A transient model for the heat exchange in a solar thermal once through cavity receiver

•A dynamic model of a steam cavity receiver for paraboloidal dishes was developed.•A switched moving-boundary formulation was used, adapted specically for the receiver.•Model simulations were compared with experimental data from the ANU 500 m2 big dish.•Good agreement with data shows the model can be used for control applications.

This paper presents a dynamic model of a once-through-to-superheat solar steam receiver for electricity generation. The receiver is a mono-tube cavity boiler mounted at the focal point of a 500 m2 paraboloidal dish concentrator at the Australian National University. The dynamic model is derived from physical principles of mass and energy conservation, and uses a moving boundary formulation, coupled with a switching approach, to represent outlet flow, ranging from sub-cooled liquid to superheated steam. A method to compute outlet mass flow rate for all three receiver outlet flow conditions is included. This modelling approach results in a compact state-space representation of the receiver which is useful in the development of model-based control strategies for the operation of the receiver in a concentrator plant. The model is implemented in TRNSYS 16 and validated with experimental data from the Australian National University 500 m2 dish system.