Life after EVs: Can we repurpose old electric car batteries to charge new ones?

Future Transport Systems, a company offering R&D and consultancy in the fields of mobility and energy management, examines novel opportunities for re-using electric vehicle batteries to store and optimise renewable energy.


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Introduction

Adoption rates of electric vehicles (EVs) and plug-in hybrids (PHEVs) continue to soar, with many public sector fleets leading the charge. According to the Society of Motor Manufacturers and Traders (SMMT), year-on-year sales of cars eligible for the Government’s Plug-In Car Grant more than trebled in May 2015.

However this shift to more sustainable and less polluting transport brings new challenges as well as environmental benefits. More EVs and PHEVs on Britain’s roads mean more demand on our strained electricity network, particularly in urban areas. And there is also the question of what to do with the electric car batteries at the end of their life?

Lithium-Ion batteries can be recycled, but the costs are prohibitive. Recycling companies charge around £5,000 per tonne to recycle Li-Ion, compared to circa £500 per tonne for lead acid batteries.

Government Funding

Recognising these challenges, the Department of Energy & Climate Change (DECC) issued a call for projects and in late 2013 announced a £3.7 million grant to fund the EVEREST (Electric Vehicle Embedded Renewable Energy Storage and Transmission) consortium. This collaboration of companies and other organisations aimed to find a combined solution to these issues of grid reinforcement, increased charge infrastructure load and re-use of EV batteries.

The consortium produced a proof of concept unit, which is now in operation at the Lotus Cars factory in Norfolk. It utilises an aggregated 160kWh of second life EV batteries to store energy generated by a combination of solar and micro wind power, which can recharge EVs via a 50kW rapid charger. Following successful field trials, one of the consortium partners, Future Transport Systems, is commercialising this product, as the E-STOR.

Behind the meter

The E-STOR business case for local authorities and public sector fleets is in “behind the meter” applications where it can provide benefits to both site owners and the electricity network operators.

Rapid charging posts typically require electricity supplies in multiples of 50kW, which can often exceed the existing connection capacity. Deploying E-STOR can be much more cost-effective than upgrading grid infrastructure. When positioned behind the meter, the system can also deliver cost savings to the site owner.

The operating software enables the system to respond to signals from the National Grid and Distribution Network Operators. This means that along with reducing the export of renewable energy generation, it can draw down and store energy when it is available on low tariffs, then utilise it at peak tariff periods.

The owner/operator can use the software to set specific priorities on how, why and when the storage unit charges and discharges. Weightings can include

• managing the maximum load on the local grid network

• charging at low-cost tariff periods

• discharging to offset site loads at high tariff periods

• managing capacity to provide demand response services to National Grid

The software can also aggregate several E-STOR systems in multiple locations, creating an optimised storage network. Users can monitor and operate the system locally or remotely.

The Business Case

The capability to operate behind the meter and flexibility on charging and discharging presents additional commercial opportunities, such as for solar panel installations on commercial buildings.

The optimum business case exists for sites with requirements for multiple EV rapid charging stations. However a strong case can also be made wherever a site’s energy profiles include load spikes, loads during peak tariff periods, on-site renewable generation with weekday or weekend export, relatively predictable load profiles and a need for a grid connection upgrade.

FTS can use existing site load, generation and tariff data to simulate the operating model, assess potential benefits and determine business case feasibility.

The National Grid’s distribution system causes transmission losses of more than 2% of peak output. Locally-generated energy also reduces system losses, thereby increasing grid efficiency. Local energy storage capacity also helps to optimise renewable energy generation, as it can store electricity generated off-peak for use in peak periods.

EV Market Boost

Creating a secondary application for EV batteries significantly reduces their environmental and financial cost per cycle; as it is creates additional value before recycling.

Typically after five-to-seven years an EV battery’s energy storage capabilities will have degraded by 20%, rendering them less useful to their owners and unattractive to used car buyers.

This has also caused problems in the fleet market, where vehicles are often leased for three years rather than bought outright. Fleets pay a slight premium for EVs because they have lower residual values – this is the sale price the fleet management company can expect to realise for the vehicle when you return it after three years. The most popular EV in the UK is the Nissan LEAF. According to Glass’s Guides, after three years and 60,000 miles it has lost around 71% of its value.

The establishment of an energy storage market for second life batteries should therefore also underpin and even enhance the residual value of EVs. This will help further bring down EV costs and make them even more attractive to public sector fleets.

Conclusion

Public sector organisations continue to lead the way in the adoption of ultra-low emission vehicles in their own fleets, as well as providing public infrastructure to support wider uptake of EVs. Innovations such as E-STOR create virtuous circle solutions to support these objectives, by delivering locally-generated, cost-effective renewable energy stored in second-life electric car batteries and used to rapid charge EVs.


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