Those thermocouples are less than 10% efficient, usually less than 5%.
This means you have to dissipate more than 10 times more energy as heat than the energy you actually want to use as electricity.
Dissipating heat in space is not easy because unlike earth there is no surrounding fluid to dissipate heat into through convection. This means you have to spend precious mass budget on huge (compared to your energy budget) direct heat radiation systems that cannot leverage convection efficiencies.
Thus, a significant energy efficiency increase would be a big deal for RTG powered spacecraft design. It is curious that the article above does not consider this.
Bonus thought: consider what this lack of convection problem means for "Hyperloop" type vehicle systems that operate in a vacuum tunnel, as most conventional trains dissipate excess braking energy through convection from resistive heating elements atop the roof.
Conventional trains that run under wires can also dump excess braking energy into the overhead. That seems feasible even if you had to have your resistive heating elements somewhere outside the tunnel system.
This means you have to dissipate more than 10 times more energy as heat than the energy you actually want to use as electricity.
Dissipating heat in space is not easy because unlike earth there is no surrounding fluid to dissipate heat into through convection. This means you have to spend precious mass budget on huge (compared to your energy budget) direct heat radiation systems that cannot leverage convection efficiencies.
Thus, a significant energy efficiency increase would be a big deal for RTG powered spacecraft design. It is curious that the article above does not consider this.
Bonus thought: consider what this lack of convection problem means for "Hyperloop" type vehicle systems that operate in a vacuum tunnel, as most conventional trains dissipate excess braking energy through convection from resistive heating elements atop the roof.