On frequency and temperature dependence of limiting efficiency in direct utilization of quasi-monochromatic radiation

The solution to the problem on limiting (thermodynamically permissible) efficiency ηm of direct conversion of energy of quasi-monochromatic radiation into work known from the literature leads to physically unacceptable results (ηm<0) in the range of small frequencies ν and temperatures Tν of converted radiation. It is shown that the noted feature is a consequence of the approximate character of the mentioned solution obtained without taking into account background heat radiation: the exact solution obtained for ηm is valid for all ν and Tν ≥ 0 and turns into the solution known earlier for Open image in new window and hν ≳ kT (where T is the temperature of the surroundings).