Solar radiation models for the city of Tirana, Albania

Mathematical models for evaluating the solar radiation potential are not available for every country or specific sites. In this paper, different solar radiation models (linear, exponential, power) for the city of Tirana-Albania, are built and tested. These models are used to estimate the monthly average total solar radiation on horizontal surface, based on measured data. Measured data include solar radiation on horizontal surface and sunshine duration data, which are used for the development of the models. Calculated and measured values are compared and evaluatedby using statistical test methods. Calculated values obtained from the proposed solar radiation modelsshow a good agreement with the measurements. In the best solar radiation model, the percentage error is e_max = 3.452 %, MBE = -0.001465 kWh/(m² day), MPE = -0.015 %, RMSE = 0.074 kWh/(m²day), and R² = 0.998.