Thermal Storage Tank
Vacuum-Insulated High-Temperature PCM Containment Vessel
Stainless-steel double-wall insulated tank with vacuum-jacketed multi-layer insulation, sized to contain ~5 tonnes of PCM at 230 °C with <100 W of standing thermal loss to the lunar environment, supporting >5000 freeze/melt cycles over 25 years.
Purpose
Hold the entire PCM thermal storage inventory at melting temperature with minimal energy loss, protect against micrometeoroid penetration, accommodate volumetric expansion during melt, and provide access for heat exchanger and instrumentation.
Context
Houses L3-ESS-THRM-PCM; integrated with L3-ESS-THRM-HEX (internal tubes or jacket); insulated externally with vacuum + MLI; supported by L1-STR; cooled externally to lunar surface (radiation only).
Principles
- ▸PCM expansion during melt (~10–15% volume) accommodated by ullage space or bellows expansion vessel
- ▸Vacuum jacket + MLI achieves <1 W/m² heat loss at 230 °C inner / 130 °C outer
- ▸Tank shell sized for hoop stress at internal pressure (typically 1–2 bar absolute, since PCM is mostly liquid/solid)
- ▸Inner liner Inconel 800H or 316L SS for salt compatibility; outer shell 304 SS for vacuum jacket
- ▸Internal baffles and tube grid prevent stratification and improve heat transfer to HEX tubes
- ▸Robotic access ports for inspection and PCM top-up via L1-MNT
Typical implementations
- ▸CSP molten-salt tanks (Solar Two, Andasol-1, Solana) — terrestrial 10-100,000 t scale
- ▸Cryogenic LH2/LO2 vacuum-jacketed tanks (Centaur, ACES) — heritage for vacuum + MLI
- ▸Industrial high-T heat-treatment tanks
- ▸NASA lunar TES tank design studies (NTRS literature)
Lunar considerations
- ▸Lunar regolith berm provides micrometeoroid protection and additional thermal mass
- ▸1/6 g enables thinner shell walls; hoop stress dominates only at high internal pressure
- ▸Vacuum jacket on the Moon is 'free' (external vacuum) — only need to maintain inner vacuum-jacket integrity
- ▸Long-life seals at access ports critical — robotic-grade quick-disconnects
- ▸MLI degradation under cosmic radiation expected; outer surface emissivity tracked over time
- ▸Drainage trench under tank in case of catastrophic leak — molten salt is non-volatile but corrosive
Specifications
Functional
| primary function | Insulated containment for PCM thermal storage inventory |
| inputs | PCM mass at fill (~5 tonnes), Internal HEX tube grid, Sensor wiring (thermocouples, ullage pressure) |
| outputs | Tank-level telemetry (temperature distribution, internal pressure, ullage), Containment of PCM under all operating modes |
| internal volume m3 | 3.5 |
| pcm capacity tonnes | 5 |
| design temperature c max | 260 |
| design pressure bar abs | 2 |
| standing thermal loss w max | 100 |
| vacuum jacket pressure torr | 1e-05 |
| cycle life | 5000 |
| design lifetime years | 25 |
Physical
| mass kg empty | 600 |
| dimensions | 2.0 m diameter × 1.5 m height (cylindrical) |
| materials | Inconel 800H inner liner, 316L stainless intermediate shell, Vacuum jacket: 304 SS outer shell, 30-layer MLI between shells, Inconel-lined access ports with metal seals, Ceramic-fiber upper-ullage insulation |
| operating temperature c | 50, 260 |
| exterior temperature c | -180, 130 |
| ultimate load g | 6 |
Operational
| power consumption w | 0 |
| thermal range c | 50, 260 |
| lifetime years | 25 |
| mtbf hours | 300000 |
Interfaces
Provides
- Insulated containment volume
- Mounting/penetrations for HEX tube grid
Requires
- Foundation pad with insulation between tank and regolith
- External radiator path (passive) for standing heat loss
Cite this entry
Lunar Ark Codex. "Thermal Storage Tank" (L3-ESS-THRM-TANK). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ESS-THRM-TANK
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.