# Evolutionary Maximization of Energy Amount Harvested by Means of Panel of Thermoelectric Modules
## 1 Introduction  
The natural environment protection is a crucial task of present times and this radically increases the importance of research in domains of electric energy clear production and its saving methods. Everybody wishes to have easy access to electric energy in any place and time, but conventional power plants cause unacceptable pollution and have limited efficiency as well as defined electric power production and distribution possibility. In this situation, the new techniques of wasted thermal energy harvesting and its conversion to the electric energy are very much desired. They may reduce the mentioned inconveniences and can be helpful in many areas, e.g., medicine [1, 2], power supply to secluded places [3] or automotive related solutions [4, 5, 6]. Thermoelectric generators (TEGs) are modules which allow the conversion of thermal energy to the electric one in the direct way, i.e., without engaging any rotated elements, the ones present in conventional mechanical electro-generators, turbines, so this kind of system characterizes very high life cycle, guarantees maximal reliability, and, of course, assures electricity in any places with zero emission of additional pollution. The main disadvantage of the TEG system is its low efficiency of energy conversion and relatively high cost of installation, especially for lower temperatures [7]. On the other hand, a rising development of microelectronic technology and numerous studies on optimal utilization ofmatrices (panels) of TEGs [7; 8; 9; 10] as well as TEG's cells being specifically constructed [11; 12] should reduce the troubles pointed out here. The proposed work describes a thermoelectric generator constructed from less expensive, standard Peltier modules, typically applied as ones used for cool production. Due to the duality of Seebeck-Peltier phenomena, these converters can be successfully applied to the electric energy production too. It should be emphasized that the proposed solution assures the optimization of operational points of energy conversion in local string sections. The groups of thermoelectric (TE) modules are connected in series to increase the produced voltage before the boost operation by means of DC/DC converter. Duty cycle coefficients of waveforms which control switching transistors of simple local boost converters are, in the proposed system, determined by means of evolutionary computation. The implemented optimization algorithm is convergent on the square signals with pulse width modulation (PWM) levels which assure maximization of electric power generated from the panel of thermoelectric module strings. This specific maximal power point tracking (MPPT) algorithm corrects transistors switching cycles durations, respectively, to the changes of load condition and operational points of TEG module groups. References [13; 14] present a general review of the MPPT known techniques, in [15] an MPPT evolutionary technique that uses particle swarm optimization is proposed, however in [16] there is one applying a differential evolution computational method. It should be underlined that contrary to previously published works, which were depicted as evolutionary MPPT methods, the version proposed here allows the optimization of PWM signals duty cycles concurrently to all TE groups (strings) of global system. This unique feature makes possible the establishment of the thermovoltaic panel global optimum of operational point by respective trimming of local DC/DC converters operating points. Besides, specific procedure of fitness determination as well as original structure of chromosomes, dedicated method of population genetic recombination and its succession increase algorithm convergence speed significantly. The described evolutionary technique characterizes low computational cost and implementation capability to chip microcontroller module, which was confirmed by laboratory measurement results achieved in the practical example system.