The idea of using electric vehicle batteries as back-up storage for power utilities seems obvious enough at first glance, and it’s often suggested as the ultimate step in stabilizing an all-renewable grid. But Greentech Media explains that vehicle-to-grid (V2G) systems aren’t nearly as simple as they seem.
“The idea is attractive because of the growing amount of lithium-ion battery capacity tied up in electric vehicles, and the fact that this capacity is not being used for around 95% of the time,” Greentech notes. And “ten new Nissan Leafs can store as much energy as a thousand homes typically consume in an hour.” But “despite numerous pilot studies over the last decade, V2G has yet to become a commercial reality.”
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Overall, “V2G is intuitively appealing for all the obvious reasons, but it’s not a slam-dunk, at least not in the short term,” said Colin McKerracher, head of advanced transport research at Bloomberg New Energy Finance. “Private customers are still hesitant, and many of the revenue numbers you see rely on tapping mostly into frequency regulation markets, which are high-value but can quickly become oversupplied.”
There are also technical questions to be answered—beginning with the increased stress V2G would place on battery packs that are among the most expensive parts of an EV. “It is still unclear who would cover the cost of battery replacements and how vehicle owners should be compensated for taking part in V2G programs,” Greentech notes.
The lack of progress toward commercialization has doubters like Tesla Motors Chief Technology Officer JB Straubel describing V2G as “something I don’t see being a very economic or viable solution—perhaps ever, but certainly not in the near term.”
Greentech traces a V2G research project that is part of a £30-million government effort in the UK to make the country a leader in low-carbon vehicles. The study by energy storage firm Moixa Energy set out to “develop driver-centred business models to support a rapid rollout of V2G technologies, allowing millions of electric car batteries to become a vital part of the UK energy system,” the company said in a release.
While the study will consider how electric vehicles can support the grid while earning revenue for their owners, CEO Simon Daniel said there’s also value in learning how a growing EV fleet can charge up in a more flexible way.
“One analysis by Wood Mackenzie last year predicted that just a quarter of a percent of Texas’ cars could sink the grid if they all charged simultaneously,” Greentech notes. “However, with the right balancing market design, all this capacity could be used to create a sink for excess generation when needed. Similarly, halting vehicle charging in response to a grid signal could help the electricity network cope with short-term increases in demand.”