Vehicle to grid charging

How can your electric car support the national grid?
03 March 2020

Interview with 

Claire Miller, Octopus Electric Vehicles




Apart from the potential to avoid pollution - and power a vehicle with renewable energy - electric vehicles also offer another advantage: when the vehicle is standing idle, which most cars do most of the time, the batteries that supply them are also ideally suited to powering the national grid. And that’s where companies like Octopus have seen a gap in the market: the idea is quite simple - your car gets charged with surplus electricity when energy is cheap and readily available. Then, when the tables are turned and the grid needs a helping hand, your car sells some of its stored energy back to support the supply. But first, you need to plug it in! Here, Megan McGregor gets to grips with charging an electric car, then you'll hear from Claire Miller and Katie Haylor...

Megan - We've just opened the, I want to say petrol cap, electricity cap? And there's two sockets inside. One's got an orange cap on top, that I'm just going to open. This is on the front of the car, not the side of the car, like the petrol cap. So now I have the cable and one end goes into the car. Presumably the other end goes into the charger. And now I have the RFID tag, which just looks like a loyalty points card, for example. And I scan that on the thing. And now the blue lights on the dashboard are flashing and the car is charging. And so if I wanted to do, I could go about my business now. And it's as simple as that.

Katie - Megan was plugging in at the Madingley Park and Ride there, in Cambridge, but charging the car at home can unlock some interesting opportunities. It's possible for electric vehicles to put electricity back onto the grid via a process known creatively as, vehicle-to-grid. Claire Miller, director of technology and innovation at Octopus Electric Vehicles, laid out what you need to make this work.

Claire - You need a car which is suitably enabled. Nissan Leaf is one of the very few vehicles that can do that. And a special charger, which can take the energy back from the car as well as to put it into the car. When you plug your car in around five, six, seven o'clock at night, you'd see the car start to put energy back onto the grid. And that's because at that time of night, everyone comes home, wants to make their tea, put on the television, use a lot of electricity. And so that's a good time for your car to be able to give some electricity back to the grid.

And then overnight in the small hours of the morning, when electricity is cheap on the grid, and often there's a lot of it available, particularly as we have more renewables becoming available. So for example, on a windy night, there's lots of electricity on the grid that needs to go somewhere. You would see your car start to charge up.

Katie - We know that over time lots of charging and discharging can lead to battery degradation. Just look at what happens to your phone battery life. So what does the added charge and discharge of vehicle-to-grid do to your car battery life? Well, turns out not all battery cycles are created equally.

Claire - Early studies are showing that the way that a vehicle-to-grid cycle works for the car battery, is actually a really safe way to charge and discharge the battery. If you imagine when you're doing a vehicle-to-grid cycle, you plug the car in. The way that the energy is removed from the battery. We've done a lot of work to make sure that our, we call them battery profiles, is done in a very smooth way.

If you compare that with the way that we drive our electric vehicles, we might be driving in town, stop, start, accelerating, braking, and then out onto the motorway, so driving fast, and then slowing down again for traffic. That's a much more uncontrolled way of using our battery. Discharging the battery, using energy from the battery, to put it back onto the grid is a much smoother way of using energy.

Katie - The jury is still out on the longterm effects of vehicle-to-grid on battery life. Some studies suggest it might improve long term battery life, while others have suggested neutral or negative outcomes. It all seems to depend on how much battery degradation happens while the car is at a standstill. However, the advantages of vehicle-to-grid extend beyond a potential increase in electric vehicle battery life, it could help improve the resilience of our electricity grid.

Claire - So the advantages for the grid, when there's that spike in demand at tea time, it gives access to sources of energy beyond say burning gas, which in the UK we do to meet that demand very quickly. So it really helps to balance the grid. And what that means is that lots of people are demanding or asking to use electricity, and so the grid has to get it from somewhere.

Katie - If that's somewhere is going to be electric car batteries, some pretty sophisticated management software is required. For one user, it can be a smart meter or a phone app, but for a whole fleet of vehicles, software that can coordinate charging and discharging will be needed. Vehicle-to-grid advocates see this technology as part of a new approach to home energy management, where the car is just one part of a larger system that gives consumers much finer control over their energy usage.

Claire - Vehicle-to-grid is just one way in which we'll be able to control and decide where we use energy, and where we put energy in the future. If you imagine a home which has solar panels on the roof, and maybe a static battery in the garage, for example. Maybe you've got a Nissan Leaf as well. We're looking at developing systems where you'll be able to choose. Do I charge my car with energy from the grid for example, because it's nighttime, there's lots of wind, so it's green energy on the grid and it's very, very cheap. So you might choose to charge your car from the grid, and you might charge to top up your home battery from the grid as well. Another time it might be tea time, for example, tea time, peak demand, and you might choose to actually put energy from your car and/or your battery back on the grid, because you know that the grid needs the energy and you might get paid for it.

So we are absolutely looking at ways of helping people to control and decide where they use energy, how they store it at home, most people don't have a way of storing energy at the moment, and making those decisions. So both on a financial perspective, will I get paid for it, and will it be cheap for me? And also, is it a green way of charging my car, or can I help the grid by avoiding burning fossil fuels?


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