modeling and control of energy systems
T. Radeva, Use of Photovoltaic Energy for Own Needs for an Educational Center for Out-Of-Class Activities and Culture

Key Words: Photovoltaic systems; solar power generation; educational institutions; design engineering; energy management.

Abstract. The solar modules that are produced have a rather fragile structure and must therefore be mechanically protected on both sides. For this purpose, a so-called sandwich structure is used, in which the photovoltaics are placed on a solid base and covered with a transparent upper protective layer. The coefficient of thermal expansion of the materials of the upper and lower protective layers must be the same and, moreover, comparable to that of the photovoltaic cell and the bonding resin used. Currently, the most widely used materials are glass and plastic. Photocells sealed under glass have the advantage that they do not change their optical, mechanical and electrical properties during prolonged outdoor operation. Polymers cannot prevent the penetration of moisture, so they are only suitable when the photovoltaics and metal contacts are protected by an anti-corrosion coating. Plastics are lighter than glass, but they have the effect of aging with prolonged exposure to atmospheric conditions, which strongly affects their qualities. The upper transparent protective layer allows easy cleaning of the solar cells, but during their installation, they must be placed in such a way as to avoid their heavy contamination and the retention of snow on them. This is practically achieved by the southern orientation of the panels and their placement at an angle corresponding to the latitude of the site, as well as taking into account the season of operation. Some panels are oriented to the southwest so that they can produce the necessary energy for the afternoon maximum. For most locations, a slope angle close to horizontal will provide the most energy year-round. The cells used today have an efficiency of 3-20% in converting solar energy into electricity. A photovoltaic generator is a set of modules that convert solar energy into direct current (DC) electricity. It consists of a module formed by several photovoltaic cells, connecting several such modules form a panel, and several panels connected together form an array. Connecting several arrays electrically in parallel forms a photovoltaic generator or photovoltaic park. By connecting a certain number of photovoltaic cells in parallel and in series, any desired power can be obtained. The main element of the photovoltaic generator is the photovoltaic cell, where the conversion of solar radiation into flowing electric current takes place. The present work presents a practical task of a photovoltaic energy system for a public educational building. The purpose of the case study is to provide technical measures to improve the energy efficiency of the building, according to the technical specification and the current regulations. Public school buildings are mainly used during the daylight hours, where solar energy will be used for self-consumption.