By Giles Parkinson in Queensland

On June 18, the Australian government finally announced the winning tenders from its $1.5 billion solar flagship program – a 250MW, gas-boosted solar thermal energy plant to be built in Queensland state using Areva’s compact linear Fresnel reflector technology; and a 150MW solar PV plant to be built near Moree in New South Wales state by a consortium led by BP Solar and Spain’s Fotowatio Renewable Ventures.
 
It was also the day that Prime Minister Julia Gillard and energy minister Martin Ferguson flew to the coal city of Newcastle for the formal opening of the CSIRO (Commonwealth Scientific and Industrial Research Organisation) solar tower, and the largest solar thermal research hub in the country.

Big leap for solar Brayton

The centerpiece of the research facility – located within the CSIRO’s National Solar Energy Centre - is a demonstration project that features a 30m high solar tower surrounded by 450 heliostats that is capable of generating temperatures of 1,500C and more. The facility has been pioneering Solar Brayton Cycle technology that generates super-heated compressed air (900C) to drive a 200kW turbine.
 
The technology is considered to be well suited for Australian conditions, because it does not use water like other solar thermal technologies, and it can be built on a modular basis, so could meet the demands of remote mining sites and the like.
 
James McGregor, the energy system manager at the CSIRO facility, says the newly-commissioned plant has so far performed to expectations. Particularly pleasing has been the optical performance of the heliostats, which went out to local tender and have delivered an optical error of less than one milli-radian (millimeter per meter). “That is a world class result,” he says.
 
That means that so far, generating heat has not been as much of a challenge as to what to do with it. “These arrays can produce temperatures up to 1600C. But w

hen you go beyond 950-1000C, you are starting to melt things,” McGregor says. “It’s good fun for research, but a problem for commercial plants.”

Consequently, much of the ongoing research at the centre will revolve around the development of high temperature receivers, as well as options for thermal storage.

Australian PM, Julia Gillard, takes a tour of CSIRO's solar Brayton demonstration project

Breaking new ground 

For the last three months, the solar tower has been testing a receiver in collaboration with Mitsubishi Heavy Industries. McGregor says he is not in a position to give details of the materials used. “We were right on the outer limit of commercially available materials,” he says. “We will announce the temperatures soon, but it’s right up there with the best in the world.”
 
He says the centre is now looking at a whole suite of new high temperature receivers, using new materials - ceramics, alloys, composites - that will accommodate temperatures above 1500C.  “They are starting with a blank sheet of paper,” he says of the researchers.

Dispatchability options

The centre also has an Au$8.5 million three-year grant to investigate thermal storage options. McGregor says the research is not limited to molten salts, and will investigate solids (including graphite), and nitrate salts. It will be investigating options on storage for electricity production as well as for industrial processes.
 
Other research includes a high temperature steam project that will look at, among other things, using solar towers to augment the temperatures produced by trough-based collectors. In the same manner, it is also looking at using towers as a boost for geothermal steam. “In Australia, the best geothermal resources happen to be the same place as the best solar resource,” he says. The idea is to overlay steady 24-hour low temperature steam from geothermal sources with a solar boost system to potentially gain a dramatic lift in efficiency.
 
The centre will also look at the development of self-cleaning nano-coating technologies. However, this research is being conducted at a separate installation, known as “nano house”, while the heliostats in the main hub have been tested with various cleaning options and intervals.

“Before we invest in self cleaning glass technology, we need to find out if there is a substantial loss of performance by not cleaning the glass.” And they need to analyse whether the coating absorbs the energy as well. “We’ve got the data, but we are now preparing the report,” he says.
 
McGregor says one of the big learnings of this technology has been its potential to overcome the so called “Valley of Death”, which yawns Grand Canyon-like in a relatively small economy like Australia’s. “We’ve never had the financial clout to make the jump from 400kW electrical to 100MW electrical, but with the Brayton cycle one thing that has jumped out for us is that it can be built on a small scale. You can start at the 1MW-5MW and then build it out. That is really important in terms of getting early deployment.”

McGregor says there is a lot of commercial interest in the technology. He is confident it will be brought to market in the next few years.
 
“It’s a very exciting time for us.” McGregor says. “I took the boss (PM Gillard) up the tower. From up there it’s a good juxtapositon – from the top of tower you can see the Newcastle coal loaders, a wind turbine, and you are standing on one of the most advanced solar installations in the world. What you can see is the low carbon road map.” 

Click here to watch the video of CSIRO's Bratyon tower.

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Rikki Stancich: rstancich@csptoday.com

Image credit: Images courtesy of CSIRO