∼15,500 MW at 90% illumination. The variation in generated power with lunar time of day ranges from a factor of 1.1–∼3. These results suggest that sufficient solar power could be available for currently anticipated base or mining needs. Ensuring this power supply may require careful governance agreements.