engleski

COMPARISON BETWEEN THE CALCULATION MODELS FOR ESTIMATION OF THE SOLAR IRRADIATION IN SOLAR HOT WATER SYSTEMS

Normally, solar collector is mounted inclined to the horizontal surface and, at the same time, oriented at the arbitrary azimuth angle. In order to properly size a solar system it is necessary to calculate hourly, daily, monthly or yearly values for solar incident irradiation on the collector surface. This work provides comparison between the two models for calculation of the solar irradiation on the angled surface widely encountered in the engineering applications, being performed for the local area of the city of Zagreb. First, more comprehensive, model is based on the hourly meteorological data, whilst the simpler one uses empirical coefficients for characteristic day in a particular month. The results presented in the diagrams reveal smaller differences between computed values for hourly irradiation in the middle of the day, while larger discrepancies occur earlier in the morning and later afternoon. Provided that the differences between two models are smaller in the periods of a day with the highest irradiation, the simpler model appears to be more appropriate when sizing vast majority of the solar hot water systems. The other one, more complex model, can be applied when detailed hourly analysis of the system operation is needed.

calculation model; solar hot water system; solar collector; solar irradiation

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