UNSW's Neeraj Sharma who is working on a cheap and environment-friendly battery for storing solar energy. Quentin Jones

Cheap, renewable power could get a boost with a battery that works on salt water. Being developed at the University of New South Wales, the battery could eventually provide the ultimate storage device that the renewable energy sector has been searching for.

"You can have the best solar cell in the world, but if the sun's not shining, it's not going to produce any energy," explains chemist Dr Neeraj Sharma at UNSW's school of chemistry. "But if you couple that solar cell with the right battery, then you can produce a constant energy output."

Not only will the battery be cheap, but non-toxic and environment friendly unlike the more powerful lithium ion batteries that are in vogue today. The sodium-ion battery Sharma envisages runs on seawater.

Lithium-ion batteries are being used for energy storage but can be expensive for residential use while the lead acid batteries are heavy and inefficient.

By replacing the lithium with sodium available in salt water, he expects to bring down the cost to a fifth. Starting with a simple sodium battery with just two electrodes into seawater, he is working on structural changes to obtain 8-10 hours of power from the battery.

"Sodium ions are a bit bigger and harder to pull in and out than lithium, so we have to design an electrode material that has more space," says Sharma. "It's visualising this process that's our area of expertise. And we can use that information to build better electrodes."

He has been studying the battery by shooting X-rays or neutrons at it using powerful machines housed at the Australian Synchrotron and the Australian Nuclear Science and Technology Organisation (ANSTO). The team has already made significant improvements with its cathode performing on par with a modern lithium-ion battery. Work is now on with the anode.

"Energy is a massive challenge for humankind. If we can control the chemistry to make a better battery, it would make renewable energy more affordable and reliable," says Sharma. "We're essentially producing a way to get people off fossil fuels."

The global installed capacity of solar electricity has increased by six times to 135GW in 2013 from 23GW in 2010. Solar energy would become the cheapest source of electricity in many parts of the world within the next 10 years, according to experts.

But while prices of photovoltaic keep dropping, the problem has been of storage which alone can make up for the intermittent nature of generation. Often storage systems developed in the lab have failed to be scaled up at reasonable costs.

World electricity generation is forecast to grow by 67% from 22,126 terawatt-hour in 2011 to 37,000 in 2030. A large part of this will come from fossil fuels. Electricity production from fossil fuels accounts for more than 40% of man-made CO2 emissions.