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 worldwide 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."

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Turning from a mesh network to a point-to-multipoint system, or "star" system – the typical cellular solution of putting up centralized base stations that talk to lots of devices in the field – could also prove more expensive in the long run, said Tommy Childress, senior director at Silver Spring.

"We'd argue at some point, on a star, it's not scalable," he said "For fewer points, you can do low latencies. But when you start scaling up to hundreds of thousands, you have to add more stars... Enough time and money can make anything work. The question is – can you make a business on it?"

Yes, Grid Net's McGarry said. The company has demonstrated with its SP AusNet contract, as well as in a project with utility Energy Australia, that it can scale up to reliably serve a large number of utility endpoints with a few central base stations, she said.

Another benefit of WiMax, McGarry added, is that it maintains persistent network connections between base stations and the smart meters and other devices that it serves, giving it real-time device status awareness.

Many utilities say they'd like to deliver new variable prices to smart meters to give to energy management systems in people's homes (see Utilities Mull Price Points, Policies for Home Energy Management). That could require more frequent and date-intensive data exchanges than the 15-minute or hourly "polling" that many smart meter networks now offer, she said. 

"No one else is really doing that," she said, but many distribution automation systems "have to be in real time."

McGarry said that Grid Net's PolicyNet software allows for remote software upgrades to individual meters, each with its own unique identity. That could offer utilities more flexibility in how they roll out those pricing programs, she said.

WiMax's bandwidth and low latency also makes it a candidate for other functions, like managing remote security cameras and voice communications for workers in the field, she noted. San Diego Gas & Electric, for example, has landed a $28.1 million DOE grant for its GridComm project, a utility-wide communication network that will include WiMax from an as-yet unspecified vendor to suppors those kinds of uses (see Green Light post).

Silver Spring, for its part, is supporting distribution automation for American Electric Power (see Silver Spring, AEP Team on Smart Grid), and is providing home networking for utility Oklahoma Gas & Electric (see Green Light post). But networking video cameras is beyond the company's scope, Dresselhuys said.

"The big picture is, there's a ton of stuff out there," he said. "Will it take a bunch of carrier technologies? Absolutely. We don't do streaming video. We don't do voice."

How Open Should the Network Be?

The federal government is calling for all smart grid communications to adhere to certain standards. In an industry rife with proprietary technologies that leaves the definition of "standards" an open question (see Smart Grid Standards Roadmap Unveiled).

Silver Spring has developed networking based on internet protocol, something it says will be important in opening up the heretofore proprietary networks of smart meter companies to increased collaboration and competition.

But Silver Spring's 900-megahertz radios are not based on open standards, since none exist for that technology. That's led some competitors to complain that the company isn't as open as it likes to claim (see Smart Grid: A Matter of Standards).

"Today, Silver Spring is developing against essentially a proprietary mesh technology," Grid Net's McGarry said. "Pieces of it are open [IP] but a whole lot of it is their proprietary radio."

Silver Spring has said it is committed to working on standards for wireless mesh technologies. In the meantime, utilities have turned to it as a low-cost technology that suits their purposes (see RF Mesh, ZigBee Top North American Utilities' Smart Meter Wish Lists).

WiMax, on the other hand, is an open standard that has vendors such as Samsung and Motorola — the latter providing equipment for the SP AusNet project – building equipment to serve it, McGarry said.

In Australia, SP AUsNet is using the network of Australian WiMax carrier Unwired to link its GE-Grid Net smart meters. But in the U.S., the WiMax network being rolled out by Sprint and Clearwire is only in a handful of cities right now, though the two have said they plan to expand it to cover 120 million people in 80 markets by 2010 (see Sprint Stakes Smart Grid Claim).

A public network isn't neccessary. Texas utility CenterPoint is using GE WiMax radios for a so-called "backhaul" network to link smart meter mesh network collection points to the utility's back offices (see GE Offers WiMax Smart Meter Solution).

Still, the uncertainty could give utilities second thoughts, Silver Spring's Dresselhuys noted. Going with a privately-owned WiMax bnetwork leaves utilities with the need to gain access to licensed spectrum, and utilities that choose to "rent" their networks will "have to pay potentially large fees to a carrier forever," he said in an email.

Similar questions of pricing have confronted other public cellular providers that want to "rent" their networks to utilities to link smart meters and other smart grid systems, industry watchers have noted, though they also report that carriers appear to be lowering their prices to win utility business (see Qualcomm's Machine-to-Machine Smart Grid Moves and Your Electrical Meter Becomes a Cellphone).

Wireless mesh is generally considered to be a cheaper alternative than WiMax at present for utilities, though McGarry notes that this could be changing.

"A year ago, costs used to be a big argument and a big concern," she said. But GE's Grid Net-backed WiMax smart grid systems can show cost competitiveness with wireless mesh solutions, she said.

On the other hand, mesh networks that use unlicensed frequencies could potentially open them to "crowding" from other devices using the same frequencies, she said. Similar arguments have been made by companies that own licensed spectrum they're seeking to provide to utilities, including of course the big wireless providers, as well as startups like Arcadian Networks (see Arcadian's Smart Grid: Licensed Spectrum Network to Own or Rent).

Dresselhuys said that Silver Spring has millions of devices using unlicensed spectrum without issue. Still, concerns about the growth of smart grid devices has led some utilities to request that the Federal Communication Commission set aside spectrum for their use – a move opposed by companies like SmartSynch that use public cellular networks for smart meters (see Smart Grid News for an overview).

Interact with smart grid industry visionaries from North American utilities, innovative hardware and software vendors and leading industry consortiums at The Networked Grid on November 4 in San Francisco.