Al-air battery beats li-ion on weight and price

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Even given recent advances, lithium ion batteries are still plagued by weight and cost issues.

So, Phinergy Marine’s aluminium-air batteries, which promise to be significantly lighter and cheaper per kilowatt hour, should draw an audience.

The energy is created by the reaction between the aluminium anode, a cathode immersed in electrolyte and the oxygen in the air itself. The interesting point is this is battery is reloaded, not recharged: the racks are furnished with new aluminium plates and the old water-based electrolyte (which is circulated a number of times before being refreshed), can be recycled to return the alloy. It’s also inherently safer, there’s no chance of thermal runaway and range is consistent, even in cold or hot weather - both challenges for li-ion systems.

Despite the common, low-cost ingredients it delivers a surprising bang for its buck: roughly 8kWh per kilo of aluminium, explained Phinergy founder and CEO Udi Erell.

To put this in context, a current, commercial li-ion 40kWh battery roughly 1.6m by 1m by 0.2m, weighing in at 278kg can be contrasted with a 40kWh al-air battery of 0.8m by 0.25 by 0.2m weighing 20kg, which even with the electrolyte only brings the weight up to around 100kg - although a clever, space saving trick is to use one of the vessel’s own tanks for storage. However, Erell also explained that the containerised version of this battery itself creates the pure water that makes up 70% of the electrolyte by utilising the process’ excess heat.

Most importantly, it’s far, far cheaper than the usual alternatives: “Taken by kilowatt hour, the total costs for the containerised version comes to about a third of what you pay for lithium ion,” said Erell.

Usefully, the technology can be scaled up or down: a 40ft container model will output 7.2MW, while Phinergy also offers an automotive solution with a range commensurate with most non-electric cars.

It’s obviously very different from conventional battery storage, more suited to a level output than ramping up and down. Therefore it’s ideally paired with a (small) lithium unit which can absorb a charge from the al-air pack when the loads are low and provide for peak demands.

Al-air could prove useful for a number of vessels with a regular duty cycle, underlined Erell, as reloading can be accomplished very quickly at the quay.

By Stevie Knight