The power density is much higher than traditional photovoltaics (more in line with concentrating photovoltaic power), so in theory the cost should be low, altho

The power density is much higher than traditional photovoltaics (more in line with concentrating photovoltaic power), so in theory the cost should be low, although one probably needs more sophisticated cells to achieve reasonable efficiencies. On the other hand, since there are no moving parts, the temperature can be very high, which increases the maximum theoretical efficiency. (Carnot limit applies.) The major issues I can see are (1) achieving sufficient efficiency at a reasonable cost, by recycling the low-energy photons instead of absorbing them as heat (2) avoiding radiation damage to this sophisticated device - maybe this isn't too hard with a liquid salt heat exchanger?