Electric Vehicles

Report outlines feasibility, benefits of controlling EV load

Using a new communication protocol, utilities can essentially eliminate electric vehicle charging during peak periods without affecting the needs of drivers while saving them money, according to a report on a pilot project funded by the California Energy Commission.

If not managed carefully, the growing number of plug-in EVs can stress local distribution circuits, requiring expensive transformer or distribution circuit upgrades, ChargePoint, which conducted the pilot study, said in the report,Next-Generation Grid Communications for Residential Plug-in Electric Vehicles.”

Residential EV participation in grid stabilization efforts requires detailed data collection, coordinated charging by charging stations owned by different parties and a real-time understanding of each vehicle’s state of charge, ChargePoint, an EV charger company, said in the Jan. 25 report, which outlined the results of the pilot project.

Currently, there aren’t adequate interfaces to facilitate communication between utilities, charging stations and residential customers, the report said.

However, under the pilot project, ChargePoint used the International Organization for Standardization/International Electrotechnical Commission 15118 standard to develop cloud-to-cloud “open automated demand response” communication so a consumer can receive daily rate schedules from a utility.

The pilot, which included 1,005 charging events, tested the ability of ChargePoint chargers to receive price signals from San Diego Gas & Electric as well as ChargePoint’s ability to send opt-out/opt-in notifications to the 27 drivers participating in the project.

It also tested ChargePoint’s ability to receive and implement the drivers’ preferences and the company’s ability to send charging schedules to the charging stations.

During the project, ChargePoint was able to get information on individual chargers, including time of charge, duration of charge, power level used, total energy used and customers’ daily opt-in or opt-out decisions.

“This information, coupled with the addresses and local distribution grid data, provides the utility significant insight into these potentially controllable PEV loads,” ChargePoint said, noting it could manage the chargers as a group.

Lawrence Berkeley National Laboratory, a project partner, used software to assess the vehicle-grid integration effects on the wider electric grid and the benefits of load control for when people have more EVs.

By coordinating charging schedules, LBNL found that EV charging loads can be nearly eliminated during peak demand periods without inconveniencing drivers.

“This suggests that given the appropriate technology – specifically networked Level 2 charging stations – PEVs can be highly flexible loads and conducive for participation in load control programs,” the report said. “This load flexibility can reduce the stress on the grid and be used to defer transformer or distribution level upgrades by managing the peak load in an area.”

Also, customers can save money because controlled charging can make sure EV batteries are being recharged when electricity prices are lowest. In the study, customers paid 28.6 cents per kilowatt-hour when their charges were uncontrolled. When the charging times were set via the communications protocol, they paid 15.6 cents/kWh.

“Ultimately, this controlled charging strategy is a win-win situation as the drivers are able to complete all their charging needs with minimal behavior change and at a lower cost, while the utility is able to achieve load shifting that better supports grid operations,” the report said.

ChargePoint used the “smart charging” feature of the 15118 communications protocol, which allows the EV to specify the amount of energy requested and lets the vehicle’s supply equipment to specify the power levels and relative cost of energy for the charging session.

The tested EV could change its power draw based on the varying levels of available power using the 15118 data element, according to the report.

“This charging adjustment indicates that using the 15118 standard allows for a more sophisticated method of data exchange and communication between the grid, charger, and vehicle,” ChargePoint said.

ChargePoint intends to offer a 15118 enabled-charger when vehicles using the standard become available on the market.

The report is available here.