By Wilson da Silva
THEY’RE fast-charging, deliver more power for half the cost and don’t look anything like your average lead-acid battery – they are vanadium redox cells. Developed at the University of New South Wales (UNSW), they have the potential to radically alter the way we use electricity and make renewable energies economically viable.
In fact, talking to the small but committed team of chemical engineers at the UNSW can leave you believing that they have the problems of solar and wind power licked. They are also very confident that, despite working on a shoestring budget for seven years, they have eclipsed teams with fat funding cheques in Japan and Germany.
“Our battery is one of, if not the, most efficient batteries being developed anywhere in the world,” said Associate Professor Maria Skyllas-Kazacos. “What makes it attractive is that it’s very flexible. You can design a battery for a specific application.”
The batteries, which look more like film processing machines, store power indefinitely, can be charged as quickly as they are used up, deliver 50 percent more power for half the cost, and can – in theory at least – be re-used forever.
Skyllas-Kazacos and her team have recorded energy efficiencies of 88 per cent with their vanadium cells compared with between 55 and 65 percent for lead-acid batteries. And vanadium batteries can be recharged in one-eighth of the time taken for lead-acid cells, the group said.
Their results have attracted attention. Funding has come from the federal Energy Research and Development Corp., the New South Wales Department of Minerals & Energy, Mount Resources Ltd and Pacific Power, and an Australian venture capital company has taken a six-month option on the technology and is now assessing its potential for worldwide marketing.
Bangkok’s Thai Gypsum construction company has ordered a 10 kilowatt (kW) battery and wants to build 5,000 houses across Indonesia utilising many more of them, while a large Japanese conglomerate has flown the scientists to Japan to talk about the technology, and are deep in negotiations with the the UNSW’s marketing arm, Unisearch Ltd.
The first commercial applications are around the corner. The Prospect County Council has asked about building a five megawatt facility in the Blue Mountains to operate alongside a conventional lead-acid battery farm. Surplus energy would be stored there on a large scale for release during peak periods, the sort of thing for which conventional lead-acid batteries are the most efficient.
Vanadium is a greyish powder found commonly with other ores but in only minute quantities, and is used by industry to toughen steel. The team of four chemical engineers and six students has found that, mixed with two eletrolytic fluids in separate tanks and cycled through membrane cells in a battery casing, vanadium oxide generates electricity, and the energy output can be controlled by the amount of mixture added.
A vanadium battery requires 30 litres of electrolytic fluid for each kilowatt-hour of power needed. The power-giving mixture lasts indefinitely, allowing continuous recycling and endless battery life, with only the membranes needing replacement.
A study by Japan’s Electrochemical LaboratoryXXX calculated the cost of applying vanadium batteries to large-scale storage, and found their vanadium cells the winners, even when compared against new, experimental batteries. Assuming four-hour storage, vanadium cells could store power for $254 per kilowatt hour, compared with $450 for lead-acid batteries, zinc-bromine’s $330 and sodium-sulphur’s $380 dollars per kilowatt hour.
They are also cheaper than mechanical storage, or using excess power to hold compressed air or water underground, which is later released to drive turbines during peak demand, the study said. Storing water above ground for turbine-driving – such as in a dam – is cheaper at $225 dollars per kilowatt hour, but most of the world’s easy hydro-electric sites have been exploited, making future damming more costly and less of an economic propect. Even here, vanadium overtakes the field if power is stored for more than eight hours.
The promise of vanadium redox batteries is most obvious in large-scale uses, and could bring power generation down to the home.
“With the availability of low-cost energy storage, a dramatic shift in energy dependence will be possible in the future,” Skyllas-Kazacos said. “The totally self-sufficient house with solar panels on the roof, large battery banks in the basement or garage and an electric vehicle – run on solar rechargeable batteries – could become a reality.”
But there is a drawback – vanadium, at around $10 a kilogram, is much more expensive than lead, and more costly to extract. However, its proponents argue that making vanadium redox batteries takes less effort, needs fewer parts and little processing.
“Even though the cost of lead is cheap, conventional batteries require days and days of complicated processing, so in the end, they are not so cheap,” said chemist and husband Michael Kazacos. “For vanadium batteries, there isn’t much processing involved. It will be cheaper than lead-acid batteries to produce, and we’re forecasting them to be half the cost of lead-acid for large storage systems.”
The environmental attraction of such a battery alone is obvious – it would eliminate many of the disposal problems plaguing today’s lead-acid batteries. The researchers say the membranes last between two and 10 years, depending how high-quality a membrane is used.
The UNSW team envisages vanadium battery farms sprouting across major cities, storing the electricity delivered to the area but not used by all homes. During off-peak times, the area’s homes would tap the power at reduced prices.
The cells overcome many of the problems of experimental batteries, such as iron-chromium cells being developed by Japanese companies. Contamination problems have forced iron-chromium cell development by Mutsui in Japan to be abandoned. Then there is the toxicity and corrosiveness of batteries under development, like zinc-bromide cells which present serious environmental problems, and sodium-sulphur batteries which run at high temperatures and are prone to leakage of molten sulphur and failure of the whole battery. Meanwhile, research into improving lead-acid cell performance suggests the technology is near its zenith and only marginal improvements are possible.
Skyllas-Kazacos said although some experimental batteries have claimed 85 per cent efficiencies to rival the group’s vanadium wonders, these were obtained under special conditions and require slow charging. Vanadium cells, on the other hand, are fast-charged and still produce high efficiencies.
The batteries promise to solve one of the biggest problems with solar, wind and other alternative and renewable power systems. Although environmentally friendly compared with coal and oil fired plants, their power input fluctuates as clouds obscure the sun or winds die down. Vanadium batteries would allow power to be collected during high energy input times – during the day or when winds are blowing – for release during peak demand, or when energy generation fell below that required by a household or area.
One of the exciting prospects vanadium offers is ‘instant recharge’. Buses, trucks and forklifts could simply exhange their used electrolytic fluid for a recharged solution, and return to work. Meanwhile the spent fluid would be recharged in 20 to 30 minutes – a tenth of the time for lead-acid batteries. And it would never be thrown away, but go on being re-used and re-charged. They would also be ideal for submarines, allowing the electrolytic fluid to fill spare spaces in its hull and even take the place of some of the ballast, Skyllas-Kazacos said.
The batteries do not go through the solid phase changes during charging and discharging which curtail battery life, and can be charged at two volts then discharge 100 volts without affecting performance of battery life.
Their attractiveness for large-scale power storage comes from the fact that the system’s cost per kilowatt hour drops as storage capacity increases. Most of the cost is in the infrastructure surrounding the cells, and once that is built, more banks with larger electrolytic capacities can be added.
Prototype batteries of up to three kWs have been built at the UNSW, but this “has just about reached our limit in the lab,” said Michael Kazacos. Without a production line, the group does not think it can build the five megawatt facility Prospect wants but believes a 100 kW vanadium facility is possible with some corporate engineering back up.
Although they are widely patented, this may not be enough if the Japanese decide to launch a multi-million dollar assault to catch up with the group’s lead.
“They’ve spent lots of money in the last few years trying to match us,” said Kazacos. “When we were there, they said they were very interested in working with us, but said they could of course do the job without us.” Kazacos saw this as a strategy to entice the UNSW group to agree to a smaller cut of the profit cake or else face the possibility of zero return on their investment if the Japanese spent heavily on matching the group’s lead.
The group is keen to commercialise the technology in Australia, but is having trouble just getting quality components made. It has had several local suppliers custom-make conductive plastic electrodes of the type the group makes painfully slowly in the lab, but has yet to find a quality maker. They have imported expensive electrodes from Japan, noyl to find their hand-made ones better, and are now trialing one last Australian supplier and one Belgium-American firm.