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Why are liquid metals considered for use in MHD generators?

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magnetohydrodynamic power generator Comparison of the operating principles of (A) a turbogenerator and (B) an MHD generator.

Liquid metals are considered for use in magnetohydrodynamic (MHD) power generators primarily because of their high electrical conductivity.1

While ionized gases or plasma are more commonly associated with MHD systems, liquid metals offer distinct advantages for electrical machine operation. However, because liquid metals cannot serve directly as a thermodynamic working fluid, they must be utilized in specific ways:21

Two-phase flow: The liquid metal is combined with a driving gas or vapor to create a two-phase flow within the generator duct.1
Ejector systems: The metal can be accelerated by a thermodynamic pump and then separated from the driving gas before passing through the duct.1

Despite their high conductivity, liquid metal MHD systems are limited by the physical properties of the metals to operating temperatures of approximately 1,250 K (about 975 °C, or 1,800 °F). Consequently, they compete with other energy-conversion technologies that operate within that same temperature range.1