After spending $1 billion in Maine to build 11 projects, wind energy companies have a problem: The transmission lines connecting them to the New England grid sometimes are too weak to carry all their power.

When that happens, the region’s grid operator orders the wind farms to reduce output or stop running, a process called curtailment. Letting them all operate at certain times could overload the grid and jeopardize reliable service.

The problem could get worse in the future, according to the grid operator, if many more wind projects go on line, as planned.

Wind companies knew about these constraints when they built the plants. But federal utility rules meant to encourage renewable energy let them install feeder lines that meet only minimum standards.

Upgrading transmission lines will take money, and that will come from ratepayers. It’s too soon to say how much the upgrades would cost.

But the investors in wind farms still make money, even if the power isn’t sold on the grid, because of how these projects are financed and the rates companies have negotiated for their energy.


Projects in Maine, where most of New England’s wind output is located and where far-flung additions are planned, appear most at risk for being taken off line or cut back. That’s because they are located in remote areas most likely to be serviced by dated transmission lines. Boston-based First Wind, Maine’s leading developer, says roughly 20 percent of the power at four Maine projects was curtailed last year, although at least half of that was due to construction in a major transmission corridor.

Several strategies are under study by the power grid’s independent systems operator, or ISO, to better integrate wind power into the system. Wind power produced 1 percent of New England’s energy last year, up from virtually nothing in 2005.

Until now, the systems operator hasn’t tracked how much wind power is being turned away, or which projects are most at risk of curtailment. It’s starting to collect that information.

ISO-New England also is starting to develop more sophisticated ways to forecast what will be available from wind for next-day power production. That will become essential if New England develops an offshore wind industry, because wind patterns are different in the mountains than they are along the coast.

But these measures won’t eliminate the need to beef up transmission lines closer to the turbines, according to Stephen Rourke, vice president for systems planning at ISO-New England.

“As we get more and more wind, we are going to need to see some enhancement to the network, more transmission lines built, to unlock large amounts of wind,” Rourke said in an interview with the Maine Sunday Telegram. “Our work will help but not solve the problem.”


In a recent background paper on the issue, ISO-New England set out the challenges.

The region now has 700 megawatts of installed wind capacity, with 500 megawatts in Maine. That’s enough installed capacity to supply more than 150,000 homes, based on average annual output. Projects that could triple today’s capacity are in the planning stages. The trouble is, most are located in rural areas, far from customers.

“The transmission resources in these parts of New England were built to serve the native load, but not designed to accommodate the addition of generation sources or the movement of large amounts of power,” the paper explains.


More than 8,000 miles of high-voltage lines connect 350 power plants in the six New England states. Many lines are being upgraded, including Central Maine Power Co.’s backbone system that runs from Orrington through southern Maine. As part of CMP’s upgrade, big 345-kilovolt lines were extended to Detroit and Lewiston.

But the Maine Power Reliablity Project wasn’t designed to hook up individual power plants through smaller, 115-kilovolt lines, according to John Carroll, a CMP spokesman.


“The MPRP is the highway and those are access roads to the highway,” he said. “We did improve access, but it’s a long way to the western mountains, where you’re going to have those constraints.”

Conventional power plants that hook into the grid are required to design their connections to meet certain technical standards for voltage and thermal performance. These standards are meant to keep lines from becoming too hot or electrically unstable. But federal utility regulators have allowed wind projects to connect with only minimum standards.

“However,” the ISO paper continues, “this standard does not ensure that the resource will be able to put its full output on the grid. Generators that do not fund additional elective upgrades to enhance their access to the transmission system, or connect to a relatively weak area of the system, are at a higher risk of being curtailed.”

So far, every wind generator that has hooked up to CMP’s system has chosen to meet only the minimum standards, Carroll said.

Compounding the problem for wind is the way ISO-New England schedules power plant output for the next day, based on a generator’s price and ability to run. Wind farms often can’t predict how much power they can produce the next day. And even if they do have power to offer, they may not be called on by the ISO, because firm commitments from natural gas, hydro and other plants already are in the queue.

Power plants don’t get paid when they aren’t selling energy, according to the ISO. The exception is plants that receive capacity payments, essentially a stipend for being available for emergencies.


But even with curtailment, wind companies and their investors can still make money. That’s because wind qualifies for above-average rates, long-term power contracts and production tax credits meant to encourage renewable energy. Some projects also got millions of dollars in federal stimulus money during the recession, and investors received tax benefits.


To critics of wind power in Maine, curtailments are just another reason to limit the number of new projects.

“In the last few years, $1 billion has been spent on wind, and it doesn’t make a material contribution to the grid,” said Chris O’Neil, a lawyer who represents Friends of Maine’s Mountains. “If another $1 billion is spent, how much worse will congestion be, and how much more will that increase transmission rates?”

O’Neil said that locating wind projects on remote mountains, far from cities, “is a recipe for failure.”

Curtailment could become a bigger issue as more wind is placed in the system, First Wind acknowledges.


First Wind had 185 megawatts of installed capacity operating in Maine last year, enough to power 66,000 homes. The company is planning the biggest wind farm in New England, a 186-megawatt project around Bingham that will include 62 turbines. Last week, it received approval to build a 54-megawatt project next to its Bull Hill Wind farm at Township 16, in Hancock County.

First Wind had 20 percent of its power curtailed last year at its Bull Hill, Stetson I and II and Rollins projects, according to John Lamontagne, a company spokesman. At least half of that was due to CMP’s construction, he noted, and that won’t be an ongoing issue.

First Wind also is spending money to upgrade a transmission line in Lincoln, Lamontagne said. That will help projects in eastern Maine but not solve the overall problem.

“While developers can improve the transmission system on a project-by-project basis, we believe the region is in a better position to make upgrades that will benefit the whole region by allowing more wind penetration,” he said.

Wind developers want ratepayers to pick up a larger share of the upgrade costs, and they have a recent ruling by federal utility regulators on their side. To the extent that New England policy makers decide in the coming years that more renewable energy benefits the region, customers will help pay for new transmission lines.



Beyond upgrading transmission lines, the ISO has some ideas how to improve wind’s availability and reduce curtailments.

The systems operator is planning to incorporate wind forecasting and weather information, as well as historical data, to help schedule turbines. Generators will be asked to automatically communicate real-time power output and weather conditions.

The ISO also is upgrading the algorithm, or data-processing calculations, used to dispatch wind plants. It will let plants know every five minutes how much power they can safely put onto the grid. These and other enhancements are expected to be done in early 2015.

New England also may learn some lessons from Texas, the country’s leader in wind generation.

Three years ago, wind power expansion began to overwhelm the existing transmission network and the state’s grid operator began backing wind down. Since then, it has reduced curtailments with a computerized data tool that helps balance massive amounts of wind power from West Texas with the Gulf Coast and northern Panhandle.

On one day last year, the management tool helped integrate 7,500 megawatts of wind power into the Texas grid, according to a report in Greentech Media. That added up to a record-setting 22 percent of the state’s entire electric load. 

Tux Turkel can be contacted at 791-6462 or at:


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