The amount of wind generation in the PJM Interconnection is currently causing congestion issues that will require at the minimum transmission upgrades, Steve Herling, PJM’s vice president of planning, told TransmissionHub. If more wind is integrated into the system, much larger transmission solutions will be required.
Wind has been causing light load congestion over the midnight period, creating operational issues for the RTO, Herling said. By nature, wind generation is less available during peak load periods, for which PJM typically plans and models. In the summer on the East Coast, for example, wind availability is at about 13%, compared to baseload fossil generation availability of about 90%, Herling said.
However, during the midnight period, wind generation increases to 80% to 90% availability, while load decreases to about 50%, he said. In northern Illinois, for example, nuclear generation is at full capacity and baseload coal plants are running at a fairly high availability, while wind generation, including some from the Midwest ISO, has increased exponentially. At the same time, natural gas plants during this time are typically cycled down, leaving limited options for generation curtailment.
“The energy has to go some place, and we’ve started to see some overloading problems over those light load periods,” Herling said. “What you’ve got is a lot of generation that wants to run at that time and you have to shut it down or see what else you can do about it.”
“Basically, it gets down to, can you move the coal, and to what degree?” Herling said.
Nuclear power plants are designed to run at a certain level and have scheduled refueling outages structured around running at that level, which takes them out of the range of options for generation curtailment. Curtailing wind would be one possible solution, but it also has its limitations, he said.
“The wind is often spread out over large areas, so it’s sometimes operationally challenging to dispatch the wind down,” Herling said. “We can go into negative locational pricing but we have observed some operational problems [with that].”
To address these congestion issues, PJM has begun to include modeling for light load periods in its planning process, as well as peak deliverability periods.
“If the lines are going to be overloaded, we’ll require that we make some upgrades,” Herling said.
The discussions the RTO has been having around changes to its planning process, which looks five to 15 years down the road, include evaluating how it plans to address public policy requirements, “which may or may not involve us planning more proactively for wind,” Herling said. He expressed concern that should wind generation increase exponentially, to the “tens of thousands of megawatts,” bigger solutions will be required.
“We recognize that we have to look at peak deliverability as well as light load,” he said. “The consequences are likely to be there will be more transmission infrastructure required. It may involve some noticeable costs to integrate these larger amounts of wind.”
According to PJM’s website, current wind generation totals 1,157 MW.
If a transmission buildout is required, it will be to serve states farther east, Herling said, and states often have their own agendas for meeting public policy requirements. Virginia, for example, is looking at offshore wind, which would obviate the need for wind imports from the Midwest.
“It’s going to take a little bit of time to figure out what is the optimal transmission buildout to serve all of these needs and what is most consistent with the needs and interests of different states that have established these renewable requirements,” Herling said. “For us to suggest that the buildout will be large amounts of transmission from the Midwest to the east would be premature until states have had the opportunity to evaluate the costs and benefits of meeting renewable requirements.”
These efforts are in the advanced information-gathering stages, he noted. Dominion Resources (NYSE:D), headquartered in Virginia, on March 13 released a study that found that one offshore substation platform with two 230-kV power lines would be able to send to shore 500 MW to 700 MW of offshore wind generation. Western PJM states have asked PJM to do an analysis of offshore wind and are starting to build a business case to best meet their needs, Herling said.
“It could be a little while yet before making this decision and pulling the trigger on some combination of wind and transmission infrastructure,” he said. “This year in particular we’re going to start to see a lot more information on the table as to different ways for states, individually or collectively, to meet their needs. Then the states will have to start weighing the pros and cons of the dollar signs and see what they’re prepared to do.”