Charles-Alexis Asselineau

Integration of Monte-Carlo ray tracing with a stochastic optimisation method: application to the design of solar receiver geometry.

A stochastic optimisation method adapted to illumination and radiative heat transfer problems involving Monte-Carlo ray-tracing is presented. A solar receiver shape optimisation case study illustrates the advantages of the method and its potential: efficient receivers are identified using a moderate computational cost.

Development of a higher-efficiency tubular cavity receiver for direct steam generation on a dish concentrator

An integrated model for an axisymmetric helical-coil tubular cavity receiver is presented, incorporating optical ray-tracing for incident solar flux, radiosity analysis for thermal emissions, computational fluid dynamics for external convection, and a one-dimensional hydrodynamic model for internal flow-boiling of water. A receiver efficiency of 98.7% is calculated, for an inlet/outlet temperature range of 60–500 °C, which is the ratio of fluid heating to receiver incident irradiance. The high-efficiency design makes effective use of non-uniform flux in its non-isothermal layout, matching lower temperature regions to areas of lower flux. Full-scale testing of the design will occur in late 2015.

Experimental testing of a high-flux cavity receiver

A new tubular cavity receiver for direct steam generation, ‘SG4’, has been built and tested on-sun based on integrated optical and thermal modelling. The new receiver achieved an average thermal efficiency of 97.1±2.1% across several hours of testing, and reduced the losses by more than half, compared to the modelled performance of the previous SG3 receiver and dish. Near-steady-state outlet steam temperatures up to 560°C were achieved during the tests.

Development of ASTRI high-temperature solar receivers

Three high-temperature solar receiver design concepts are being evaluated as part of the Australian Solar Thermal Research Initiative (ASTRI): a flux-optimised sodium receiver, a falling particle receiver, and an expanding-vortex particle receiver. Preliminary results from performance modelling of each concept are presented. For the falling particle receiver, it is shown how particle size and flow rate have a significant influence on absorptance. For the vortex receiver, methods to reduce particle deposition on the window and increase particle residence time are discussed. For the sodium receiver, the methodology for geometry optimisation is discussed, as well as practical constraints relating to containment materials.

Improved Tubular Receivers for Point-focus Concentrators

Optics, thermal emissions, convection and internal flow are treated in a unified model for a tubular cavity receiver for a dish concentrator; a new design is presented that shows a 40% reduction in receiver losses.

Geometrical exploration of a flux-optimised sodium receiver through multi-objective optimisation

A stochastic multi-objective optimisation method is used to determine receiver geometries with maximum second law efficiency, minimal average temperature and minimal surface area. The method is able to identify a set of Pareto optimal candidates that show advantageous geometrical features, mainly in being able to maximise the intercepted flux within the geometrical boundaries set. Receivers with first law thermal efficiencies ranging from 87% to 91% are also evaluated using the second law of thermodynamics and found to have similar efficiencies of over 60%, highlighting the influence that the geometry can play in the maximisation of the work output of receivers by influencing the distribution of the flux from the concentrator.