Solar Power Subsystem
Photovoltaic Array System (PVA)
The photovoltaic array system is a secondary power generation subsystem comprising approximately 20 m² of multi-junction semiconductor cells (GaInP/GaAs/Ge) designed to generate 5 kWe of peak daytime electrical power, supplementing primary nuclear baseload generation. Operating on the lunar surface exposes the arrays to unattenuated solar flux of approximately 1361 W/m² alongside severe environmental constraints. Lunar night lasts 336 hours (roughly 14 Earth days), resulting in zero solar generation and requiring full baseload reliance on non-solar sources. Without an atmosphere to filter radiation, arrays experience direct ultraviolet exposure and roughly 1% annual radiation degradation, while abrasive regolith dust accumulation degrades power output by approximately 2% per lunation without regular cleaning.
Secondary power generation using photovoltaic arrays during lunar day to supplement nuclear baseload
Purpose
Supplement nuclear power during the ~14 Earth-day lunar daytime, reduce nuclear reactor thermal stress, provide power diversification, and serve as backup generation if nuclear power is temporarily reduced for maintenance
Context
Secondary power source in the N+2 redundancy architecture. Provides significant power during lunar day but zero during 336-hour night. Requires dust mitigation (interface with L1-DST) and tracking mechanisms. Complements L2-PWR-NUC (primary) and L2-PWR-RTG (emergency).
Principles
- ▸Photovoltaic effect converts photon energy to electrical current in semiconductor junctions
- ▸Multi-junction cells (GaInP/GaAs/Ge) achieve 30%+ efficiency by capturing different wavelength bands
- ▸Solar flux at lunar surface is ~1361 W/m² (no atmospheric attenuation)
- ▸Single-axis or dual-axis tracking increases energy harvest by following sun across sky
- ▸Series-parallel string architecture provides fault tolerance (bypass diodes)
- ▸Cell degradation from radiation and thermal cycling reduces output over time
Typical implementations
- ▸ISS solar arrays: Si cells, 84 kW BOL, ~240 W/m² (older technology)
- ▸Mars InSight: Triple-junction GaAs, degraded by dust accumulation
- ▸Artemis/Gateway: Roll-Out Solar Arrays (ROSA), high power density
- ▸Lunar surface concepts: vertically-oriented arrays for polar locations
- ▸IMM (Inverted Metamorphic Multi-junction) cells: 33%+ efficiency
Lunar considerations
- ▸336-hour lunar night: zero solar generation for ~14 Earth days
- ▸Polar rim locations may have near-continuous illumination ('peaks of eternal light')
- ▸Regolith dust accumulation severely degrades output (~2% per lunation without cleaning)
- ▸No atmosphere: full solar spectrum reaches cells, including UV degradation
- ▸Extreme thermal cycling stresses cell interconnects and substrates
- ▸Micrometeorite impacts can damage cells and coverglass
- ▸Low gravity (1/6 g) allows lighter support structures
- ▸Electrostatic dust levitation complicates cleaning
Specifications
Functional
| primary function | Convert solar radiation to DC electrical power during lunar day |
| inputs | Solar radiation (~1361 W/m² at lunar surface), Pointing commands from tracking system |
| outputs | DC electrical power: 3-5 kWe during lunar day, Telemetry: array current, voltage, temperature, pointing angle |
| peak power kwe | 5 |
| array area m2 | ~20 m² (at 25% system-level efficiency) |
| cell efficiency pct | 30+ (BOL, multi-junction) |
| design life years | 20 |
| dust cleaning frequency | Every lunar day (minimum) |
| radiation degradation pct per year | 1 |
Physical
| mass kg | 200 |
| dimensions | ~20 m² array area, configuration TBD (deployable or fixed) |
| materials | GaInP/GaAs/Ge multi-junction cells, Coverglass (CMG or CMX radiation-resistant), Carbon fiber composite substrate, Aluminum or titanium structural frame, Kapton/copper flex cable harness |
| operating temp c | -170°C (night/shadow) to +120°C (full sun) |
| solar flux w m2 | 1361 |
| dust accumulation | Up to 2% per lunation degradation |
Operational
| power consumption w | 50 |
| thermal range c | -170, 120 |
| lifetime years | 20 |
| mtbf hours | 80000 |
Interfaces
Provides
- Raw DC power from PV arrays, variable voltage depending on illumination and temperature
- Array performance telemetry: current, voltage, temperature, efficiency metrics
Requires
- Keep-alive power for tracking motors and electronics during lunar night (~50W)
- Operating mode commands, tracking angle setpoints
- Foundation and mounting for array support structure
- Electrodynamic dust shield (EDS) activation or robotic cleaning for dust removal
- Robotic inspection and possible cell replacement or cleaning
Decomposes into
Cite this entry
Lunar Ark Codex. "Solar Power Subsystem" (L2-PWR-SOL). Retrieved 10 September 2026, from https://lunarark.com/entry/L2-PWR-SOL
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.