Soot to solar: Unmasking the coal plant reliability myth

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The myth that coal power equates to grid reliability is not unique to Australia. Here’s what happened when an old clunker was removed from the grid in northern Illinois.

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Oftentimes the coal industry and utilities will raise the false specter of the lights going out if their aging, polluting power plants are shut down.

Last week UCS released a new report entitled Soot to Solar: Illinois’ Clean Energy Transition. Among our key findings was that the coal-burning power plant owned by NRG in Waukegan, Illinois, can be retired with no impact on electric grid reliability.

When asked about our report, NRG implied similar sentiments as the above in saying it hadn’t had the opportunity to review our study or our “assumptions on impact to grid reliability.”

In this post, I highlight Soot to Solar’s analysis of electric reliability and retiring the Waukegan plant to further explain our process and what we found.

Chicago’s ring of fire

As recently as ten years ago, the Chicago region was surrounded by six coal-fired power plants. Today the Waukegan plant is among the last to continue operating. The Fisk, Crawford, and State Line plants have been retired and the Joliet plant was converted to run on natural gas (another coal-fired unit continues to operate in nearby Will County).

For several years, local residents and the grassroots organization Clean Power Lake County have been pushing for the retirement of the Waukegan coal plant and creation of a just transition plan for workers and the community. The Waukegan effort is featured in a companion case study to Soot to Solar.

The Waukegan coal units were built in 1958 and 1962. In recent years they have only operated at around a 30% capacity factor, which is a measure of how much electricity a plant produces compared to its full potential output. This is a sharp reduction from the 60-70% range in 2011 as shown in the charts below (“ST 7” and “ST 8” are unit designations for the two coal boilers):

While the Waukegan plant is burning less coal than it used to and did install some equipment to reduce emissions in 2014 and 2015, we analyzed what effects, if any, there would be on the power grid if the plant was retired.

Retiring the Waukegan coal units does not affect electric reliability

For this part of our Soot to Solar analysis, we retained PowerGEM, an electric engineering and transmission firm, to conduct a retirement analysis of the existing generation at the Waukegan site. In addition to the coal units, there are also four oil-fired combustion turbines at the site totaling about 100 megawatts of capacity. These turbines run only a handful of hours a year.

Community leaders stand with local residents at Waukegan Municipal Beach to demand healthier clean-energy economies. At Clean Power Lake County’s (CPLC) Hands Across the Sands event, September 2014. [Photo by Karen Long MacLeod for CPLC]
The power grid functions across the eastern U.S. with electricity flowing throughout the Eastern Interconnection, under the control and management of grid operators like PJM and the Midcontinent Independent System Operator (MISO).

The needs of the Northern Illinois area are met from power plants both nearby and distant, based on the economics of supply and demand, and the limits of the transmission system.

PowerGEM used what is known as a power flow model from PJM which details what the electric grid will look like in 2022, and what will limit the delivery of energy to the Chicago area.

So, what happened when PowerGEM removed the existing Waukegan power generation from the model? It was replaced by uniform increases from other resources in the PJM system.

In other words, the test for removing the Waukegan plant was to verify that other power generators could pick up the slack with no problems showing up in several technical categories designed to ensure the grid functions properly (known as base thermal, voltage, generator deliverability, and load deliverability). The Waukegan plant passed this test.

Another part of the analysis, known in the technical jargon as N-1-1, looked at what would happen to the power grid in the ComEd/Chicago service area during a sequence of events such as loss of a large power line, followed by system adjustments, followed by loss of another transmission line or plant.

PowerGEM found that needs shown in the N-1-1 analysis for the retirement of existing Waukegan generation could be solved by placing a new 100 megawatt generator at the Waukegan site to replace the oil-fired combustion turbines.

As discussed in Soot to Solar, it could also be solved through installing the same amount of clean energy options like solar, storage, demand response, efficiency improvements, and other distributed generation located across many cities and towns surrounding downtown Chicago.

Retiring the Waukegan plant opens the door to clean energy and cleaner air

As we discuss in detail in our report, coal-fired power plants emit numerous harmful air pollutants and carbon pollution, create troublesome coal ash waste disposal areas, and use up valuable land that could be put to other important uses for communities.

Thanks to the Future Energy Jobs Act, clean energy is expanding across Illinois. Opportunities abound for places like Waukegan. Now is the time for NRG and local officials to respond to the desires of community members and develop a plan for closing the plant, cleaning up the site, and providing support for economic development to create good jobs for the community and replace lost tax revenue.

The myth that the Waukegan coal plant is needed for grid reliability should not stand in the way of this important transition.

Source: Union if Concerned Scientists. Reproduced with permission.

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