TVA has now approved a total of $350 million in nuclear funding for the SMR project. The federal utility approved an initial $200 million at its February 2022 board meeting.

TVA is among the investors in GE Hitachi’s BWRX-300 SMR, a 300 MWe water-cooled, natural circulation reactor with passive safety systems that leverage the design and licensing basis of GEH’s ESBWR boiling water reactor.

The BWRX-300 leverages a unique combination of existing fuel that is currently used in operating reactors (and does not require HALEU), plant simplifications, proven components and a design based on already licensed reactor technology. 

TVA is currently preparing a construction permit application for a BWRX-300 at the Clinch River Site. The utility is also exploring additional sites in the TVA service area for potential SMR deployments.

“We believe advanced nuclear technologies will play a critical role in our region and nation’s drive toward a clean energy future,” said Jeff Lyash, TVA President and CEO. “Small modular reactors are an energy innovation technology that America must dominate – for our energy security, which is really our national security.”

The TVA Board also took action to accelerate the agency’s deployment of clean technologies, including 10,000 MW of solar by 2035. The Board approved TVA’s FY25 budget, which includes a rate increase to support sustained growth and ongoing construction of nearly 3,500 MW of additional generation.

Utilities everywhere are projecting increased demand, and TVA is no exception. According to TVA, the region’s population is growing three times faster than the national average. To address the need for more electricity, TVA is investing nearly $16 billion through FY27 to build new generation and infrastructure and enhance the reliability of existing assets.

Komm most recently served as plant manager at Browns Ferry, TVA’s first and largest nuclear plant. Komm joined TVA in 2021 when he served as the assistant plant manager at Browns Ferry, which has three boiling water reactors producing about 20 percent of TVA’s total generation capacity. Browns Ferry can produce up to 3,954 MW of electricity

Prior to joining TVA, Komm spent 18 years with Southern Nuclear Company where he got his start as an engineer and held a variety of roles, including Operations Director at Hatch. He also served as Work Management Director at Plant Vogtle. Komm has led three stations as plant manager from 2018 to 2020 including Vogtle, Farley and Hatch.

Earlier this month TVA also named new leadership for its Watts Bar nuclear plant near Spring City, Tennessee.

Chris Reneau was named site vice president, effective June 12. Current Watts Bar Site Vice President Tony Williams will step into the role of Vice President, Outage Services and Supplemental Resources for TVA’s entire nuclear fleet.

Reneau most recently served as vice president for operations support at the TVA Nuclear Fleet Center in Chattanooga. Since joining TVA in 2009, he has held multiple leadership roles, including Senior Manager Systems Engineering, Senior Manager Design Engineering, Site Engineering Director and Director of Operations before becoming Plant Manager at the Sequoyah Nuclear Plant in 2021.

Watts Bar is TVA’s second largest nuclear plant—its two pressurized water reactors produce about five percent of TVA’s total generation capacity. Each unit produces about 1,150 MW of electricity.

“Solar energy enhances Mississippi’s economic competitiveness, and Origis is removing limits to a cleaner, brighter future by building the region’s clean-energy infrastructure,” said Johan Vanhee, chief commercial and procurement officer for Origis. “Golden Triangle II is the first step in fostering a zero-carbon economy across the state that supports our nation’s economic and energy security goals.”

The other two Origis undertakings in Mississippi are Golden Triangle I, in Lowndes County, a 200 MWac project with 50 MW of battery storage; and Optimist, in Clay County, a 200 MWac project with 50 MW of battery storage. According to the company, this represents the largest battery storage portfolio under construction in the state. Once completed in 2025, Origis expects its Mississippi portfolio to have a total capacity of 550 MW plus 150 MW of battery storage.

“As a national clean energy leader, TVA is on the forefront to drive carbon reduction across all sectors of the economy and provide the clean power needed to fuel our region’s growth,” said Amy Tate, TVA Southeast region executive. “Together, with partners like Origis, TVA is developing carbon-free energy solutions that create jobs and investment in the communities we serve.” 

Origis Energy developed, constructed, and will operate the three projects for TVA. Each site will deliver clean energy at competitive rates under Power Purchase Agreements (PPAs) executed between TVA and Origis. TVA says it will use the power to help meet the energy demand and sustainability goals of some of its large industrial customers, through its Green Invest program, including Meta. Golden Triangle II will support Meta’s operations in the TVA area as part of the more than 1,000 MWac capacity Meta has partnered with TVA on, per the companies.

“Partnering with TVA on the Green Invest program has made it possible for our operations in the Tennessee Valley to be supported by new solar energy constructed in the region,” said Urvi Parekh, head of renewable energy at Meta. “This solar farm is Meta’s first renewable energy project in Mississippi, and we’re excited to see it come online.”

“Origis Energy and TVA’s announcement of the commercial operation of Golden Triangle II represents a significant milestone in our commitment to advancing clean energy solutions,” stated Tom Cornell, president and CEO of Prevalon Energy. “We are honored to be part of this project, enabling more renewable generation in TVA’s service territory. By generating carbon-free electricity, this project not only supports Mississippi’s economic competitiveness but also contributes to a cleaner, brighter future for the region. We are excited to be part of this endeavor and look forward to continuing to support sustainable energy initiatives with Origis and TVA.”

As coal and gas plants are taken offline to be replaced by wind and solar, grid stability and system strength can become serious challenges. This is due to the inherent inertia provided by rotating assets. To compensate, various approaches have evolved to provide the inertia, system support and stability the grid needs. These include capacitors, static VAR compensators, static compensators, a new batch of advanced electrical systems and transforming aging generators into synchronous condensing units.

Inertia and grid stability

Generators, motors and turbines provide inertia as they rotate at the same frequency as the electricity grid. Their presence acts as a buffer against power spikes and changes in frequency. During the evening peak, for example, frequency falls as people turn on air conditioning, heating, lighting and appliances. During the course of the day, frequency highs and lows must be balanced by grid operators to stay in the correct range (60 Hz for the U.S).

“In extreme cases, rapid changes in frequency can even take an entire neighborhood offline to maintain grid integrity,” said Morgan Hendry, President of SSS Clutch. “Failure to do so could damage equipment and if the situation worsened, lead to a regional blackout.”  

The potential for grid events has increased in recent years due to the growing presence of wind and solar. According to Industrial Info Resources (IIR), just five years ago the number of planned power generation projects to be built in the U.S. broke down to 57% renewables and 41% natural gas. This year, IIR reports that new-build power generation projects scheduled to begin construction in the United States between January 2024 and December 2028 will almost all be for renewable energy – 94%. That equates to 482 GW of new renewable generation by 2028.

Unfortunately, the addition of wind and solar coupled with the removal of coal and gas plants increases the potential for grid stability and disruption. In wind, for example, frequency converters operate between wind turbines and the grid that prevent the kinetic energy of the wind blades rotating mass from providing inertia. There is also the factor of the many ups and downs in available wind and solar energy capacity. At some points in the day, there are massive amounts of capacity and at others, capacity falls away. This causes havoc for those dealing with grid stability who are tasked with maintaining voltage and frequency values across their networks. To do this, they must balance electricity production with consumption. Frequency rises if energy production is greater than the energy consumed and declines when more energy is consumed than produced. Such ups and downs make the grid susceptible to events such as sudden generation loss, load variation, ability to arrest frequency changes following a disturbance, grid frequency instability, lack of system strength or even cascading failures.

Peaking plants are on standby to take up the slack as a primary approach to maintaining grid stability. But the presence of rotating assets by itself also acts to slow any potential surges or plunges in grid frequency.

“Inertia is energy stored in a generator or motor which keeps it rotating,” said Steve Scrimshaw, Executive Director Siemens Energy UK & Ireland. “It helps slow the rate at which the grid frequency changes, as rapid changes can create instability in the system.” 

Another challenge to overcome is the location of wind and solar assets. Many U.S. wind and solar farms are far from load centers. Their output needs transmitted over long distances and that leads to system losses as well as reactive power issues. Reactive power can be regarded as the form of electricity that creates or is stored in the magnetic field surrounding a piece of equipment. It is measured in volt amperes reactive (VAR).

“Long transmission lines operating at heavy loads consume VARs,” said Hendry. “Failure to replace the lost reactive power leads to conductor heating, voltage failure, system instability or collapse, motor damage and electronic equipment failure.”

Improving the grid

There are a great many technologies and approaches in existence to address lack of inertia, grid instability, and reactive power while providing overall system support.

Capacitor Banks  

Drive by any electrical substation and you will see rows of capacitor banks (or shunt capacitors as they are sometimes known). They are inexpensive and reliable, hence their widespread deployment. But they aren’t enough. They eat up real estate, can only supply reactive power (not absorb it) and don’t do well on large load or voltage drops.

Static VAR Compensators (SVC) 

SVCs are basically switches that consist of a series of shunt capacitors and other electrical devices that improve voltage control capabilities compared to regular capacitors. Static VAR compensating devices can be placed close to power load to lower reactive current demand on the transmission system. They can absorb or supply reactive power. But they don’t respond rapidly to sudden changes in the grid and their reactive power output varies according to the square of the voltage. Hence, they struggle when addressing voltage instability or collapse. Some recent versions, though, are faster and more sophisticated as they can be customized to expected grid conditions and requirements. Hitachi Energy’s SVC control system, for example, can be utilized to control external shunt banks. GE’s SVCs, too, can be customized based on the utility’s technical requirements.

Static Compensators (STATCOM)

STATCOMs use power electronics and have a response time of a few microseconds compared to the slower mechanical solutions like capacitors. They are pricy compared to other options, but effective. American Superconductor’s Dynamic VAR (D-VAR) system scales from 2 MVAR and has overload capabilities of three times its rated capacity for up to three seconds. Hybrid systems combine SVC and STATCOM functions in one device. Hitachi Energy’s SVC Light Enhanced offers power quality and grid stabilization technologies as well as reactive power support.

Synchronous Condensers

A synchronous condenser is usually a large piece of spinning machinery composed of a generator and often paired with a flywheel to provide rotating inertia without generating any power. These machines spin at grid frequency to contribute to system stability by dampening frequency fluctuations and providing voltage stability through reactive power.

“Synchronous condenser is the name given to a synchronous machine that is connected into an electrical network to help in maintaining the system voltage,” said Dr. James F. Manwell, Emeritus Professor of Mechanical and Industrial Engineering at the University of Massachusetts, Amherst. “The synchronous machine is essentially a motor to which no load is connected.” 

Vendors like GE Vernova, Siemens Energy and Hitachi Energy provide different approaches to synchronous condensing. Siemens Energy’s solution is comprised of a horizontal synchronous generator connected to the high-voltage transmission network via a step-up transformer. It is started up and stopped with a frequency-controlled electric motor (pony motor) or a starting frequency converter. When the generator reaches synchronous speed, it provides reactive power to the transmission network as well as inertia and active power injection or absorption during sudden load unbalance events. GE’s synchronous condenser/flywheel combo is air cooled and rated up to 300Mvar+.

Using Existing Generators

With so many steam and gas turbines being decommissioned, a popular approach to grid stability is to maximize the investment in these rotating assets by fitting them to operate as synchronous condensers. Instead of discarding these machines, a synchronous self-shifting (SSS) clutch can be added to disengage the generator from the turbine. The turbine brings the generator up to speed so it synchronizes with the grid, at which point the turbine disconnects from the generator and shuts down. The generator then uses grid power to keep spinning, constantly providing leading or lagging VARs as well as other forms of grid support and the needed inertia. When active or real power is needed, the SSS Clutch automatically reengages for electric power generation. This feature is useful in renewable focused grids where there may be a sudden need for peaking power.

“For coal plants being closed down, the steam turbine generator can be easily converted to a synchronous condenser by removing the turbine and adding an acceleration drive with an SSS Clutch,” said Hendry.

New gas-fired power plants being built can also be configured to operate as a synchronous condenser. Hendry listed 45 recent clutch orders intended for GE LM6000 PF+ Sprint models. In those cases, the clutch is built into a load gear as the unit operates at a higher speed than 3,600 rpm, which is needed for a 60 Hz. As result, a gear is needed to create synchronization with the grid.

By far the biggest recipient of these clutched LM6000 PF+ units is the Tennessee Valley Authority (TVA). It has received 10 SSS Clutches so far and another 20 are on order. Reason: The TVA is in the midst of rolling out 1 GW of wind turbines and solar PV in Tennessee and decommissioning coal and other rotating assets. Its new order of LM 6000s are there for peaking power to support. By enabling them to run as synchronous condensers, the TVA is ensuring it has enough inertia, system stability and reactive power support. Far from being a novel arrangement, the SSS Clutch being connected to the load gear is a well-established practice.

“The mounting arrangement in the load gear is the same as nearly 300 Frame 5 and 6s gensets GE has done in the past for synchronous condensing,” said Hendry.

About the Author: Drew Robb has been working as a full-time freelance writer in engineering and technology for the last 25 years. For more information, contact drew@robbeditorial.com.

Proposals must be submitted by June 21, 2024 and must be for 50 MW to 500 MW for various periods through December 2029. TVA is seeking “Firm Generation Resources” or “Firm System Commitments” as defined in its RFP. Proposals should complement TVA’s existing generation resources and be delivered to the TVA service area, TVA said.

TVA recently received attention for moving ahead with a plan for a new natural gas plant in Tennessee despite warnings that its environmental review of the project doesn’t comply with federal law. The utility announced in April that it would replace the aging coal-burning Kingston Fossil Plant with gas amid growing calls for the agency’s new board of directors to invest in renewables.

Decommissioning the Kingston plant, the site of a massive 2008 coal ash spill, is part of TVA’s overall plan to reduce its reliance on coal. In analyzing alternatives to replace the plant, the utility considered either a new 1,500-MW gas plant or 1,500 MW of solar combined with 2,200 MW of battery storage. TVA concluded that a 2027 deadline for retiring the current plant does not give it enough time to develop the renewables alternative.

This article includes reporting from the Associated Press.

NASHVILLE, Tenn. (AP) — The nation’s largest public utility on May 9 pledged to be more transparent after it took months to disclose that a general budget vote by its board last year also gave the CEO the final decision over several proposed natural gas power plants.

The Tennessee Valley Authority’s board announced the transparency changes during its quarterly meeting in Nashville. The decision followed an August meeting in which the federal utility’s board cast the budget vote that quietly gave President and CEO Jeff Lyash the final say over the projects, including the replacement of the aging coal-fired Kingston Fossil Plant with a natural gas plant.

The public didn’t find out about those provisions until documents with specific details were released several months later, some via public records request, said Amanda Garcia, a senior attorney with the Southern Environmental Law Center.

The decision stood in contrast to a more publicized vote in May 2023 when the board, with a new majority selected by President Joe Biden, took back the final decision-making authority on the Kingston plant. Lyash had been granted the authority for Kingston and the natural gas switch at Cumberland Fossil Plant, both in Tennessee, when the board had a majority picked by former President Donald Trump.

“One of the changes the chair asked me if I would do, which I can, is to take the resolutions, precisely what is being voted by the board, and make those resolutions publicly available, get them on the website rapidly after the meeting,” Lyash told The Associated Press.

Board member Michelle Moore, who was absent but had a statement read on her behalf, said some decisions are better delegated to the CEO because they span years and multiple board cycles, but others require board decisions because of “exceptional, regional and even national significance.” Additionally, Lyash said the board maintains oversight authority when the CEO is the decision maker.

TVA’s plans to open more natural gas plants have drawn the ire of advocates who want a more aggressive move away from fossil fuels and into solar and other renewables. They note that even with six of nine board members appointed by Biden, TVA is off track to meet the Biden administration’s goal of eliminating carbon pollution from power plants by 2035 to try to limit the effects of climate change.

Several of its proposals for new natural gas plants have received criticism from the U.S. Environmental Protection Agency, including a warning that its environmental review of the Kingston project doesn’t comply with federal law.

Southern Environmental Law Center staff attorney Trey Bussey said the transparency changes should have been in place “before TVA decided to spend billions of dollars on new gas plants and pipelines — not after,” adding that the board can still halt the buildout of gas plants. In April, the law center said it recently found out that the board had given decision-making power back to the CEO.

Although TVA has not embraced renewables, the utility still says a majority of its energy is carbon-free because 42% comes from nuclear and another 9% is from hydropower. Purchased wind and solar make up another 4% of its energy portfolio. The utility currently produces 1 megawatt of its own solar and has 20 megawatts of battery storage. The Kingston project includes another 3-4 megawatts of solar and 100 megawatts of battery storage. TVA estimates that the new gas plant will produce 1.68 million tons (1.52 million metric tons) of greenhouse gases a year, noting that it is a steep decline from Kingston’s current emissions.

TVA says its power mix was at 55% last fiscal year, with a goal of net-zero emissions by 2050. The utility has said it intends to build 10,000 megawatts of solar by 2035. Its solar goals have hit some snags, including supply chain issues, interest rates and land costs, according to Lyash.

As the region grows in population and TVA looks to add power plants, the utility says it also has a goal of reducing consumption by 30% over the next decade through energy efficiency and demand response programs.

TVA provides power to 10 million people across seven Southern states.

The new units are expected to deliver up to 850 MW of electricity, which TVA says will help enhance the reliability of the energy grid once installed at the Complex on the Clinch River arm of Watts Bar Reservoir near Kingston, Tennessee.

“The Kingston Energy Complex highlights the way diverse generation works together to ensure TVA can provide more reliable, resilient and affordable power,” said TVA Chief Operating Officer Don Moul.  “These aeroderivative units will help us meet demand during peak energy usage and supplement solar generation on days when sunshine is limited.” 

GE Vernova’s LM6000VELOX packages, expected to start operation in 2028, feature dual-fuel capability to operate on natural gas or on liquid fuels, if needed. Additionally, GE Vernova says the DLE combustor configuration is capable of meeting environmental regulations and emissions limits.

TVA has reduced emissions by 57% from 2005 levels. Nearly 60% of TVA’s energy comes from carbon-free sources including nuclear, hydropower, storage, and solar.  

“This milestone project marks GE Vernova’s commitment to supporting TVA’s efforts to ensure affordability and reliability of electricity while focusing on more efficient and sustainable energy generation,” said Dave Ross, President of GE Vernova’s Gas Power in the Americas region. “TVA is actively integrating more renewables into the system, investing in new technologies, and retiring older, less efficient generation and they are doing this in a holistic way that helps to ensure affordability, reliability, and resiliency for their 10 million customers.” 

GE Vernova’s LM6000VELOX package, announced in October 2023, features enhancements aiming to reduce site construction time. The solution features a “quick package installation” in a simple cycle configuration, with an expected reduced installation and commissioning schedule.

The three units at Paradise add 750 MW to TVA’s generation fleet. While the units were announced at a dedication event on April 10, they started commercial operation in late December.

TVA said the fast-starting units can reach full power within 11 minutes to help meet demand peaks.

“These units provide the flexibility, responsiveness, and reliability needed to support the power grid,” Roger Waldrep, TVA’s Vice President of Major Projects said. “They allow us to meet demand during normal loads as well as peak periods, like the extremely cold days we experienced this winter, and the warm days that are ahead this summer.”

The expansion of Paradise is part of TVA’s plan to build more than 3,800 MW of new generation by 2028 that includes solar, energy storage, combustion turbines and combined-cycle natural gas.  

The new units join three other combustion turbines that began operating in July 2023 at the Colbert site in northern Alabama.

In 2020, TVA shut down the last coal-fired unit at Paradise Fossil Plant after 50 years of operation. Paradise Unit 3, located in Muhlenberg County near the Green River, began operation in 1970 with a net generating capacity of 1,080 MW. It generated enough electricity to supply more than 800,000 average homes.

TVA’s Board of Directors voted in 2019 to retire the unit. The other two coal-fired units at Paradise were retired in 2017. That generation was replaced with a combined-cycle natural gas plant with a baseload capacity of 1,025 MW, which began operation next to the fossil plant site in 2017.

That was the verdict from TVA’s Final Environmental Impact Statement issued by the federal utility Feb. 16 after a public review process last year over how to replace the coal-fired units at Kingston. TVA anticipates making a final decision in March 2024.

TVA mainly evaluated two options to provide at least 1,500 MW of generation to replace the capacity to be lost, plus additional capacity to support anticipated load growth.

The first option would include the construction of a single combined-cycle gas plant paired with 16 dual-fuel Aeroderivative combustion turbines, a 3 to 4 MW solar site and a 100 MW battery energy storage system on the Kingston Reservation. The combined-cycle plant would be capable of burning 5 percent hydrogen by volume at commissioning and 30 percent hydrogen with modifications to the balance of plant once a reliable source of H2 was identified, TVA said.

The first option would also include Eastern TN Natural Gas (ETNG) constructing and operating a 122-mile natural gas pipeline, gas compressor station and metering and regulator stations.

The second option would consist of constructing multiple solar and energy storage facilities at alternate locations, including in Eastern Tennessee. The construction of a pipeline would be subject to Federal Energy Regulatory Commission (FERC) jurisdiction and additional review.

TVA said its preferred option is the first. The federal utility said a combined-cycle plant paired with dual-fueled aero turbines would be the “best overall solution to provide low-cost, reliable energy to TVA’s power system, and could be built and become operational sooner” than the solar and storage in the second option.

The utility said it also preferred the gas plant option to provide the flexibility needed to bring 10,000 MW of solar onto the system by 2035.

‘Increased wear and tear’ for coal units

Kingston’s nine units can generate about 1.4 GW of electricity at capacity. The plant, located about 35 miles west of downtown Knoxville, entered operations in the 1950s.

TVA said frequent cycling of Kingston’s units, reflected in start-up and shutdown events, are currently averaging more than 85 times per year, which the utility said is outside the intended design of the plant.

This is resulting in “increased wear and tear, which presents reliability challenges that are difficult to anticipate and expensive to mitigate.”

TVA also said Kingston has experienced a “significant decline” in material condition over the last five years, including the need for repairs to the lower boiler drum, which the utility said are symptomatic of age-driven material condition failures which are difficult to proactively address.

The utility said based on these factors, it has developed planning assumptions for the timing of the proposed retirement of Kingston.

In general, TVA said its aging coal fleet is experiencing deterioration of material condition and performance challenges. Performance challenges are expected to increase because of the fleet’s advancing age and the difficulty of adapting coal within the changing generation profile.

TVA has reduced carbon emissions from its entire generating fleet by about 60% since 2005, thanks to a combination of closing coal plants and building solar and wind.

D&Z will also perform scaffolding, coatings, insulation, asbestos abatement and lead abatement work. The $985 million contract spans five years, with the option to renew for an additional five years.

D&Z has more than 25 years of experience working with TVA, according to John McCormick, president of D&Z’s maintenance and construction division. In April 2022, TVA named D&Z its 2022 Prime Supplier of the Year through TVA’s Diversity Alliance Program.

TVA is a corporate agency of the U.S. that provides electricity for business customers and local power companies, serving nearly 10 million people in parts of seven southeastern states. In addition to operating and investing its revenues in its electric system, TVA provides flood control, navigation and land management for the Tennessee River system and assists local power companies and state and local governments with economic development and job creation.

The electricity TVA delivers is nearly 60% carbon-free through its 29 hydroelectric projects, TVA’s nuclear fleet and other renewables such as solar. TVA owns four fossil plants, three nuclear plants, 29 hydro plants, one pumped storage hydroelectric plant, nine natural gas combustion turbine gas plants, eight natural gas combined cycle gas plants, one diesel generator site and 13 solar energy sites.

TVA is reducing its reliance on coal and plans to expand its natural gas fleet to provide the ongoing flexibility needed to reliably integrate more renewables.