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New solar thermal project - what a gas!

Australian scientists have combined solar energy and natural gas in a novel process capable of producing large-scale energy to power the country's future industrial and domestic needs.

The Solar Thermal Project uses a parabolic dish to harness the heat of the Sun, causing methane to react and form a gas that can hold more energy than methane alone.

The project has just won the 2002 Institution of Engineers Australia Award in Engineering Excellence (Environmental category).

"The process is a means of capturing solar energy in a form you can then distribute," said project leader Dr Greg Duffy at CSIRO Energy Technology. "You can store it in a mechanical form as re-formed gases to use onsite, or distribute it via pipes for use later on."

The reaction occurs in a solar thermal concentration dish designed and constructed by Solar Systems Pty Ltd. The dish is lined with mirrors that focus the Sun's rays onto a reactor. This has the time of day and the date programmed in it, so it can track the Sun's movements continually.

The dish is in the shape of a parabola, so the rays are reflected up to the focus of the dish, eight metres away. The reactor is in the focus point, operating in 800-850 degrees centigrade.

The dish needs sun to operate. "We are relying on solar radiation," said Dr Duffy. The best days are cloudless winter days when humidity is low and the sky is clear.

The reactor is a standard type of reactor used in chemical processes – not a nuclear reactor despite being situated at Lucas Heights. It is packed with a catalyst to set off the reactions.

Water and natural gas (methane) are pumped up separately to the reactor. As the water heats up, it creates steam which reacts with methane to produce a high energy gas called 'synthesis gas' or syngas.

The methane is converted into CO and H2 in the reaction. "These product gases have between 25 per cent and 40 per cent more energy content than the methane we put into the process in the first place," said Dr Duffy.

For example, a gigajoule of energy as methane will go through the process and come out as 1.3 gigajoules of energy.

The demonstration facility at Lucas Heights produces gas with up to 40 per cent of its energy value as embodied solar energy. It is the only one of its kind in Australia and among just a few in the world.

Dr Duffy anticipates that initially the high energy gas will be blended with regular gas and not require adaptation of appliances or pipelines. But if syngas is used alone, then appliances will have to be converted.

The exciting aspect of the process is the potential to create energy that can be burnt with zero emissions. "By decarbonising the fuel, you end up with hydrogen before you burn it," he said.

"It is relatively simple to remove the CO2, leaving the H2 behind. You can take the CO2 and sequester it."

The engineers hope soon to attract the interest of the Government – on both a State and Federal level – or gas producers to create a more commercial-sized demonstration. This makes economic sense. For example, if the dishes were built on a larger scale, their cost would come down exponentially.

In the longer term, Dr Duffy envisages larger solar thermal installations adjacent to gas producing wells.