This document presents the analysis of a hybrid system for household self-sufficiency with electric energy from solar radiation and wind. In the introductory part, we learn something about renewable energy sources and the importance of self-sufficiency in electric energy. Self-sufficiency from renewable energy sources, together with the battery, is becoming an increasingly attractive option for households and for companies that want to reduce their dependence on the power system. One of the key reasons why people decide to set up a system for self-sufficiency of electric energy is to reduce their monthly costs The paid monthly amount can be lower indeed, but with very high initial and maintenance costs, the investment is not always economically justified, given the lifespan of the components.
In the core, the self-sufficiency of electric energy in Slovenia is firstly presented, namely with solar and wind power plants. The importance of the battery storage of electric energy, which plays an important role in self-sufficiency, is also explained. In the following, we move on to the mathematical model of the individual components of the hybrid system for self-sufficient power supply, together with weather data. The typical electric energy consumption of a household with and without a heat pump is presented. There is an explanation of solar radiation, solar geometry, shading, and the effect of temperature on the operation of photovoltaic modules. The main topic of this chapter is the calculation of power and energy obtained from solar radiation and wind. The theoretical equations used in the Microsoft Excel program for calculations are explained.
Finally, the mathematical model of battery storage is described, along with all parameters and equations. The results of the mathematical model are explained including production and consumption of electric energy and the state of charge of the battery during one year at the locations Ljubljana - Bežigrad and Razdrto. Sensitivity analyses for changes of some parameters are provided: the area of solar modules, household consumption, battery size, wind speed for both locations, and the height and nominal power of the wind turbine. For various combinations, the share of self-sufficiency is indicated, which is what we are most interested in, in addition to the profitability of the investment.
The last chapter describes a simple calculation of the economic justification of the investment. A total of all the costs of the investment throughout its lifetime is made, which are converted to a net present value for easier comparison with the costs of electric energy for the same period. The results show less favorable economic justification compared to one presented in media.
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