Friday, September 15, 2023

The Ideal Retirement

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A series of white papers and screening tool help determine clean energy options for retiring coal plants.

In July 2023, the utility DTE Electric made an announcement that has become increasingly common over the past few years. As part of an agreement seeking regulatory approval of its integrated resource plan (IRP), the Michigan utility proposed shutting down all its coal-fired power plants by 2032. The proposal accelerates the closure of the 3,000-plus megawatt Monroe power plant by three years.

Announcements of U.S. coal plant closures are so frequent that they are difficult to track. Indeed, a report issued earlier this year by the Institute for Energy Economics and Financial Analysis found that the United States is on pace to close half of all coal-fired power plants by 2026, with coal-fired generation falling from a peak of 318 gigawatts of capacity in 2011 to 159 gigawatts in 2026 and 116 gigawatts by 2030.

In the recent past, coal plants slated for closure were often replaced by new natural gas-powered plants or redeveloped for other uses. However, a mix of policy and corporate and utility decarbonization goals are driving many utilities to consider repurposing coal plant infrastructure to site energy centers of the future.

For example, according to an analysis by the Smart Electric Power Alliance, nearly 80 percent of all U.S. customer accounts are served by a utility that either has a 100 percent decarbonization target or is owned by a parent company that does. Additionally, in 2021, the U.S. Congress and the Environmental Protection Agency specifically encouraged companies closing coal plants to redevelop the sites for renewable generation. The Inflation Reduction Act (IRA) passed in 2022 also allocated $5 billion to support the newly-created Energy Infrastructure Reinvestment program. The program is designed to provide loan guarantees that enable existing energy infrastructure no longer in operation to be repurposed for clean energy and other decarbonization uses.

Guidance Drawn from EPRI’s Broad Expertise

Over the past 18 months, EPRI has produced a series of white papers and, more recently, a customizable screening tool to help utilities assess coal sites for clean energy generation technologies. Led by EPRI’s plant decommissioning program, the effort also integrates the expertise and experience of nine EPRI programs.

“My program is good at closing power plants down, but we don’t necessarily understand what it takes to turn a coal plant into X technology,” said Lea Millet, a senior technical leader who oversees EPRI’s decommissioning program and spearheaded the development of the tool and the white papers. “We needed expertise from these nine other programs to tell us what you need from a coal plant for hydrogen or solar or advanced nuclear to be successful.”

Retiring coal plants have many built-in features that make them promising candidates for future clean energy use. “These coal sites are generally good generation sites,” said Brandon Delis, an EPRI director. “In a lot of cases, these were first-choice sites, meaning that the coal plants were sited, and then the transmission network was basically built around them. So, when you look at things like transmission, water resource availability, and transportation, they all line up well.”

Other inherent advantages of former coal plants for second lives in renewable generation include existing interconnection, land use, and environmental permits that can streamline the often protracted permitting process. Retiring coal plants also have buildings, warehouses, and even equipment, such as generators, that can be repurposed for less than it costs to build entirely new facilities.

Coal power plant

Not all Uses are Created Equal

The white papers and screening tool acknowledge and highlight that the choice about the optimal reuse of coal plants for new generation is not simple. Some sites are better suited for solar photovoltaics, others for advanced nuclear or energy storage. “The point of this effort was to help people narrow in on the best opportunities because, from a macro level, you look at all these sites and say, well, they’re all good,” Delis said. “But if you really get into evaluating a technology at a particular site, the differences are not trivial. The intent was to help narrow down particular technologies for given sites and at a fleet level.”

The white paper series delves into some of the factors that make a coal site suitable (or not) for a range of commercially viable generation technologies. For example, Repowering Coal-Fired Power Plants for Hydrogen Production with Electrolysis explains the interest and market activity in green hydrogen production as a way to both utilize excess intermittent renewable generation and enhance grid stability and reliability. There have been times in Great Britain and the United States when an oversupply of renewable generation has resulted in negative electricity prices. That electricity could instead be used to fuel electrolysis to produce carbon-free green hydrogen.

There are many nuances to sort through to determine whether a coal site with these features is a good candidate for green hydrogen production. Depending on the planned capacity of the production facility, the transmission and distribution (T&D) lines may need to be modified or upgraded to handle the incoming power. The coal site’s interconnection may also need to be upgraded by adding a substation and step-down transformers.

Separate white papers consider what makes coal sites good candidates for battery energy storage, bulk energy storage, advanced nuclear, solar PV, net zero industrial clusters, and natural gas and hydrogen-fired generation. At the same time, another examines the equity and environmental justice considerations of repowering coal plants.

A Tool to Help Drive Better Conversations and Prioritization

The recently released screening tool allows utilities and other stakeholders to input site-specific information to evaluate different repowering options. The information required is expansive but readily available to most utilities. It includes factors like the availability of buildable land, existing permits and interconnection, available transportation infrastructure, population density of the surrounding area, and T&D line capacity. The tool weights the inputs based on the repowering option being considered and provides a high-level score about the site’s suitability for different possible uses.

“We assigned points, and the tool goes through a calculation to give you an evaluated score,” Millet said. The tool aims to provide objective information for stakeholders to begin understanding which repowering options hold the most promise for different sites. “What you have here is an efficient way to compare and contrast options and understand what’s important,” Delis said. “The utilities will still have to do the multi-million-dollar site evaluation with a consulting engineer after the fact. But this tool allows them to feel confident in what they’re studying before they make that investment.”

The tool can also be helpful beyond the evaluation of individual coal sites. Utilities can use it to inform their integrated resource plans. “If my IRP says that over the next ten years, I’m going to develop X percent of solar or battery storage or some other type of energy,” Millet said, “this tool can help investigate what sites I already have that may be amenable to that type of energy.”

Externally, the tool can also help inform conversations with policymakers, regulators, and other stakeholders who may have definitive ideas about how retiring coal plants should be used to support decarbonization. The tool is a resource for more objective and data-driven conversations about the optimal technology choice for repowering a coal site. The tool can also be helpful to utilities as they develop pilot programs to test clean energy technologies.

“We’ve seen through the years where a utility will test a technology, but they will do it at a bad site,” Delis said. “If it doesn’t work, they’ll conclude it is a bad technology. But it may just be that they chose a bad site. This tool can help avoid that problem.”

EPRI Technical Experts:

Lea Millet
For more information, contact