A method for generating synthetic hourly solar radiation data for any location in the south west of Western Australia, in a world wide web page

• We generate hourly direct, diffuse and reflected irradiance on tilted surfaces.
• Simple relations for diffuse and reflected irradiance with cloudiness were developed.
• Our model was calibrated to the south west region of Western Australia.
• Our model is about as accurate as models made for other regions.
• Our model is simple enough to be implemented in a World Wide Web page.

An algorithm was developed to generate synthetic hourly cloudiness data for any time of the year at any location in the south west region of Western Australia (WA). To enable the algorithm to be used for simulation of the power output of both tilted photovoltaic and concentrating solar power systems, a metric of cloudiness was defined which modifies the clear sky beam, diffuse and reflected solar transmittance. Seasonally and positionally adjusted values of daily cloudiness were generated by roughly mimicking the geographic pattern of annual rainfall in WA. Rather than longitude and latitude, distance along the coastline and distance inland from the coast were used as the positional coordinates. Hourly cloudiness data was generated from the daily values using a first order autoregression algorithm with time varying mean and standard deviation. Two years of measured hourly horizontal solar irradiance data from a network of 31 weather stations was used to calibrate the algorithm. The algorithm was simple enough to run inside a world wide web page and has the potential to be adapted to other regions with a similar pattern of declining inland rainfall.