Solar thermal energy systems for electricity production are less prevalent than other renewable energy systems such as photovoltaics, wind and biomass. While many sites in Australia would be suitable for small-scale solar thermal power systems, the lack of suitable technologies creates an opportunity. Small-scale steam turbines are expensive or uncommon and require minimum temperatures of around 350°C. With low boiling point fluids, Organic Rankine Cycles (ORCs) are able to function with temperatures as low as 90°C. Although ORCs are not a new technology, up until now they have been very expensive and seen as a novelty.

This paper will describe transient modelling used to predict the performance of a solar thermal organic Rankine cycle (ORC) system. The approach taken was predict the amount of solar heat that can be captured in heat transfer oil of a concentrating parabolic collector, trough, and then calculate the resultant electrical output from a commercial ORC. These solar heat predictions were made for every hour of 1995 for Sydney from real solar insolation and weather data. The electrical output was calculated from empirical equations describing the ORC. These analyses were performed in a spreadsheet and also using the commercial transient system simulation program Trnsys. The progression to small-scale commercial systems is discussed.