Concentrated Solar Thermal Power (CSP) is a burgeoning technology in the renewable energy space, with many international organisations collaborating to develop and implement CSP around the world. Most notably, large scale CSP plants are being successfully built in regions such as China and the Middle East. For example, in Qinghai province of China, the SUPCON operated Delingha 50 MW Tower CSP plant was reported to have outputted 11.016 GWh of power in January of 2020.
Photograph of the SUPCON Solar Delingha 50MW CSP Plant in Qinghai province, showing the solar field and central receiver tower. Image Courtesy: Supconsolar
The most promising configuration of CSP plants is the tower configuration, as shown in the photograph of the Delingha CSP plant. In this configuration, thousands of large mirrors known as ‘heliostats’ are organised in an array known as a solar field. These heliostats track and reflect sunlight so that the reflected sun rays are focused onto a central receiver that sits at the top of a tower. A heat transfer fluid is pumped through the central receiver and absorbs the thermal energy from these concentrated sun rays. The heat transfer fluid is then transferred to other parts of the power plant, such as a power block consisting of a typical steam Rankine cycle to generate electricity and an energy storage system comprised of molten salt. Energy storage is important because it allows a power plant to provide dispatchable ‘on demand’ power that smooths out power supply during periods of low sunshine or at night time.
ASTRI’s CSP tower configuration including the various sub-systems for energy storage and electricity generation
In Australia, research in the CSP space has been primarily driven by the Australian Solar Thermal Research Institute (ASTRI), which is an eight-year, $87 million research program that involves many research partners locally and internationally. QUT’s AMDTR group is proud to be one of these research partners, with on-going collaborations with other Australian institutions such as CSIRO, Flinders University, Australian National University, University of South Australia and many more. Our collaborators include international organisations such as the National Renewable Energy Laboratory (NREL) based in the United States of America and industry partners such as VAST Solar. The ASTRI program is supported by the Australian government through the Australian Renewable Energy Agency (ARENA).
Find out more about AMDTR’s research partners.
The 30-year design life of a CSP plant requires full understanding of material compatibility and associated characterisation of material degradation to make adequate design decisions, material selection and cost estimates. Across the energy industry, project delays, cost overruns, shortened asset life and injury have been attributed to poor material selection. As part of the Advanced Materials Project coordinated by ASTRI, the AMDTR group’s main objective is to demonstrate the suitability of selected materials for specific CSP applications within the ASTRI CSP plant context. The group’s research focusis centered on the characterisation and testing of the structural materials used in the various sub-systems of a CSP plant, this includes the tank materials of the energy storage system, the piping material throughout the plant and the containment materials used in the central receiver and power block. The degradation rates for candidate metals in relation to contained storage or heat transfer fluids will be characterised.
We perform exposure tests of various alloys in different environments such as molten salt, liquid sodium, air, argon and carbon dioxide, all at high temperatures in excess of 700 °C. By testing potential alloy candidates, such as nickel based alloys, our goal is to provide useful data in the prototyping of more advanced and improved CSP plants. Specifically, stainless steels and certain nickel alloys will be exposed to sodium (Na), supercritical carbon dioxide (sCO2) and various candidate sensible thermal energy storage solutions. The degradation (mechanism and rate) of these containment metals when exposed to these fluids (at the temperatures and pressures of interest to ASTRI) will be studied to assist in developing appropriate engineering solutions.
Project deliverables for the advanced materials program involves providing specific answers to many material issues and closely associated research gaps for ASTRI’s solar thermal technologies. Examples include providing engineering material degradation test data to identify corrosion, cycle fatigue, and other material issues for specific alloy/thermal energy storage media, alloy/sCO2 and alloy/sodium compatibility. This project has already had a direct impact on the materials choices being made with ASTRI and for CSP industry partners and will continue to de-risk material and the design choices leading to the full development and demonstration of an operational CSP system within Australia.