# Methods Improving Energy Efficiency of Photovoltaic Systems Operating under Partial Shading
## 5 Conclusions  
The existing methods for the selection of electrical energy from solar PV installations operating in conditions of partial shading, consisting of the use of shunt diodes, individual matching converters, micro-inverters, reconfigurable switching systems, and differentiated maximum power take-off systems, in some cases are not effective or economically justified solutions. Shunt diodes disconnect (shunt) solar cell groups that are partially shaded and lead to voltage mismatch at the maximum power point of parallel PV arrays. IMC add significantly to installation costs and lead to voltage mismatches in parallel arrays of modules. Micro-inverters significantly increase the cost of installations, reduce their efficiency in conditions of uniform illumination, and cannot be used in existing stations with a central inverter. Reconfigurable switch systems are expensive and inefficient with a small number of shaded solar modules. Differentiated maximum power take-offs are also costly, energy inefficient solutions. To increase the energy efficiency of PV installations with mixed switching of PV modules, it is proposed to use a method consisting of voltage matching at the points of maximum power of parallel arrays of modules by sequentially including an APE with variable electrical characteristics. The value of the output voltage APE is set by the micro-controller device. The value of this voltage is equal to the value of the voltage mismatch of the parallel-connected arrays of PV modules. Electric energy is supplied to the APE from the same arrays of PV modules, through a device providing galvanic isolation or from any other source of electrical energy. An important feature of this method is that, to match the modules, it is not required to convert all the electrical energy they generate, but only a small part of it, determined by the level of mismatch. Comparative results of calculating the energy losses of a PV installation formed of 10 parallel-connected groups of PV modules show that, with partial shading of one of ten modules, the proposed method can increase the energy efficiency of an array with a shaded module by 30% when the MPPT is installed by the AMP controller and by 40% in LMP. At the same time, in the case of partial shading of two or more modules, the shaded array without matching devices practically does not generate electrical energy. We suppose that the partial shading (including the low-intensity light of artificial indoor light sources) will also have a negative impact on the efficiency of batteries with organic photovoltaics cells, described in [21,42]. The degree of influence of partial shading on the efficiency of such a battery will depend on the type of connection of the cells (serial, parallel, or mixed) and the type of the partial shading (uniform or uneven). In addition, the efficiency of such a PV battery will be significantly influenced by the presence of shunt diodes and the method of taking electrical energy that is used. The models presented in the article allow the calculation of energy losses due to partial shading of batteries with organic photovoltaics cells. However, for the case of organic photovoltaics elements, it is necessary to obtain specific values of parameters and coefficients (ideality factor, internal resistances, photocurrent, temperature coefficients, etc. ), but it is a separate interesting actual research problem.