Dr Kotub Uddin, with colleagues from the university’s Energy and Electrical Systems group and the car maker, which does not yet have an electric model, demonstrated that vehicle-to-grid (V2G) technology could boost the lifetime of the batteries by around 10%.
Through fifty long-term degradation experiments on commercial C6/LiNiCoAlO2 batteries, the team has built one of the most accurate battery degradation models to predict battery capacity and power fade over time under various ageing acceleration factors such as temperature, state of charge, current and depth of discharge.
Using this validated degradation model, the team developed a smart grid algorithm, which intelligently calculates how much energy a vehicle requires to carry out daily journeys, and – crucially – how much energy can be taken from its battery without negatively affecting it, or even improving its longevity.
The researchers used the algorithm to power their International Digital Laboratory – a large, busy building which contains a 100-seater auditorium, two electrical laboratories, teaching laboratories, meeting rooms, and houses approximately 360 staff – with energy from EVs parked on the University of Warwick campus.
They worked out that the number of EVs parked on the campus (around 2.1% of cars, in line with the UK market share of EVs) could spare the energy to power this building – and that in doing so, capacity fade in participant EV batteries would be reduced by up to 9.1%, and power fade by up to 12.1% over a year. It has previously been thought that extracting energy from EVs with V2G technology causes their lithium ion batteries to degrade more rapidly.
Given that battery degradation is dependent on the age, capacity throughput, temperature, state of charge, current and depth of discharge of the cells, the V2G algorithm is an effective optimisation tool. “These findings reinforce the attractiveness of vehicle-to-grid technologies to automotive Original Equipment Manufacturers: not only is vehicle-to-grid an effective solution for grid support – and subsequently a tidy revenue stream – but we have shown that there is a real possibility of extending the lifetime of traction batteries in tandem,” said Uddin.
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