Restoring Power Plants to Dependable Peak Efficiency

Two peaker plants in the southern U.S. found the experience and know-how of a seasoned rotating equipment services provider indispensable during a control system upgrade and a generator rewind project.

Every year, power grids are facing more and more intense impact from climate change, whether the result of blizzardy, icy winter conditions or scorching summer heat waves. In early September 2022, a heat dome settled over the U.S. West Coast and brought temperatures that set all-time record highs. The extreme heat fueled wildfires and stressed the power grid before a tropical storm moved in and cooled things down. Mere months later, an arctic outbreak that occurred in February 2023 shattered records in the Northeast, including –108F wind chill, and put a dire strain on the region's power supply.

When a drastic rise or drop in temperature like this occurs, energy usage abruptly increases as people turn to their thermostat-controlled heated or air-conditioned homes to avoid the uncomfortable weather. But when all of the heaters or all of the air conditioning units are on, power grids everywhere must work overtime to keep our energy sources online. And sometimes the stress can be too much for the grid to take.

Enter "peaker power plants" or "peakers" for short. Peakers generally use gas turbines to supply temporary power to the grid in addition to the power that baseload power plants provide. Baseload plants typically generate electricity at a fairly steady level throughout the day, all year long, while peakers fire up and then power down over a short duration of time, typically less than 1,500 hours per year—and some may operate as low as 250 hours per year.

Reliability is an absolute must for these peakers to fulfill their role as a power grid's contingency plan to help not just meet, but sustain demand during a dramatic uptick in usage. As such, the upkeep and maintenance of peaker plants is vital to ensure they are able to fire up quickly when called upon. Not tending to a peaker plant's poorly configured control system or faulty generator could mean the difference between a trusted power backup source or a dramatic state of emergency.

This article will go into deeper detail on how plant operators at two different peaking facilities worked with an outside rotating equipment services provider—EthosEnergy—to address similar operations issues. In order to maintain a higher level of reliability and meet their commitment as a redundant power source, both plants took proactive means to improve their capabilities before a crisis occurred.

A multi-unit peaker plant in Texas contacted the rotating equipment services provider and inquired about control system capabilities and solutions. Facility managers wondered if there was anything EthosEnergy could do to help overcome the plant's issues with output and reliability. The site was experiencing significant reliability issues and not meeting required start times or output requirements. As a peaking facility, it was having to purchase power to meet contractual commitments and increase staffing to troubleshoot operational issues.

The rotating equipment services provider performed an on-site assessment and found the control system to be a major contributing factor to the plant's reliability issues. Technicians then began to troubleshoot the problem by monitoring units remotely, and performed plant health and diagnostics (engine performance) evaluations.

The customer awarded EthosEnergy a purchase order and began an outage to correct the issues. The provider's controls engineers upgraded the turbine and balance-of-plant (BOP) controls, and corrected uninterruptible power supply (UPS) issues, power distribution issues, and wiring issues (Figure 1), among other problems. The scope also included reconfiguring existing hardware and upgrading/replacing hardware where necessary.

1. A control system upgrade at a Texas peaker plant improved startup reliability, increased output, and provided more stable performance, among other things. Courtesy: EthosEnergy

All of the upgrades applied met a standard, repeatable solution, whereas, the original configuration was very ad-hoc. The outage commitments were met and the customer has continued to retain the rotating equipment services provider to provide remote support long-term.

As a result of working with EthosEnergy, the peaker plant's start-up reliability increased dramatically and power output increased by more than 2% per unit. The rotating equipment services provider solved sync-to-grid problems to satisfy a 10-minute startup to full load. Turbine controls now provide stable performance and repeatable startup. System manuals and drawing documentation were updated with additional content and improved, and extensive on-site training was given during commissioning. The facility has seen a tremendous return on its investment, with units operational for more than 180 combined hours during the Texas winter storms of 2021, a critical time of need for power generation.

With the high-demand season approaching, a peaking power plant in Louisiana needed to be in prime condition. For this peaking facility, ensuring its ability to run at full operational capacity by the start of the summer season was critical.

Unfortunately, the peaker started to experience tripping on a GE Frame 7A6 generator attached to one of its gas turbines, causing a major problem. The generator had been experiencing high levels of vibration for about a year and a half, but in early-March 2021, those vibrations started tripping the unit. As the unit was critical to power generating capacity, the plant decided to commission a generator rotor rewind, but it would need to find a partner who could work to a tight deadline—operational in less than 60 days. If its unit was not online by May 1 that year, it would be stung by significant financial penalties under its power contract.

Because of the incredible sense of urgency, a request for support was sent out by the peaking plant to outside rotating equipment services providers on March 5, and due back by March 9. There was heavy competition, with five bidders in play. A key concern for the peaker's management was having the May 1 deadline met. That was something EthosEnergy was confident could be achieved. Further, the rotating equipment services provider was also able to save the peaking plant money by carrying out the reassembly work on a single shift.

On March 11, the client verbally awarded EthosEnergy the generator rewind contract. Within just four days, the provider mobilized its field service crew and subcontracted the required crane. The rotating equipment services provider then fully disassembled the unit and transported the generator to its Farmington facility in New Mexico. There, workers dismantled the rotor, removing the copper and stripping it back to its bare metal. They then examined and corrected the failure mechanism, and installed new insulation.

Once the unit was reassembled in the provider's workshop, a high-speed balance and a heat run were performed. This allowed the provider to confirm with the peaking plant that there would be no recurrence of the vibration issues experienced previously on-site. The unit balanced quickly and well below industry targets of 2.5 millimeters/second (mm/s) throughout the entire speed range, from zero to 3,600 rpm. The final balance achieved was 0.5 mm/s.

By working with EthosEnergy, the rotor (Figure 2) was back on-site and mechanically assembled by April 28, three days ahead of the deadline. From beginning to end, the project took the rotating equipment services provider just 45 days to complete because of their experience and knowledge in dealing with these kinds of issues. This was as much as 10 days quicker than many experts normally expect for a turnaround on a project of this nature—especially during the high-heat outage season in the U.S.

2. A generator rewind was required at a Louisiana peaker plant due to high vibrations. The job was done in just 45 days, improving reliability and restoring output while also extending the generator's lifecycle by 20 years. Courtesy: EthosEnergy

The rotating equipment services provider also saved the peaker plant approximately 15% in maintenance spend by working a single shift. The peaker now had a unit that would reliably run at full capacity during peak season and the generator rewind extended the lifecycle by 20 years, improved reliability by about 80%, and output was back up from 60 MW to the expected levels of 93 MW.

Since the installation, the peaker plant's unit has been running exceptionally well with no operational issues. The rotating equipment services provider has managed to build upon that first job, cementing a solid relationship with the client resulting in successful bids on further projects at the peaker plant including carrying out testing on three identical units and putting a plan in place for future repairs.

The power grid is more heavily reliant on peakers than ever to sustain energy usage in response to unplanned situations. Whatever the need, climate-related or not, working with a trusted service provider to help ensure operations are at their peak performance before a problem occurs enables power plants to provide reliable service to their customers when most in need.

—Chris Wilkinson is senior vice president of Growth with EthosEnergy.

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