Vermont Gov. Peter Shumlin on July 26 urged ISO New England (ISO-NE) to consider whether it could do more to integrate and fully use renewable resources into its grid operations, including during times of peak demand where use of other “more expensive and dirtier resources” may be avoided.
His letter to ISO-NE President and CEO Gordon van Welie was in response to ISO-NE’s decision to curtail Kingdom Community Wind’s energy production during the heat wave on the week of July 15.
Information on how much power was curtailed was not available on Aug. 5.
According to Green Mountain Power (GMP), the company partnered with Vermont Electric Cooperative to build 21 wind turbines on Lowell Mountain, and the Kingdom Community Wind project began generating electricity at the end of 2012. At full operation, the plant is expected to produce about 186,000 MWh annually.
Representatives for GMP and Vermont Electric Cooperative could not be immediately reached for comment on Aug. 5.
Shumlin said in his letter, “While I understand ISO-NE’s reliability mission, I urge you to ensure that it is exercised with clear regard for the clean energy goals of Vermont and the region,” noting that Vermont has implemented policies to increase the production of local and renewable energy projects, including wind.
“ISO-NE’s curtailment of renewable resources at a time when it instead asked for generation from our oldest and dirtiest power sources to shoulder the burden during peak energy usage runs counter to these goals,” he said.
Shumlin also said that ISO-NE has previously noted deficiencies in the transmission system surrounding Kingdom Community Wind and elsewhere in the region where curtailments have occurred. He urged ISO-NE to consider whether its planning assumptions used for approval of projects align well with its operation assumptions.
“Vermont has a clear preference for renewable resources and would have preferred that the local renewable energy produced by this utility-owned resource had been used to meet regional power needs in the Northeast Kingdom and surrounding communities where homes and businesses were also experiencing a period of high demand last week,” he said.
He also called on ISO-NE to fully account for growing distributed generation renewable resources in its transmission planning assumptions.
“Ensuring that these resources are counted in ISO-NE’s planning assumptions may save money by lowering transmission buildout requirements, and will also help support regional renewable energy goals,” Shumlin said, later adding, “With the very real threat of climate change facing our region, we need a strong commitment from ISO-NE to help reduce greenhouse gas emissions and integrate renewables into our regional grid.”
ISO-NE spokesperson Marcia Blomberg told TransmissionHub on Aug. 5 that in that area of Vermont, as in many other areas in northern New England where wind is located, the transmission system is limited and was built originally to serve native load.
“They’re not very populous regions, but those are also areas where the wind is fairly rich,” she said, adding, “When all the resources in that area of Vermont are operating, the transmission system is not sufficient to carry out all the power that they produce. In terms of Kingdom Community Wind, they interconnected to an area where we determined – after much study in 2011, working with them – that they needed to install some equipment to boost their interconnection to the grid.”
ISO-NE required Kingdom Community Wind to install a synchronous condenser to boost their interconnection, and that upgrade has not been completed yet.
“All things being equal, if all resources in an area are operating, but we need to curtail some because they can’t all get their power out – they would overload the system, otherwise – if they cannot get their power out, then we would need to curtail someone,” she added. “We would curtail the resource that hasn’t completed its interconnection upgrades first.”
Blomberg said, “The synchronous condenser will help, but it will not eliminate all the need to curtail at times because the transmission system will remain limited. So, hypothetically, if there was more robust transmission, that would help.”
She also noted that ISO-NE operates the system under mandatory federal reliability standards.
Furthermore, there were other renewable resources in that area in Vermont – other wind and hydro – that were able to put their energy out on the system during the heat wave when Kingdom Community Wind was curtailed.
ISO-NE spokesperson Ellen Foley told TransmissionHub on Aug. 5 that ISO-NE will finalize its response to the governor this week.
ISO-NE memo to stakeholders on curtailments
As reported, Eric Wilkinson, external affairs with ISO-NE, told New England stakeholders in a June 28 memo that certain activities, such as improvements to the elective transmission expansion process, could help reduce the amount of wind power curtailments.
Such improvements could help by allowing more efficient identification of marginal interconnections and transmission constraints. A more efficient elective expansion process would better complement the existing generator interconnection process, he said, adding that the possibility and nature of potential changes to interconnection studies is under consideration at ISO-NE.
While ISO-NE does not collect specific data related to the amount of time that any particular resource is curtailed, it has begun a process to collect indicators of curtailments related to wind generators. That data collection effort is part of ISO-NE’s enhanced wind power forecasting project, which, when fully operational, is expected to provide a better understanding of the magnitude of curtailments, Wilkinson added.
ISO-NE is also undertaking an initiative that will incorporate wind forecasting and wind resources into its processes, scheduling and dispatch services. The project will acquire external wind power forecasting services, create operator situational awareness displays, partially integrate wind into the real-time dispatch and maintain historical wind data for future use of the forecast service, auditing and other analysis. That project, Wilkinson added, is scheduled for implementation in the second half of this year.
After the wind power forecast integration project becomes operational, all wind resources will be required to provide real-time telemetry indicating current output and additional meteorological data, which will support ISO-NE’s short-term wind power forecast system and improve the system operators’ situational awareness during changing weather conditions.
Among other things, he said, “Resources are less susceptible to curtailment if they interconnect in areas with particularly strong transmission infrastructure (generally closer to the load), or elect to install upgrades to the grid.”
When the output from any resource, such as wind, jeopardizes reliability, curtailment may be needed, and ISO-NE, at times, needs to curtail wind resources to ensure that the bulk power system and/or sections of the system are not overloaded, and service to customers is maintained, he said.
Such factors as transmission constraints, interconnection choices and the technologies associated with wind generators can contribute to the need to curtail wind resources.
Transmission constraints, at the regional and local levels are the most significant cause of curtailments, he added.
Article amended at 1:27 p.m., EST, on Aug. 6 to note that the heat wave occurred on the week of July 15.