Realising the Potential of V2G EV Charging

­Vehicle-to-grid technology (V2G) – which in its most advanced form, enables a bidirectional flow of energy from the grid to an electric car and back again – holds the potential to become a hugely effective means of balancing electricity demand and reducing the risk of power outages while allowing the individual to participate in energy markets by selling excess energy back to the grid. Encouraging the grid's further electrification could also become a critical tool on the route to net zero.

Indeed, V2G is set to become big business – and fast. The latest research shows that the global V2G market, worth around $1.7 billion at the start of the decade, is projected to reach $15.03 billion by 2031, growing at an impressive Compound Annual Growth Rate of 25.3%. Much of this expansion will be based on the bidirectional segment, which is expected to record the fastest growth during the forecast period.

So why is V2G in the ascendency? The reasons coalesce around two key areas – regulation and technology. In terms of the former, there is increased policy support for V2G globally, as governments worldwide recognise its potential to support energy integration, grid stability, and reduce emissions. In the UK, for instance, multi-million-pound funding programmes have been available through the Department for Transport to develop and deploy V2G, supporting trials and demonstrations in real-world settings. Similar schemes have been adopted in many other parts of the world.

However, technology has also played a critical role in the evolution of V2G, with significant advances in bi-directional charging having been achieved. At the same time, efforts have been made to encourage the standardisation of protocols for V2G systems for interoperability between EVs, charging infrastructure, and the grid. The ISO 15118 standard for communication between EVs and charging stations includes specifications for bi-directional charging, enabling secure and automated authentication, authorisation, and billing processes, and facilitating interoperability between various EVs and charging stations. Meanwhile, the CHAdeMO protocol enables V2G functionality and interoperability among CHAdeMO-compatible vehicles and infrastructure in markets such as Japan and parts of Europe.

Why V2G Holds Such Significant Promise

The scene is set, then. Interest in V2G is rapidly increasing. And now, as renewables generate a growing proportion of electricity, V2G's storage and grid-balancing capabilities could play a primary role in supporting the development of more flexible energy systems.

In simple terms, renewables' intermittency presents a challenge to utility providers. Windy conditions during the night mean that energy is often provided at the precise time that consumer demand is at its lowest. Therefore, charging electric vehicles overnight can use this renewable energy, saving car owners a significant amount of money.

However, bidirectional flow also provides significant advantages when the electricity demand is high, and the grid is under pressure. EVs plugged in at home can be used to send energy stored in batteries to the grid, helping electricity suppliers to manage peak demand. EV batteries are well-suited to be a nearly instant power source, as they are available more quickly than spinning up other power generators such as gas-powered plants. It is this kind of flexibility that makes V2G such an attractive proposition.

Technically, achieving smooth and responsive bidirectional flow is already possible. The barriers to adoption are found in other areas. Introducing bidirectional capability to an EV adds cost, which often has to be passed on to the consumer. Some EV owners have also expressed concerns that the additional charge/discharge cycles from V2G may accelerate the wear and tear on their EV's battery, reducing its lifespan.

Additionally, there are concerns about the round-trip efficiency as AC electricity from the grid is rectified to DC, stored in the car's battery, discharged from the battery, inverted back to AC again, and delivered back to the grid – with each step resulting in power losses. Charging stations for EVs typically use AC for residential and home chargers, while DC designs are increasingly common for fast chargers at roadside locations.

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There is also the debate around who should pay for the new infrastructure that supports V2G, particularly the systems required to convert between the alternating current (AC) used in the grid and the direct current (DC) used to charge and discharge the EV battery at roadside fast chargers. Power companies prefer using AC bidirectionally to add stored energy into their grids seamlessly. However, automakers are concerned about the costs of adapting vehicle electronics to meet the grid's demanding technical and safety standards.

Ultimately, regulation and legislation are likely key to more widespread adoption of V2G. In the US, for example, California congresswoman Julia Brownley recently announced the introduction of the Bidirectional Electric Vehicle Charging Act, claiming that allowing electric vehicle owners to send power back into their homes during a blackout or even back to a utility network during peak hours would enable EVs to operate as a 'mini power plant on wheels' by helping to maintain access to power during natural disasters and emergencies. Meanwhile, California's proposed Senate Bill 233 sets a deadline of 2027 for most new EVs and chargers sold in the state to support bidirectional charging. Such legislative efforts may take time, though.

Driving V2G Forward

In the meantime, the electronics and automotive industries continue to collaborate to drive forward various aspects of more effective EV charging, covering areas such as communications, security, user interface functions, and power conversion. It requires using one or more microcontrollers (MCUs) that run physical layer (PHY) and application software. Communication standards may include Wi-Fi, Bluetooth, or cellular, with devices like NXP's IW620 dual-band solution or its OL2385 RF transceiver for sub-GHz protocols.

Ensuring bidirectional charging requires robust security systems in chargers and vehicles, encompassing confidentiality and authenticity. Hardware-based security solutions, such as the NXP EdgeLock SE05x/A5000 secure element, offer easily integrated options for system designers. NXP provides EdgeLock 2GO, a fully managed cloud platform, to handle the complexity of keys and certificates.

To speed up development, NXP provides an EV charging station development platform that enables rapid prototyping and system design. This platform allows customers to swiftly load Azure RTOS-based application software onto NXP’s i.MX RT1064 crossover MCU and securely connect the simulated EV charging station to the cloud.

NXP also recently unveiled the automotive-qualified i.MX 93 family of power-optimised processors. Helping the next-generation of V2G systems to be deployed at the edge of infrastructure, the i.MX 93 is part of NXP’s EdgeVerse portfolio and offers an ideal combination of high-performance and energy efficiency. This balance is achieved through its integrated scalable Arm Cortex-A55 application core and Arm Ethos-U65 microNPU, which allow developers to build advanced machine learning (ML) applications that are more capable, cost-effective, and energy-efficient. To further streamline integration into automotive V2G systems, the i.MX 93 family supports a wide range of peripherals and connectivity options, including CAN-FD, USB and ethernet, as well as featuring NXP’s EdgeLock secure enclave.

In EV chargers, wide bandgap (WBG) semiconductors like gallium nitride (GaN) and silicon carbide (SiC) offer superior efficiency compared to silicon alternatives. This is particularly crucial. For instance, Renault and CEA recently introduced a new bidirectional charger supporting V2G, claiming a 30% reduction in energy losses during conversion thanks to the implementation of WBG materials.

A Bright Future for E2V

There is no doubt that bidirectional EV charging will become an increasingly important technology, offering substantial benefits for both utilities and end-users alike. By enabling EV batteries to receive power and feed it back into the grid, energy usage is optimised, and grid infrastructure becomes more resilient. These technical attributes enhance the flexibility of electrified energy networks and position V2G as a pivotal player in the transition towards a net-zero carbon economy.

Platforms such as the Nissan Leaf and Ford F-150 Lightning already support bidirectional charging. Meanwhile, other carmakers, including BMW, GM, and Mercedes-Benz have limited deployment or are actively involved in research projects, underscoring bidirectional E2V charging’s position as a beacon of innovation for a greener future.

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