By Wilson da Silva
SYDNEY – Scientists in Australia have developed a new battery they say is the world’s most efficient.
Vanadium redox cells store power indefinitely, can be charged as quickly as they are used up, deliver 50 per cent more power for half the cost and can theoretically be used forever, they say.
“Our battery is one of, if not the, most efficient batteries being developed anywhere in the world,” said Associate Professor Maria Skyllas-Kazacos, an electrochemical engineer whose team has developed the battery over the past six years.
If Skyllas-Kazacos and her University of New South Wales (UNSW) colleagues are right, vanadium redox batteries could capture a large slice of the world’s battery market and cause a radical change in the way society uses electricity.
The team has recorded energy efficiencies of 87 per cent, compared with between 55 and 65 per cent for lead-acid cells. And vanadium batteries can be recharged in one-eighth of the time needed for lead-acid cells, the group says.
It has received grants from state energy corporations and believes the technology is ready for commercial application. Vanadium, a greyish powder found commonly with other ores but only in minute quantities, is mostly used to toughen steel.
The team of five chemical engineers found that, mixed with two electrolytic 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.
The battery requires 30 litres (eight gallons) of electrolytic fluid for each kilowatt-hour of power needed. Its power-giving mixture lasts indefinitely, allowing continuous recycling and – in theory – endless battery life, the scientists say.
In fact, they say only its membranes need replacement, something that would please environmentalists as the battery would eliminate many of the disposal problems that plague lead-acid batteries.
The membranes last between two and 10 years, depending on the quality.
Vanadium’s first application is likely where conventional batteries are weakest – large-scale energy storage, where power is stored during low-use hours for release at peak demand.
UNSW has found vanadium batteries to be more efficient for large-scale storage, even against new, experimental batteries.
Assuming four-hour storage, vanadium cells could store power for 254 dollars (200 U.S.) per kilowatt hour, compared with lead-acid’s 450 dollars (355 U.S.), zinc-bromine at 330 dollars (260 U.S.) and sodium-sulphur’s 380 dollars (300 U.S.) per kilowatt hour, the UNSW team found.
They are cheaper than mechanical storage, such as using excess power to hold compressed air or water underground, to be used later to drive turbines during peak demand, UNSW says.
Although vanadium costs more to extract than lead, making vanadium redox batteries takes less effort, the team says.
“Even though lead is cheap, conventional batteries require days and days of complicated processing, so in the end they are not so cheap,” said chemist Michael Kazacos, husband of Maria Skyllas-Kazacos.
“For vanadium batteries, there is not much processing involved. It will be cheaper than lead-acid batteries to produce and we are forecasting them to be half the cost of lead-acid for large storage systems,” he said.
Also, research into improving lead-acid cell performance suggests only marginal improvements are possible.
The UNSW team envisages battery farms sprouting across major cities, storing the electricity not used by homes in their area. Later, the area’s homes would tap the power at reduced prices.
The batteries could solve one of the biggest problems with solar and wind power: although more environmentally friendly than coal and oil-fired plants, their power input fluctuates as clouds obscure the sun or winds die down.
Vanadium batteries would permit power to be collected during high energy input times for release in periods of peak demand or when energy generation fell below the norm. “What makes it attractive is that it’s very flexible. You can design a battery for a specific application,” Skyllas-Kazacos said.