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

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 500m² 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 500m² dish system.