Used EV Batteries to Stabilize the Grid

by Emil Morhardt

If a single used electric vehicle (EV) battery, still functional but with it’s storage capacity degraded by 20%, could be used to store energy from photovoltaic panels at home (see Dec 30 post), a bank of them could be used to stabilize the whole grid, according to Gillian Lacey and colleagues (2013) at Northumbria University in the UK. Their particular emphasis is “peak shaving”—supplying enough electricity at times of peak demand that additional fossil-fuel generation can remained turned off. This would also help regulate the line voltage and allow some “upgrade deferral”­—putting off investing in needed new or more efficient sources of energy. A particular value of this type of storage is that it would be at the low voltage end of the distribution system, closer to the end user, thus decreasing the potential line losses that would occur if peak power were supplied by regular generation systems, and increasing the life of transformers which are particularly stressed under peak loads. This might also mean that this type of storage would be “distributed”—maybe one battery per residential transformer. Since most large-scale current photovoltaic generation stations generate at low voltage, used EV batteries might be useful there as well.

In grid applications, the authors have assumed only a single charge-discharge cycle per day (matching the daily peak—probably exactly what would occur at home PV installations as well), which would be effective in prolonging the life of the batteries.

Lacey, G., Putrus, G., Salim, A., 2013. The use of second life electric vehicle batteries for grid support, EUROCON, 2013 IEEE. IEEE, pp. 1255-1261.

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