Two-way street: getting vehicle-to-grid charging off the ground

Vehicle-to-grid charging systems could turn electric vehicles into a new layer of energy storage and grid balancing for the decentralised power systems of the future. As Dr Jim Scott of EBRI – operator of the UK’s first permanent V2G unit – explains, the economic hurdles are formidable, but with time, effort and the right business model, the concept could pave the way to a stronger and more flexible grid.


Electric vehicles (EVs) represent a rapidly maturing technology that has become a relatively prevalent means of continuing to gradually decarbonise transport networks. In 2012 there were approximately 180,000 EVs on the road globally, making up just 0.02% of total passenger cars, but numbers are increasing rapidly and the Electric Vehicle Initiative aims to see 20 million in use by 2020.

But beyond providing an eco-friendly mode of personal transport, could EVs and plug-in hybrids be doing more to strengthen energy systems as their numbers increase? An emerging technology called vehicle-to-grid (V2G) charging suggests that, in time, they could start to play an interesting role in a less centralised power network that makes greater use of energy storage.

The V2G concept, which was initially developed in Japan as a response to post-Fukushima power supply disruptions and is now being tested in several countries in Europe and North America, expands the role of EV charging stations by allowing electricity to flow both ways - in the traditional direction from the grid to the car, and the reverse, from the car into the grid.

This concept holds significant promise, its proponents affirm, as a smart new method of supplying energy storage and grid balancing services to help tackle the energy supply crunch that some countries are expecting as coal-fired and nuclear plants continue to be taken offline.

V2G in the UK: could it work?

The first permanent electric V2G charging system in the UK is installed on the campus of the European Bioenergy Research Institute (EBRI) at Aston University in Birmingham. In partnership with EV specialist Cenex, researchers at EBRI have been running the V2G system, which was made by IKS Japan and supplied by European distributor E8 Energy, as part of the institute's micro-grid to investigate how V2G can improve the efficiency of distributed energy systems by turning an EV into dispatchable load.

"One of the things that's really obvious about vehicle-to-grid, and one of the reasons it's exciting, is that cars are parked doing sod-all for most of the time," says EBRI research associate Dr Jim Scott matter-of-factly. "Nearly 100% of their life, they're stationary on your drive. And that's a really stupid utilisation of a very expensive resource."

"Under that business model, I think [V2G] stinks - it's never going to work at the moment."

Now that EBRI has had months of experience working on its V2G charging system, the million-pound question is clear - can the technology realistically be used to feed electricity back into the grid in a way that makes economic sense? While Scott is positive about the equipment's robustness and its unusual scale (EBRI's three-phase, 10kVA V2G unit is designed to connect to a 400V distribution panel in a large building, while many other V2G systems are essentially domestic-scale devices), it has a 10% efficiency loss and, based on EBRI's data, would be uneconomic in the UK as a means of offsetting energy costs based on time of use.

"Under that business model, I think it stinks - it's never going to work at the moment," says Scott. "Because any building manager is going to look at the additional cost of buying the V2G capability over the bog-standard charger, and that's the bit that's not worth it. The marginal cost isn't worth any benefit that you would get from load lopping or anything like that."

Finding a viable V2G business model

The unforgiving economics of V2G deployment might be no different from any emerging technology that needs to reach critical mass through cutting costs and driving market adoption, but they put a dampener on the technology's immediate prospects. Nevertheless, EBRI's work on developing V2G business models has highlighted a possible route forward in the form of demand-side response (DSR), which would involve essentially making a contract with National Grid to pump power into the grid during peak hours.

"In that model, you're looking at the frequency all the time, and when the frequency goes high, that means there's more generation in the grid so you charge your car and you bring load on to the grid," Scott explains. "In the reverse situation when there's not enough generation in the grid, you can provide a service to the national grid by discharging your vehicle into the grid."

There are certainly challenges to making V2G a provider of decentralised DSR - there has to be a certain scale involved because, as Scott says, "National Grid won't pick up the phone, really, until you've aggregated about 10MW, which is a lot of cars."

And the time it takes for V2G units to switch from charging to discharging would need to be to be cut substantially to respond fast enough to the grid's needs. "You have to be able to switch on and off, charge or discharge, really quickly," says Scott. "And ours takes an age. That's the next big breakthrough that I think [developers] should be working on."

Still, there are signs that the likes of Ofgem and National Grid are starting to become more accommodating to unconventional ideas on demand-side frequency response, and the private sector is responding. In May 2016, power company Enel and Nissan - a leader in EV tech and manufacturer of the Leaf, the world's best-selling fully -electric car - announced the first V2G trial in the UK, with more than 100 pilot units allowing owners of the Leaf and e-NV200 electric van to sell stored energy back to National Grid.

Scott, who notes that EBRI is hoping to expand on the DSR idea in the coming months, also points out the potential for financing deals to open up dual revenue streams for V2G providers to offset the technology's high capital cost. "You'd probably provide the charging equipment for free to a building operator, and then you charge people to charge up, and part of the deal of charging up is that at any given time, you can decide to discharge that person's car, but only within certain limits, so never below 80% or something like that," he says. "So you're providing a back-end service to National Grid and then a front-end service to the vehicle charger, and between those two services maybe you can justify the additional cost."

Clearing the road to a V2G future

Nissan's trial mayight provide a speculative glimpse into a future when electric vehicles form an invisible DSR safety layer for grids around the world. But that day is still many years away, if it's destined to arrive at all, and there are many challenges that need to be overcome in the meantime. The most fundamental of these is cost.

"I think our unit was about 50% more expensive than a standard [non-V2G charging] unit," says Scott. "We could have never tolerated that if it wasn't a research project."

This process of driving costs down is simply a matter of time, if industry and academic researchers can use that time to refine and commercialise the technology. More time would allow, for example, work to be done on the fundamental design of V2G charging units, and there is plenty of work to do at this early stage.

"The future prospects for V2G are tied to the fate of EV market adoption."

"[Cenex] is doing a project at Manchester Science Park where I think they're looking at some models where the vehicle-to-grid part is onboard the car, and some models where it's on the street, which seems like quite a fundamental question about this technology that's not been answered yet," says Scott.

An open approach to V2G technical standards could also accelerate technical development by ensuring interoperability of devices and eliminating development bottlenecks, and many EV evangelists are calling for open standards like the Open Charge Point Protocol and Open Automatic Demand Response (OpenADR) for standardising grid management and communications protocols.

Ultimately, the future prospects for V2G are tied to the fate of EV market adoption on a wider level. With a larger base of vehicles on the road and sat idle in garages and on driveways, the potential for intelligent applications like V2G rises in step. Although a tidal surge of EV ownership hasn't quite materialised yet, Scott is optimistic that the era of EV, and all that comes with it, will come in due time.

"The big indicator that I think is important is that you can now buy a BMW 3-series plug-in hybrid, and that's for the company car market, the people who used to buy Mondeos, and it's not a big deal," he says. "It used to be a big deal to drive a Prius. The penetration of electric vehicles, I think, is still pretty disappointingly low. But the way I think of it, this is only going in one direction.

"It's written in all of the big energy company strategies, it's written into the big motor vehicle strategies, that they're going to get smaller and smaller petrol tanks, bigger and bigger batteries. Smaller and smaller petrol engines, bigger and bigger electric motors. I think the trap is to think that it's going to be a cliff that we all fall off and then suddenly everybody's driving around in the future like the Jetsons. It's not going to be like that - it's a transition."