AUSSIES WATERLESS SOLAR POWER PLANT

Steam-free CSP: Dry technology for thirsty locations
Rikki Stancich, 17 June 2010 (CSP Today)

"In April this year, Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO), announced its intention to build a new CSP technology demonstration plant that will generate super-heated compressed air to drive a 200kW Brayton Cycle turbine...The Brayton Solar System’s zero water requirement promises to resolve a major issue…[of] acute water scarcity in high DNI areas… [It] has the core components of a compressor, combustion section and power turbine, which drives the compressor. In this case, around 450 heliostats will direct solar heat onto a 30m-high tower. The concentrated solar heat from the solar field will replace the combustion element needed to drive the turbine…[I] ts modular design means makes it an attractive, lower risk investment compared to other large-scale CSP technologies…"

[James McGregor, energy system manager, Solar Brayton Cycle demonstration field:] "[I]t has zero water requirement, given that it doesn’t require cooling…As part of our heliostat development programme, we are looking at developing a coating system that does not require washing…We are also assessing the optical performance of mirrors that are not washed, and weighing it against the economics of the energy and resource requirement to clean the glass…"

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[James McGregor, energy system manager, Solar Brayton Cycle demonstration field:]
"Most solar thermal plants use a steam-based cycle. Water is a key component, though dry cooling is possible at a cost…The better the solar resource, the better the economics – but water is the constraint…[T]he Brayton cycle resolves [this]… Another advantage is the higher operating temperature…[Instead of] 540 degrees Celsius…The Brayton cycle…operates at temperatures of above 900 degrees Celsius, which enables a significant step-up in power block efficiency…[and] a solar field two thirds of the size…"

[James McGregor, energy system manager, Solar Brayton Cycle demonstration field:] …"[Y]ou could use the waste heat for cooling – to generate chilled water for cooling industrial buildings. The attraction of the modular system is that you can scale it down and bring it to large consumption sites – you could build it next door to an industrial park…The primary limit is the receivers. We will use commercially available material to begin with, but will develop more advanced receivers to handle higher temperatures."

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[James McGregor, energy system manager, Solar Brayton Cycle demonstration field:]
"Molten salt is the most understood [storage] medium, but it presently does not work at the temperatures involved and we are looking at alternative options. We have just started looking at this – we are trying to define the characteristics of the ideal storage medium…The Brayton Cycle can [also] be co-fired with gas. In this sense it is a particularly good transitional technology…"

[James McGregor, energy system manager, Solar Brayton Cycle demonstration field:] "Cost reductions could be achieved through a number of areas. Firstly, scaling up and achieving economies of scale…[T]here is technology for improving efficiency and lowering the cost of components; heliostats account for around 40% of the project’s total cost…[I]mprovements in efficiency [can also come] through higher operating temperatures…[and] we are trying to optimise the overall efficiency by matching the power block with the receiver…So, we are looking at incremental improvements in those 3 key areas."