[Paper Review] Towers on the Peaks of Eternal Light: Quantifying the Available Solar Power

Amia Ross, S. Ruppert+2 more|arXiv (Cornell University)|Feb 23, 2021

Building Energy and Comfort Optimization12 references4 citations

TL;DR

This paper quantifies the maximum solar power available at Peaks of Eternal Light (PELs) on the lunar south pole, modeling how tower height and self-shading affect energy yield. Using illumination maps from 2 m to 2 km above terrain, it finds that 20 m towers can deliver ~55 MW average power at >70% illumination, while 2 km towers could enable ~21,000 MW at the same threshold, with significant variation over the lunar day.

ABSTRACT

The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south pole, have been suggested as a source of solar power for mining the water and other volatiles in the nearby permanently dark regions. As mining is a power-intensive activity, it is interesting to estimate the maximum solar power that could be generated at the PELs. Here we use average percentage illumination maps for a range of heights above the local topography from 2 m to 2 km to determine the total power available as a function of time of lunar day. Overshadowing of highly illuminated areas by towers placed in sunward locations (at a given time of day) limits the total power to much smaller values than the highly illuminated area would suggest. We find that for near-term realizable towers (up to 20 m), the upper limit to the time-averaged power available is ~55 MW at >70% illumination, and ~6 MW at >90% illumination. For the more distant future a maximum time-averaged power of order 21000 MW at >70% illumination could be realizable for towers up to 2 km in height, and ~5270 MW, respectively, at 90% illumination. Towers 1 km high provide about a factor 2.7 times less power. The variation with lunar time of day ranges from a factor of 1.1 to ~ 3.

Motivation & Objective

• To assess the maximum time-averaged solar power available at Peaks of Eternal Light (PELs) on the lunar south pole.
• To evaluate how tower height and self-shading affect solar energy collection at PELs.
• To quantify the trade-offs between tower height, illumination duration, and power output for sustained lunar surface operations.
• To provide performance estimates for near-term (up to 20 m) and long-term (up to 2 km) tower deployments.

Proposed method

• The study uses high-resolution lunar topographic data to model illumination conditions at PELs across a range of tower heights (2 m to 2 km).
• It generates average percentage illumination maps for each height, simulating the time-averaged exposure to sunlight over the lunar day.
• The analysis accounts for self-shading, where towers block sunlight from reaching adjacent high-latitude regions, reducing effective power generation.
• Power output is calculated based on the time-averaged illuminated fraction and solar irradiance, assuming ideal photovoltaic conversion.
• The model evaluates power availability at different illumination thresholds (>70% and >90% illumination) to reflect mission-critical reliability.
• Results are presented as time-averaged power estimates, with sensitivity to lunar day/night cycles and tower height.

Experimental results

Research questions

• RQ1 What is the maximum time-averaged solar power that can be harvested at Peaks of Eternal Light using towers of varying heights?
• RQ2 How does self-shading from towers reduce the effective power output compared to the theoretical maximum of the illuminated area?
• RQ3 What is the trade-off between tower height and power availability, particularly at high reliability thresholds (>70% and >90% illumination)?
• RQ4 How does the power output vary over the lunar day, and what is the dynamic range of power availability for different tower configurations?

Key findings

• For near-term towers up to 20 m in height, the maximum time-averaged solar power available at PELs is approximately 55 MW when requiring >70% illumination.
• At the same 70% illumination threshold, the maximum time-averaged power drops to ~6 MW when requiring >90% illumination, reflecting stricter reliability constraints.
• For future towers up to 2 km in height, the maximum time-averaged power reaches ~21,000 MW at >70% illumination, and ~5,270 MW at >90% illumination.
• Towers of 1 km height yield about 2.7 times less power than 2 km towers under the same illumination conditions.
• The variation in power output over the lunar day ranges from a factor of 1.1 to as high as ~3, indicating significant temporal fluctuations.
• Self-shading from towers significantly limits the effective power generation, reducing the total available power far below the theoretical maximum of the illuminated area.