GM’s Approach to Integrating Smart Plug-ins to the Smart Grid Leverages Emerging Standards and OnStar
While the ultimate vision of plug-in electric vehicles (PEV) operating as smart nodes in the smart grid offers compelling benefits for both end users and utilities, achieving that vision will require coordinated development and a staged, evolutionary implementation involving both the utility and automotive industries, according to George Bellino, GM manager of strategic programs, in a presentation at the Plug-in 2009 conference in Long Beach, California last week.
Among the basic requirements for successfully implementing smart vehicle/smart grid combination are specific, standardized requirements and solutions for vehicle-to-utility communications, and compatible methods to bridge the many gaps in the charging and communications infrastructure until North American and global standards are in place.
The emerging smart grid system is characterized by three elements, Bellino noted:
- A sensor system to determine the current state of the grid;
- An intelligent power management system to determine and to communicate the desired state of the system to the smart loads; and
- A network of smart loads with communications to report their current state and act on smart grid commands.
Plug-in electric vehicles (i.e., plug-in hybrids, extended range electric vehicles and battery electric vehicles) are smart loads, and so fall into the third element. As such, PEVs must have the ability to communicate with as well as process control signals from the smart grid—PEV integration requires smart charging.
The basic concept of smart charging integrates three elements with different communications responsibilities:
- A smart grid utility systems operation center. The operation center handles real-time rate information; TOU (time of use) rate information; critical peak pricing information; load control signals; demand response signals; and account authentication.
- The emerging automated meter interface (AMI) infrastructure (smart meter/smart outlets). These are responsible for premise identification; revenue metering; vehicle identification binding; pass through; rate information; load control information; demand response signals; and customer response.
- The smart PEV. The vehicle is responsible for communicating vehicle identification; energy desired; charging status; charger voltage; duration; demand response; customer preference; and opt-in/opt-out.
The basic intent, Bellino said, is that the vehicle—wherever it is—connect to the grid and intelligently communicate its ID, and tap into particular charging programs with the participation of the owner of the vehicle. There are a number of significant barriers to realizing this, however, including:
- Diversity in AMI protocol implementation among utilities.
- Legacy and near-term production PEVs with no communications ability.
- Interconnectivity and communications with Home Area Networks and Energy Management Systems.
- No communications connectivity between PEV and utility in Non-AMI utility environments. 85% of United States will not have AMI implemented for at least another 10 to 15 years, Bellino noted.
- Derivative solutions that may impact compatibility and standardization.
In other words, while the optimal configuration is to have the smart functionality in all three elements—vehicle, outlet and grid—the reality is that such a condition will be fairly rare in the near- and medium-terms.
The fundamental requirement for successfully navigating this situation will be the development and application of standards—specifically SAE J2847 and SEP 2.0, Bellino said.
SAE J2847 is an emerging automotive industry standard that will specify communication between PEVs and the grid; the ZigBee Smart Energy Profile (SEP 2.0) is an application layer utility industry standard that focuses on communications related to efficiency, usage, price, and messaging.
There has to be harmonization between SAE and SEP.—George Bellino
It will be important, Bellino noted, that any gap or derivative solutions developed by the auto and utility industries be forward compatible with the long-term direction provided in the standards. It is also important, he noted, to avoid allowing for incompatible alternatives within the standard.
|GM’s forward-compatible, standards-compliant smart charging communications solution. Source: GM. Click to enlarge.|
J2847 and SEP 2.0 support compatibility and interoperability among alternative message transport protocols—they do not specify the physical layer. This enables GM’s basic smart charging communications technology vision of a standard language that operates with optional communication transports—including the use of OnStar for a non-AMI communication path (cellular data as transport layer). (All Chevy Volts will come with OnStar.)
OnStar can provide smart charging communications using a J2847/SEP 2.0-compliant message structure directly between the PEV and the utility systems operations center in situations where there is no AMI communication path.
OnStar also offers the potential to aggregate and report aggregate charging data. Bellino said that GM is reviewing the technical and business requirements for an enhanced data mining capability that will be of potential value to AMI utilities.
“This market is going to grow slowly,” said Sunil Chhaya, of the Electric Power Research Institute (EPRI) in another presentation at Plug-in 2009.
Automotive and AMI technology implementation has a lead time of 3-5 years for the maturation of standards, suppliers, technology and capacity. The challenge is, if standards are not ready today, what do the OEMs design to, knowing that the life of plug-ins introduced next year will overlap with mature [future] standards?
The answer is to use a forward compatible transport layer...and a version-controlled application layer.—Sunil Chhaya
Report to NIST on the Smart Grid Interoperability Standards Roadmap (EPRI, June 2009)
NIST Smart Grid Standards Roadmap (George W. Arnold, Eng.Sc.D. National Coordinator for Smart Grid Interoperability, NIST, 19 July 2009)