Utility officials, regulators look for ways to harness surplus wind power

Since 2005, New England's wind power potential has exploded, from about 2 megawatts (mW) to 700 mW at the outset of this year.

The Lowell Mountain and Sheffield wind projects in Vermont's Northeast Kingdom account for more than 10 percent of that regional capacity, but the grid in Vermont's rural region cannot handle all of the renewable generation feeding through it when generators are at full capacity. As a result, ISO New England, the operator of the New England power grid, orders wind projects to cut back - or curtail - their production.

ISO summarized the wind power and curtailment situation in a recent letter to the Public Service Department.

"In New England, most of the commercially operating wind resources are located in Maine, New Hampshire and Vermont. They tend to be located in rural areas, far from concentrations of customers, and notably, in areas with the least robust transmission facilities," ISO spokesman Eric Wilkinson wrote. "Curtailments generally arise when the maximum potential output of a resource would exceed the capacity of the existing transmission system."

That is what's happening in the northern Vermont grid. The transmission load, or appetite for power, in the region is roughly 120 mW, while the generators in that region can produce about 420 mW, according to a Public Service Department white paper submitted to energy legislators Thursday.

"Load and generation need to be balanced to ensure system stability," state officials wrote. "If there is more generation on the New England system than is needed to provide power ... then ISO-NE curtails generators to keep the system in balance."

When the northern wind plants are producing more energy, state officials write, "electricity must travel relatively long distances on transmission lines not originally designed to carry significant amounts of generation."

Curtailing wind projects results in lower revenues for their operators because many energy credits are directly tied to a project's generation. State officials note that if a utility-owned project is curtailed for extended periods of time, ratepayers would absorb those costs.

The Lowell Mountain wind project, for example, sells renewable energy credits (RECs) and brings down federal tax credits based on the number of kilowatts it produces in an hour (kWh). Green Mountain Power spokesman Robert Dostis previously said the utility sells RECs for 5 to 6 cents per kWh, and the federal tax credit for commercial wind production is set at 2.3 cents per kWh.
Green Mountain Power spokesman Robert Dostis greets visitors to the Kingdom Community Wind project site. GMP is giving tours of the site through August. Photo by Andrew Stein/VTDigger

But state and GMP officials say the situation will get better.

GMP is installing a device known as a synchronous condenser for the Lowell project to generate or absorb extra voltage. Officials say this development should result in greater production consistency and less curtailment mandates.

"With the installation of the synchronous condenser, we expect the effect of curtailment on the plant to be significantly diminished," Dostis said.

Public Service Department officials note that ISO New England is creating a wind forecasting system to provide wind plants with better information ahead of time, and they say storage technology is improving to the point where it can help provide more consistent power throughout the course of a day from an intermittent power producer, like a wind plant.

Rep. Tony Klein, who chairs the House Natural Resources and Energy Committee, said that as ISO New England innovates and as the Northeast Kingdom develops under Bill Stenger's $600 million plan the curtailment problem would recede.

"Curtailment is not a long-term issue," Klein said. "It's a bump in the road, and it's caused by a variety of issues. It's caused by a temporary decrease in load demand at the moment, and it's caused by a changing generation landscape. ISO is going to have to adapt to those changes, and they're going to have to modernize."

The Public Service Department also recommends that the Public Service Board should not permit new generation projects unless an applicant has demonstrated to the quasi-judicial board that the project would bring "minimal expected curtailments."

Department officials plan to speak to the board in upcoming weeks to determine if the board could implement such a change, or whether there is a need for legislative action.