The transition to electric transport is being driven by the need to address important issues such as global warming. Consequently, it is vital that the maximum benefits of battery propulsion are utilised and that includes optimising activities throughout the whole life cycle of the batteries used in electric vehicles. From a sustainability perspective, one key contribution can be made by extracting as much use as possible from an EV battery before it reaches the end of its life and is recycled to make new batteries. This makes even more sense when the numbers of batteries becoming available is taken into account. It has been predicted that even by as soon as 2025 there will be around 3.4 million of these batteries available globally, and that by 2040 there will be approximately 560 million electric vehicles in existence.
For a typical electric vehicle, the battery life may be up to ten years. Yet there could be several more years of potential further use in secondary applications. Thus, when the performance of an EV battery drops to the point where it is no longer suitable for use in a vehicle, it should not mean that it is automatically consigned to recycling or materials recovery. Although it will have reduced performance, it is possible to identify less-demanding uses, where the reduced capacity is not a significant issue. Extending the lifetime of batteries makes them more sustainable and goes some way to adopting an enhanced circular economy approach; it reduces demand for new batteries, thereby decreasing the negative impacts of battery production. Indeed, the idea of encouraging the secondary use of ex-EV batteries is so important that the subject has been taken up by the European Commission (EC). The EC has reached an innovation agreement with several European manufacturers to adopt the objective of promoting the reuse of lithium-ion batteries before they are recycled for materials recovery.
An important specific example of one of these uses for second life batteries is in energy storage and supply balancing at the domestic level. Second life batteries are now being used for energy storage directly linked to the enhanced charge management of electric vehicles in an attempt to reduce demand at peak times, thus preventing potential overloads on electricity supply grids. There are already a number of products commercially available for energy storage, including ‘Offgen’ from Aceleron, ‘PowerWall 2’ from Tesla and the ‘Powervault 3’ from Powervault. The ‘Offgen’ and ‘Powervault 3’ battery storage units are both designed and assembled in the UK and are specifically aimed at the storage of solar or off-peak electricity in both residential (and commercial) buildings. The company Powervault found that, by using lithium-ion batteries recovered from Renault EVs instead of new ones, it was possible to reduce the cost of one of its smart battery units by 25%. The Powervault 3 is available as the greener Powervault 3 eco-version, which uses recovered and tested second life batteries.
Outside of the UK, there have been numerous other examples of recovered batteries being reused to store electricity. For example, a second-life energy storage system was developed by a team at the University of California’s Davis Green Technology Laboratory. Approximately fifteen ex-Nissan Leaf battery packs were assembled in a shipping container to give a unit with a 300 kWh capacity. This was used as a power source to reduce the peak energy demand and carbon footprint of a winery, brewery and food processing complex. By finding secondary uses like this, it is also possible to reduce overall energy costs, thus providing benefits to both consumers and electricity providers through renewable energy integration and regulation of energy management.
However, it should be noted that only some energy storage products use second life lithium-ion batteries, as manufacturers often prefer to use brand new cells. Using second life batteries is potentially a way of offering a product at a reduced price compared to the same model using new batteries, but there may also be potential longer-term reliability issues and thus shorter warranties. Tesla prefers to directly recycle its batteries to make new ones and does not use ex-EV batteries in its PowerWall products. The reasoning is that an EV battery will reach end of first life after around 8 to 10 years. By this time, Tesla suggest that both the battery capacity and pricing will not be comparable with the latest technology, i.e. it will be more cost effective to use new batteries.
Although there will undoubtedly be a growing demand for battery-based energy storage systems, there are still some questions about the overall benefits of using second life ex-EV batteries, as highlighted by Tesla. In order to be able to reuse EV batteries in second life applications, it is necessary to have detailed information about the condition of each battery and this requires a level of testing that adds to the costs. If such information could be recorded via, for example, the original battery management system and by using more modular battery management approaches in the new units, this might become less of an issue. There are also broader concerns about the overall cost-benefit of using battery-based storage at the consumer/domestic level. The situation is rather complex, being dependent on a number of variables including the cost of power from conventional suppliers via an electricity grid. Using renewables such as solar and battery storage can be significantly more expensive, so it is probably likely to be more of a benefit to off-grid users, or those living in more remote areas, at least initially.
While there is clearly a need for more energy storage capacity, especially as the shift to renewable energy expands, and as the development of more intermittent sources of energy accelerates, the area is relatively new and will need considerable support until it is better established. Second life batteries could provide a lower cost option compared to new batteries. It was, therefore, disappointing to see that, according to the European Association for Storage of Energy (EASE), Europe’s energy storage growth activity was reduced during 2019 due to a slowdown in large-scale storage schemes for energy from renewable sources. The downturn was particularly related to projects that connected directly to energy grids, and which were designed to store renewable energy when solar and wind generation was less available. At the time of writing (August 2020), there was another negative impacting factor in the form of the Covid-19 pandemic. Depending on its duration and overall impact on the global economy, it seems likely that it will further reduce the implementation of government policies aimed at supporting energy from renewable sources and thus result in fewer battery installations, at least in the short term.
Nevertheless, although the situation is rapidly evolving, it is clear that there are circular economy and sustainability benefits to keeping former EV batteries in use for as long as possible. There are various less-demanding applications that can utilise ex-vehicle batteries for a number of additional years after first use and before they need to be recycled. However, as with the whole story around the EV-battery lifecycle, the situation is complex; there are even those who are testing and reusing EV batteries in vehicular applications, i.e. for lower cost replacement batteries. It will be interesting to see how the opportunity develops over the next twenty years as battery production, use and the need for recycling increase dramatically. Secondary use of EV batteries in energy storage could play a major role in helping to shape the future of our electricity generation, distribution and use.
Written by Martin Goosey, Envaqua Research Ltd.