Thermoelectric Generator
PbTe/TAGS Thermoelectric Converter Assembly
The PbTe/TAGS thermoelectric converter assembly is a solid-state power system that uses the Seebeck effect across lead telluride and TAGS semiconductor couples to convert thermal energy from a General Purpose Heat Source directly into electricity. Operating with no moving parts to achieve a demonstrated mean time between failures exceeding one million hours, typical configurations produce 292 W of beginning-of-life electrical power from a 4,500 W thermal input. Lunar operations require rejecting waste heat entirely through dedicated radiator fins, while the surrounding vacuum promotes thermoelectric material sublimation at the 500 °C hot junction, necessitating hermetic sealing to prevent conversion degradation over extended missions.
Thermoelectric couples converting GPHS heat to electricity via the Seebeck effect
Purpose
Convert radioisotope thermal energy to electrical power with no moving parts for ultimate reliability
Context
Child of L2-PWR-RTG within the Lunar Ark power generation system
Principles
- ▸Seebeck effect generates voltage proportional to temperature difference across dissimilar conductors
- ▸PbTe (lead telluride) and TAGS (Te-Ag-Ge-Sb) thermoelectric materials used at hot junction ~500C
- ▸Skutterudite materials offer improved efficiency for next-generation designs
- ▸No moving parts means extremely high reliability (MTBF >1M hours demonstrated)
Typical implementations
- ▸GPHS-RTG: 292W BOL from 4500Wt, ~6.5% efficiency
- ▸MMRTG: 110W BOL from 2000Wt, ~5.5% efficiency
- ▸eMMRTG (enhanced MMRTG) with skutterudite couples, ~8% projected efficiency
- ▸NASA NGRTG targeting >7% efficiency with improved thermoelectrics
Lunar considerations
- ▸Hot side temperature limited by GPHS operating envelope (~540C max)
- ▸Cold side rejection to lunar environment via dedicated radiator fins
- ▸Thermoelectric degradation over decades reduces conversion efficiency
- ▸Sublimation of thermoelectric materials in vacuum requires hermetic sealing
Specifications
Functional
| primary function | Thermoelectric couples converting GPHS heat to electricity via the Seebeck effect |
Physical
| materials | PbTe n-type thermoelectric, TAGS p-type thermoelectric, Copper electrodes, MIN-K insulation |
Interfaces
Provides
- DC electrical power ~500We from thermoelectric conversion
Requires
- Thermal power from Pu-238 heat source
- Cold-side heat rejection maintaining temperature differential
Cite this entry
Lunar Ark Codex. "Thermoelectric Generator" (L3-PWR-RTG-TEG). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-PWR-RTG-TEG
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.