Aumento de rendimento e potência em painéis fotovoltaicos por reconfiguração das interconexões e arrefecimento geotérmico

Abstract

This doctoral thesis deals with the reconfiguration of photovoltaic interconnections linked to PV panel cooling by surface geothermal energy through water circulation to increase efficiency, power and lifetime of the modules. In this study, simulations are performed with a PV array based on its physical model to identify efficiency losses caused by shading and temperature variation. The reconfiguration strategies found in the literature do not consider the overall effects caused by temperature variation of the module. According to the experimental and simulated results, when PV panels connected in parallel presents a large temperature difference, power losses occur due to the voltage differences at the maximum power point (MPP). In relation to the performance of the reconfiguration strategies of PV panels found in the literature, these strategies use too many switches, either do not appreciably reduce shading losses, or use too many power converters, which increases the final cost and reduces the PV array efficiency when there are not shaded modules. Thus, this thesis proposes a new strategy of PV reconfiguration in conjunction with geothermal cooling, where the PV array MPP is very close to the MPP of each one of the modules in most cases, resulting in increased power, efficiency and lifetime. The reconfiguration strategy proposed in this thesis allows one or more lines of unshaded parallel modules to remain in the main PV total cross tied (TCT) sub-array and the other modules to be connected in an auxiliary PV TCT sub-array, where both arrays are composed by converters to obtain the PV array MPP. In this case, shading losses are minimized by PV current equalization even when there is only a single shaded module. The geothermal cooling of PV modules results in increased lifetime, output power and efficiency by reducing the operating temperature of each module closer to its nominal operating temperatures, allowing closer MPP PV voltage levels. Another advantage of the structure proposed by this thesis are the heat exchanges between the PV modules and the circulation water used to assist in the water pre-heating for electric showers to reduce the consumption of electric energy. Therefore, unlike the works found in the literature, only modules interconnections reconfiguration and photovoltaic modules cooled by geothermal energy proposed in this thesis allow the PV array to act at a MPP closer to or identical to each of the individual modules.