Increasing the efficiency of Concentrating Solar Power (CSP)
CSIRO has a comprehensive portfolio of R&D into CSP. That portfolio spans the spectrum of temperatures that CSP can provide. It includes R&D into thermal storage, heliostats and receivers associated with using CSP to produce and use:
- high temperature heat for industrial processes
- high temperature heat for electricity generation using advanced fluids such as supercritical CO2
- very high temperature heat to produce solar gas, hydrogen or electricity
The CSIRO's research into electricity generation using very high temperature heat was initially focussed on the air Brayton cycle due to its reduced requirements for water. However, gas turbines only achieve around 30 per cent efficiency at such temperatures. In addition, the relatively rapid cost reductions for PV's reduced the relative economic competitiveness of this technology.
Small heliostats and central receiver technology research and development
To respond to this challenge, the focus of the research program was shifted towards studying the supercritical CO2 Brayton cycle. The aim of the CSIRO's research in this area is to achieve around 50 per cent turbine efficiency. CSIRO is currently regarded as the world leader in this field of research. Recently, the US Department of Energy awarded over US$160M funding towards this cycle.
This case study is focussed on two different streams of CSP research. One is R&D into low cost, small heliostats where the aim of the research effort is to reduce the cost of heliostats to around $100/m2 while maintaining high optical performance. The other is research into advanced central receiver technology. The aim of the research is to increase the receiver temperature from around 600 degrees to 700 degrees while maintaining (or increasing) receiver efficiency. Improving the efficiency of conversion is one of the most important ways to reduce the cost of solar electricity. Efficiency improvements reduce costs across the board as it not only means a reduction in solar field size, but also a reduction in number (or size of) receivers, towers (in case of central receiver systems), land area and associated balance of plant, etc. The reduction in the amount of installed plant also translates to a reduction in operating and maintenance costs.
Lower cost heliostats and improved thermal efficiency
The Concentrating Solar Power (CSP) project has produced the following outcomes:
- Software that optimises the design and positioning of heliostat collector fields and receivers
- Larger, lower cost heliostats that are suitable for mass manufacture
- A high temperature receiver that operates at a thermal efficiency of 90% or more
- The NPV of the estimated benefits to 2036 is $188.1 million in 2017 dollars under a 7 per cent real discount rate
- The project has an estimated benefit cost ratio (BCR) of 36.1
The development of a heliostat design that is potentially suited for mass manufacturing is an important outcome as 'learning by doing', through higher production numbers, will help drive down unit costs. The software to optimise the design and positioning of a heliostat collector field and receiver in a way that best matches the terrain and the scale of the system required has already demonstrated that it can provide significant cost savings and there is considerable potential for its use worldwide.
In the longer term, there is the potential for Australia to make a significant contribution towards the development of the next generation CSP power plant utilising the high efficiency CO2 Brayton cycle turbine.