Using Eqs. (1)–(6), (21), and (24)–(27), one can draw threedimensional
projection graphs of the power output and efficiency
of the hybrid system varying with RL1 and RL2, as shown in Fig. 9.
Fig. 9(a) and (b) illustrates that the power output and efficiency
of the hybrid system first increase and then decrease as RL1 and
RL2 increase. There exist optimal values of RL1 and RL2 at which
the power output and efficiency attain their respective maximum
values. These optimal conditions occur at RL1;opt ¼ 3:81 X; RL2;opt ¼
14:41 X, and Tp;opt ¼ 328:39 K. The present computational results
are consistent with the experimental results in Ref. [33]. Obviously,
for different values of G and c; RL1; RL2, and Pmax will have different
optimum results. For a given value of c, the larger the solar irradiance
G is, the larger both Pmax and RL2;opt and the smaller the load
resistance RL1;opt. For a given value of G, a large structure parameter
c will result in large Pmax and RL1;opt and a small RL2;opt, as indicated
in Table 3. Table 3 implies that the optimal load of the PV–TEG
hybrid system must satisfy