As electric vehicle (EV) ownership expands in the coming decade, electric utilities have their work cut out for them. EVs will not only be in use at private residences, but also for publicly and privately owned fleets of light-duty and heavy-duty vehicles. New infrastructure will be required to support commercial EV charging stations for both individual EVs and fleets; EV chargers must be enhanced to better work with the electric energy grid; and electric utilities must consider infrastructure and energy cost recovery.
EVs also present opportunities for electric utilities, including grid support during underfrequency events and climate-friendly disaster recovery efforts. For electric utilities to embrace these benefits, they must begin working to prepare the grid for expanded EV ownership today. Read on to learn specific ideas that electric utilities can use to create an EV preparedness strategy so that they are ready for the widespread integration of EVs.
EV Grid Support
Bidirectional EV chargers can support the grid during overfrequency, underfrequency, and low voltage events. These events are more likely to occur as the number of distributed renewable energy resources continues to expand. Level 2 chargers are ideal for grid support because EVs tend to be connected to them for longer periods of time. Level 2 chargers can be programmed to transition between charge mode, standby mode, and grid support mode depending on grid conditions.
When grid frequency is between 59.98 hertz and 60.02 hertz, Level 2 chargers will operate in the normal mode, either charge or standby, depending on the battery’s charge level and predetermined settings. When frequency is between 59.92 hertz and 59.98 hertz, Level 2 chargers will transition to or remain in standby mode. When frequency rises above 60.02 hertz, Level 2 chargers will recognize overfrequency on the grid, and transition to charge mode regardless of normal settings. This is a method of supporting the grid by removing excess energy when it is available.
On the other hand, when frequency is below 59.92 hertz, Level 2 chargers recognize an underfrequency event, and will transition to the grid support mode. The EV battery will discharge its stored energy to the grid until the charge drops to 50% of capacity, when grid support mode will end and the battery will transition to standby mode, even if the underfrequency event persists. In most cases of underfrequency events, additional energy sources can be brought online within 10 minutes, meaning EV batteries would provide critical support for only about 10 minutes, preventing a cascading depression in energy that could lead to a wide area blackout. Using EVs to support the electric energy grid can eliminate the standby energy costs that electric utilities refer to as spinning reserve.
Though rare, a wide area undervoltage event could have costly consequences, including a wide area blackout in a major metropolitan area or even across state lines. The Washington, D.C., Area Low-Voltage Disturbance, which occurred on April 7, 2015, is an example of a disturbance that would have been worse had it occurred in August when air conditioning load is at its peak. If light rail parking lots within the Washington, D.C., metropolitan area were equipped with Level 2 smart chargers that were connected to EVs at the time of this event, recovery from this low voltage disturbance would have been assured. More on partnering with light rail systems below.
Grid support mode should also be a feature of residential Level 2 chargers. EV owners who keep their vehicles connected to the charger anytime they are at home could provide the grid with essential energy during grid disturbances.
Renewable Energy Considerations
In the early days of electric vehicles, electric utilities recommended that EVs be charged during off peak hours, such as late at night. However, most renewable energy is produced during daylight hours. With the rapid expansion of renewal energy sources, excess energy is available during April, May, September, and other times when solar panels and wind turbines produce more energy than consumers demand. Rather than turn solar panels off and feather wind turbines, EV chargers should be designed to activate charge mode whenever excess energy is available. When less energy is available, EV chargers will then shift to standby mode.
Maximize Daytime Energy Availability
To maximize availability of EV chargers during daylight hours, when EV owners are often away from their residential chargers, electric utilities could develop partnerships with transit authorities, specifically owners of light rail systems. A light rail parking lot can be equipped with 300 Level 2, eight-hour, 10 KWH next generation chargers that EV owners connect to when they park their car on the morning commute. Next generation chargers will detect EV battery charge level and energy availability of the grid and adjust the charger function accordingly.
By partnering with light rail transit authorities, far fewer additional electric utility facilities will be needed to charge EV batteries. This is because the electric load on light rail facilities is intermittent, and the electric energy connection can be used to charge EVs when trains are not using the facilities. Many major cities across the US have existing light rail transit systems with large parking lots for commuters.
Parking garages also present an opportunity for partnership with electric utilities. By installing only three Level 3, 30-minute, 100 KWH chargers, and providing valet service, a parking garage can charge 300 EVs in one 8-hour workday. This also creates job opportunities for valet drivers. Similar arrangements can be established at shopping centers, hospitals, or anywhere drivers park for 30 minutes or more at one time.
To maximize the effectiveness of Level 2 chargers in parking lots, EV owners should be charged for dwell time (similar to demurrage charges), as well as for energy, when they are parked over a maximum number of hours. Commuters would not be charged for dwell time between the hours of 7 am and 6 pm at light rail and transit center parking lots. Outside of these hours, and at non-commuter parking lots, dwell time should be factored into EV charging prices. Dwell time charges will increase the number of EVs that can be accommodated.
Commercial and Fleet EV Charging, Energy Cost Recovery, and more
For more information, check out my full length whitepaper by the same title, accessible on my website www.prescientelectric.com/whitepapers. Or email Alyssa Sleva-Horine at [email protected] to receive a copy.