Antenna processes

The absorption and generation of photons in the abcd (Fig. 2) and spet (Fig. 4) processes is accompanied by the production of work. No work is done in the st process (Fig. 2). This difference can be used to divide all processes with the absorption and generation of photons into two types. The first type includes processes in which the matter and radiation do work, that is, participate in the working process. The second type includes processes in which the substance absorbs and emits radiant energy without doing work, that is, participates in an antenna process. The spontaneous evening out of the temperatures of the matter and radiation is an example of antenna processes, and radiant energy conversion in a solar cell is a combination of processes of the first and second type.

The highest efficiency of a combination of work and antenna processes is described by the line AB in Fig. 8. If the work is performed during a non-Carnot cycle then efficiency of the work and antenna processes is described by the LB line. The difference between nosnU and Пь is 94.8-93.1=1.7%. For analysis of antenna processes one should choose the temperature dependence of the value because in this case a conversion process is reversible.

The CEB line in Fig.9 shows the efficiency of a combination of work done by matter (in a Carnot cycle with the efficiency no), by radiation (in a non-Carnot cycle with the efficiency nAS) and a background antenna process with the efficiency nU. The n coordinates of the CEB line divided by nL describe the largest contribution of working processes to the efficiency of solar energy conversion if nL is taken as one. The contribution of the antenna process is then 1- nonASnu/nL.

It follows that the efficiency of conversion higher than nonASnU (the region between the LB and CEB lines, Fig. 9) can be obtained by perfecting the antenna process only. The efficiency of solar energy conversion is maximum in this case if all antenna processes are reversible. The efficiency is minimum if all antenna processes are irreversible.

The n coordinates of points between the LB and CEB lines are then proportional to the fraction of reversible antenna processes. An irreversible antenna process corresponds to the 1 – n/nL value. The character of this dependence will not be discussed here. Only note that Fig. 9 can be used to calculate the fractions of work and antenna processes, as well as contributions of reversible and irreversible antenna processes in solar energy conversion if experimental data on the temperature dependence of the solar cell efficiency are available.

So, the antenna processes in Landsberg engine are reversible. When antenna processes are made irreversible, then the efficiency of transformation of radiant energy decreases from nL=94.8% down to n0nASnU=5.79% at TA=320 К. We have to select the opposite way.

Updated: August 23, 2015 — 3:06 pm