Efficiency Enhancement of Gas Turbines - SP1

Research Scientist
451 66 065

This subproject focuses on the design of Combined Cycle Gas Turbines (CCGTs) where the exhaust heat runs a bottoming cycle for additional power generation and increased efficiency. For this, we need new, compact, and efficient heat recovery heat exchangers. Design of efficient CCGTs includes development of effective control strategies for gas turbine and CCGT operation.

MAIN OBJECTIVE

The main objective of SP1 is to reduce the emissions related to offshore gas turbine operation. A larger share of part-load operation is expected due to the inclusion of renewable energy sources into the offshore energy system. One goal of SP1 is therefore to increase the part-load efficiency of the gas turbine (addressed in Task 1.2). Using the exhaust gas from a gas turbine to run a bottoming cycle to produce steam or additional electricity is another measure to reduce emissions. This concept has been implemented before. However, the weight and footprint of a bottoming cycle system need to be minimal to enable widespread implementation. In SP1 we develop more compact and lightweight designs considering thermodynamic optimisation, possibly using other working fluids than steam (addressed in Task 1.3). Analysing their operation and proposing optimal operational strategies for the CCGTs is the goal of Task 1.1.

Results 2021

MAIN RESULTS IN 2021

  • Further development of in-house framework for simultaneous optimisation of component
  • Specifications and process parameters for bottoming cycles. Model reformulation for improving robustness. Web interface (WEB-GUI) for thermodynamic simulation of bottoming cycles delivered this year.
  • Simulation results for a simple steam power cycle and for a recuperated CO2 cycle.
  • Definition of standard configuration for a combined cycle to be used for coordinated work between Task 1.1 and Task 1.3.
  • Creation of a new Dymola package "LowEmission_SP1" with a simple and self-explaining package structure to be used for the analysis of dynamic operation of steam bottoming cycles. The package includes gas turbine models, 1D dynamic process models of once-through steam generators (OTSG), a steam turbine model and a condenser model.
  • Definition of the control problem for bottoming cycles for power production. Beginning of the work for implementation of control structures in Dymola.
  • Participation in the 6th international seminar on ORC power systems, Munich-2021 “Improving the off-design efficiency of Organic Rankine bottoming cycles by variable area nozzle turbine technology" by PhD student Mohammad A. Motamed and supervisor Ass. Prof. Lars O. Nord. Full (peer-reviewed) paper published.

IMPACT AND INNOVATIONS

Improvement of robustness of new methodology for simultaneous optimisation of component specifications and process parameters. This methodology was implemented in the web interface for analysing bottoming cycles.

Results 2020

  • Further development of framework for simultaneous optimisation of component design and process parameters by
    • Including full geometry description of plate heat exchangers and finned tube heat recovery heat exchangers.
    • Adding a recuperator to the cycle for improved effi ciency.
  • The heat recovery heat exchanger is a key component of a bottoming cycle, but most simulation models are 1D-models. A dynamic 2D-model was developed in 2020 to enable more detailed simulations.
  • PhD student Mohammad Ali Motamed started working in the summer. Tentative title for his thesis is "Assessment of alternative concepts for combined cycle gas turbine operation under varying loads".
  • Summer researcher Knut Andre Grytting Prestsveen successfully developed a web interface to the process optimisation model. This will be launched 2021.

Impact and innovations

  • Compact bottoming cycle designs, possibly with new working fl uids, which could enable widespread implementation.
  • New methodology for simultaneous optimisation of component specifications and process parameters.

Results 2019

This SP focuses on the design of Combined Cycles Gas Turbines (CCGTs) where the exhaust heat runs a Steam Bottoming Cycle (SBC) for additional power generation and increased efficiency. New, compact, and efficient SBC heat exchangers, designed for varying heat transfer and boiling regimes along the heat exchanger tubes, are essential. Design of efficient CCGTs includes development of effective control strategies for gas turbine and CCGT operation.

Main objective

The main objective is to reduce the emissions related to offshore gas turbine operation. Two approaches are being investigated. The first one is increasing the gas turbine's efficiency during part-load operation. The second approach is to recover heat from the exhaust gas to produce electricity and/or heat in a bottoming cycle.

This concept has been implemented before,  but the large weight and footprint impede widespread implementation. Focus is therefore one developing more compact and lightweight designs, possibly using other working fluid as steam

Main results

  • PhD position announced. Topic: "Assessment of alternative concepts for combined cycle gas turbine operation under varying loads".
  • A report about gas turbine operation and transient behavior was written as basis for future research.
  • A first working fluid screening was performed to compare possible working fluids that can  be used in a bottoming cycle (as alternative to steam).
  • The dynamic modelling and simulation of a combined cycle gas turbine was initialized in cooperation with Siemens.

Impact and innovations

  • More efficient gas turbine operation
  • Compact bottoming cycle designs, possibly with new working fluids, enabling widespread implementation
Early-stage dynamic simulation model of a combined cycle gas turbine in Dymola.