Batteries for renewable energy storage could be made cheaper

A team of scientists in Germany has shown that liquid metal batteries used to store renewable energy can be made much cheaper.

It has previously been possible to create liquid metal batteries on a small scale but these have encountered mixing problems when they are scaled up to the sizes that are required to store energy from renewable energy sources, such as solar panels and wind turbines.

The so-called ‘stirring’ that occurs in larger liquid metal batteries is a result of the liquids being mixed up due to forces that arise when the current flows between the anode and the cathode.

‘This mixing destroys the functioning of the stratification and the functioning of the battery,’ said Dr Frank Stefani from the Institute of Fluid Dynamics at Helmholtz-Zentrum Dresden-Rossendorf.

The Japanese came up with a solution to overcoming the mixing problem — using sodium and sulphur as the two liquid layers — but this is still relatively expensive. Stefani explained that his team’s approach, which uses relatively cheap metals such as indium, gallium and tin, could be three to five times cheaper than the Japanese batteries.

Stefani and his team realised that the structure of relatively cheap liquid metal batteries can be maintained by simply incorporating a tube into the electrolyte that sits between the two metals.

The tube is said to help maintain a stable magnetic field so that stirring does not occur. ‘In order to make batteries very large and very cheap we will need a tube in the middle that reverses the flow of the current,’ explained Stefani.

The diameter of the tube is likely to be approximately 10–20 per cent of the vessel’s overall diameter.

The team has applied for this technology to be patented and is planning to carry out experiments on even larger batteries.