  Solar irradiance is the primary input for all solar energy generation
systems. The amount of available solar radiation over time under the local
weather conditions helps to decide the optimal location, technology and size of
a solar energy project. We study the behaviour of incident solar irradiance on
the earth's surface using weather sensors. In this paper, we propose a
time-series based technique to forecast the solar irradiance values for shorter
lead times of upto 15 minutes. Our experiments are conducted in the tropical
region viz. Singapore, which receives a large amount of solar irradiance
throughout the year. We benchmark our method with two common forecasting
techniques, namely persistence model and average model, and we obtain good
prediction performance. We report a root mean square of 147 W/m^2 for a lead
time of 15 minutes.
