The breakthrough could revolutionise the renewable energy industry by making hydrogen – touted as the clean, green fuel of the future – cheaper and easier to produce on a commercial scale.
Professor Leone Spiccia, Mr Robin Brimblecombe and Dr Annette Koo from Monash University teamed with Dr Gerhard Swiegers at the CSIRO and Professor Charles Dismukes at Princeton University to develop a system comprising a coating that can be impregnated with a form of manganese, a chemical essential to sustaining photosynthesis in plant life.
“We have copied nature, taking the elements and mechanisms found in plant life that have evolved over 3 billion years and recreated one of those processes in the laboratory,” Professor Spiccia said.
“A manganese cluster is central to a plant’s ability to use water, carbon dioxide and sunlight to make carbohydrates and oxygen. Man-made mimics of this cluster were developed by Professor Charles Dismukes some time ago, and we’ve taken it a step further, harnessing the ability of these molecules to convert water into its component elements, oxygen and hydrogen,” Professor Spiccia said.
“The breakthrough came when we coated a proton conductor, called Nafion, onto an anode to form a polymer membrane just a few micrometres thick, which acts as a host for the manganese clusters.”
“Normally insoluble in water, when we bound the catalyst within the pores of the Nafion membrane, it was stabilised against decomposition and, importantly, water could reach the catalyst where it was oxidised on exposure to light.”
This process of “oxidizing” water generates protons and electrons, which can be converted into hydrogen gas instead of carbohydrates as in plants.
“Whilst man has been able to split water into hydrogen and oxygen for years, we have been able to do the same thing for the first time using just sunlight, an electrical potential of 1.2 volts and the very chemical that nature has selected for this purpose,” Professor Spiccia said.
Testing revealed the catalyst assembly was still active after three days of continuous use, producing oxygen and hydrogen gas in the presence of water, an electrical potential and visible light.
Professor Spiccia said the efficiency of the system needed to be improved, but this breakthrough had huge potential. “We need to continue to learn from nature so that we can better master this process.”
“Hydrogen has long been considered the ideal clean green fuel, energy-rich and carbon-neutral. The production of hydrogen using nothing but water and sunlight offers the possibility of an abundant, renewable, green source of energy for the future for communities across the world
“Spread in military rows across 300 acres of sun-baked earth, Nevada Solar One’s trough-shaped parabolic mirrors are the core of this CSP plant – also called a “solar thermal” plant. The mirrors focus sunlight onto receiver tubes, heating a fluid that, at 735 degrees F., flows through a heat exchanger to a steam generator that supplies 64 megawatts of electricity to 14,000 Las Vegas homes.”
“Today the United States has 420 megawatts of solar-thermal capacity across three installations – including Nevada Solar One. That’s just a tiny fraction (less than 1 percent) of US grid capacity. But Nevada Solar One could signal the start of a CSP building boom.
Efforts to generate another 4,500 megawatts of solar thermal power are now in development across California, Nevada, Arizona, and New Mexico – all of which have the flat, near-cloudless skies most desirable for solar thermal, the Solar Electric Industries Association reports.”
“In fact, there’s a land rush at the federal Bureau of Land Management. As of July, the BLM reported more than 125 applications to build solar power on about 1 million acres of desert, up from just a handful of proposals a few years ago.”
“Dr. Mehos says perhaps 100,000 megawatts (100 gigawatts) could be built across the US Southwest over the next 30 years.”
“You could supply the entire US with the sun power here in a little piece of the Southwest,” says Dan Kabel as he strolls beneath a row of trough-shaped mirrors. Mr. Kabel is chief executive of Acciona Solar Power, which owns the $266 million Nevada Solar One project. “As fossil fuel costs rise, this plant is unaffected. “If America doesn’t do this, if we don’t install many more of these clean solar-power systems, we’ll just end up seeing a lot more fossil-fuel plants instead.”
“What’s different now from the ’80s and ’90s is that we have much higher natural gas prices than back then,” Mehos says. “I don’t think people foresee a serious drop in natural gas prices now. Even if they fell 30 percent, CSP would look attractive.”
“Concentrating solar technology produces electricity for about 17 cents per kilowatt hour (kWh), Mehos estimates. But subsidies remain critical to solar thermal development in both the US and Spain, two global hotbeds of CSP development. With the federal investment tax credit, or ITC, costs drop to about 15 cents per kWh – low enough to compete with natural gas.
A key feature of solar thermal is its potential to use heat-storage technology to generate power after the sun sets. Nevada Solar One is considering adding a molten-salt or similar system to allow it to supply power for several hours after sundown.
With such storage systems, solar thermal becomes even more attractive to utilities, experts say. Arizona Public Service is contracting with Abengoa to build a 280-megawatt solar thermal plant near Phoenix that will cost more than $1 billion and have molten-salt heat storage.”
“So far, US development of solar thermal is dominated by a handful of big overseas companies, including Abengoa and Acciona (Spain), as well as Solel Solar Systems (Israel), Solar Millenium (Germany), and Ausra (Australia), now headquartered in Palo Alto, Calif.
“To stimulate development, Spain has deployed hefty, long-term feed-in tariffs. But in the US market, solar thermal is hanging by a thread. The investment tax credit, which covers 30 percent of a CSP facility’s cost, will expire at year’s end unless renewed by Congress. But bills to renew the ITC have been blocked eight times this year by Senate Republicans.”
“What we’re seeing with all these companies lining up for solar thermal is hugely promising,” says Monique Hanis, spokeswoman for the SEIA. “But without the ITC, all of these solar thermal plants will be put on hold.”