Development is proposed of a thermal storage unit (TSU) for thermionic power systems for space aircraft, ground and naval platforms. The TSU has extremely high thermal energy storage capability per uit volume which will enable or compliment future high performance Stirling cycle thermal conveters or a multitude of other thermal systems. The high performance TSU is especially suited for storing thermal energy from solar collector systems, but may also find application with other heat sources in systems where very high intermittent peak power demands are required. The high performance TSU uses no expensive, rare, or strategically sensitive materials and can be made at low cost. The system may be repeatedly discharged and recharged with no limit to the number of cycles or the depth of the discharge. There is no known upper limit to the system size or power level. High power levels may be achieved by combination of modular units. There are multiple military, civil, and domestic applications where the proposed high performance solar energy thermal storage power unit might be used in place of electric storage batteies, fuel cells, capacitors, etc. Specific applications might also include high efficiency transportation power systems and storage for remote solar-based power systems
