The mission of TURBO-REFLEX is the development and optimisation of technologies, applicable to a selected set of turbomachinery engine components, which can be used to retrofit existing power plants as well as new machines in order to enable more flexible operation, providing the flexible back-up capacity needed for introducing a larger share of renewables in the energy system.


Three global objectives have been defined for the improvement and advancement of current generation of fossil power plants. The TURBO-REFLEX innovations will be the key to reach these objectives.


OB 1: Reduction of costs per cycle

In short: Reduce the costs per cycle at typical warm start in combined cycle plants, from currently 50€/MW to ca. 35€/MW, by increasing the part load efficiency, the resistance to wear, and by having more accurate life information.

TURBO-REFLEX will address reduction of cycling costs by improving component materials, component design (methods), and resulting from this, overall damage prevention.
With regard to the objective of cycle cost reduction, the following key components will be improved:

  • Compressor: TURBO-REFLEX aims at developing an advanced, retrofittable compressor aero design for part load conditions which improves the part-load efficiency by minimising bleed flows and desensitising performance to tip clearance variation
  • Turbine: TURBO-REFLEX aims at the development and validation of improved mechanical design tools for harsh and transient operation of gas and steam turbines. It will improve the prediction accuracy of plant component loading and damage in transient operation; for example, during rapid changes of load, speed and temperature, and in off-design operating conditions. This will be achieved by transient component monitoring, improved material damage prediction models, and advanced cooling schemes.


OB 2: Increasing low load capability of existing plants

In short: Reduce the number of hot starts required by 33%, from currently 150 per year to 100, by increasing the low load capability of existing plants, enabling them to operate at low load level for extended periods of time instead of being shut down.

It is evident that plants which have a very high low load capability can be run more flexibly without being forced to full shut-down/start-up, resulting in less cycling. The main aim is to enable increased low load capacity of thermal power plants by retrofitting the critical components of existing assets as follows:

  • Compressor: Development of an advanced, retrofittable aero design for part load conditions which improves the part-load operability and efficiency. A larger stable operating range. This allows a further closure of Inlet Guide Vane (IGV) with reduced minimum environmental load. Another aim is to optimise the blow-off valve opening to reduce the minimum environmental load. Investigate the compressor off-design performance and operability during charging and discharging of a novel energy storage system to enable low load.
  • Combustor: Identifying the operation limits of existing designs to develop new, retrofittable combustor designs that extend the operation regime to lower minimum loads. In particular, improve combustion models concerning their ability to describe lean blow-off limits (LBO) for jet stabilized flames at very low loads. Also the combustor modifications required for integrating Compressed Air Energy Storage (CAES) or Liquefied Air Energy Storage (LAES) technology into gas turbine engines will be identified.
  • Steam turbine Improve the accuracy of prediction of steam turbine component loading and damage in low load operation. In particular, introducing a life assessment model enabled by real-time measurements in the last stage blading of the steam turbine through automated sensors usable under harsh operating conditions.


OB 3: Increasing load following capability

In short: Double the load following capability of the existing combined cycle plants from a ramp rate from currently 6% per minute to 12% per minute

An electrical power system has to be in constant balance, with a perfect continuous match between electricity consumption and generation. Flexible generating capacity is a promising immediate way to address grid stability requirements.

To achieve the required ramp rate increase, TURBO-REFLEX will provide the following component improvements:

  • Combustor: exploitation of several gas turbine operational modes and combustor design modifications for improving LBO limits and operability during charging and discharging
  • Turbine: development of new cooling schemes yielding lower thermal gradients in hot gas path components during transients and thereby improving substantially the ramp rate
  • Storage integration: Increasing the flexibility of existing combined cycle plants through the integration with energy storage capabilities such as CAES or LAES technology


To reach the global objectives, critical turbomachinery components have been chosen for investigation and advancement. In particular, improvements in compressor, combustor, the hot gas path and turbine will be sought.


Technical Objective State-of-the-Art TURBO-REFLEX Objective¹ OB1 OB2 OB3
MEL² 40% of full load 30% of full load      
Part load GT efficiency   +0.75%      
MEL 40% of full load 30% of full load      
Ramp rate 200K / min 300K / min      
Gas Turbine          
Cycles between major inspections 1,200 cycles³ +20% cycles      
Ramp rate 200K / min 300K / min      
Rotor life extension⁴ 30,000 EOH⁵ 40,000 EOH      
Steam Turbine          
Hot start up time 20 min 16 min      
Low minimum 10% of nominal load 5% of nominal load      
Condition base monitoring Not applied Real-time assessment      

¹ Given as industrial state-of-the-art (in service) and for the TURBO-REFLEX technologies as in service (TRL9) figures. Entry into service of the technologies is expected in less than three years after the project

² Minimum environmental load (baseload figure given for typical F-class power plant)

³ Typical number of cycles (# of cold, warm, hot starts) between major inspections

⁴ Applies to CHP plants with multi-shaft GT

⁵ Equivalent operating hours (penalties are added for cyclic operation up to a factor of 10 per cycle)

These objectives are complemented by new sensor and monitoring technologies.


Online plant analytics & monitoring


Condition-based monitoring is an impactful approach to better understand the behaviour of plant as operated rather than as designed or as manufactured. It will therefore impact all three above mentioned objectives:

  • The cost of cycling (OB1) will be reduced as component failure can be better identified and the cost of unplanned downtime avoided, achieving a data driven optimisation of existing thermal fleet including machine learning approaches
  • The low load capability (OB2) of the steam turbine can be reduced based on a better understanding of inlet valve clearance in throttled operations enabled by a new sensor
  • Components can be operated closer to their actual physical limits resulting in better ramp rate and improved load following capability (OB3)


Whole plant performance assessment


The above-described component optimisations will strongly contribute to the flexible operation and therefore on the overall performance of existing thermal power plants. In order to determine the optimisation potential of the component improvements, the assessment methodology developed in the FLEXTURBINE project will be further advanced to a high fidelity whole plant analytics and modelling, which is needed to better transfer component technology gains into market measures such as efficiency, flexibility and emissions. Further, this model will be able to simulate the plant’s ability to react to changes in environmental or control shifts. This will include startup, ramp rate, minimum generation, and regulation performance. The model will provide insights into speed, stability, emissions, and stresses as well as predict the limitations of the plant with configuration and operational changes.

To reach the global objectives, critical turbomachinery components have been chosen for investigation and advancement. In particular, improvements in compressor, combustor, the hot gas path and turbine will be sought.

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TURBO-REFLEX Newsletter Issue 1