A fleet of 16 million electric vehicles (EVs) consumes roughly 30 TWh of electricity per year - the equivalent of all the electricity generated in Ireland. That’s according to the International Energy Agency (IEA), which also predicted the number of EVs on the world’s roads to reach 145 million by 2030. If those predictions come true, that’s 270 Irelands worth of energy.

Even if the actual number of EVs totals half of that, the grid will be hard-pressed to meet these vehicles’ energy requirements while transitioning to renewables.

As a key driver of the increase in electricity demand, an EV could also offer a reprieve. In the ever-evolving landscape of e-mobility and renewable energy integration, innovative ideas are emerging about how to use an EV for more than travel.

Enabled by smarter grids, EVs are expected to support the grid through several emerging technologies. Amongst these are Vehicle-to-Grid (V2G) and Vehicle-to-Home (V2H).

Yes, the EV serves to transport people and cargo. However, it is in essence a large battery on wheels, and its energy can be leveraged wherever on-demand electrical storage is needed.

Typically, when the EV isn’t in use, it is idling in a driveway or parking spot, likely connected to a charger. In periods of high demand yet low supply, there is the potential for a connected EV to distribute electrical power back into the energy grid, powering its neighborhood or even remote villages with its reserve of electricity. This exemplifies V2G technology.

On a household level, the EV might prove to be a valuable backup and reserve. During periods of blackout, which in some places is becoming more common either due to extreme weather or ebbs in renewable energy supply, the EV battery may be useful for powering refrigerators, heating systems or charging phones. This represents V2H technology.

Practical differences between V2G and V2H charging

Thus far, V2G charging has garnered the greatest interest. The technology has captured widespread attention for its potential to harness the energy stored in EV batteries to balance and stabilize the electricity grid. For example, electric car owners can charge their vehicles during periods of low energy demand at off-peak rates and sell the stored energy back to the grid during periods of peak demand, using the income to offset the costs incurred in installing the bi-directional system.

For energy suppliers, V2G acts as a cost-effective, decentralized virtual energy grid that in times of high demand can add energy through smart management without the capital expenditure typically associated with grid energy storage. Thus, when aggregated across many EVs, V2G offers an electricity power supplier access to on-demand power and active power regulation. At the same time, mass energy storage facilitates the blending of variable renewable energy sources into the grid, load balancing, and current harmonic filtering. V2G also enables ancillary services, such as voltage and frequency control.

V2H technology, on the other hand, enables an EV capable of bi-directional charging to supply power to a home or building during an outage, or as an additional power source. It allows the vehicle to act as a temporary backup power supply, providing electricity for essential appliances and systems.

This allows the EV to function as a localized household battery system and helps increase self-sufficiency, especially when combined with rooftop solar. V2H can also reduce energy costs, helping to offset the initial investment in the EV and the supporting V2H technology. However, the most important benefit of V2H is its ability to supply backup power to the home or building during a blackout.

While both V2H and V2G present exciting opportunities to optimize energy usage, reduce costs, and enhance grid reliability, V2H faces fewer barriers to rapid widespread implementation.

Why V2H will likely be first

While both V2G and V2H face similar challenges, V2G faces additional obstacles arising from its direct access to the wider electricity grid.

Thus, the first requirement shared by both V2H and V2G is that the EV supports bi-directional charging, which enables the vehicle battery to receive energy and discharge energy to a destination other than the vehicle itself. While it is not yet common for EVs to be equipped with bi-directional charging, each year more models are being released with this capability. Some EV manufacturers even offer one-stop-shop packages that include all the components needed for V2H, including solar panels.

Furthermore, for implementation, V2H requires additional hardware such as a smart energy meter (CT meter) and fixed bi-directional charger (similar to current home chargers). The CT meter is used to monitor energy flow and has to be installed at the main grid connection point.

When the system detects a demand for grid energy by a home or building, it signals the bidirectional EV charger connected to the vehicle to discharge an equal amount. This is controlled by way of a link - using the communications protocols ISO 15118 and OCPP 2.0.1 - between the charger, the vehicle and the EV charging management platform.

V2G, while requiring similar systems to V2H, also has to meet standards that are complex as they involve regulating the safety, power and electrical requirements when discharging energy into the grid.

An EV with bi-directional charging capability cannot simply be allowed to connect to the grid and start feeding power into the network without having approval from the operator. For it to work, the grid operator must be able to manage the bidirectional charger remotely and control the amount of energy injected into the grid. This remote management is typically done via a Virtual Power Plant program. However, the lack of a standard protocol for V2G communication and grid interaction is making it difficult for different V2G systems to interoperate.

For V2G to work, it has to be implemented across a variety of platforms at low cost. Smart charging and payment for charging or injecting power into the grid have to be uniform. This requires policymakers to formulate interoperability standards that support the build-out of charging infrastructures.

These standards are still under development and are similar to solar inverter standards and requirements. For instance: UL9741 is a proposed safety standard for bidirectional EV charging system equipment, built around the UL1741 and IEEE1547 standard for interconnecting distributed energy resources with electrical power systems.

Another norm that directly impacts operability and the rollout of bi-directional charging is the standard related to the Combined Charging System (CCS). ISO 15118 is the key document for the communication, and without finalization, onboard charger makers are unwilling to commit to bidirectional designs.

This standard specifies the terms and definitions, general requirements, and use-cases for conductive and wireless two-way charging, which raises another issue.

All the projects are based around bidirectional cable connections, although the standards are now approved for commercial vehicles such as buses that can be powered by an overhead pantograph. However, with wireless charging just entering the market, the standards will have to be adapted to also support bidirectional wireless charging.

Even though V2G trials are taking place, and industry and governments are working hard on developing and finalizing standards to ensure V2G technology can safely integrate with grid networks worldwide, there is still a lot of work to be done before V2G will be ready for mass adoption.

A smarter grid done right, in seamless communication with connected EVs, will completely change the way electric energy is stored, managed and distributed, opening the door to a bi-directional charging economy. Infusing the grid with the intelligence of a modern data network, EVs can become a key part of any distributed energy network, oscillating between taking from and replenishing the grid as needed.

However, the complexity of the standards and regulations required to ensure safe bi-directional charging to and from the grid implies that the greater benefit of V2G is likely to be realized after the somewhat simpler implementation of V2H.

About the author

Peter Els is a South Africa-based former automotive engineer. This includes time with Nissan South Africa’s Product Development Division, Daimler Chrysler, Toyota, Fiat/Alfa Romeo, Beijing Automotive Works (BAW), as well as tier-one suppliers Robert Bosch and Pi Shurlok. After consulting to the local industry for 15 years, Els has ventured into technical writing and journalism about the latest trends, technologies, opportunities and threats facing the new world of mobility.