ASHRAE Journal - November 2011 - B27

is, utility to customer) demand response programs, serving as a second important input to the EI Technical Committee. The EI architecture is very simple, reduced to service interactions between two parties. A party can be a facility EMS or device, demand response provider, market operator, distribution system operator, microgrid, or any other participant Figure 3: Transaction process in energy interoperation. in a DR event or market transactions of energy. Parties may participate in many interactions concurrently as well as over time. In theory, any party can transact with any other party subject to applicable regulatory restrictions. In practice, markets will establish interactions between parties based on regulations, economics, credit, locations, and other factors. Figure 4 presents this architecture from the EI Event interaction perspective. This ﬁgure introduces the notation of Virtual Top Node (VTN) and Virtual End Node (VEN), the two abstract parties in the DR event interaction. The VTN is Figure 4: Directed graph of example demand response interactions. the node coordinating a response, and the VEN is the responding node. In Figure 4, certain parties (B, E, and Feedback service (EiFeedback), which communicates inforG) act as both VTN and VEN. This directed graph with arrows mation about the state of the resources, and the Status service from VTN to its VENs could model a reliability DR event ini- (EiStatus), which communicates information about the state of tiated by an ISO (at A) who would invoke an operation on its an Event. Apart from DR event interactions, there is a separate second level VENs B and E, which could be aggregators. The set of transactive services for party registration, quotes, tenders second level VTN B in turn invokes the same service on its (bids and offers), transactions, and delivery. VENs F, G, and H, who might represent industrial parks with EI was developed on the principles of loosely coupled intermultiple facilities or a company headquarters with facilities in actions at a clearly deﬁned interface (the ESI), and composition many different geographical areas, who then invoke the same of standards, as reﬂected in the Service Oriented Architecture12 operation on their VENs. Each interaction can have its own se- approach. Different interactions require different choices for curity and reliability composed as needed—the requirements security, privacy, and reliability. EI deﬁnes only the core inforvary for speciﬁc interactions. Figure 4 does not mean to imply mation exchanges and services; there is no optionality related a hierarchy, since a customer EMS could be the VEN for a DR to security or reliability in EI. event message, and at the same time be the VTN for a DR reEnergy Interoperation is the NIST/SGIP-recommended and source bid to market. supported national standard for demand response. This stanDifferent EI services provide for the communication of DR dard for DR signaling and market interactions enables: event details, including both simple and more complex sched• Effective response to price signals and DR events; ules. In addition to the EI Event service (EiEvent), there are • Trading of load curtailment and distributed generation; and supporting services for DR program enrollment (EiEnroll), • An EMS vendor to sell EI-“speaking” products that allow facommunication of schedule constraints (EiAvail) and opting cility systems to interact with any utility (or other service provider) out of events (EiOpt). There are two other DR services: the implementing EI without custom programming of the interface.

ASHRAE’s Role in Smart Grid
OASIS Energy Interoperation is the key cross-domain DR and market transaction standard. ASHRAE members have been actively participating in the SGIP process: discussing the nature of the ESI and developing the standards framework at the customer interface to the grid. ASHRAE is developing two key standards for Smart Grid: ASHRAE Standard 201, Facility Smart Grid Information Model
November 2011

(discussed in an accompanying article in this issue), and ASHRAE Standard 135, BACnet. In essence, the Standard 201 information model incorporates the Energy Interoperation DR event and EMIX pricing models to address energy interactions within the customer domain as well as across the ESI. BACnet then uses that same information model and provides tools for enabling facility energy management for demand response. A future article will address recent advances within BACnet for Smart Grid.
B27

B A C n e t ® To d a y & t h e S m a r t G r i d | A S u p p l e m e n t t o A S H R A E J o u r n a l

ASHRAE Journal - November 2011

Table of Contents for the Digital Edition of ASHRAE Journal - November 2011