This roadmap defines R&D pathways for enabling flexible operation of generation fleets. Specific R&D is pursued on natural gas, coal, and hydro assets that can enable flexible operation while balancing the need for asset integrity.

For natural gas, coal, and hydro assets and fleets, innovations are being pursued in the following areas:

  • Operational and control strategies to optimize ramp rates, startup times, minimum load capabilities, minimum online and offline times, and layup and shutdown practices
  • Improved approaches, technologies, and methods for identifying and managing damage caused through increased operational flexibility
  • Prioritized and informed approach to engineered and operational solutions to mitigate damage impacts through condition assessment and management, including fuel switching strategies
  • Component and system upgrades and replacements for improved response and performance to support flexibility of the existing and future fleet
  • Fleet level approaches to optimize the overall delivery of flexible generation

These innovations will help fleet managers, plant managers and workers maintain electrical system reliability by maximizing operational readiness to respond to changes in supply-demand curves and market conditions and maintain system resiliency by understanding and managing the impacts to equipment under flexible modes of operation. New knowledge and advanced technology for enabling flexible operations also will help owners of central-station generation increase the cost-competitiveness of new assets and improve fleet-wide performance.

EPRI has developed its spectrum of flexible operation to help map solutions and strategies for power plants to achieve electrical system needs while remaining safe, reliable, affordable, and environmentally responsible.  Enabling cost-effective, flexible operation of central-station generation is a core aspect needed to increase the use of intermittent cleaner energy.  Key to achieving this is integrating new technologies such as advanced sensors into the management of generating assets.  EPRI is partnering with the DOE to develop some of these integrated management solutions.

Spectrum of Flexible Operation

In the longer term R&D—as advanced power cycles, possibly incorporating carbon capture utilization and storage, are developed—flexibility will be a key operational aspect. Bulk energy storage solutions R&D is another area of focus which over the longer term may significantly change flexible operation needs, EPRI has partnered with the DOE to look at bulk thermal energy storage.


Diversity of Generation

For continuous steady-state operation, performance indicators include overall reliability, heat rate, and production costs. Flexible mission profiles involve more frequent and faster startups, faster ramping, more frequent load changes, more frequent minimum-load operation, and longer reserve shutdowns. The new paradigm requires economic and environmental objectives to be achieved while maintaining operational readiness to respond when called to run, to meet ramp rate requirements, and to be available during the highest-demand periods. Coal-based units that switch to lower-grade fuels face particular challenges.

Generation Excellence

Relative to baseload duty, flexible operations decreases energy production and leads to increased equipment wear and tear, reduced fuel conversion efficiency, and degraded environmental control system performance. Often, revenues fall, production costs rise, and reliability suffers. These top-line and bottom-line pressures can threaten the economic viability of existing plants and increase the overall cost of energy supplied to the grid. Advanced control, maintenance, and investment strategies are needed to improve reliability, reduce the cost of part-load operation, and make the best use of available staffing.

Near Zero Emissions

Operating at less than full load boosts heat rate, affects fuel-air mixing, and can cause fouling in selective catalytic reduction systems, increasing NOx emissions. The performance of other control technologies, measured in environmental releases and parasitic energy consumption, also may be impacted. Operational readiness must include managing startup and cycling—and adverse impacts caused by fuel switching—to achieve cost-effective compliance and help maintain a diverse energy supply portfolio.


By the mid 2020s, existing assets owned by EPRI members will have successfully transitioned from baseload resources optimized for continuous steady-state operations into flexible assets ready for cost-effective operation as needed in response to changing grid conditions. In addition, new generating assets designed for flexibility will offer rapid startup, fast ramping, low turndown, and other desired operational attributes with reduced impacts on production efficiency, reliability, and environmental performance.

Generation fleets—mixing existing assets with new builds—will have the capability to supply energy and capacity on a reliable and affordable basis while helping firm variable-output renewables and provide supply diversity. Staffing resources and maintenance expenditures will be optimized to ensure operational readiness in response to varying load requirements and market opportunities. Safe operating ranges and informed startup, layup, and shutdown practices will protect vulnerable equipment.


To realize the full value of existing central-station plants in a transformed marketplace, asset owners require state-of-the-art knowledge, practices, and technologies supporting operational flexibility. They also must develop the near-term confidence required to justify sustained investment in site-specific maintenance and modernization programs at individual fossil and hydro units. This creates immediate needs for advanced condition assessment techniques and economic forecasting methodologies, enabling component-by-component and plant-by-plant evaluation and comprehensive management of the life-cycle cost, value, and risk associated with different modes of cyclic operation.

Adapting to change demands enhanced plant defense strategies that utilize systematic processes. Flexibility is complex and requires strategic countermeasures to protect assets undergoing the new operating regimes.

Managing fleet flexibility requires the inclusion of both quantitative and qualitative actions that drive awareness, apply best practices, encourages benchmarking and most importantly, integrates modifications and defense strategies to protect assets.

EPRI’s Mission Profile Working Group (MPWG) formed in 2015 provided the basis formalized R&D priorities, building off decades of R&D on flexible operation.

This roadmap defines collaborative R&D pathways leading to new knowledge and advanced technology for optimizing operational flexibility—both for existing assets and future capacity additions—over a timeframe 5 to 10 years out, and beyond.  Areas of focus are introduced below.

Relevant R&D is under way across the Generation Sector’s base programs and through collaborative projects engaging EPRI members, government agencies, and other stakeholders in developing and testing higher-temperature materials, advanced power cycles, and other innovations.  This roadmap also encompasses ongoing and planned work through EPRI’s Technology Innovation (TI) program and under its long-term R&D relating to Advanced Power Cycles and Carbon Capture, Utilization, and Storage and Bulk Energy Storage.

Advanced Materials, Components and Systems

Fundamental research and development is needed to improve the understanding and identification of damage mechanisms associated with operational flexibility.  Advanced materials and coatings are needed as cost-effective solutions for remediating damage to specific components and increasing overall tolerance to creep, fatigue, and other cycling-relevant mechanisms.

Ongoing and planned EPRI R&D activities address the following topics:

  • First Principles. Improved understanding of material properties and individual and interacting damage modes relevant to flexible mission profiles for combustion and steam path systems, auxiliary components, and hydro plant equipment.
  • Materials & Coatings. New and improved base metals, weld fillers, and surfacing materials engineered for ensuring long-term reliability under flexible mission profiles.
  • Manufacturing & Fabrication. Novel component prototyping, manufacturing, and surfacing methods based on powder metallurgy, 3-D printing, and other advanced technologies.
  • Advanced Component & Systems. Innovations enabling retrofit and repowering projects leading to faster startups, higher peak outputs, improved ramp rates, increased cycling tolerance, and other cost-performance benefits.
  • Temperature & Fatigue Management: A better understanding of damage in order to manage thermal transients, hot spots, and other cycling-related phenomena that may lead to life-limiting fatigue damage in combustion and steam path systems.
  • Cycle Chemistry: Characterizing surface film, corrosion, and water-steam conditions to control cycle chemistry, manage additive levels, and ensure adequate protection during low-load and cycling operations and during layup and reserve shutdown periods

Condition Assessment and Management

Accurate lifing and real-time condition assessment—accounting for operating history and current status, as well as the individual and interacting damage modes relevant at specific locations under different duty cycles—are dependent on continued advancement in basic knowledge and in component inspection, nondestructive evaluation (NDE), and predictive modeling capabilities.

Ongoing and planned EPRI R&D activities address the following topics:

  • Improved and Enhanced Sensor Capabilities: New and novel sensing applications as well as enhanced use of existing sensor technologies will enable more complete information for understanding and determining equipment health.
  • NDE & Component Testing. Innovations in field inspection and characterization optimized for thermal fatigue and other cycling-relevant damage mechanisms and for materials such as creep-resistant steels.
  • Lifing & Modeling. Tools supporting cumulative damage assessment and predictive analysis of remaining lifetime for existing and advanced materials under more frequent unit starts, higher load ramp rates, lower minimum loads, and more frequent and longer-lasting reserve layups.
  • Condition Based Maintenance.  Analytics linking fleet-wide online monitoring systems with equipment reliability and preventive maintenance will enable condition-based maintenance practices through greater understanding of component, system and plant health. Technologies and methods for repairing and reinforcing damage-prone welds and components, for reducing or eliminating postweld heat treatment (PWHT) requirements, and for joining higher-strength steels and nickel-base alloys.

Cross Functional Solutions for Engineering and Operational Improvements

Cross functional solutions approaches are needed in order to enhance startup and ramping capabilities, lowering minimum turn-down levels, ensuring shutdown protection, and being ready to provide reliable, low-cost energy and capacity as needed hourly, daily, or seasonally.  Lessons learned and experience through a holistic perspective will drive innovative component and system designs to create opportunities for retrofitting and repowering existing assets to increase flexibility consistent with site-specific cost-performance objectives, including control of carbon dioxide emissions.

Ongoing and planned R&D activities address the following topics:

  • Flexibility Assessment. Improved understanding of flexibility requirements, capabilities, and limitations—and associated cost, performance, and reliability impacts—across major components and systems will prioritize flexibility needs and inform investment decisions.
  • Stable and Consistent Operations. Defining the operating envelope and identifying flexibility improvements within existing and expanded design margins will allow for increased operating ranges while meeting system restrictions.
  • Advanced Control Strategies. Advanced tools, practices, and strategies for controlling process conditions, optimizing performance tradeoffs.
  • Combustion Optimization: Advanced sensors and control technologies for monitoring fuel quality, combustion parameters, species concentrations, and critical components to optimize process conditions, control slagging, and maintain reliability in response to cyclic operations.
  • Environmental Controls:Many times the most limiting systems, advanced tools and practices, SCR technologies, and process monitoring and control capabilities for cost-effectively optimizing system interactions.
  • Plant Modifications and Retrofits:  Engineered solutions that take cost and improved capability into account will enhance the existing operating fleet to meet the changing mission profile.

New Plant Design

Materials, components, and systems designed and engineered to achieve the higher operating temperatures and conversion efficiencies anticipated in lower-emitting fossil plants also need to meet startup, ramping, turndown, and other flexibility objectives. Concentrating solar power and bulk energy storage technologies offering improved economics offer potential to help in firming variable-output renewable generation while reducing the need to cycle coal- and gas-fired power plants.

Ongoing and planned R&D activities address the following topics:

  • Gas-Fired Generation.Advanced compressor, turbine, emission control, and steam generator systems and integrated plant designs promising improved flexibility and reliable long-term operations.
  • Coal-Fired Generation. Advanced ultrasupercritical coal plant and integrated gasification combined cycle (IGCC) plant designs and components optimized for flexible operations and reliable long-term performance.
  • Advanced Technologies:Novel working fluids, energy conversion technologies, environmental control and carbon capture processes, energy storage systems, and plant design configurations offering step-change efficiency gains and high degrees of flexibility.