This paper compares two commonly used functions, the Weibull and Rayleigh distribution functions, for fitting a measured wind speed probability distribution at a given location over a certain period. The monthly and annual measured wind speed data at 84 m height for the years have been statistically analyzed for the country with a large capacity -Kitka. The analysis is made in the case of the implementation of all the predicted capacity of wind turbines and by virtue of the probability of power distribution. The Weibull and Rayleigh probability distribution functions have been determined and their parameters have been identified. The average wind speed and the wind power density have been estimated using both distribution functions and compared those estimated from the measured probability distribution function. The Weibull distribution function fits the wind speed variation better than Rayleigh distribution function. The average wind speed was found to be 4.5 m/s and the average wind power density was 114.54 W/m According to results, we can conclude that such a distribution of winds in this region yields an appropriate average value of wind power.

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<p>Nowadays the main goal of sustainable energy supply is the use of renewable energy sources and, in addition, the increased efficiency of the energy used. One possibility of using renewable energies is the use of solar energy through photovoltaic panels. Taking into account the meteorological characteristics of the country in which the study takes place, it appears that the use of photovoltaic panels will be available most of the time during the year. We applied a model of hybrid solar collectors for maintaining the cell temperature near 25°C by introducing a flat plate cover integrated with solar cells. This method represents a way to increase the efficiency of the solar collector. This will enable the production of electricity from the part of the photovoltaic panel incorporated into the solar collector, in which the water temperature will increase, and this heat from the water is due to the effect of sunlight and as a result of cooling the part of the photovoltaic panel. This represents an increase in the efficiency of the system and the main purpose of our analysis.</p>

In this paper, we analyze the method of passive over/under voltage for protection and distribution of PV systems connected to the utility grid. The method in question is analyzed by non-detection area and based on the possibility of degradation of output power quality, which is a known weak point of this method. The analysis focuses on the worst case detection when the energy produced by the photovoltaic system is the same energy that takes the load when there is no change to the parameters at the common point of connection to the utility grid. An algorithm is proposed to solve the problem of the creation of the so-called islanding of generators connected to the grid. Simulations were conducted with Matlab Simulink software. Streszczenie. W artykule analizowano pasywną metodę detekcji pracy wyspowej z wykorzystaniem zabezpieczenia nad/pod napięciowego w przypadku systemu dystrybucyjnego zawierającego system PV. Analizowano obszary nie-wykrywania zagrożeń. Skoncentrowano się na najgorszym przypadku, w którym energia wytwarzana przez system fotowoltaiczny jest w całości pobierana przez odbiór, podczas gdy nie występują zmiany parametrów w punkcie wspólnego przyłączenia do sieci elektroenergetycznej. Przedstawiony algorytm rozwiązuje problem kryteriów dla detekcji pracy wyspowej jednostek wytwórczych przyłączonych do systemu elektroenergetycznego. Eksperymentalna analiza pasywnej metody wykrywania pracy wyspowej i zabezpieczenia falownika