Research Outline

Fundementally, my research is dedicated to the study of the conversion of radiation into thermal energy and the interaction of radiation with geometrical structures. The key application in focus is the conversion of concentrated solar radiation into useful energy in Concenterated Solar Power (CSP) systems.

In CSP systems, solar radiation incident on a concentrating optics system is focalised on a receiver that converts it into heat at high-temperature. The resulting heat can be used in a variety of systems: a thermodynamic engine to produce electricity, a chemical reactor to run thermo-chemical processes (eg. solar fuels production), as industrial process heat (eg. drying and cooking processes) or stored in a thermal energy storage system for later use (at night time or peak pricing hours on the electricity grid for example). My objective is to improve the economical viability of CSP systems by improving the performance and lowering the cost of concentrating optics and receivers. This task requires the consideration of the whole chain of heat-transfer processes: the emission of thermal radiation by the sun towards the earth, the optical concentration process, the absorption of radiation on high-temperature absorber surfaces and the transport of the absorbed thermal energy outside of the receiver control volume.

Concentrating optics

Concentrating optics systems generally work within the geometrical limit of optics and redirect solar radiation, using reflective or refractive optics, to focal lines or points and allowing higher temperatures and thermodynamic efficiencies to be reached. There are fundemental limits associatied to this process and some of them relate to the geometrical distribution of radiation in space.

My research in concentrating optics includes the development of optical modelling tools and methods for existing and new concentrator designs using open-source softwares (Tracer, SolarPilot). This work makes extensive use of Monte-Carlo Ray-Tracing (MCRT) techiques to simulate radiative fluxes in non-ideal geometries and provide accurate results for the design of complex systems. Typical systems include heliostat fields, parabolic dish concentrators, solar furnaces and hybrid versions of these systems.

In a more theoretical aspect of my research, I study the fundemental thermodynamic limits to the conversion of concentrated radiation into work, analysing the consequences of the second law of thermodynamics in concentrating and high-temperature radiant systems. This fundemental understanding of the irreversibilities in optical and radiant systems can highlight their limitations and potentially help improve their designs and efficiency.

Receiver optimisation

The energy conversion process in receivers involves coupled radiation/heat-transfer modes that depend on the geometry of the device, materials used and surface properties. Many avenues of research have been suggested to improve the efficiency of these receivers, my interest is on the geometrical considerations involved in the design process, both at the macroscopical and microsopical levels.

The preferred method to study non-trivial radiative heat- transfer problems in such systems is MCRT. MCRT can be very flexible and accurate but relatively slow and computationally intensive. This limitation hinders the potential for optimisation which in turns impact the efficiency of the overall technology. My approach to this problem is to develop stochastic optimisation methods embedded in MCRT to optimise receiver geometries with an affordable computational time. In addition, by introducing multi-objective optimisation criteria and evolutionary algorithms, my methods can be used to refine designs and explore the complex behaviour of high temperature optical systems. This work borrows techniques from the optimisation, computer science and machine learning fields and applies them to the design of solar energy systems.

The methods developped have been successfully used to design a world-record direct-steam-generation receiver for the Big Dish concentrator at the ANU.

At the micro and nano-scale, I am interested in studying how high-temperature surface gratings, self-assembled structures and photonic crystals can potentially help to improve receiver effciencies by influencing the spectral and directional selectivity of radiant surfaces. This work stands at the crossroad between optical physics, material science and thermodynamics and explores an alternative option to efficient high-temperature photo-thermal conversion.

Projects

USASEC Project: Radiative heat-transfer simulations, SG3 dish optics and receiver simulation, receiver shape optimisation.

ASTRI: P12 Receiver sub-project: geometrical optimisation of Flux Optimised Sodium Receiver (FONaR) concepts. P42 Solar Fuels sub-project: design and modeling of Solar Supercritical Water Gasification (SSWG) reactors for algae feedstock.

SMILE: Heliostat field optics modelling and receiver design modification for a cogeneration system based in Caicara, Brasil for the company Solinova.

ANU - Vast Solar: Heliostat characteristaion and heliostat field optics modeling for the company Vast Solar.

Scientific interest

• Thermodynamics and radiation exergy
• Coupled heat-transfer problems
• Monte-Carlo ray tracing
• Concentrating optics
• Stochastic optimisation and maxhine learning
• High-temperature photonics

Applications

• Concentrated solar technologies.
• Optical modeling of radiative heat-transfers in cavity receivers using ray-tracing techniques.
• Receiver design and geometrical shape optimisation through stochastic and multi-objective optimisation methods.
• Applied exergetic analysis.