Success Story: How Electric Vehicles Can Give Back to the Grid
May 18, 2022
Story
I used to think electric vehicles (EVs) were invented recently in response to the global outcry to reduce carbon emissions. So, you can imagine my surprise when I learned EVs have been in and out of popularity since the late 19th century but didn’t stick until the 21st century mostly because fossil fuels were just so available.
[Editor's note: Listen to this story in the Embedded Insiders podcast wherever you get your podcasts or in the embedded player below.]
But the EV revolution, spearheaded by the likes of Tesla and the Toyota Prius, not only made these vehicles popular (especially in the U.S.), but also revealed an utter lack of charging infrastructure. And now many countries have instituted policies requiring all vehicle sales be electric by 2030.
Assuming there are enough charging stations available by then to accommodate all the EVs on the road (a big assumption, I know), will the electric grid be robust enough to accommodate them too? Or, with so many people worldwide needing to charge their vehicles daily, are we in for regular apocalypse-class blackouts from power grid overload?
“The problem with that is if we all transition to EVs we’ll be putting a huge load onto the grid,” explains Dunstan Power, Director of ByteSnap Design, an electronics engineering consultancy headquartered in the U.K.
“There's this concept of what they call vehicle-to-grid (V2G), which is where instead of the energy going into the vehicle, energy's coming out of the vehicle,” he continues. “That energy coming out of the vehicle can either be used to reduce the power a building it's connected to is drawing from the grid, or it could even be used to put energy all the way back into the grid itself.”
V2G technology is also probably older than you think. In 2018, ByteSnap Design, Nortech Management, Grid Edge, and Aston University formed the V2G Consortium, an industry-academia partnership funded by the U.K.’s Office for Low Emission Vehicles (OLEV) and the Department for Business Energy and Industrial Strategy (BEIS).
Their work focused on the design, development, and testing of an EV discharge platform under the VehIcle-to-Grid Intelligent controL (VIGIL) Project. The resulting VIGIL platform intelligently monitors the energy distribution network for demand constraints and communicates that information to bi-directional charge points that can efficiently manage and regulate EV battery charging and discharging.
Before you get concerned about some future municipality commandeering your car for its stored power, in practice EVs would not be required to participate in V2G discharging activities and could elect whether and how much energy they export back to the grid. And they (well, their owners) would likely be compensated for the energy they share.
When Vehicles Talk Back
Although it’s a vehicle to grid solution, VIGIL actually doesn’t have any components onboard the EVs themselves. Rather, it’s composed of three core components: an active network management (ANM) system, V2G/building controller, and smart charge point controller.
- ANM – Nortech Management delivered the ANM scheme that allows VIGIL to monitor the voltage levels and available capacity of local substations connected to the grid.
- V2G/Building Controller – Provided by Grid Edge, the V2G/Building Controller allows the platform to control and optimize all the distributed energy assets connected to a VIGIL network. It ensures the service conditions of transformers as well as VIGIL platform components are maintained.
- Charge Point Controller – ByteSnap contributed a charge point communications controller that transmits messages using version 2.0 of the Open Charge Alliance’s Open Charge Point Protocol (OCPP). Called MantaRay, the OCPP adapter instructs charge points when and how much to charge or discharge an EV’s battery and communicates with energy management systems for localized power load balancing (Figure 1).
Figure 1. The MantaRay embedded controller from ByteSnap Design/Versinetic acts as an OCPP protocol converter that makes any charge point interoperable with the VIGIL platform.
The OCPP protocol is an interesting thread that ties all this infrastructure together, as it can talk to the cloud or local building energy management systems to provide low-latency control. In addition to carrying diagnostics and metering data, it’s used to authorize vehicles to charge at specific charging stations and can facilitate payment between charge point operators and EV owners.
“The ANM system sends a signal to the V2G controller saying, ‘This is the headroom available for you to optimize charging or discharging,’” says Preye Ivry, network innovation engineer at Nortech Management Ltd. “The V2G controller takes that signal and sends it to the OCPP adapter, and that accepts the signal and passes it on to the charge point itself to then act.
“The V2G charge point now speaks another language with the vehicle. And in our case, it was CHAdeMO, which is a DC protocol,” Preye went on. “The cable that connects from the charge point to the electric vehicle accepts commands and control signals from the charge point.”
These building blocks delivered all the functionality necessary for the VIGIL Project to support AC/DC and DC/DC V2G power conversion using standard IGBTs and MOSFETs.
The VIGIL (Auto)Pilot
From 2018 to 2020, the VIGIL pilot tested four vehicles, three of which were Nissan Leafs — one of the few vehicles that supports V2G. They were leased from Electric Zoo who, of course, was informed of their intended use prior to leasing.
The VIGIL team also put its money where its mouth is by using Dunstan’s car during the tests.
Three EV charge points equipped with ByteSnap’s MantaRay embedded OCPP adapter were installed on the Aston University campus. The primary VIGIL user interface was hosted in Nortech’s cloud-based iHost data management platform.
The pilot consisted of three test cases that, at any time, charged or discharged no more than 10 kW from EV batteries:
- A bidirectional V2G setup where power flowed from charge point to vehicle and vehicle to charge point using IGBT or MOSFET inverters for DC/AC and AC/DC conversion.
- A test setup that only discharged the EV battery to the charge point.
- A standard, unidirectional power flow from charger to vehicle that used rectifiers for AC/DC conversion. This served as the pilot’s control test.
Today’s EVs use both AC (for the motor) and DC (stored and dispensed by the battery), which explains all the conversion activity happening at the charge point. Whenever the Grid Edge V2G/Building Controller determined more energy was required by the grid or an adjacent building, the VIGIL platform’s ANM system sent a message to the charge point(s) over OCPP.
Once received, the MantaRay board embedded within the charge points would translate VIGIL OCPP messages into control messages the charge point could understand and vice versa, effectively allowing the VIGIL platform to interoperate with any V2G charger.
During the trial period, the testers recorded conversion efficiencies of around 90 percent in either direction, which is on par with today’s high-efficiency EV chargers. And, importantly, there wasn’t any recordable impact on battery health or performance.
Waiting for the Automotive World to Catch Up
Members of the V2G consortium have experienced individual successes and setbacks on the other side of the VIGIL pilot program. Grid Edge has gone on to deploy its controllers in shopping malls, HVAC environments, and EV settings as a means of monitoring and optimizing energy demand and delivery. Nortech, on the other hand, is seeking additional funding for further testing of their ANM scheme.
ByteSnap launched a business out of its participation in the VIGIL pilot called Versinetic.
“We saw VIGIL as a great way of bootstrapping development and getting our own IP in an OCPP library,” Dunstan says. “We’ve gone on to create a bunch of other boards to make a modular smart charger.”
As a greater percentage of the world’s energy comes from renewable sources, members of the V2G Consortium also anticipate increased interest in the technology to help offset the inconsistent generation of power sources like wind or solar. Beyond the V2G Consortium, there are other early-stage projects focused on developing V2G capabilities within vehicles themselves.
However, the biggest gains will come from widespread adoption of the technology by automakers and their suppliers. Preye noted the limited availability of V2G-enabled charge points, which meant the pilot had to use chargers from a single manufacturer, possibly skewing test results.
“It’s got a lot of potential to solve problems, not only around the use of EVs loading the grid but to solve issues around the lumpiness of renewable energy generation,” Dunstan points out. “The main challenge is getting the auto makers on board to actually enable V2G in their cars.”
