Get ready for one more home network, the home-area network (HAN). Most of you already use a home network to share your high-speed Internet service with multiple family members. The most common networks use Wi-Fi wireless technology to connect your main PC or several laptops to the cable or DSL modem. Another home network growing in popularity carries HD video from your cable, Internet Protocol television (IPTV), or satellite box around the home so multiple TV sets can access it.
Coming to your home next is the HAN. It has a separate application altogether: to connect your heating, ventilation, and air conditioning (HVAC) system and other power-hungry appliances to your electrical meter and the local power utility. The goal is to help you monitor and control your energy usage to save you money and to take the pressure off of the utility. Alternately, the HAN will work with the utility, which could control your various appliances to cut power usage at selected times.
A NETWORK OF NETWORKS
The electrical power distribution grid is a huge one-way network that generates electrical power and delivers it to everyone. The Smart Grid is an effort to update that network with a communications component that will enable monitoring and control so it could be automated to save energy.
The communications systems within the grid are networks that perform in its various sectors or domains. The Internet will be used for some of that communication while the electrical transmission and distribution domains of the grid will use a combination of fiber, wireless, and powerline communications (PLC) capabilities. Ethernet will play a major role. At the end of the grid network is the ultimate user of the electricity, the home. This is where the HAN comes in.
The HAN could be connected to the grid directly through backhaul to the utility’s substation or not. It will provide a way for the consumer to monitor energy usage. It also will provide manual or automated control of appliances to reduce energy usage, reducing energy costs while also relieving the utility of a continuous increase in loads and the pressure to add more energy production capability.
Power comes into the home from the main power lines, but that could be supplemented by power from wind or solar (Fig. 1). Even a plug-in electric vehicle battery pack could provide additional power. The central connecting point is the electric meter. This utility-supplied meter is an electronic equivalent of the older electromechanical meters and measures power usage.
There are two versions of the meters: Automated Meter Reading (AMR) and Advanced Metering Infrastructure (AMI). The AMR meter’s built-in one-way communications lets the utility read the meter remotely by powerline or wireless connectivity. The newer AMI meters have two-way communications with a powerline or wireless link to the utility for reading the meter, in addition to a second link via powerline or wireless to the HAN. The HAN connection potentially allows the utility to monitor and control the home HVAC or appliances. It also lets the homeowner monitor energy usage and provides some programmability or control of the HVAC and appliances.
There are several levels of HAN functionality. The simplest is just a connection from the meter to some monitoring device in the home that lets the homeowner see the amount of energy being used over time, for example, via an LCD display panel with touch controls. Using this monitoring device as a guide, the homeowner can make manual adjustments to the HVAC, lighting, or appliances. The monitoring panel may also communicate with thermostat. And, the thermostat can be programmed to turn off and on at appropriate times to save energy.
The most sophisticated version of the HAN uses wireless or powerline technology to talk to the thermostat or special controls that operate the lighting and key appliances. Initially, appliances can be controlled with load control modules, which turn devices off or on under the command of a wireless or powerline link. In the future, many appliances will have the communications and load control capability built in.
According to Thomas Pickral Jr. of Home Automation Inc. (HAI) (Fig. 2), the HAN and its functions are separate from what is called home automation. HAI has been in the home monitoring and control business since 1985 with products for the control of home lighting and other fixtures. These products are not part of the HAN. The HAN targets heavy energy users like HVAC systems, pool pumps and heaters, hot water heaters, washers and dryers, refrigerators, and any plug-in electrical vehicle charging station.
Two main types of technologies are competing for HAN dominance: wireless and wired. Both are affordable and sensible. The homeowner may or may not have a choice depending on what the utility is offering. The electric meter connectivity essentially determines the choice. Both wireless and wired variants exist. A combination of powerline and wireless may be needed to provide the most convenient and optimal interconnection of all of the devices involved.
WIRED NETWORKING TECHNOLOGY
There are three basic wired networking technologies for the home: ac PLC, coax, and telephone wiring. No installation of new wiring is necessary. All of these technologies are used now to distribute video around the home. There are multiple mostly proprietary standards. For instance, some U.S. cable companies use the internal home cable TV coax to transmit high-speed digital data including compressed video from room to room. The standard is set by the Multimedia over Coax Alliance (MoCA), and Entropic makes chips.
The HomePNA Alliance supports another popular standard called HD-PLC. It offers a method of distributing high-speed data, including video, over the internal CAT3/UTP telephone wires in all homes or on coax. AT&T uses this method with its U-verse IPTV service.
Using the ac powerline to transmit data is another popular option. Multiple standards have existed for years along with many non-interoperable consumer networking products. Rob Ranck, president of the HomePlug Alliance, says that HomePlug is a 10-year-old powerline standard that has emerged as the powerline technology of choice. With more than 45 million products already in the field, HomePlug has proven itself as a solid powerline communications method. With its new audio-video (AV) standard, which is capable of data rates up to 200 Mbits/s, it is a viable video distribution option.
Two additional factors are making HomePlug the powerline technology of choice. First, HomePlug AV is the basis for the new IEEE P1901 powerline standard. With an IEEE standard as backing along with a compliance testing and certification process, HomePlug is even more attractive. Second, HomePlug is working on a new variation called Green PHY (GP) that specifically targets the HAN and Smart Grid applications. This cost-reduced version consumes less power and runs at a more modest 1-Mbit/s speed, which is more than adequate for power applications. A final approved version is expected to be available this month.
Both HomePlug AV and HomePlug GP use 1155 subcarriers of orthogonal frequency-division multiplexing (OFDM) over the 2- to 30-MHz band on the ac line. Subcarrier spacing is 24.414 kHz. HomePlug AV can use any flavor of phase-shift keying (PSK) and quadrature amplitude modulation (QAM) to 1024 to get speeds up to 200 Mbits/s for video transfer. HomePlug GP only uses quadrature PSK (QPSK) and supports data rates from 4 to 10 MHz.
Finally, HomePlug is a great complement to ZigBee wireless, as it will run the ZigBee Smart Energy 2.0 profile protocol. Combinations of ZigBee and HomePlug running the same protocol should provide a tough to beat combination for any home. HomePlug is also working with MoCA to achieve some interoperability between products.
PRIME and G3, two other powerline communications technologies of note, are primarily European efforts. PRIME, for Powerline Related Intelligent Metering Evolution, is based on OFDM in the CENELEC A band. CENELEC is the European Committee for Electrotechnical Standardization. OFDM carriers are distributed over the A-band range from 9 to 95 kHz. The data rate can be from 16 to 130 kbits/s. Echelon and STMicroelectronics make chips for this standard.
The G3 standard uses OFDM as well in the 10- to 490-kHz band. It can be used successfully over low-voltage (120/240 V) lines as well as medium-voltage lines to 7 kV, making it a backhaul network candidate (see “Backhaul To The Utility”). It has an IEEE 802.15.4 media access controller (MAC) layer and can achieve data rates to 250 kbits/s. It also has a 6LoWPAN adaption layer to transmit IPv6 packets. G3 uses AES-128 encryption and can coexist with IEEE P1901, ITU G.hn, and IEC 61334.
Then there is the upstart G.hn, or the ITU G.9960 standard for wired home networking. Based on OFDM, this new international standard can use any of the common wired media. It isn’t in use yet, but companies are working on chips. According to the HomeGrid Forum, products should be emerging later this year and next year.
There are three basic profiles: a wideband version with rates to 200 Mbits/s, a Smart Grid version that targets backhaul with a rate to 25 Mbits/s, and a new narrowband version. Called G.hnem, the new narrowband version for energy management is being developed to serve the HAN marketplace. G.hnem is a less complex version of the primary standard with data rates below 500 kbits/s. It will be optimized for PLC, home energy management, and home automation in a Smart Grid environment. Work on the G.hnem standard is in process, and a final approval is expected in February 2011.
G.hn is late to the home networking game, but the standard is versatile and solid. It is not interoperable with the powerline standard P1901 or HomePlug AV or GP. The HomeGrid Forum will provide certification testing to ensure fully interoperable products once it’s available.
Wireless dominates the home networking space right now, with all homes using Wi-Fi IEEE 802.11 standards to connect PCs to broadband modems. It’s convenient and reliable. However, it’s a very complex and high-speed option that is overkill for HANs. That’s why other wireless standards have emerged to fill the need for a simple, low-cost lower speed wireless device for home monitoring and control.
The unofficial winner of this competition seems to be ZigBee. Based on the IEEE 802.15.4 standard, ZigBee uses the 2.4-GHz band to get a data rate to 250 kbits/s. It adds a unique stack structure to enable mesh networking. Furthermore, the ZigBee Alliance has developed two versions or profiles that directly address home automation and smart energy applications.
The ZigBee Alliance recently announced the availability of its Smart Energy version 2.0, which focuses on the HAN. With ZigBee radios widely available and affordable, plus the profiles, it’s an easy choice. Some AMI meter manufacturers also incorporate a ZigBee slot. The interoperability with the HomePlug PLC standard additionally makes it an attractive option. The ZigBee Smart Energy 2.0 profile can run over Wi-Fi enabled devices as well.
Another outstanding choice is the Z-Wave wireless standard. With hardware made by Sigma Designs that’s incorporated into hundreds of home automation products, Z-Wave makes an excellent case for incorporation into Smart Grid HANs. These wireless modules are available in thermostats, energy monitors, lighting controls, controls for fans and drapes, and general appliance control units.
Not to be left out of this huge market, Bluetooth, one of the oldest short-range wireless standards, recently established the Smart Energy Study Group to look at the potential for a HAN profile. With its low-cost chips and well-known profiles in the cellular headset business, Bluetooth is just now beginning to make a case for its use in HANs. Bluetooth wireless devices are networkable and offer very low-power versions for sensor monitoring applications. Watch for future announcements.
An interesting new option is the forthcoming ISA100.11a wireless standard from the International Society of Automation (ISA). Developed based on user needs in the tough industrial environment, this family of wireless specs specifically targets industrial automation and process control. Now complete, this standard is making its way through the four-stage ISA standards process.
The standard is expected to go to ANSI and then to IEC for their blessing. Products based on the standard are just now coming to market. What will make the standard widely used is the testing and interoperability assurance that will come from the Wireless Compliance Institute (WCI), a subsidiary of ISA established to handle the compliance certification of products.
The standard itself is based on the IEEE 802.15.4 specification for a 2.4-GHz radio that uses direct-sequence spread spectrum (DSSS) to achieve a 250-kbit/s data rate. It uses a unique channel-hopping scheme with channel black listing to find which of the 16 assigned channels aren’t being used. It actively seeks out quiet channels to avoid Wi-Fi and other radio signals in the band and then adjusts as conditions change to ensure a highly reliable transmission.
The standard has a mesh option and uses AES 128 and PKI encryption for security. And unlike some other industrial wireless protocols, ISA100.11a can handle 10,000 channels for sensors or actuators, which is more than any other radio protocol. It addresses non-critical applications and guarantees a maximum 100-ms latency. Numerous profiles are being developed for different applications. A related backhaul standard is in the works. ISA100.11a is applicable to Smart Grid uses and is a serious candidate with the National Institute of Standards and Technology (NIST).
With the potential for millions of new HANs, most semiconductor companies are addressing this incredible opportunity with relevant chips. For example, Atheros Communications recently introduced a PLC system development kit that will enable engineers to rapidly design Smart Grid products and applications. The kit is one of the company’s first steps toward the market deployment of its comprehensive Smart Grid strategy targeting the home energy market.
The initial kit is based on the existing HomePlug AV-compliant INT6400 chip (Fig. 3) with support for a UART serial interface, which is ideal for connecting to a wide variety of CPUs commonly found in Smart Grid applications. Future versions of the Smart Grid system development kit will support the recently announced AR7400 HPAV/IEEE1901-compliant chipset for high-performance, broadband applications, as well as future solutions optimized for the new HomePlug GP specification for narrowband, ultra-low-power applications. OEMs can be assured that their end products are based on global PLC standards IEEE 1901, HomePlug AV, and HomePlug GP.
Thanks to its recent acquisition of PLC pioneer Intellon, Atheros is leading the adaptation of PLC technology to Smart Grid applications. The company has made significant technical contributions to the HomePlug GP specification. HomePlug GP, which interoperates with HomePlug AV, is a profile of the new IEEE 1901 draft standard and is tailored for low-power, cost-effective Smart Grid applications.
The Cypress Semiconductors Powerline Communications (PLC) solution uses a robust frequency shift keying (FSK) physical layer (PHY) modem with a 130-kHz carrier and a variable data rate to 2400 bits/s. It integrates the data link, transport, and network layers and supports bidirectional half duplex transmissions. Also, it uses an 8-bit cyclic redundancy code (CRC) error detection scheme with data retransmission for reliability.
The Cypress PLC modem is on-chip with one of the company’s programmable system-on-a-chip (PSoC) embedded controllers. The CY8CPLC20’s on-chip coupling circuit (Fig. 4) simplifies the connection to the powerline, which includes 120/240 V ac and 24 V ac or dc . Reference designs and development kits are available.
Gigle Networks also makes HomePlug AV/P1901-compliant PLC chips. The GGL301 is a 200-MHz Intelligent Multi-PHY switch with an on-board programmable network processor and memory. Also included is an analog front end (AFE) for the powerline and a 10/100 Ethernet port. The GGL541’s 1-Gbit/s PHY can be used on the powerline or optionally on coax or phone lines. It too complies with HomePlug AV/P1901.
Maxim Integrated Products, another powerline chip provider, offers several options. The MAX2982 is HomePlug compatible and works with the MAX 2981, a PLC AFE and line driver IC. The MAX2990 is designed to use OFDM in the 10- to 490-kHz band. It works with the MAX2991 AFE. Both are G3 compatible. The forthcoming MAX2992 will support IPv6 packets.
Texas Instruments also has a development kit that lets you experiment with spaced FSK (S-FSK) or any OFDM-based PLC technology. It uses TI’s TMS320F28 series 32-bit DSP processors along with the company’s OPA564 and PGA112 AFE components. The F28 handles the modulation and demodulation of any PHY scheme. Then, the remaining protocol can be implemented in another processor.
No G.hn chips have been announced yet, but some are expected perhaps from companies like CopperGate, DS2, Gigle, Lantiq, Ikanos, and possibly even TI, which recently joined the HomeGrid Forum. Look for specific announcements later in the year.
There are also lots of wireless product choices. The Analog Devices ADF7242 short-range transceiver targets short-range wireless systems in the global 2.4-GHz industrial, science, and medical (ISM) band. It supports the IEEE802.15.4 standard and may be used to implement solutions based upon protocols such as ZigBee, IPv6/6LowWPAN, ISA100.11a, and Wireless HART. It also offers the flexibility to implement proprietary FSK-based protocols with data rates of up to 2 Mbits/s. Applications include smart meters and the Smart Grid, wireless sensor networks, building automation, industrial wireless control, wireless remote controls, consumer electronics, and healthcare.
The leading ZigBee chip vendor, Freescale Semiconductor, commands a market share that’s greater than 60% in 802.15.4 transceivers and related products. Freescale’s MC13213 chip integrates one of the company’s MC1320x 802.15.4 transceivers and an MC9S08GT MCU plus memory and I/O that targets ZigBee applications. Texas Instruments is another major 802.15.4/ZigBee radio vendor. Its CC2530/31 are complete SoCs designed for ZigBee products. RF Micro Devices also offers a front-end module with a power amplifier (PA) and low-noise amplifier (LNA) that greatly extends the range and reliability of ZigBee links.
Ember, another leading ZigBee vendor, supplies chips and software as well as complete modules and systems. The EM250, EM260, EM351, and EM357 chips with EmberZNet PRO software make it easy to put together a complete HAN product. Ember has already shipped more than 10 million ZigBee chips, which are already showing up in smart meters (Fig. 5).
The Silicon Laboratories Si1000 wireless MCUs are ideal for HAN applications. This family of devices combines a 25-MHz 8051 core with the Silicon Labs EZRadio PRO, a sub-1-GHz ISM band transceiver, 64 kbytes of flash, and a 10-bit analog-to-digital converter (ADC). The Si1000 devices have integrated power and low-noise amplifiers and provide a link budget of greater than 140 dB without any active external components. All this comes in a 5- by 7-mm package with very low power consumption.
Silicon Labs also teamed up with Synapse Wireless to introduce a wireless mesh networking solution. It uses the Silicon Labs Si1000 RF chips and Synapse’s SNAP network operating system. This hardware/software combination is available as the Synapse RF Engine module, which makes it easy to deploy scalable low-power small-footprint wireless mesh networks for applications like smart metering, building automation, commercial lighting control, and asset tracking systems.
Real and functional HANs are a ways off. It may even be a decade before we see full-scale adoption and the realization of benefits. The starting point is the smart meter rollout. As utilities install AMI meters and provide energy monitoring and flexible pricing, consumers will then have the option of installing their HAN. Only 13 million meters, of an estimated 112 million total, were installed at the end of 2009. But 40 million to 50 million more will be installed in the next four to five years, says research firm Parks Associates.
There are no firm standards for any of the communications and networking technologies. NIST has a working list of technologies and protocols it considers worthy of consideration. As of now, it includes most of what has been discussed here. While interoperability may be an issue in the overall grid, it does not appear to be a necessity in the HAN. As a result, the HAN technology will no doubt be selected by the utility, and multiple standards and technologies will be adopted.
The key to getting the benefits of the Smart Grid according to Parks Associates is consumer buy-in (see “Consumer Attitudes Will Shape The Smart Grid’s Success”). Customers do not have to implement a HAN. Ultimately, they will have to be convinced that the savings are real. With an investment in the HAN, thermostat, monitor, and software and load control modules, customers will have to view the savings as significant or at least break even.
Consumers may even end up paying more for energy to achieve a green condition at the utility. Parks indicated that as many as 35% of surveyed homes will never want a HAN, particularly one with utility control over their power. With the significant initial investment in the HAN and the costs of the AMI meter passed along to the customer, it will be a while before anyone sees benefits, though the potential is there.