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Smart grid watchers spend a lot of time discussing which is better for networking homes — ZigBee or Wi-Fi — and the relative merits of public versus private wireless networks for the smart grid at large. Do answers to the debate lie in the wiring? Power line carrier (PLC) technologies, which send data and commands to devices either over household wiring or along the grid’s power lines, have features that could give them a bigger share of the smart grid market than they’ve had so far.
What do they offer? Let’s take a look at some of the technology’s advantages:
Hard-Line Accessibility. Using existing power lines to carry data is already a preferred choice in urban settings, where housing is denser and wireless has a hard time reaching from a basement electrical meter to hundreds of apartments above. Still, for North American utilities at least, wireless remains the predominant choice for linking smart meters and home energy management devices in all but the most dense urban environments. Smart grid analysts I’ve talked to have guessed that PLC will eventually provide about a fifth of the overall smart meter-home connectivity in the U.S.
But beyond smart meters are all the smart appliances — electric vehicle chargers, load-shifting air conditioners and other such household energy-aware gear — utilities want to connect to. With certain exceptions, most of those appliances are already plugged in. If PLC can offer advantages in bandwidth, reliability and connectivity to plug-ready points in the home that wireless might have a harder time reaching, why not use it?
A Sizable Market. As for linking smart meters to the distribution grid, wireless is king in almost all big U.S. plans (Duke Energy’s partnership with Echelon Corp. is an important exception). But in Europe, PLC is taking a far larger role. PLC leader HomePlug Alliance already has its higher-bandwidth AV technology in about 45 million devices, mostly IPTV in European households. Best Buy and Carrefour stores in England and France have HomePlug devices for sale, and France Telecom and other telecommunications companies are selling HomePlug adapters.
Italy’s 30-million smart meter networks runs on PLC based on technology from Echelon Corp., and France and Spain are looking to PLC as their main way to link up nationwide, multi-million smart meter networks. Then there’s China, which wants a low-cost PLC technology to connect tens of millions of its households. While the U.S. is driving the smart grid market today, China is expected to drive it in the future; giving North American and European smart grid companies good reason to develop PLC tech to serve it.
HomePlug’s new energy specific Green PHY specification is also being tested by utilities including Energy Australia and Germany’s Yellostrom. In a pilot project with Michigan utility Consumers Energy, General Electric is is using HomePlug AV in its smart meters. GE is a HomePlug board member, and has smart meters, smart appliances and EV chargers in its portfolio, all of which could see an appeal in PLC connectivity.
Additional Functionality. Intertwining the delivery of data within the flow of power in wiring gives PLC technologies some unique ways to help manage power more effectively. Echelon says its smart meters and upcoming smart grid “edge control nodes” can provide features rarely found in wirelessly enabled smart meters, such as “automated topology mapping” that provides a view of the status of every PLC-connected device and its relation to the transformer that’s powering it. That could make it useful to balance EV charging and load control devices in homes based on a reading of how each is affecting the home’s transformer.
Compatibility. PLC players aren’t going it alone. Echelon includes radios in devices it’s selling to utilities including Duke Energy and Finland’s Fortum. HomePlug is working with with ZigBee and Wi-Fi alliances on interoperable Smart Energy Profile 2.0 devices, and expects to have testing and certification ready by mid-2011. That’s important, given that the smart grid industry agrees that no one technology will be able to serve the entire range of utility smart grid needs.