Repowering is an option that many owners consider to extend the life of power plant facilities by replacing older equipment with newer assets with higher capacity, greater efficiency or both.

There are a few different methods a repower project can pursue, one of which is heat recovery repowering. This involves demolishing the coal boiler at a coal-fired plant while keeping the steam turbine. The boiler is replaced with a gas-fired combustion turbine and a heat recovery steam generator (HRSG).

Burns & McDonnell professionals have been helping develop a large heat recovery repowering project for a client we previously helped on another, smaller repower effort. The new project includes installation of an advanced, J-class gas turbine as a 200-MW coal-fired plant is repowered to a 550-MW gas-fired combined-cycle plant.

The process of working through this project has shed light on five of the common myths and misperceptions about repowering.

Myth: It’s too hard to budget a repowering project.
Reality: Part of the project is new construction, and part is reviewing and repurposing existing equipment. Estimating for new construction is routine. Reviewing the existing equipment — to determine what to keep, what to upgrade and what to replace — does require a thorough, systematic review, but that approach pays off with more budget certainty and fewer unexpected costs popping up along the way.

Myth: Repowered units aren’t competitive with new units for plant efficiency.
Reality: Steam turbine technology hasn’t changed much in the last two decades, but there are significant opportunities for efficiency gains with the combustion turbine and HRSG. This current project has designed efficiency that is superior to what has been published for some recent new plants and likely will be among the most efficient gas turbines installed in the U.S. to date.

Myth: Repowering will lead to the elimination of plant jobs.
Reality: There is ample work inside the powerhouse during a repower job, dealing with upgrades, updates and replacing small components. This corresponds with the maintenance work that current staffers likely have been performing for the last 30 years. They can continue that support role inside the powerhouse while the new construction is proceeding outside. Plant staff can assist during startup as well.

Myth: The existing equipment won’t last.
Reality: While plants typically have a design life of 30 years, older coal unit components have proven to be very robust. There are operating coal plants in the U.S. that have been around for more than 70 years with existing equipment intact and operational. Therefore, tacking another 30 years onto the life of steam components at a 30-year-old facility being repowered is still well within demonstrated results we can see in the industry.

Myth: Construction at an existing site is too difficult.
Reality: The concern is that new construction might come across something unexpected. To mitigate this concern, lidar scanning can be utilized for aboveground structures and existing piping systems that the new equipment will tie into. The new construction site can be excavated in order to uncover all underground utilities or other unknown obstructions.  

Repowering projects are not the right fit for everyone. Many owners study the option and decide to build a new plant instead. What is important is for decisions to be based on accurate information rather than misconceptions. Our deep experience with power projects in general and repowering projects in particular can help identify when the gains are worthy of consideration.

 

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by
Craig Demmel, PE, is a project manager in the Energy Group at Burns & McDonnell. His duties include managing engineering, construction and startup activities, as well as interfacing with project owners.