Design considerations on a small scale supercritical CO 2 power system for industrial high temperature waste heat to power recovery applications

Transcription

1 on Supercritical CO 2 (sco 2 ) Power Systems Design considerations on a small scale supercritical CO 2 power system for industrial high temperature waste heat to power recovery applications, S. A. Tassou, Y. Ge, H.Jouhara, K. Tsamos A. Leroux, M. De Miol Wien, 29/09/2016

2 2 /21

3 I-ThERM Project aim is to Investigate, design, build and demonstrate innovative plug and play waste heat recovery solutions to facilitate optimum utilisation of energy in selected applications with high replicability and energy recovery potential in the temperature range This project has received funding from the European Union s Horizon 2020 research and innovation programme under grant agreement No /21

4 Scope of the I-ThERM s sco 2 project Power output kwe 1 st law efficiency 20 % Low CAPEX (short PBP) Design of sco 2 system and Test rig Design and manufacturing of turbomachinery and Heat exchangers Experimental campaign 4 /21

5 Outline Reference thermodynamic cycle Preliminary turbomachinery design Heat exchangers Simulation platform Results and discussion Future work 5 /21

6 Thermodynamic cycle Recompressing cycle layout is the optimal configuration for large sco 2 installations (~MW) such as nuclear and CSP ones 2 compressors + 2 recuperators 1 compressors + 1 recuperator However, if target output power is smaller, simple regenerated cycle becomes the most suitable architecture /21

7 Turbomachinery for sco 2 systems Sienicki et al. (2011) High revolution speeds + small impeller diameters 7 /21

8 Specific speed and diameter Velocity triangles Balje s charts available for CAD air and water turbo machines Loss correlations available for air Need of coupling CFD tools with thermo-physical properties of CO 2 (dll libraries or look-up tables) Need of importing thermomechanical properties in FEA tools if custom materials are employed CFD FEA 8 /21

9 Multiple technologies currently available Corrosion issues to be considered High thermal stresses HXs account for up to 90% of the overall CAPEX Aggressive designs might spoil the overall economic Heat exchangers feasibility of system Shiferaw et al. (2016) 9 /21

10 sco 2 Modelling approach Simple regenerated cycle Real gas properties 1 st and 2 nd law analyses Detailed loss breakdown Steady state approach Implemented in EES 10 /21

11 Input data: Inlet conditions of hot heat source (exhaust gas) Inlet conditions of cold heat source (water) HXs and machines efficiencies Pipes pressure and heat losses Parameters: Min and max temperature Min and max pressure Recuperation ratio (R) Output data: Electrical power recovered Cycle efficiencies (1 st,2 nd law) Loss breakdown Turbomachinery design 1 st European Seminar 11 /21

12 start Get Turbine Ns CGT revolution speed Compressor Ns Cordier s line for turbine Cordier s line for compressor Optimal Turbine Ds Optimal Compressor Ds Turbine wheel diameter Compressor wheel diameter end D s,c = N s,c D s,t = N s,t only for radial machines 12 /21

13 Turbomachinery Design choices Revolution speed <100 krpm Wheel diameters >40 mm Subsonic flows Heat exchangers Adequate pinch point ΔT Moderate temperature levels 13 /21

14 Assumptions Constant compressor and turbine isentropic efficiencies Constant HXs effectiveness Gaseous fluid at compressor inlet No pipe pressure drops or thermal losses Simulation parameters Turbine inlet temperature and pressure (i.e. cycle pressure ratio) Inlet conditions of exhaust gases (flow rate and temperature) Influence of recuperation Turbine specific speed 14 /21

15 max min 15 /21

16 max 2MAX min R = h 5 h 6 h 5 h 2MAX 16 /21

17 outlet (p=p s ) Turbine design Absolute velocity inlet (p=p tot ) Mixing plane approach RANS equations Steady state simulations Peng-Robinson EOS Star-CCM+ software Min Absolute pressure Max 17 /21

18 Conclusions sco 2 systems could be successfully applied on industrial waste heat to power generation applications The most limiting device in small-scale sco 2 units ( kwe) is the compressor Theoretical performance of the I-ThERM s demonstration unit exceed 21% global cycle efficiency 18 /21

19 Future work Design and manufacturing of the compressorturbine-generator (CGT) unit and its controls HXs selection and design Transient modelling of the sco 2 system Experimental campaign 19 /21

20 on Supercritical CO 2 (sco 2 ) Power Systems Design considerations on a small scale supercritical CO 2 power system for industrial high temperature waste heat to power recovery applications, S. A. Tassou, Y. Ge, H.Jouhara, K. Tsamos A. Leroux, M. De Miol Wien, 29/09/2016