Second-life EV batteries hold the key to the global shift to a renewable power supply, acting as a crucial resource to power homes, stabilise new and existing grid infrastructure, and even power airports, according to the World Economic Forum.

The storage capacity of the lithium-ion batteries found in electric vehicles can begin to degrade in as few as eight years, with factors like recharging frequency, the use of high-speed DC chargers, and even exposure to high temperatures when parked – a particular problem in countries like Australia – all impacting the longevity of the cells.

Once a battery has reached the end of its usable life in a vehicle, however, the cells can still be used for power storage, grid stabilisation, or to power a home or business that might otherwise run on renewable energy, with the World Economic Forum suggesting they could solve the “energy-storage conundrum” presented by solar and wind-power generation.

It is a market primed to expand as more electric vehicles come on stream, and their batteries reach the end of their vehicular lives. A McKinsey report predicted second-life storage from EV batteries could exceed 200 gigawatt-hours by 2030, and grow to meet the annual energy needs of the US in the “decades to come”.

Premium car maker Audi has found that once batteries reach the end of their usable in-car life, they retain up to 80 per cent of their original storage capacity, giving them a second-life term of more than 10 years and offsetting the emissions generated in their creation over two lifespans.

Audi recently partnered with energy company RWE to deliver an energy-storage facility in Herdecke, Germany, driven by second-life batteries taken from Audi E-Tron development vehicles.

The vast battery-storage facility, comprising three 12m containers of 552 battery modules, each with 100 second-life lithium-ion cells, can store around seven megawatt hours of energy – enough power for an electric vehicle to drive around the globe 1.5 times – which can be fed into the grid for around one hour when needed.

“Powerful battery storage plays an essential role in the energy revolution. Flexible storage technologies are needed to compensate for short-term fluctuations in renewable energy and to stabilise the grid,” says Roger Miesen, chief executive of RWE.

“Battery-storage systems are ideally suited for this purpose. Together with Audi, in Herdecke we’re testing how end-of-life high-voltage batteries from electric cars behave as stationary energy-storage devices when connected together.

“The continued use of such second-life storage is a sustainable alternative to brand-new batteries. The experience gained from this project will help us identify the applications in which we can most cost effectively operate such battery systems.”

While the Audi and RWE program is a pilot, second-life solutions are already in play around the world.

The Nissan Leaf was one of the world’s first mainstream EVs, launching globally in 2010, and so is also one of the only vehicles old enough to be able to put second-life batteries to use in significant numbers.

One project, run in partnership with energy company Enel Group, has seen those batteries put to work in Melilla, a Spanish city on the North African coast that is not connected to Spain’s electricity grid.

Instead, 78 Nissan Leaf batteries, 48 of which have been recycled, are used to deliver 1.7MWh of electricity storage – enough to stabilise the city’s thermal power supply, or to deliver power for 15 minutes in the case of a short-term blackout.

And in Italy, plans are underway to develop a 30MW solar park at Rome’s Fiumicino airport, which will link to a bank of recycled EV batteries delivering 10MWh of storage, capturing excess energy generated during the daylight hours and deploying it during evening peaks.

Extracted in full from: Used EV batteries get a second lease on life | The Australian