Hybrid Renewable Energy System (HRES) can effectively supply sustainable electrical energy in standalone remote areas. However, in order to design a reliable site and a robust controller, uncertainties in sustainable energy resources need to be modeled properly. This paper proposed a stochastic model of hourly solar irradiance for four locations across the UK. The goodness-of-fit of the proposed model has been evaluated using the Kolmogorov-Smirnov (K-S) test. The proposed model has been employed to simulate the amount of hourly solar irradiance for a location in the UK.