1.Performance Analysis of High Temperature Sensible Heat Storage System during Charging and Discharging cycles By Likhendra Prasad, Hakeem Niyas, P.Muthukumar Department of Mechanical Engineering IIT Guwahati4th International Conference on Advances in Energy Research IIT Bombay

2. Outline of Presentation Introduction Objectives of present work Thermal modelling Results and discussions Conclusions 12/10/2013ICAER 20132 3. Potential of Renewable Energies Global Primary Energy Consumption (GPEC) Solar energy (1800 Wind energy (200 Biomass (20GPEC) GPEC)GPEC)Geothermal energy (10GPEC)Ocean energy (2GPEC)Hydro energy (1GPEC)Source: Nitsch, 2007 12/10/2013ICAER 20133 4. Solar PowerSolar Energy12/10/2013Solar PV Solar ThermalSolar Cell CSP ICAER 2013Solar Power4 5. Concentrating Solar Power (CSP)(a) Parabolic Trough(b) Linear Fresnel Reflector(c) Parabolic Dish(d) Solar Tower Source: www.csp-world.com12/10/2013ICAER 20135 6. Solar thermal power plant with TES system HTFSteamSuperheaterTurbine SolarBoilerTES FieldPreheaterP12/10/2013ICAER 2013PCondenser6 7. Thermal Energy Storage Methods Sensible Heat Storage (SHS) Q s V C p s Tch ( J ) Concrete, Cast steel, Concrete, etc. Latent Heat Storage (LHS)TmT2Q s , pc m V C p s , pcm dT l , pc m H f g l , pc m C pl , pcm T1Tm Phase change material (PCM) Thermochemical Heat Storage (THS) - Reversible chemical reactions Metal Hydrides12/10/2013ICAER 20137(J ) 8. Materials for SHS Requirements ofSHS MaterialsOperatingTemperSpecific heatThermalature (K)(kJ/kg K)conductivitySHS materials Large operating temperature(W/m K) Reinforced concrete6731.001.52200Silica fire bricks9731.001.51820Solid NaCl7730.8572160Cast iron6730.56377200Cast steel9730.60407800High heat capacityHigh thermal conductivityHigh DensityStabilityLow cost and availabilityHigh thermal conductivity materials Low cost and easily available materials 12/10/2013ICAER 20138 9. Objectives of the present work To develop a 3-D thermal model for predicting the performances of SHS systems. To optimize the number of charging tubes in the storage bed based on charging time. To predict the performance of SHS bed of high conductivity solid material (cast steel) of capacity 50 MJ. To predict the performance of SHS bed of low conductivity solid material (concrete) of capacity 50 MJ by incorporating the axial fins (copper) on charging tube surfaces. 12/10/2013ICAER 20139 10. Design and Optimization of SHS model12/10/2013ICAER 201310 11. Thermal modelling of SHS model Assumptions The inlet velocity profile of HTF is fully developed. SHSM is isotropic. The flow is considered as unsteady, laminar and incompressible. Axial Conduction is negligible Governing Equations: Physical model of SHS bedFluid flow: Continuity and N-S Eq. . v 0 Dv 2 f P v Dt 12/10/2013Heat transfer: Convection (solid- liquid interface)Heat transfer: Conduction (solid) ICAER 2013Schematic of mathematical model 11 12. ICs and BCs : Performance parameters Charging / discharging time.Energy stored / recovered12/10/2013Exergy efficiencyQ s V C p s T ( J ) Exergy Tch T (t) Tch TatmICAER 201312 13. Validation of SHS modelFig.10 (a)Input parameters for validation [4] Sl.Parameters1Density of concrete (kg/m3)22002Specific heat of concrete (J/kg K)10003Thermal conductivity of concrete (W/m K)1, 2, 54Diameter of the charging tube (m)Values0.025 12/10/2013[31]623666313 14. Flow and temperature variation of HTF inside the charging tube12/10/2013ICAER 201314 15. Heat Transfer into the cast steel bed during charging12/10/2013ICAER 201315 16. Results and Discussions - Charging3650 s683 s62.39 MJCharging time of concrete and cast steel beds 12/10/201362.85 MJEnergy storage rate of concrete and cast steel ICAER 2013beds16 17. Results and Discussions - Charging4493 s3650 s3379 sEffect of HTF velocity on charging time of 12/10/2013concrete bed1400 s683 s430 sEffect of HTF velocity on charging time of cast ICAER 2013steel bed17 18. Results and Discussions - ChargingAxial Temperature variation of HTF during 12/10/2013charging of concrete bedAxial Temperature variation of HTF during ICAER 2013charging of cast steel bed18 19. Results and Discussions - Discharging7200 s 1820 s59.78 MJDischarging time of concrete and cast steel beds 12/10/201362.75 MJEnergy discharge rate of concrete and cast steel bedsICAER 201319 20. Results and Discussions - DischargingEffect of HTF velocity on discharging time ofEffect of HTF velocity on discharging time ofconcrete bedcast steel bed12/10/2013ICAER 201320 21. Results and Discussions - DischargingAxial Temperature variation of HTF during 12/10/2013discharging of concrete bedAxial Temperature variation of HTF during ICAER 2013discharging of cast steel bed21 22. Results and DiscussionsExergy efficiency variation 12/10/2013ICAER 201322 23. Conclusions Thermal models for predicting the charging and discharging characteristics of SHS systems have been developed.The number of charging tubes has been optimized based on the charging time of the SHS bed.Heat transfer enhancement technique is implemented by adding fins on the outer surface of charging tubes.The charging time and energy stored in the SHS bed are found to be 3650 s and 683 s, 62.39 MJ and 62.85 MJ for concrete and cast steel respectively.The predicted discharging time of SHS beds are 7200 s for concrete bed and 1850 s for the cast steel bed.The energy discharged from the beds in their respective discharging times are found to be 59.78 MJ for concrete bed and 62.75 MJ for cast steel bed.12/10/2013ICAER 201323 24. References [1]Gil A., Medrano M., Martorell I. and Cabeza F. (2010) State of the art on high temperature thermal energy storage for power generation. 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(2012) Analysis of high temperature thermal energy storage for solar power plant, Proceedings of the 3rd IEEE International Conference on Sustainable Energy Technology, pp. 438-444.[7]John, E.E., Hale, W. M. and Selvam, R. P. (2011) Development of a high-performance concrete to store thermal energy for concentrating solar power plants, Proceedings of the 5th ASME International Conference on Energy Sustainability, pp. 523-529.[8]Tian, Y. and Zhao, C.Y. (2013) A review of solar collectors and thermal energy storage in solar thermal applications, Applied Energy, 104, pp. 538-553.12/10/2013ICAER 201325 26. THANK YOU12/10/2013ICAER 201326