Impact of EV chargers on grid
Although the growth of EVs and their associated charging stations has a positive impact on the environment and the economic viability of countries, it can have detrimental effects on the power grid. These effects need to be understood before moving to possible remedies or ways to mitigate them. For instance, the high charging loads associated with fast charging stations result in:
- Increased peak demand
- Reduced reserve margins
- Voltage instability
- Reliability problems
Distribution companies should consider installing fast charging stations on strong buses to prevent potential breakdowns and reduce the impact on the performance parameters of the grid, especially if the number of charging stations are increased. An upgrade of the system is required if you intend to go beyond recommended numbers.
If the fast charging stations are installed on weak buses, the smooth operation of the system can be curtailed, leading to sharp voltage drops and sharply increasing power loss. This can incur a higher amount of economic loss. It is interesting to note that weak buses can handle slow charging stations.
It is necessary that utilities identify the strength of buses and allow installation of chargers accordingly. It has been found that the distribution of fast charging stations between multiple buses is more suited as compared to placing multiple charging stations on a single bus. In one case, it was observed that placement of even one fast charging station at a weak bus incurred approximately US$1.4 million in economic loss.
It is important to note the levels of power transmission are as follows:
Generation → High Voltage → Medium Voltage → Low Voltage → Homes
Residential or commercial users get power directly from low voltage, where this low voltage side is the most vulnerable one. There are fast charging solutions, for instance, Fastned, which installs fast charging stations at the medium voltage side that can bear more load compared to the low voltage side of the grid.
Solutions to mitigate effects on the grid
Smart charging
Smart charging is another remedy to curtail the impact of EV charging stations on the grid. It enables us to intelligently manage EV charging without overloading or destabilizing the grid.
It works by opening pathways, enabling utility companies and charging operators to communicate with each other, optimizing the charging process. Smart chargers increase or decrease the power provided to the EV depending on the load on the grid. EVs cannot simply plug in and extract as much energy as they want in smart charging. This technology provides a network operator the ability to adjust the flow of energy into EVs and this, in turn, benefits consumers because it enhances the reliability of the grid.
Smart charging has three main features:
- Power sharing
- Power boost
- Dynamic power sharing
It is a one-way process and is essential for the increased number of EVs in the market and to make an effective transition from ICE-powered vehicles to EVs, avoiding chaotic disruption.
Vehicle-to-grid integration
Vehicle-to-grid integration (V2G) is a technology that enables transmission of power from the battery of an EV back to the grid. The idea behind V2G is similar to smart charging but allows the grid to control the charging of the EV, increasing or decreasing the charge per the grid's requirement. In addition, it enables the charged power stored in the battery to be withdrawn and transmitted back to the grid to balance fluctuations in energy production and consumption.
V2G enhances the grid's ability to balance itself, which will come in handy with the increase in the amount of solar and wind energy coming online. Without V2G, energy will have to be brought back from reserve power plants situated at long distances. This will increase electricity tariffs because initiating reserve plants not only takes time, but the process is also costly. Localized balancing of the grid is what V2G provides, potentially increasing stability and reducing losses.
EV charging stations (EVSE) with storage
EVSE with storage is another method to mitigate the effects of EV charging stations on the electricity grid. Although the growth of the EV market is a welcoming change, it will also mean that the power sector will be required to add generation, transmission, and distribution capacity to meet the added demand, especially during peak hours. This will give a rise to pollution levels coming from these power plants.
Peak time is when maximum power draw from the grid occurs. This issue has been under great focus of legislators, policymakers, regulators, and utilities on how to deal with the added demand that charging of EVs during peak times will add. There are conventional responses, as discussed previously, but there is an alternative response to it as well.
One possible solution requires installing distributed storage at or near EV charging stations. Storage is charged during off-peak hours with low-priced off-peak energy and can be served to EV owners during peak hours. This would satisfy customers and provide a smooth demand curve to utilities without having to add additional capacity.
Another benefit would be to assist with distributed storage as EV charging could become a part of the strategy to integrate distributed PVs and enhance service reliability in the area.
Microgrid ecosystem
To further enhance the capability of the grid to manage an increase in demand during peak hours, we look toward the development of a microgrid ecosystem. Schneider Electric defines a microgrid ecosystem as a locally interconnected system within clearly defined electrical boundaries:
- Incorporates loads and decentralized energy resources, including storage.
- Multiple energy sources.
- Can be grid connected or be off grid.
- A single entity with its own independent control in both modes.
- Power can range from several kilowatts to multiple megawatts with a voltage range up to megavolts.
Energy management systems are put in place to allow clean energy, for instance, from solar power to be stored in on-site batteries, so EVs can still be charged when electricity tariffs are higher during peak hours. It will be difficult to incorporate such infrastructure in urban areas, so it opens possibilities for installation of EV charging stations in rather remote areas, for instance, intercity roads or in smaller, less congested towns, where upgrading of the network is not economically viable.
Conclusion
With the increase in EVs around the world, the potential for revenue also grows, inciting a wide range of players to tap into that potential and experiment with the overlapping business models. Key players in this regard are utility companies.
Utility companies globally are exploring ways to provide EV charging to customers because of the various opportunities attached with it. Regulated transmission companies, which earn a return on allowed investments, may see EV charging as a way to boost long-term revenue. Power companies with generation infrastructure may see an opportunity in rising demands.
Haphazard installation of EV charging stations, especially fast charging ones, can be destabilizing for the power grid, but with a little planning and modern solutions (that is, smart charging, V2G), these effects can be mitigated.
Utility companies are key players in this regard, and they need to prepare for EV uptake beforehand. The primary focus should be on identification of weak and strong buses in their systems followed by potential reconfiguration and business models. Some utilities may see EV charging as a way to improve grid operation and better use of grid infrastructure with demand response, whereas others may see branding and image building potential.
