By using the residual heat for hot water and for heating in winter and cooling in summer, the global efficiency typically becomes well above 80%.
Even the best Diesel generators may reach around 55% efficiency, while working at much lower maximum temperatures.
For a few seconds I thought that this thermophotovoltaic technique is great, until I have seen that the emitter must have a temperature above 2000 Celsius degrees. For such a great temperature it is very easy to make heat engines with much better efficiency and which might even be less expensive, because these multijunction III-V photovoltaic cells are many times more expensive than normal solar panels.
If these were used for solar power, the concentrators would also be very expensive. Already the concentrators that produce temperatures around 1000 Celsius degrees, which is more than enough for easily reaching 40% efficiency with closed-cycle heat engines, are much more expensive than the concentrators that reach only lower temperatures, like 650 Celsius degrees, which would still be good enough for a steam turbine or for a closed-cycle supercritical carbon dioxide engine.
The only real advantage is that these should need less maintenance than turbo-generators, which may be essential outside Earth or in remote locations, but less important than cost and efficiency otherwise.