Dynamic modelling of adiabatic compressed air energy storage using packed bed thermal energy storage Wei He and Jihong Wang School of Engineering, University of Warwick UKTES2016

Background and motivation Dynamic modelling library and framework of CAES-TES Case study of A-CAES using PBTES Conclusion

Background  Preliminary design of components (geometry and operation) subject to overall system performance  Extended thermodynamic analysis of A-CAES into components  Dynamic modelling of the whole system using component-level mathematical models  We need energy storage!  Adiabatic Compressed Air Energy Storage (A-CAES) using Thermal Energy Storage (TES) is promising  Lack of detailed simulation tools in CAES-TES (CFD modelling of component and thermodynamic analysis of system) Motivation

Dynamic modelling library and framework of CAES-TES Electric motor CompressorAir StorageExpanderElectric generator Heat exchanger Sensible heat TES Latent heat TES  Component level mathematical modelling sub-library Thermodynamic properties of working fluids and TES materials

Test case of A-CAES using PBTES Air tank Packed Bed Thermal Energy Storage (PBTES) Radial Turbine Generator Piston Com- pressor Motor Charge period Discharge period

 System level dynamic modelling framework A-CAES with TES Parameters initialisation (t=0) Update variables (t=t+1) t<t end Yes CA TES Mechanical connection AS TES MC E G Three trajectories tracking: mass or/and energy balance

 Flow of CA E Full-admissionPartial-admission Stator (nozzle) Rotor (blade) Inflow radial (IFR) turbine – Mean-line model Euler equation of turbomachinery Conversion of kinetic energy and potential energy of CA Energy losses: incidence loss, frictional loss, exit loss, etc. Performance map of IFR turbine (design and off-design operations)

 Flow of CA C Image is from Mass and energy conservation: Ideal gas theory and the first law of thermodynamics Pressure variation Geometry based volume variation

 Flow of TES TES Fluid ChargeDischarge Charge Discharge x H Energy Equations of CA and TES Initial and boundary conditions Pressure drop of CA Insulation material Tank wall

 Flow of CA AS ChargeDischarge Mass and energy conservation: Ideal gas theory and the first law of thermodynamics Energy equation can be rewritten as

 Flow of CA Thermodynamic properties of working fluids and TES materials CA properties CoolProp PCM properties Enthalpy method Solid phase: Phase changing: Liquid phase: [1] Bell, Ian H., et al. "Pure and pseudo-pure fluid thermophysical property evaluation and the open-source thermophysical property library CoolProp." Industrial & engineering chemistry research 53.6 (2014):

 Validation of model library – IFR turbine Experiments Modelling Experiments Modelling Experiments Modelling [2] Jones, Anthony C. "Design and test of a small, high pressure ratio radial turbine." ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994.

 Validation of model library – latent heat PBTES [3] Izquierdo-Barrientos MA, Sobrino C, Almendros-Ibáñez JA. Thermal energy storage in a fluidized bed of PCM. Chemical Engineering Journal. 2013;230: Experiment [2] x=0.075 m x=0.125 m x=0.175 m Time Temperature

Test case of A-CAES using PBTES Air tank Packed Bed Thermal Energy Storage (PBTES) Radial Turbine Generator Piston Com- pressor Motor Charge period Discharge period

 Charge period AS TES MC Time Cylinder pressure Time Cylinder pressure

Temperature Inlet air temperature at PBTES Time Outlet air temperature at PBTES Time Temperature  Charge period AS TES MC Time Temperature stratification in PBTES Temperature [4] Agyenim, Francis, et al. "A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS)." Renewable and Sustainable Energy Reviews 14.2 (2010):

 Charge period AS TES MC Time Pressure Air pressure in AS

 Discharge period TES E G AS Time Pressure Air pressure in AS

 Discharge period TES E G AS Time Pressure Outlet air pressure at PBTES Time Temperature Outlet air temperature at PBTES Temperature Time Temperature stratification in PBTES

 Discharge period TES E G AS Time Efficiency Isentropic efficiency of IFR turbine

 System performance Power Time Power consumed by compressor Power Time Power generated by turbine

Conclusion  Dynamic modelling framework using CAES-TES model library is capable to study the transient operation of A-CAES  Preliminary design of components can be carried out, including compressor, turbine, PBTES and etc.  Potential high cycle efficiency of A-CAES using PBTES  Calls for further optimisation of both system and components design

Thanks!