I did not investigate it properly but at first glance the efficiency is obtained via low current density of the electrolyser. That means high efficiency but low volume. That translates to more hardware needed to produce a unit of power.
State of the art electrolyzers are run at 1000x current densities. That roughly means 1000x installation cost.
State of the art electrolyzers are run at 1000x current densities. That roughly means 1000x installation cost.