The much-anticipated technology is clearing the regulatory barriers. Michael Shaughnessy looks at what electrical professionals need to know about vehicle-to-grid.

Vehicle-to-grid (V2G) is poised to make an impact on the grid and electric vehicle (EV) affordability. With the ability to act as a battery on wheels, an EV with V2G capability can offset load at peak times by feeding into the building’s electrical installation and/or the grid.

Offsetting load can be of tremendous value to consumers, V2G can offer an additional revenue stream through exporting to the grid, when it needs it the most. Customers on simple time-of-use (TOU) tariffs with two-way pricing could potentially make $1,500 per year. For customers exposed to the spot price through retailers like Amber, they could make even more.

With the publishing of the new versions of AS/NZS 4777 in August, a key barrier to installations in Australia has fallen. All that needs to happen now is for the Clean Energy Council to amend their listing requirements, start processing applications from manufacturers of V2G kit, and of course for distributed network service providers (DNSPs) to continue allowing connections off the Clean Energy Council (CEC) list, business as usual.

Those following the technology will recall that it’s been technically possible and warranted for about 12 years since Nissan first officially started exporting the Leaf to Australia. SA Power Networks made an exemption to allow V2G inverters to be installed in the state. The Wallbox Quasar came to market at a cool $10,000 each and take-up was understandably subdued. This has been a source of frustration for industry people, who’ve seen a desperate need for integration of storage into the grid, to keep electricity prices down and ensure fossil fuel generators exit the market on schedule.

How’s it going to work?

There are at least three different possible modes, all of which start with DC at the EV battery terminals and AC at the switchboard: DC V2G using a wall box, AC V2G using a modified version of the onboard rectifier and AC V2G using modified versions of the onboard inverters.

DC V2G using a wall box

This is the configuration most commonly thought about for V2G and is used by existing Japanese vehicles including the Nissan Leaf, Mitsubishi Outlander and Mitsubishi Eclipse Cross.

It is a relatively simple concept in that it utilises an inverter on the wall, much like a solar and/or battery inverter, to invert the DC voltage from the battery into synchronous AC suitable for injection into the building electricity installation and/or grid. The inverter will have hard-wired safety features such as phase-fail relays, automatic change-over contactors for usage in a blackout, as well as anti-islanding features and grid-protection functionality.

One advantage of this configuration is that export capacity is only limited by the size of the inverter on the wall and the warranted limit set by the EV manufacturer (OEM), which could potentially be hundreds of amps.

Caption: DC vehicle-to-grid with backup

AC V2G using modified versions of the onboard power conversion equipment

The onboard power conversion equipment is used for converting AC electricity to DC and vice versa. A modified version could allow it to invert DC from the battery to synchronous AC suitable for injection into the home electricity installation and/or grid.

This configuration may have cost benefits in that you don’t need a complex box on the wall to connect to the EV.

There may be drawbacks in that should the user want to supply the building in the event of a blackout, a more sophisticated box on the wall (denoted ‘Adaptor box’ in the diagram) would be required to ensure grid safety, hence losing some of the cost-benefit. Another drawback may lie in the technology being integrated into the vehicle, making it more difficult to update or upsize.

Vehicle OEMs are typically not practised in producing inverters capable of interacting with the grid and therefore will need to work with OEMs who are.

Caption: AC V2G with modified power conversion equipment, including backup.

The diagrams above all show a backup box in circuit so that the vehicle could continue to supply the building, in an event where grid supply is not available. This does not have to be in place but does not take a lot more work and without it, the lights will go out if the grid goes down.

The CT meter measuring energy flow at the main switch will be necessary for dynamic load control and export limiting capabilities.

What about selling and installing V2G systems?

V2G systems are ready to come to market now, pending the aforementioned listing process. Companies such as Wallbox, Sigenergy, SolarEdge, Delta and others have advertised products ready to go.

Whereas connections of solar and battery inverters to the network have to date been the domain of solar and battery accredited installers, it is not anticipated that electricians would need such an accreditation to install V2G inverters. There are however several standards and regulations to be aware of.

AS/NZS 4777.1 covers the installation connection of inverters to the network, no matter the energy source. AS/NZS 3000 has useful information in Appendix P on installing EV chargers such as; RCD and overcurrent protection. Requirements for isolators will likely be clarified in the next version, currently being written. Installers should refer to their state/territory electrical regulations and service and installation rules for connecting inverters to the networks.

The process for installing solar/battery inverters looks a bit like the dot points below, minus some rebate paperwork. The process for installing V2G systems will likely be very similar, if not identical in the case where the V2G plug is integrated into the solar/battery inverter.

1. Select the V2G system from the CEC list (SA – ensure electric vehicle supply equipment is listed by the office of the technical regulator)
2. Win the job with the customer
3. Apply to DNSP for pre-approval
4. Receive pre-approval
5. Installation, including any DNSP management, testing and commissioning
6. Submit a certificate of electrical safety
7. Inform DNSP of the completed installation

If this is the space you work in or would like to, it’s time to start researching the brands you want to sell and talking to your customers about V2G and the great benefits it can have for them and the network.

If you’d like to discuss these matters further, learn more at the EVC’s website (evc.org.au) or contact them at office@evc.org.au.