Nissan, manufacturer of the all-electric LEAF, made two EV batteries related announcements at an event in London that will see lithium-ion batteries built for its electric vehicles employed as domestic energy storage systems.
One announcement, a partnership with power management company Eaton, will give a second life to battery cells taken from old LEAF vehicles – packaged into a wall-mounted power unit called xStorage. A separate project, working with multinational power company Enel, will make use of the LEAF vehicle itself as a connected energy store, using vehicle-to-grid technology.
Both ventures aim to unlock the potential of having high-capacity battery storage available at home, allowing a household to time-shift its electricity consumption. For example, a home fitted with solar panels could store power generated during a sunny day for use in the evening, when domestic usage tends to be higher. Similarly, batteries could be charged overnight using an economy tariff, with the power being released again during peak times when the cost per unit from the grid is higher, thus saving money.
There is also the potential to sell stored energy back to the National Grid, helping to smooth out the peaks and troughs in the nation’s power demand. As National Grid non-executive director Steve Holliday noted at the launch: “There are times on this island when electricity has a negative price – we will pay you to shut down.”
Currently, National Grid offers incentives to large industrial consumers to help it balance load. Big companies are paid to go off grid during times of high demand, often firing up their own back-up diesel generators to carry on working. In the future, the capacity of many xStorage units could be aggregated to provide a much cleaner way of shedding grid demand.
Static energy storage in EV batteries
When Nissan launched its LEAF electric car in 2010, the company forecast that each car’s valuable batteries would outlast the vehicle and go on to a second life in static energy storage systems. Six years on, having produced and sold 230,000 LEAFs around the world, Nissan is ready to embark on that second phase.
Nissan’s xStorage is very similar in concept to Tesla’s recently announced Powerwall, though the two differ in capacity, cost and other features. Nissan’s xStorage product will be available to order from September 2016 with the first installations due before the end of the year.
The standard xStorage unit is roughly the size of a domestic gas-fired boiler and contains a quarter of a used LEAF battery. Larger units with higher capacities will also be offered for business and industrial applications through Eaton.
While Nissan did not break down its financial calculations, it stated that a household should be able earn back about £600 per year from an xStorage unit, through the savings outlined above. The unit will cost about £3,000 to buy, including fitting via Eaton’s network of approved installers. With a working life of at least 15 years, Nissan said, payback should take five years followed by a decade of profit.
The limited lifespan is due to the gradual degradation seen in the capacity of batteries as they go through multiple charge and discharge cycles. The xStorage unit contains a nominal 6kWh of cells but makes use of only 70% of this capacity – 4.2kWh. The difference is because the batteries are not new and because full charging and discharging are avoided to help prolong cell health.
Vehicle to grid
Nissan and Enel will launch the UK’s first vehicle-to-grid (V2G) trial later this year, involving 100 private and fleet owners of LEAF electric cars and e-NV200 electric vans.
“Smart energy management is one of the biggest challenges any nation faces for the future, which is why this trial is so critical in assessing the feasibility of using variable, more flexible energy sources,” said Paul Willcox, chairman of Nissan Europe. He added that EVs equipped with V2G technology could become “mobile energy hubs” that will help resolve looming grid capacity issues, which are likely to become more acute as EV adoption grows.
Nissan partner Enel is providing the two-way charging technology that allows energy to flow back and forth between the car’s battery and the household electricity system. The two companies have been collaborating since late 2015 and their first 40-car V2G trial began in Denmark in January this year.
Nissan said that the 18,000 Nissan EVs in the UK could collectively feed the same power into the grid as a 180MW power plant.
Among other challenges, the V2G trial will explore how best to utilise the storage capacity of an EV without leaving it low on charge when it is needed for longer journeys.
By Lem Bingley