Solar Radiation Model for Development and Control of Solar Energy Sources / Saulės Spinduliavimo Modelis Fotovoltinių Elektrinių Projektavimui Ir Valdymui

Abstract

ELEKTroNIKa Ir ELEKTroTEChNIKa ELECTroNICS aNd ELECTrICaL ENGINEErINGIn previous work a model for a clear sky direct solar irradiance was presented (Vasarevičius, Martavičius 2011). Estimating only direct component is usually enough when analysing solar thermal collectors, but PV modules also gain benefit from diffused and especially reflected radiation components when the surrounding environment has high albedo (e. g. snow, water ponds in evening and morning). Presented model is implemented in Matlab/Simulink environment and generates total solar irradiation values at a given location, described by geographical coordinates and altitude for any time of the year. Model also outputs Zenith and azimuth angles, which can be used for sun tracking applications. Due to this many analytic expressions are used, to meet computational possibilities of embedded devices and increase modelling speed in Matlab.Some control systems like MPPT tracking are very sensitive to rapidly varying solar radiation due to clouds and usually have reduced efficiency in such conditions. The main aim of presented model is development of MPPT algorithms, so the model of cloud layer simulation is included. Abstract. The model of solar radiation, which takes into account direct, diffused, and reflected components of solar energy, has been presented. Model is associated with geographical coordinates and local time of every day of the year. It is shown that using analytic equations for modelling the direct component, it is possible to adopt it for embedded systems with low computational power and use in solar tracking applications. Reflected and diffused components are especially useful in determining the performance of photovoltaic modules in certain location and surroundings. The statistical method for cloud layer simulation based on local meteorological data is offered. The presented method can't be used for prediction of weather conditions but it provides patterns of solar radiation in time comparable to those measured with pyranometer. Cloud layer simulation together with total solar radiation model is a useful tool for development and analysis of maximum power point tracking controllers for PV modules.