[1][2] It is characterized by high potential efficiencies and no moving parts except for the working fluid, which make it a candidate for space power applications.
The unique feature of the AMTEC cycle is that sodium ion conduction between a high-pressure or -activity region and a low-pressure or -activity region on either side of a highly ionically conducting refractory solid electrolyte is thermodynamically nearly equivalent to an isothermal expansion of sodium vapor between the same high and low pressures.
The AMTEC thus is an electrochemical concentration cell, which converts the work generated by expansion of sodium vapor directly into electric power.
[citation needed] High-voltage multi-tube modules are predicted to have 20–25% efficiency, and power densities up to 0.2 kW/L appear to be achievable in the near future.
[citation needed] Calculations show that replacing sodium with a potassium working fluid increases the peak efficiency from 28% to 31% at 1100 K with a 1 mm thick BASE tube.
[13] A related technology, the Johnson thermoelectric energy converter, uses a similar concept of pumping positive ions through an ion-selective membrane, using hydrogen rather than an alkali metal as the working fluid.
[14] AMTEC requires energy input at modest elevated temperatures and thus is easily adapted to any heat source, including radioisotope,[15] concentrated solar power, external combustion, or a nuclear reactor.