EV Charging Goes Bi-Directional

How Reversible Energy Flow Is Helping Meet Demand

Image Source: Jaume Pera/Stock.adobe.com; generated with AI)

By Adam Kimmel for Mouser Electronics

Published January 19, 2024

Global electric vehicle (EV) sales increased from three million units in 2020 to a projected fourteen million units by the end of 2023, an increase of 367 percent over that time period.^[1] All regions contributed to the change, with China leading the way, the EU remaining constant, and the US picking up share. EVs could account for 18 percent of total car sales in 2023, avoiding five million barrels of oil—per day—by 2030 if these trends continue. Figure 1 illustrates the smooth, exponential curve EV sales have experienced since 2016.

Figure 1:

Global EV sales by region by year. (Source: IEA 2023; Electric car sales, 2016-2023, https://www.iea.org/data-and-statistics/charts/electric-car-sales-2016-2023, License: CC BY 4.0.)

There are significant tailwinds propelling this growth:

• Battery manufacturing capacity increase for 2030, fulfilling the EV battery demand requirement for Net Zero in the segment
• Innovation of new battery chemistries to ease material supply pressure and address range, risk, and performance opportunities with legacy technology
• Continued expansion in the charging infrastructure to support consumer adoption
• Policy and investment growth, highlighting the partnership between regional governments and private industry to deliver EVs

Electrification is here to stay, as higher vehicle production rates will further reduce costs to consumers. In addition, lower costs will increase sales, which will accelerate the demand needed to fund highly capitalized automation. This trend will significantly decrease consumer costs, making EVs affordable for the mass market. A remaining headwind, opponents are quick to point out, is that charging still prevents some consumers from making the jump to an EV, citing range anxiety and lifestyle change due to excessive charging time.

Current EV Charging Methods

Today, most EVs draw power from existing power sources to charge; many of these sources are non-renewable (e.g., fossil fuels, coal). To maintain a carbon-neutral or -negative status and address the impact of climate change, the Sixth Assessment Report^[2] from the United Nations Intergovernmental Panel on Climate Change (IPCC) strongly recommends renewable energy sources. If the charging infrastructure were to move to incorporate renewable energy supplies (e.g., solar, wind, biomass, hydroelectric), there are natural limitations to the availability and reliability of that power. Nevertheless, EVs are a significant avenue toward decarbonizing the transportation sector. As a result, it will be necessary for the industry to answer questions like the following:

• What happens to solar energy at night or during cloudy days?
• What if the wind isn't blowing regularly or hard enough?
• Can the conversion of renewable energy to electrical be fully carbon-free?

To answer these critical questions, we must review the current methods for sourcing the grid's electricity and what will be needed to charge EVs.

Global Power Sourcing

Power-sourcing of the primary electrical grid varies significantly from region to region. Within a given geographic area, the proximity of energy sources can also differ. Table 1 offers a high-level view of how the world produces its energy and provides a two-year trend view between 2020 and 2022.^[3]

Table 1: How the World Produces Its Energy, 2020–2022. (Source: Mouser Electronics/Author with data from Our World in Data)

As the table illustrates:

• Coal still dominates the global landscape but is slowing (although its percentage share went marginally up).
• Gas is second and continues the flat-to-downward trend observed in 2020.
• Renewables are a small but gaining faction, with wind and solar continuing exponential gains at the same rate.
• Hydropower finally appears to have flattened.
• Bioenergy is an emerging source as well, showing linear gains.

According to Our World in Data, the world gets about 39 percent of its electricity from low-carbon sources, which include nuclear, bioenergy, and other renewable sources. Renewable energy sources such as hydropower, wind, and solar comprise 30 percent of global energy production and generally continue to increase sharply in the case of wind and solar,.

The increasing shift to renewable power has been welcomed and is needed, as the global demand for electricity is projected to rise at rates above 75 percent from 2022 to 2050.^[4] Increased population and the movement to electrification are driving this trend. However, another critical factor for higher electricity demand is increasing pressure to decrease reliance on fossil fuels—still providing nearly two-thirds of global electricity—in favor of more climate-friendly renewables.

However, such a dramatic increase in electrification will strain grid capacities and add the challenge of managing renewable storage while increasing loads at peak charging times. These hurdles create the opportunity for innovative technologies to alleviate the impact of surging demand on charging infrastructure. One such innovation reverses the direction of electricity between the grid and an EV: vehicle-to-grid technology.

What Is Vehicle-to-Grid?

Vehicle-to-grid (V2G) technology works by having easily portable energy storage units decentralized from power stations, enabling a two-way energy transfer between the grid and a vehicle. Using the electricity carried in every EV on the road can help flex power back to the grid when needed while leveraging off-grid charging capability. V2G works on the premise that many consumers use only a fraction of their battery capacity; this approach optimizes battery utilization to get more out of the same components.

The user's EV home charger is the infrastructure that gives the charge back to the grid or powers homes. The same electrical pathways that connect to the grid to move energy to the battery are used to collect excess energy from the battery and provide it to the grid—at fair market or negotiated prices. Demand and energy availability will dictate the direction of the energy—to or from the electrical grid. This structure provides an on-demand energy provision while saving excess energy for later use.

V2G optimizes the way society produces, uses, and transports electricity. Vehicle batteries would network with a remote energy storage solution to increase electricity supply during peak demand and optimize when the vehicles charge (at night, during low demand). In addition, V2G lets vehicle owners more actively manage their energy usage by providing data about their energy usage habits, which can encourage them to optimize behaviors to lower their costs. It also opens an income stream for consumers through the ability to sell their electricity back to the grid. Reducing the total cost of ownership of EVs is one of the fundamental market drivers to increase global adoption.

Furthermore, having V2G electricity data for when vehicles are using and producing electricity also aids utility companies in optimizing their energy production based on trends in demand and consumer behavior. This benefit will reduce costs for both energy providers and consumers.

A societal benefit is that V2G provides access to remote energy storage in locations that previously lacked such storage. Storing, regulating, and providing on-demand power to either the grid or a vehicle are some of the most disruptive benefits of integrating the vehicle's electric use into the grid.

Green EV charging uses solar panels that allow photons to excite electrons, creating an electrical current flowing into the vehicle and filling the battery's charge capacity. Integrating intermittent solar power with battery storage is a natural way to smooth the electricity supply capacity for on-demand use. Once fully charged, the battery can be used how and wherever needed—in the vehicle or at home. V2G solves the storage challenge for renewable energy, one of the main remaining challenges to the increased application of renewable energy.

Remaining Challenges and Barriers to Adoption

One way that electric power is beneficial is through efficiency. Batteries convert chemical energy directly to electrical energy, avoiding the need to combust fuel—a step that reduces thermal efficiency by around 30 percent. V2G represents a beneficial solution to both mitigate renewable energy’s intermittency and reduce strain on the power grid as electricity demand skyrockets. But it still must overcome several remaining challenges before EVs make practical sense for most consumers.

A compelling secondary benefit is the creation of a new renewable energy source: harvested energy from V2G. Adding the ability to direct energy to and from the grid treats the energy more like a currency, transferrable between a source and an application.

There is also a development opportunity for DC chargers that can integrate with the vehicle, along with the need to have appropriately sized converters to move from AC to DC power for energy transfer. While existing AC-to-DC converters offer up to 95 percent efficiency, many products continue to provide efficiency only in the 80–90 percent range. Therefore, power converters need to be tailored to the battery size in EVs, and the industry must work to increase conversion efficiency, which directly increases the electrical output.

Conclusion

Renewable-energy-powered EVs are essential to achieving renewable grid goals through V2G. This approach leverages the availability of green solar power to fill an EV battery's capacity and transfer it to and from the electrical grid, delivering power where it is most needed. V2G provides a flexible energy storage option, addressing a significant barrier to renewable energy while mitigating the intermittent power availability that accompanies wind and solar energy sources. V2G technology also ties energy availability to consumer demand, providing a just-in-time approach to energy supply that actively enrolls the user and provides the most efficient and cost-effective approach for both energy providers and consumers.

References

[1]

IEA, Electric car sales, 2016-2023, IEA, Paris https://www.iea.org/data-and-statistics/charts/electric-car-sales-2016-2023, IEA. License: CC BY 4.0