A METHOD FOR DETERMINING OF OPTIMAL TILT ANGLE AND ORIENTATION OF PV MODULES BASED ON MEASURED SOLAR RADIANCE DATA

For calculating and designing of photovoltaic (PV) plant, it is necessary to choose the optimal tilt angle and azimuth orientation of solar panels which will largely determine the electricity output produced by future PV plant during an operational calendar period. However, in order to determine these angles experimentally by monitoring the PV plant electricity yield at different panel’s positions, it will take many years. Therefore, it is advisable to develop a theoretical model, which a priori calculates the optimal tilt and azimuth angles of panels amounted in fixed positions. This paper assumes the maximum of the total radiation arrival per unit area on the receiving surface over the calendar period of PV plant operation as an optimization criterion for these angles. The calculation scheme has been applied for the whole year, for four year seasons and for a whole year period except winter. In the developed optimization method, the initial data are the geographical coordinates of the PV plant, the hourly sums of direct and diffuse radiation on the horizontal plane, as well as the reflectivity of the earth's surface. These data obtained by averaging the long-term measurements of the main solar radiation components are experimental ones. The developed computational scheme is based on nonlinear equations for the optimal tilt angles of panels first obtained for anisotropic solar radiation models. This scheme allows us to calculate the optimal panel angles for any operational PV plant period and for any region for which experimental radiation data are available. As the examples, we have calculated the graphs of the average daily radiation arrival dependencies on the panel’s position angles and have determined the optimal fixed tilt and azimuth angles for six cities of Russia located in different climatic zones. The method allows us to evaluate the gain in the electricity yield of PV plant when choosing the optimum tilt angles and azimuth of the panels, and to a djust the tilt angles to the optimum values for each season if this is envisaged by the PV string design.

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