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.