A precise estimation of the electrical energy produced daily by photovoltaic (PV) systems is important both for PV owners and for electrical grid operators. It can be achieved if the received solar irradiance can be accurately estimated during any type of daily solar profile (clear, cloudy, mixed sky), not only average solar profile for larger periods of time, e.g. one month or season, as used in PV system design. The paper firstly describes an existing mathematical model, based on the Meliss approach, which uses mean monthly coefficients for estimating average direct and diffuse solar irradiance. This model is satisfactory for monthly/annual intervals but is not useful for daily estimations. Therefore in the second part of the paper an algorithm which allows to generate daily variations of the model’s coefficients for clear and cloudy sky conditions is proposed. The improved model with variable coefficients was tested during several representative days and can be used for estimating the effect which different meteorological conditions as fog/dew/frost have on the quantity and quality of the solar irradiance received by a PV convertor.
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 *** The Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings Official Journal of the European Union 53 (2010).
 Aelenei L. Gonçalves H. From solar building design to Net Zero Energy buildings: Performance insights of an office building Energy Procedia 48 (2014) 1236–1243.
 Burduhos B.G. Neagoe M. Duta A. Adaptive Stepwise Orientation Algorithm for Non-concentrated Dual-Axis Solar Tracking Systems Proc. of 14th World Congress in Mechanism and Machine Science Taipei Taiwan DOI 10.6567/IFToMM.14TH.WC.OS16.006 (2015).
 Frontini F. Manfren M. Tagliabue L.C. A case study of solar technologies adoption: criteria for BIPV integration in sensitive built environment Energy Procedia 30 (2012) 1006–1015.
 Hassoun Anwar Dincer Ibrahim Development of power system designs for a net zero energy house Energy and Buildings 73 (2014) 120–129.
 Meliss M. Regenerative Energie-Quellen Praktikum Springer Berlin (1997).
 Vișa I. Jaliu C.I. Duță A. Neagoe M. Comșiț M. Moldovan M.D. Ciobanu D. Burduhos B.G. Săulescu R.G. The Role of Mechanisms in Sustainable Energy Systems ISBN 978-606-19-0571-3 Transilvania University Press Brasov (2015).
 Vișa I. Diaconescu D.V. Popa V.M. Burduhos B.G. Quantitative Estimation of the Solar Radiation Loss in the Brașov Area Environmental Engineering and Management Journal 8(4) (2009) 843-848.
 Vătășescu M.M. Moldovan M.D. Burduhos B.G. Linkages for solar tracking (in Romanian) ISBN 978-973-598-946-0 Transilvania University Press Brasov (2011).