[#SmartGrid スマートグリッド] 無線ネットワーク技術:Silver SpringとGrid Net 両社が最近話題を集めているのは、=>

スマートグリッドを支えるネットワーク、具体的にはスマートメータ間のメッシュネットワークにセルラー技術を採用するか、WiMAXを採用するか、という議論。  無線技術にはこれ以外にもBluetooth、Zigby等、複数の企画があり、どれがスマートグリッドの市場で勝者になるのかは、難しい課題である。


Silver Spring vs. Grid Net: Now vs. the Future

Silver Spring Networks’ wireless mesh has lots of utility customers. Grid Net says its WiMax-based technology is better.

 There are two ways to network the smart grid — Silver Spring Networks‘ way and Grid Net‘s way. One is the present, the other may be the future.

Redwood City, Calif.-based Silver Spring is the present. Its smart grid solution – neighborhood-sized mesh networks of smart meters and other devices, all communicating with radios using unlicensed spectrum, all owned and controlled by the utility in question – has become the technology of choice for utilities installing millions of smart meters around the United States.

San Francisco-based Grid Net, on the other hand, is backing WiMax, a contender for the next-generation of technology for public wireless networks. While still sparse in North America, a WiMax network could offer utilities a high-speed, high-bandwidth network, built on mass-produced, standards-based equipment, all operating on licensed spectrum that they could rent, instead of build.

Grid Net CEO Ray Bell – a Cisco and Intel alum who also led Silver Spring as CEO from 2003 to 2005 – has said that Silver Spring’s technology won’t go the distance for a complete smart grid (see Bloomberg). Silver Spring’s reply is that utilities are right now building their smart grids on the company’s radios and its underlying networking technology, linking not just smart meters, but distribution grid automation systems, home area networks and all the other features that make up the idea of a “smart grid.”

At stake is an estimated $19.5 billion in smart meters to be installed woldwide between now and 2015, says Pike Research (see Green Light post). The $3.4 billion in Department of Energy smart grid stimulus grants given out last week represent a one-time jolt that could propel winning technologies into leading positions that will be hard to overtake once the flood of federal stimulus fades, analysts say.

Those analysts also agree that, in the long term, both companies’ visions will find their adherents among utilities. Customers in dense urban environments need different technologies than those scattered across rural islands of power delivery, and reading meters every 15 minutes or hourly is a lot different than throwing distribution grid switches on a fraction of a second’s notice.

To serve all those needs, utilities will need “an integrated network, for lack of a better word – some combination of various technologies and public and private networks,” said Marty Travers, president of the telecom division of Black & Veatch, an engineering and construction firm that’s working on smart grid projects with Lockheed Martin (see Defense Contractors Pursue the Smart Grid). As for where a Silver Spring-style solution might win out over GE and Grid Net’s WiMax offering, or visa versa, Travers declined to speculate, saying that Black & Veatch is working with both companies.

But at present, “The utilities have a ‘now’ problem to solve, and that’s where Silver Spring has really excelled,” said Mike Carlson, a former CIO with utility Xcel Energy who is now executive vice president for smart grid software startup GridPoint. Silver Spring, along with companies such as Trilliant and smart meter maker Itron, has gotten utilities’ attention with a technology that’s cheap and reliable, he said.

“What they’ve had to trade off on are some of the capabilities of that network,” he added, such as greater bandwidth and lower latency, that is, higher speed of communications.

Those are, of course, exactly the strengths that Grid Net promises of its WiMax-based solution, now being put to the test in smart meter networks deployed by Grid Net investor General Electric. The two announced their first smart grid contract with Australian utility SP AusNet, in a country that already has a broadly deployed WiMax network — unlike the United States (see GE, Grid Net Win WiMax Smart Grid Project in Australia).

Grid Net doesn’t just offer utilities a faster, more data-rich WiMax backbone, but a software platform that allows utilities to upgrade individual meters with new “smart pricing” data, electric vehicle charging schedules, and other such futuristic smart grid functions, said Judith McGarry, the company’s vice president of marketing.

“We’re saying, if you want to build your smart grid, you need a solution architecture that’s bigger and broader,” she said. “You have to think a lot further down the road than just a couple of purpose-built applications.”

Of course, Silver Spring says it’s doing the same thing. “Everybody we’re working with has a list of features and functions that go well beyond meter reading from day one,” said Eric Dresselhuys, vice president of markets.

What Do You Want Your Network to Do?

So what do utilities want from their communications networks? One test case is in distribution automation — communicating with and controlling the array of devices that control power flow on neighborhood distribution grids. Makers of grid equipment like ABB, Siemens, General Electric and S&C Electric Co. have been testing out various networking technologies to see if they’re up to the tasks at hand, which typically require networks that can respond in tens to hundreds of milliseconds (see Green Light post).

Take Chicago-based S&C Electric‘s IntelliTEAM system of networked devices to isolate and restore faults in a distribution grid. S&C has designed its own SpeedNet radios, capable of about 5 millisecond “hops” from device to device, to handle the task, said Witold Bik, vice president of the company’s automation systems division.

That mesh architecture “is very similar to what Silver Spring Networks does,” Bik said, adding, “By the way, we work on their network.”

Latency is a big deal for distribution automation, which needs a network that can execute some commands at the speed of the grid, so to speak – that is, the 60 hertz, or cycles per second, at which U.S. utilities deliver their power.

“The unit is the cycle, so a 60-hertz cycle is basically 17 milliseconds” per cycle, said Narasimha Chari, CTO and co-founder of Tropos Networks, which serves utilities with WiFi based networks (see Tropos: Wi-Fi For the Smart Grid).

Utilities are seeking networks that can offer tens of milliseconds” of latency for the most time-sensitive distribution automation functions, and if not that, hundreds of milliseconds, he said. Comparing the best-known data about competing technologies, “I think WiFi and WiMax offer advantages for distribution automation, just because of the latency and the bandwidth, and because they’re easily deployable,” he said.

Bik agreed that “There could be faster applications if we had a WiMax solution,” which promises low latency on top of effective data rates of 2 to 3 megabits per second, compared to SpeedNet’s 650 kilobits per second.

But “To have a self-healing network, you cannot rely on a single point of failure, as you would with WiMax or cellular technology,” he said. “The guys from Silver Springs understand that… This is the key to reliability.”

Posted via email from Ippei’s @CloudNewsCenter info database

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