Latest News

Integrating the power storage potential of electric vehicles with the needs of a house is attracting interest around the world. Andrew Wade reports

The rising popularity of electric vehicles, combined with advances in energy storage, presents an exciting new opportunity to rethink the grid. Notions of car and home working in tandem have been around for a long time; vehicles charging overnight at off-peak rates, then supplying homes with leftover energy in the evening when tariffs are high. The larger batteries paraded by today’s EVs make this an increasingly viable prospect, though admittedly one which has yet to fully take off.

“I think one thing people don’t truly appreciate is how much energy a car uses in comparison to a house,” Dr Paul Niuewenhuis, from Cardiff University’s Electric Vehicle Centre of Excellence, told The Engineer.  “You can run several houses off an electric car battery system. So even when the battery pack is no longer optimised for running the car, it can still run the house for quite some time.”

While true integration of car and home may still be some years away, manufacturers are tapping into the underlying principle with a new wave of energy storage devices such as Tesla’s Powerwall and Powerpack. The boom is the result of rapid advances across complimentary technologies – primarily solar and battery storage – as well as the means to link them effectively.

“The Japanese have already been promoting this sort of model for a number of years,” said Niuewenhuis. “A lot of houses in Japan have these storage batteries, which create a sort of buffer between the grid – or sometimes between the electric car – and the house. A number of people managed to keep going for a while after the Tōhoku tsunami and earthquake, just using their systems.”

The maturity of some EV models is the source of another interesting twist on storage, as second-life opportunities emerge for car batteries past their prime. A unit designed to power a vehicle may need to be replaced after several years, with the cells no longer operating at peak efficiency. But those cells can continue to have a productive life.

Racking up worldwide sales of around 250,000, the Nissan Leaf is the most popular EV ever. First introduced in 2010, some early Leaf batteries have by now seen their best years, but the Japanese OEM has come up with a novel way to repurpose them. Known as XStorage, the venture has seen Nissan team up with power management specialist Eaton to produce a new range of storage products. Leaf batteries are removed from the vehicle, and the cells are then stripped and reconditioned.

“We package those cells into a module, so it’s a number of cells in a pack,” Frank Campbell, Eaton’s EMEA president for Corporate and Electrical, told The Engineer. “That pack then has a battery management system in it. So there’s some electronics that are required to be able to control the voltages and the discharge rates.”

XStorage comes complete with cabling and installation at a starting price of £3,200 for a 3kW inverter and a 4.2 kWh battery pack. Its creators are keen to point out that, unlike many of the solutions currently available, it incorporates all the inverters and switching gear required to feed into the pack from multiple sources, as well as deliver that power back to the home or the grid.

“Think of the brain in there as an intelligent switch that allows you to have multiple inputs, those being a renewable source – wind or solar, typically solar – a normal utility source – your grid power – and then a battery source, and then a load,” Campbell explained.

“The switching device is basically controlling what source, or multiple sources, is providing to the load, and charging or discharging the batteries at the appropriate time based on software that we can set. So it’s basically a very intelligent brain and switching mechanism, coupled with this battery pack which is simply cells off a Nissan Leaf.”

XStorage was first unveiled back in May 2016, but November saw a major milestone for the technology, with Nissan and Eaton partnering with the Amsterdam Arena on a 10-year commercial project. Using the equivalent of around 280 Leaf batteries, the system will be used for back-up power for the 55,000-seat stadium, home to Ajax Football Club. A total of 4MW of power and 4MWh of storage capacity will be available.

Read more https://www.theengineer.co.uk/charge-the-car-run-the-house/