For terrestrial applications, Lithium-Sulfur (Li-S) cells are regarded as the most promising technology for the next generation batteries due to their high theoretical capacity, the abundant and low cost sulfur resources and lithium-ion comparable cathode production techniques, and the low toxicity of sulphur compared to cobalt based cathode. Theoretically, Li-S batteries can deliver an extremely high specific energy of 2,567 Wh/kg, compared to 387 Wh/kg being the theoretical maximum for conventional Lithium-ion cells used in terrestrial and satellite applications at the moment.

A very high power solar array concept (in the order of 50-100 KW) can be efficiently designed only using very high voltage bus concept (around and above 300 Volts). Therefore, it is mandatory to develop and test high-voltage high-power solar array technology that is not yet available. Potentially this enables direct transfer of power to the electric propulsion system without voltage conversion equipment (hence saving mass).

The state-of-the art GaInP/GaInAs/Ge triple-junction solar cell technology has reached its practical efficiency limits of around 30% beginning of life (BOL) and an excellent value of 26.5% end of life (EOL). A significant efficiency increase in the order of 3-5% absolute can only be realised by a change of the cell concept.

Background and justification: