The First Step Toward a Vehicle-to-Grid Power System

vehicle-to-grid EVs
Jesse Remillard for Zondits, July 20, 2015. Image credit: stux

Although some particularly tech-savvy individuals were able to hack their Nissan  Leaf electric vehicles (EVs) to provide back-up power for their households during Hurricane Sandy without the manufacturer’s help, Nissan has announced an official vehicle-to-household (V2H)  system for US owners providing two-way charging support. This will allow the Leaf, which can provide about 25 kWh, to act as a generator powering a typical American household for up to a day.

The compact, wall-mounted systems were first released in Japan at a cost of around $4,000. They consist of an inverter and controls to monitor charging and discharging. The V2H systems are also being considered for combination with photovoltaic (PV) panels to support direct solar charging and to maximize on-site PV use.

To that end, Nissan and Hitachi are currently conducting demonstrations in Hawaii to test the functionality of pairing residential PV and EVs. Although the concept is promising, the California Independent System Operator has stated that the technical feasibility for these types of systems is currently underdeveloped and not validated.

Another exciting option for this kind of technology is peak demand management for commercial buildings, where multiple EVs connected to a building could be used to support building loads during peak periods.

If EVs could become a viable resource for building owners and grid operators, the implications would be far reaching. But in order for this to happen, controls need to be developed that are sophisticated enough to meet both the safety requirements of grid operators and needs of the consumer. Despite these challenges, the modern smart grid era may be approaching quicker than anyone anticipated, and the announcement of these products is the first sign of its arrival.

Image courtesy of Yahoo.
Image courtesy of Yahoo.

Volt-utility vehicles: garage-based grid

EIA, April 30, 2015.

After Hurricane Sandy pummelled the eastern coast of the United States, causing severe power outages, one of the smaller news items to come out of the 2012 storm was how some electric vehicle (EV) owners used their Nissan LEAFs as emergency backup power devices to reverse-charge their homes.

They were not exactly using their cars as approved, but it was still ingenious. And Nissan and other companies had already thought of the idea. After the Fukushima accident, Nissan brought out in Japan its LEAF to Home system to address demand for vehicle-to-home (V2H) power; it has since sold more 2 000 systems. The package, which sells for the equivalent of about USD 4 300, not only functions as an emergency backup device but also allows for an interconnection with rooftop solar panels. This means that during sunny hours when the car is parked at home, the battery is charging. At full charge, a Nissan LEAF battery can provide almost two days’ worth of electricity consumption for a typical Japanese household. Other companies are also developing and marketing similar systems.

Cars are parked 95% of the time, and given the increasing challenge of storing electricity generated by variable renewables as well as when and where to source the electricity to charge EVs, a framework linking them to solar-powered homes looks tantalising. The trick is to make sure that the vehicle is charged when the driver needs it, that the home utilises the battery for consumption when possible, and that the solar panels are being well used. Optimally, V2H increases EVs’ potential value, supports home solar generation and makes it possible to get off the grid to better fit overall supply with demand.

Powering much more than just homes

But a broader and dynamic application, vehicle-to-grid (V2G), can increase the reliability of the entire electricity system by helping the grid avoid peaks, like when people all plug in their EVs at much the same time after coming home from work, and providing extra decentralised energy storage. V2G is not a prerequisite for large-scale vehicle electrification, but the 2014 edition of the IEA flagship technology publication Energy Technology Perspectives estimates that the on-board battery storage in EVs could provide cost-effective demand response capacity, fully halving the need for capital-intensive large-scale storage technologies required for an electricity system that limits global temperature rise to 2 degrees Celsius by 2050.

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