Just about every press conference at this year’s Tokyo auto show began with a mention of the earthquake and tsunami that struck Japan last March. While no one can predict such disasters, lessons learned from the events have resulted in some interesting technological propositions. At Nissan, engineers are looking at the Leaf from a new angle, seeing it not only as a provider of transportation, but as device for storing electricity.
With the earthquake and tsunami wiping out power, water, and natural-gas services, people realized that the Leaf and other EVs held large amounts electricity that could otherwise be used during emergencies. And so the “Leaf to Home” concept was born.
Leaf to Home employs the same cable as the car uses to charge. Instead of connecting to an outlet, though, this new application plugs the car in to a Power Control System (PCS) that’s coupled to the home’s electrical panel, allowing electricity to flow out of the Leaf’s batteries in to the house. With a typical Japanese residence using about 10–12kW per day and the Leaf’s lithium-ion battery holding up to 24 kW, a fully charged Leaf could potentially power the home for about two days. That time would be reduced here in the U.S. since we use more power, but in times of emergency, owners would hopefully know to scale back their usage.
Additionally, the PCS could use the Leaf’s batteries on a regular basis. For example, during peak times of energy use when electricity costs more, the home could be isolated from the grid and run off the power stored in the Leaf—which presumably would have been charged during off-peak hours, perhaps in part by your rooftop solar panels. Nissan acknowledges that such use would demand a customizable software program with smartphone integration.
It might seem foolish to power a home using juice from a car—potentially stranding the owner at home—but most EVs are not the sole vehicle in the household. Nissan says there has been a great deal of interest in the system, especially from businesses and municipalities; the biggest hurdle remaining is government regulation.
Developing a Wireless Charging System, Too
Wireless charging systems (one of our 10Best Most Promising Future Technologies for 2012) are already offered for devices like smartphones and media players. It’s no surprise, then, that hybrid and EV manufacturers such as General Motors and Toyota are pairing up with companies like Powermat and WiTricity to develop the tech for automotive applications. Nissan, not to be left out, has announced that it’s developing its own wireless charging system for the Leaf. Magnetic induction uses a transmission unit placed on the ground and a receiver affixed to the car—the Leaf’s is tucked between the rear wheels. Once the car is parked over the transmission unit and the system confirms the connection, charging begins. Nissan says the wireless transmission is about 80–90 percent efficient, just a small degree less than traditional cable charging.
The company says that its unit is flexible across a wide radius, meaning it will still charge even if the car isn’t perfectly centered over the pad. The system is still in the development phase, so we’d like to offer a bit of unsolicited advice: Build that transmission unit like a tank, because it’s a matter of when, not if, drivers will run over it.
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