The increasing use of renewable energy sources necessitates accurate forecasting models for generation
scheduling. Amongst the renewable sources, solar and wind have gained acceptance and are being
increasingly used in distributed generation. The main problem with these sources is the dependence of
their power output on natural environmental parameters at a given point of time. This paper proposes
time series models for short-term prediction of solar irradiance from which solar power can be predicted.
The predictions are done for 1 day ahead using different time-series models. For each model, these
predicted values are compared with the actual values for the next day and graphs are plotted. Basic timeseries models such as moving average and exponential smoothing were tested. The decomposition
model is proposed, where the measured data is decomposed into seasonal and trend patterns and each of
them predicted separately. The model was developed for different durations of data, to identify the best
possible set of data. It is observed from the results that the prediction with decomposition model for 2
months data gave the best result with around 9.28% error.