How the Smart Grid is becoming smarter
The Smart Energy Profile (SEP) specification
The Smart Energy Profile 2.0 (SEP 2.0) specification is designed to enable a wide variety of devices that generate, distribute, and consume energy to communicate with each other over IP networks. Unlike higher level protocols, such as OpenADR, SEP 2.0 includes specifications on network insertion and management that relieves the user from having to perform any network administrative functions. This makes SEP 2.0 ideally suited for the final step of energy management to the consumer device.
The intent of SEP 2.0 is to configure all devices as peers, and any client/server relationships are built upon the SEP 2.0 foundation. This enables devices to enter and exit a network in an unplanned fashion without causing operational interruption to any of the other devices in the network. To accomplish this, SEP 2.0 uses zero-configuration networking, such as mDNS and DNS-SD. This is ideally suited for devices in the residence where networking expertise may not be available.
Other smart energy standards, such as BACnet, don’t approach the issue of network connection and administration. Such specifications target commercial, industrial, and other professional environments where the implementation of the underlying communication path is assumed to be implemented by technically knowledgeable individuals. These specifications are also more tightly focused on power utility operation or building automation outside of the residence, whereas SEP 2.0 is a far more general protocol intended to work in all environments, especially residential.
The emergence of an OpenADR/SEP 2.0 combination
A hybrid OpenADR/SEP 2.0 solution is evolving where utilities are unilaterally implementing OpenADR to solve their immediate power management requirements. This allows them to bring an intelligent grid online quickly without waiting for a far more gradual acceptance of residential protocols. This also brings a truly ‘smart meter’ closer to the periphery of the home residence.
With the implementation of SEP 2.0, residential devices/appliances are able to communicate with each other, thus minimizing simultaneous in-rush of power demand from competing devices. In addition to staggering device/appliance start-up demands, home appliances with high thermal capacity, such as water heaters, clothes dryers, and stove and oven heating elements, can switch off temporarily to reduce current draw when a heating or cooling system is starting its compressor. Such pauses will not be noticed by the user of the interrupted appliance.
Further, once OpenADR and SEP 2.0 become even more integrated, load leveling will be managed across residences to even out current loads through local distribution transformers, which will help balance the instantaneous loads across polyphase transport lines.
Requirements for SEP enabled devices. It’s imperative that SEP-enabled devices include software to support such activities as fast booting and power management capabilities, including the ability to easily switch to back-up battery in case of a power outage. Embedded systems within these types of smart devices often contain limited memory resources, meaning the software that powers them must have a small yet highly optimized footprint.
The importance of a real-time OS
A real-time operating system (RTOS) is the preferred operating system for SEP 2.0 devices because of its deterministic behavior and its ability to support the sophisticated functionality required by the SEP 2.0 specifications (Figure 3). An RTOS can provide for all the must-have capabilities within a smart device such as instant ON and stay ON; real-time responsiveness; a wide range of peripheral support; TCP/IP networking; graphics support for the UI; and network security.
Figure 3: Mentor Graphics Nucleus is a good example of an RTOS that meets all the smart grid and SEP 2.0 specifications with a variety of integrated power management services and process model capabilities.
The abilities offered by SEP 2.0 coupled with OpenADR offer a fine grain of control for the residential user who wants to take a more proactive role in control of power use in the home. This hybrid approach will no doubt provide the necessary transition that allows for the gradual increase of power consumption efficiency, while addressing the looming power shortage and at the same time allowing home owners to maintain their current standard of living.
Andrew Caples is a Product Marketing Manager for the Embedded Software Division (ESD) of Mentor Graphics. He has over 20 years of experience in start-ups and fortune 500 high tech companies and has served in a variety of roles ranging from technical marketing to sales management. He has a B.S. in Electrical and Computer Engineering from California Polytechnic University. His current responsibilities include product management for the Nucleus Real Time Operating System.
Rich Rejmaniak is a Technical Marketing Engineer for the Embedded Software Division (ESD) of Mentor Graphics. He has been an engineer for over 30 years, with the last 20 years spent as a Field Applications Engineer for various semiconductor and software companies. Rich specializes in the hardware/software boundary issues in embedded systems.