The new ZigBee Smart Energy 2.0 (SEP2.0) ZigBee Application Profile brings with it powerful new ZigBee capabilities for smart energy metering and control networks. With its ability to transport rate, demand, and load management messages to and from networks of smart energy appliances and the “Smart Grid” across a wide variety of wired and wireless media, the profile promises to be a key element of residential energy management systems.
Capable of passing energy-related messages across a HAN, or Home Area Network, using numerous different types of wired or wireless physical media, SEP2.0 is aimed at enabling the next generation of interactive smart appliances, HVAC, lighting and energy management systems – a “Smart Grid” of energy-efficient technology.
An IP-based HAN enabled by ZigBee Smart Energy 2.0 makes it possible to manage every aspect of the energy consumption and production of a home or building, whilst moving the information around a network built entirely around the Internet Protocol and interconnected with existing networks and the Internet.
The ZigBee Smart Energy 1.0/1.1 Profile was originally developed to allow 802.15.4/ZigBee low-power wireless mesh networks to support communication between smart meters and products that monitor, control and automate the delivery and consumption of electricity – and potentially other household utilities such as gas and water, moving into the future.
The functionality of the Smart Energy 1.x Profile was primarily intended to support the functional requirements of smart meters being used by electricity, gas and water utilities to manage their distribution networks, automate their billing processes, and communicate with customers’ energy management systems.
ZigBee-enabled smart meters act as communications gateways between the utility and the consumer, enabling the exchange of messages about pricing, demand response and peak load management. At least this technical capacity exists in theory, but electricity retailers will only bother with it if they have a revenue model in implementing such technology.
The ZigBee Smart Energy 2.0 Profile was created in response to the need for a single protocol to communicate with the growing universe of energy-aware devices and systems that are becoming common in homes and commercial buildings. For that reason, a diverse range of Function Sets were defined under SEP2.0, including Demand Response and Load Control, Metering, Billing, Pre-Payment, Directed Messaging, Public Messaging, Price Information, Distributed Energy Resource Management and Plug-in Electric Vehicle Management.
One or more of these Function Sets can be used to implement one of the Device Types defined in SEP2.0, such as Meters, Smart Appliances, Load Controllers, Smart Thermostats, In-Premises Displays, Inverters and Plug-in Electric Vehicles to name just a few.
ZigBee Smart Energy 1.x access the MAC/PHY layers of the 802.15.4 radio hardware via the ZigBee Pro protocol stack, but SEP2.0 replaces the ZigBee Pro protocol stack with the ZigBee IP stack, which uses the 6LoWPAN protocol to encapsulate the proprietary ZigBee packet structure within a compressed IPv6 packet. At the transport layer, IP packets bearing messages containing standard ZigBee command and data packets are exchanged using the familiar HTTP and TCP protocols.
When used in combination with the SEP2.0 Application Profile, the ZigBee IP stack provides a media-independent interface between the network and MAC layers of the stack that allows SEP2.0 packets to be carried across nearly any IP-based network.
A recent version of SEP2.0 includes support for communication across ZigBee and 802.11 wireless LANs as well as powerline communication (PLC) networks. SEP2.0 will also have improved future support for 802.15.4g, where the physical layer of the ZigBee/802.15.4 network is a sub-gigahertz radio at, say, 900 MHz for long-range outdoor telemetry or environments where the 2.4 GHz spectrum is congested. Support is also improving for other popular network technologies such as Ethernet.
Amongst the first SEP2.0 enabled products to hit the market will be Energy Service Portals (ESPs) which serve as a bridge between an energy utility’s communication infrastructure and the IP-based Home Area Network. These portals are provided to consumers by utility companies, and use the SEP2.0 Energy Services Interface profile to provide a bridge between the SEP1.x protocol used by most existing smart meters and the home’s IP-based network.
A ZigBee-enabled home energy management system can employ multiple Application Profiles to provide unified control of all home energy systems. For example, a smart home energy management system may use the Smart Energy (SE) profile to pass the utility’s load management and demand response messages to the home’s major loads and energy sources.
The Home Automation (HA) and RF for Consumer Electronics (RF4CE) profiles may then be used to communicate with Smart Appliances, lighting systems and other consumer-controlled products. Energy-aware homes will also employ a large number of end-point applications such as smart thermostats, in-home energy displays (IHDs), and tablet-based control panels that use SEP2.0-enabled ZigBee or Wi-Fi radio links to communicate with the home’s ESI and other elements of its energy management system.
SEP2.0-equipped network endpoints may also be implemented with the physical layer of the network using power line communications, networking smart appliances without RF spectrum congestion.
The ZigBee Alliance has created well-defined provisions for interoperability with, and upgrade paths from, the earlier SEP1.x standard to SEP2.0, which is good news for engineers looking to upgrade or to interoperate with existing SEP1.x technology. There is no significant increase in the processing power required in your hardware, although the key generation and exchange functions in the SEP2.0 security layer may be tough for 8-bit microcontrollers to handle unless they have security acceleration capability, handling the cryptographic maths in dedicated hardware.
Unfortunately, in terms of memory, SEP2.0 and the applications it supports require significant increases in both flash and RAM over what is required for most SEP1.x applications. Storing the code for a SEP1.x stack, a small application profile and a simple user application requires roughly 160 kb of flash in a typical microcontroller, plus 10-12 kb of RAM. Implementing comparable functionality under SEP2.0 requires about 256 kb of flash and 24-32 kb of RAM.
As an example of an existing hardware reference solution targeting SEP2.0, Texas Instruments provides an example consisting of the CC2533 802.15.4 RF system-on-chip, which runs the MAC/PHY layers of the SEP2.0 stack on its built-in 8051 core, combined with one of TI’s ARM7 Stellaris 9000-series microcontrollers as the application processor, running the remainder of the network stack and the application code.
Most of the microcontrollers in this powerful family include a fully-integrated Ethernet MAC, CAN interface, USB host controller, and enough memory and processing power to implement many simple SEP2.0 applications.
It is also worth considering some of the highly integrated single-chip solutions on the market such as the Texas Instruments CC2538, which integrates a 2.4 GHz 802.15.4 radio, ARM Cortex-M3 32-bit microcontroller core, hardware security acceleration for SEP2.0 and plenty of flash and RAM to support the ZigBee IP stack, SEP2.0 profile and application code with support for over-the-air firmware flashing capability for updates in the field, all in a single chip.
As you have just read, the new profile offers a great amount of promise in terms of functionality and convenience for the end user. Here at the LX Group our engineers have an excellent understanding of the Zigbee platform and have put this to use to create various systems for a wide range of customers – and we can do this for you too.
To get started, join us for a confidential discussion about your ideas and how we can help bring them to life – click here to contact us, or telephone 1800 810 124.
LX is an award-winning electronics design company based in Sydney, Australia. LX services include full turnkey design, electronics, hardware, software and firmware design. LX specialises in embedded systems and wireless technologies design.
Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.