IIT Bombay from India has a simulation model to analyse the Solar Thermal Power plants. Infact we are associated with them. You could contact Mr.Rajkumar Nehra on 91-9423173284 or Prof.Nayak on 91-9930404624. They would be a lot of help to you. Wishing you the very best.
NREL has published the following "Heat Transfer Analysis and Modeling of a Parabolic Trough Solar Receiver Implemented in Engineering Equation Solver". It is not complete and there are a few things that don't run correctly, but it is a great starting point. You can find it here: http://www.nrel.gov/csp/troughnet/pubs_solar_field.html
Honestly I had no information on simulators for solar application as I am not dealing with solar systems.Our good friends working in this field hv given good references.Thanks to our frofessional friends / community.