1. SUSTAINABLE ENERGY CONVERSION THROUGH THE USE OF ORGANIC RANKINE CYCLES FOR WASTE HEAT RECOVERY AND SOLAR APPLICATIONS. PhD Thesis presentation Sylvain Quoilin Energy Systems Research Unit Université de Liège, Belgium Sylvain Quoilin - PhD Thesis Presentation 1

2. Introduction Current climate concerns:  Energy sector is responsible for 84% of the greenhouse gases emissions  Primary energy consumption (mainly fossil fuels) is growing.  1.5 billion people lack access to electricity Sylvain Quoilin - PhD Thesis Presentation 2 Source: BP, 2011 EU 2050 Roadmap (-80% of greenhouse gases emissions): 1.Decrease energy intensity of building and industry 2.Shift from fossil fuels towards Electricity (e.g. for transportation and space heating 3.Renewable energy generation technologies (Wind, PV, CSP, Biomass, Geothermy, hydro). 4.Storage capacity and grid reinforcement

3. Introduction Working principle of Organic Rankine cycle (ORC) : Same components and working principle as traditional water Rankine cycle. Optional regenerator Organic fluids such as R123, R245fa, pentane,... Main advantage of ORC : Efficient conversion of low temperature heat source to mechanical power, downscaling Typical heat sources : Geothermal source Solar power Waste heat of industrial process Biomass CHP Sylvain Quoilin - PhD Thesis Presentation 3

4. Introduction Sylvain Quoilin - PhD Thesis Presentation Very few projects in the KW power scale ! Source: Enertime, 2011 4 Number of identified plants:

5. Volumetric expandersTurbomachines ScrollScrewReciprocatingAxialRadial 5 Sylvain Quoilin - PhD Thesis Presentation ORC Expansion Machines

6. Develop and optimize a small-scale waste heat recovery ORC prototype Test candidate expansion machines Develop validated steady-state models Develop dynamics models and control strategies Provide guidelines for the design, the fluid selection and the control of such a cycle 6 Sylvain Quoilin - PhD Thesis Presentation Aim of the work

7. Table of contents 7  Introduction  Experimental setups  ORC prototype  Hermetic expander  Modelling  Cycle optimization and fluid selection  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

8. ORC prototype Heat sources Two hot air streams (about 25 kWth) First source : from 150 to 200 °C Second source : from 120 to 160 °C Same flow rate Heat sink Cooling water at 10 to 20°C Main Challenges: Maximize the output power Find or develop the right components for small- scale ORCs Optimize the cycle Sylvain Quoilin - PhD Thesis Presentation 8

9. Pump Two diaphragm metering pumps Variable displacement (0 to 100%) Max outlet pressure : 12 bar Accurate control of the flow rate Very poor isentropic effectiveness Limited outlet pressure + - - Sylvain Quoilin - PhD Thesis Presentation 9

10. Evaporator Three plate heat exchangers fed with hot air Asymmetric configuration due to source temperature difference Evaporator n°1 Evaporator n°3 Evaporator n°2 to expander Cooler heat source Hotter heat source Sylvain Quoilin - PhD Thesis Presentation 10

11. Condenser Two plate heat exchangers fed with cold water Parallel configuration to limit pressure drops Condenser followed by a liquid receiver and an additional heat exchanger to control subcooling from expander Condenser n°1 Condenser n°2 to pump Subcooler Sylvain Quoilin - PhD Thesis Presentation 11

12. Oil-free scroll expander Air compressor converted into an expander Swept volume in expander mode : 31 cc Built in volumetric ratio : 3.94 Max outlet pressure in compressor mode : 10 bar Acceptable isentropic effectiveness Absence of lubrication Tightness + - + Sylvain Quoilin - PhD Thesis Presentation 12

13. Test Rig 13 Sylvain Quoilin - PhD Thesis Presentation

14. 14 Sylvain Quoilin - PhD Thesis Presentation Experimental results Maximum values:

15. Table of contents 15  Introduction  Experimental setups  ORC prototype  Hermetic expander  Modelling  Cycle optimization and fluid selection  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

16. 16 Sylvain Quoilin - PhD Thesis Presentation Expander test bench

17. Hermetic scroll expander Refrigeration compressor converted into an expander Swept volume in expander mode : 22.4 cc Built in volumetric ratio : 2.9 Max outlet temperature in compressor mode : 130°C Good isentropic effectiveness Tightness Lubrication Low volume ratio + - + - Sylvain Quoilin - PhD Thesis Presentation 17

18. 18 Sylvain Quoilin - PhD Thesis Presentation Experimental results Ambient heat losses: 15 to 40% of the output power

19. Summary WHR prototype Two types of expander tested, with very promising overall isentropic effectiveness (71%) Future work: Non-condensing gases Implementation of an automated control strategy Selection or development of a high-performance pump 19 Sylvain Quoilin - PhD Thesis Presentation

20. Table of contents 20  Introduction  Experimental setups  Modelling  Steady-state models  Dynamic models  Cycle optimization and fluid selection  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

21. Steady-state models 21 Sylvain Quoilin - PhD Thesis Presentation  Selected platform: Engineering Equation Solver (EES)  Use of acausal equations  Sizing model can very easily become simulation models  Important thermodynamic properties database  Semi-empirical models

22. 1.Supply pressure drop (su→ su,1,1) 2.Cooling-down in the supply port of the expander (su1,1 → su,1); 3.Isentropic expansion from the supply pressure down to the internal pressure imposed by the internal expansion volume ratio of the expander (su,1 → ad); 4.Expansion at a fixed volume from the internal pressure to the exhaust pressure (ad → ex,2); 5.Mixing between suction flow and leakage flow (ex,2 → ex,1) and 6.Cooling-down or heating-up in the exhaust port (ex,1 → ex). 22 Sylvain Quoilin - PhD Thesis Presentation Expander model Open-drive:Hermetic:

23. Built-in internal volume ratio  Under and over-expansion: Under & Over-expansion losses 23 Sylvain Quoilin - PhD Thesis Presentation

24. 24 Sylvain Quoilin - PhD Thesis Presentation Parameter identification Measured or calculated

25. Model validation Error max: Flow rate: 2% Power: 6% Exhaust T°: 2K 25 Sylvain Quoilin - PhD Thesis Presentation

26. Plate heat exchangers 26 Sylvain Quoilin - PhD Thesis Presentation

27. 27 Sylvain Quoilin - PhD Thesis Presentation ORC global model Pump Refrigerant flow rate Expander Evaporating pressure and exhaust temperature Evaporator Superheating Condenser Condensing pressure Causal behavior:

28. 28 Sylvain Quoilin - PhD Thesis Presentation ORC global model

29. Optimization Reduction of the subcooling Increase of the pump effectiveness Optimization of the working conditions η = 5.7 % ; W = 0.84 kWη = 9.9 % ; W = 1.95 kW 29 Sylvain Quoilin - PhD Thesis Presentation

30. Hermetic expander model: losses Most significants: Internal volume ratio and electromechanical 30 Sylvain Quoilin - PhD Thesis Presentation

31. Table of contents 31  Introduction  Experimental setups  Modelling  Steady-state models  Dynamic models  Cycle optimization and fluid selection  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

32. Conservation of energy: Conservation of mass: Metal wall: 32 HEAT EXCHANGER MODEL Simplified heat transfer and pressure drop laws: Sylvain Quoilin - PhD Thesis Presentation

33. Chattering is likely if: 33 NUMERICAL ROBUSTNESS Sylvain Quoilin - PhD Thesis Presentation Stability criteria: Proposed solutions: 1. Truncated density derivative 2. Filtered density derivative 3. Constant node flow rate 4. High number of cells

34. 34 CYCLE MODEL Performance indicators: Sylvain Quoilin - PhD Thesis Presentation

35. 35 CYCLE DISPLAY Sylvain Quoilin - PhD Thesis Presentation

36. Table of contents 36  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Screening method  Operating maps  Thermo-economic optimization  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

37. Cycle optimization Recuperator? Sylvain Quoilin - PhD Thesis Presentation Optimum operating conditions: Condensing pressure: As low as possible Subcooling at the condenser exhaust: As low as possible Superheating at the evaporator exhaust : As low as possible Pressure drops: As low as possible Evaporating temperature: Depends on the application Main optimization parameter : evaporation temperature 37

38. Selection of the working fluid High thermodynamic performance Positive or isentropic saturation vapor curve High vapor density and low volume ratio Acceptable pressures High stability temperature Good availability and low cost Low environmental impact and high safety level (ODP, GWP, etc.) Optimal characteristics of the working fluid : 38 Sylvain Quoilin - PhD Thesis Presentation

39. Table of contents 39  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Screening method  Operating maps  Thermo-economic optimization  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

40. Selection Of The Working Fluid: screening method Comparisons are usually performed:  For a given application  Maximizing the thermodynamic efficiency Additional factors such as vapor density or pressure ratio are rarely taken into account 40 Sylvain Quoilin - PhD Thesis Presentation

41. Table of contents 41  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Screening method  Operating maps  Thermo-economic optimization  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

42. 42 Sylvain Quoilin - PhD Thesis Presentation Operating maps: volumetric expanders Screw expanderScroll expander:(n-pentane)

43. 43 Sylvain Quoilin - PhD Thesis Presentation Operating map: radial turbine n-pentane:

44. 44 Sylvain Quoilin - PhD Thesis Presentation Operating maps: power ranges rpm < 50000

45. Table of contents 45  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Screening method  Operating maps  Thermo-economic optimization  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

46. Thermo-economic optimization Heat source: TherminolVP-1, 180°C, 0.3 kg/s Heat sink: Water, 15°C, 0.5 kg/s 46 Sylvain Quoilin - PhD Thesis Presentation

47. 47 Sylvain Quoilin - PhD Thesis Presentation Thermo-economic model

48. 48 Sylvain Quoilin - PhD Thesis Presentation Fluid selection & optimization Thermodynamic optimization:Thermo-economic optimization:

49. Optimization results Net output power [W] :Evaporating temperature [°C]: Specific Investment Cost [€/kW] : 49 Sylvain Quoilin - PhD Thesis Presentation

50. 50 Sylvain Quoilin - PhD Thesis Presentation Fluid selection methods: summary Future works:  Develop accurate cost functions for all components  Refine the boundaries for radial/axial turbines  Extend the operating maps to other expander types

51. Table of contents 51  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Case studies  Solar ORC  Variable heat source WHR  Conclusions Sylvain Quoilin - PhD Thesis Presentation

52. 52 Sylvain Quoilin - PhD Thesis Presentation Case study: Solar ORC Two solar ORC field trials installed in Lesotho Aim : Replacing Diesel generators, at a lower cost Low temperature (<200°C) for cost savings Use of HVAC and car components : air- conditioning scroll compressor, steering pump Self-designed autonomous control unit Aims: Size the system Evaluate the performance Determine optimal working conditions Select between one or two expanders in series

53. 53 Sylvain Quoilin - PhD Thesis Presentation Initial project area: Lesotho, South Africa

54. 50-100 patients/day 3 nurses + orderly 4-10 Clinic & staff buildings No electricity No hot water Typical Lesotho clinic: Sylvain Quoilin - PhD Thesis Presentation 54 Application: Powering rural health clinics

55. Operating Temperature: 150°C HTF: Propylene Glycol Heat collector field: 75 m² Sylvain Quoilin - PhD Thesis Presentation Proposed technology 55

56. 56 Sylvain Quoilin - PhD Thesis Presentation Models Collector model: Discretized 1D model Radiation, convection, conduction, pressure drops Validated with the SEGs plants

57. 57 Sylvain Quoilin - PhD Thesis Presentation Models Expander model: Non-dimensional polynomial fit Analytical expression for the computation of the optimal intermediate pressure: Condenser model: Polynomial fit from manufacturer data Evaporator, recuperator model: Sizing plate heat exchanger model Pump model: Constant effectiveness Performance indicators:

58. 58 Sylvain Quoilin - PhD Thesis Presentation Simulation results High under-expansion losses with a single-stage expansion Temperature limitation of the expanders Optimum very close to the critical point with two-stage expansion

59. Most efficient: double-stage, Solkatherm Smallest (=> low cost) expanders: R245fa Lowest required heat exchange area: Solkatherm (but uncertainty on the thermodynamic and transfer properties!) => Final selected solution: two-stage expansion with 245fa, possibility to switch to Solkatherm by varying expander speed. 59 Sylvain Quoilin - PhD Thesis Presentation Result analysis

60. A 3kWe (25kWh/day) Solar ORC has been developed to power off-grid institutions in developing countries The concept produces both heat and power, for which a local demand is proven. It is flexible and can be produced and repaired on-site. A demonstration plant is installed in a very visited place to foster technology awareness. Strong partnerships and knowledge transfer amongst local engineers, government, and universities The unit has been built and put into service in January 2011 Future work: Validation of the model with on-field experimental data Optimize and simulate different control strategies For more information: www.stginternational.org Sylvain Quoilin - PhD Thesis Presentation 60 Summary

61. Table of contents 61  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Case studies  Solar ORC  Variable heat source WHR  Conclusions Sylvain Quoilin - PhD Thesis Presentation

62. Degrees of freedom: 62 CONTROL STRATEGIES Controlled variables: Sylvain Quoilin - PhD Thesis Presentation

63. 63 OPTIMAL EVAPORATION TEMPERATURE Static optimization of the cycle T ev,optim depends on the heat source/sink conditions: Sylvain Quoilin - PhD Thesis Presentation

64. 64 CYCLE FEEDBACK CONTROL STRATEGIES Sylvain Quoilin - PhD Thesis Presentation

65. 65 Sylvain Quoilin - PhD Thesis Presentation Control Unit

66. 66 CYCLE FEEDBACK CONTROL STRATEGIES Sylvain Quoilin - PhD Thesis Presentation

67. Table of contents 67  Introduction  Experimental setups  Modelling  Cycle optimization and fluid selection  Case studies  Conclusions Sylvain Quoilin - PhD Thesis Presentation

68. Conclusions Feasibility of developing a small-capacity ORC has been proven Large amount of open experimental data Two types of expander tested Set of validated steady-state models, easily adaptable to alternative small-scale ORC systems Early-stage development of an open-source dynamic models library Three fluid selection methods, cycle optimization guidelines Two examples of practical applications of the proposed models and methods 68 Sylvain Quoilin - PhD Thesis Presentation

69. Future work & perspectives Extend the proposed models and methods to more advanced ORC configurations: Dual-pressure WHR cycles Zeotropic mixtures Supercritical cycles Further study of the influence of oil on the hermetic expander performance and on the heat exchanger performance Development of an oil-management system Development of purpose-designed scroll expander (higher temperature, higher volume ratio) Investigation of reliability issues Management of non-condensing gases Isolated grid-operation (thermal storage, flywheels, demand-side management, etc.) Advanced control strategies (feedforward, MPC), start & stop 69 Sylvain Quoilin - PhD Thesis Presentation

70. Thank you! 70 Sylvain Quoilin - PhD Thesis Presentation Special thanks to: My two successive advisors: J. Lebrun, V. Lemort The members of the Committee: P. Colonna, P. Duysinx, G. Heyen, P. Ngendakumana, A. Zoughaib The members of the thermodynamic laboratory: Arnaud, Bernard G., Bernard L., Cleide, Clément, Danielle, Fabrice, François, Jean-Marie, JF, José, Jules, Kevin, Ludovic, Olivier, Philippe, Pierre, Richard, Roberto, Sam, Sébastien, Stéphane, Vincent. My Family and my friends

71. 71 Sylvain Quoilin - PhD Thesis Presentation

72. 72 Sylvain Quoilin - PhD Thesis Presentation Two-phase heat transfer correlations Source: García-Cascales, 2007

73. 73 Sylvain Quoilin - PhD Thesis Presentation Oil impact on the evaporator

74. Plate heat exchangers 74 Sylvain Quoilin - PhD Thesis Presentation

75. Dynamic models: expander Steady-state model: Dimensional parameters Dimensionless model: Polynomial law for isentropic effectiveness and for filling factor Assumption: independent of the size 75 Sylvain Quoilin - PhD Thesis Presentation

76. 76 Sylvain Quoilin - PhD Thesis Presentation