A new Australian research program to looking to test new phase change materials and heat transfer techniques that can significantly reduce the volume of storage space required, and therefore costs, in solar energy systems.

The $A2.3 million project being undertaken by the University of South Australia, the Barbara Hardy Institute, and the University of Lleida in Spain, along with the Solar Oasis consortium in Whyalla, South Australia, and Aoro Solar in Israel, is looking to exploit phase change materials that can operate at high temperatures and store more heat within the same volume or mass.

Professor Wasim Saman, Professor of sustainable energy engineering at the  University of South Australia in Adelaide, said the project would be looking at a number of potential phase Change materials – most likely inorganic salts – although the final choice has yet to be made.

Compact storage solution

“The few storage systems that are being used in Spain rely on heating molten salt at high temperatures and storing it in massive tanks…. it is a little like storing water in a giant thermos,” Professor Saman said.

“So what we are looking to do, similar to what happens when you melt and freeze ice, is to store a lot of heat through the change of phase from solid to liquid and vice versa – and hopefully improve the economics of the storage system. We are looking at a number of inorganic salts – some will be suitable for linear concentration, some for point concentration.”

“Hopefully we can reduce the size of those tanks by factor of 5 to 10. That would reduce costs, but we need the technology to enable a quick enough heat transfer between material and heat source.

Professor Saman said his team is looking at a number of potential materials that can freeze and melt at 400C to 800C, In order to test these materials, a specialised test facility will be built wich will be able to accommodate storage systems operating at temperatures up to 900C.

One of the two trials will be run in co-operation with the Solar Oasis project, which is building a 40MW demonstration plant at Whyalla, using “big dish” technology developed at the ANU in Canberra. The Univerity of South Australia has a campus in Whyalla and intends to trial a small-scale storage system to work with the new plant. The other trial will be conducted with Israel’s AORA solar, whose focus is on smaller concentrating systems.

“Having dispatchable power and moving towards baseload capability is something that solar thermal with storage can do," he said. The solar world is moving towards operating with higher temperatures with a view to improve efficiencies”.

From the rooftops

Elsewhere, California-based rooftop solar system specialist Chromasun is returning its technology to its Australian origins as it seeks to refine a hybrid system that combines its unique rooftop concentrating solar product with a concentrating PV product to deliver electricity as well as heating and cooling.

Chromasun's rooftop micro-concentrator (MCT product is derived from the compact linear Fresnel reflector technology developed by Ausra, and now owned by French nuclear giant Areva. Chromasun CEO Peter Le Lievre is a co-founder of Ausra, which was based in California but had its origins in Australia.

The MCT product is suitable for commercial and industrial rooftops. It delivers heat of around 400F (204C) – considerably hotter than other solar thermal systems used for residential water.  Its micro-concentrators (MCT) uses the same technology as the utility-scale CLFR systems. Light enters the MCT panel through the glazing, is reflected off Fresnel mirror strips and is concentrated on the receiver.

Under a $A9.6 million project sponsored in part by the Australian Solar Institute, Chromasun is installing its MCT units at a hospital in Echuca, in a solar rich region in the state of Victoria. The unit will be couple with a double-effect absorption chiller to provide air conditioning directly from sunlight.

A separate pilot project in Western Australia, on the rooftop of the Little Creatures Brewery, will combine the MCT unit with an ammonia chiller to simultaneously provide chilled water and heat for boiler feedwater. A second phase of the project will see the MCT hybridized with CPV units at pilot facilities at Australian National University in Canberra and University of Queensland in Brisbane to provide electricity and hot water.

Australian made

The goal of the project is not just to test the technology, but to test the market in Australia for a domestic manufacturing capability. The utility scale CLFR technology is now owned by the French, and other PV technologies developed in Australia are now owned by Chinese or German companies. The Australian government is now keen to try and repatriate some of its R&D successes to create a domestic clean-tech industry.

Le Lievre told CSP Today that the MCT technology is well established, and it was inevitable that it would develop into the MCT-hybrid product. “The technology is fairly straight forward and a natural extension of the utility scale (Ausra) technology,” he said. “It has the same functionality but in a rooftop product.
“Our goal with the ASI is to bring back the manufacturing of concentrating thermal panels in Australia – and, in second phase, to finally add a hybrid receiver that can produce electricity and hot water.” He says the MCT-Hybrid product will work at 75 per cent efficiency, compared with up to 20 per cent for the best rooftop PV panels.

Le Lievre said the ability to drive high efficiency chillers and heat for boiler feedwater means that it is ideal for a range of industries such as food, beverages, steam laundries, as well as facilities such as hospitals.

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Rikki Stancich: rstancich@csptoday.com