Experimental and numerical investigation of potential filler materials for thermal oil thermocline storage

Abstract A thermal energy storage system (TES) is a key technology to ensure continuous power supply from solar thermal power plants. Choosing the appropriate storage method and the suitable material for energy storage remains a major challenge in research and development in the solar power field. The sensible heat storage in solid media using thermocline system is a significant cost-effective option when compared to liquid storage material in two tank system. An incorporation of this potential concept is the oil/rock thermocline system which is based on the direct contact between natural rocks chosen as filler material and thermal oil as the heat transfer fluid (HTF), and it is used in the Concentrated Solar Power (CSP) plants. The present paper highlights the thermal energy storage potential of six rocks (quartzite, basalt, granite, hornfels, cipolin and marble) proposed as filler material for thermal oil thermocline storage concept. These rocks were chosen according to their abundance in Morocco. Different technical methods were performed in order to assess the rocks properties (physical, chemical and thermal) at temperatures up to 350 °C (temperature operating conditions using linear Fresnel reflectors or parabolic trough). The thermal performances of the studied rocks inside a thermocline storage system were evaluated using a validated numerical model. Based on the experimental investigation two rocks (Quartzite and Cipolin) were identified as the most suitable filler materials to be used in direct contact with the studied HTF (synthetic oil). While, the numerical analysis revealed that Basalt rock has the best thermal performances inside the studied thermocline storage system concept, but it isn’t chemically compatible with synthetic oil. Hence, it can be used advantageously with other heat transfer medium (e.g. Air).

[1]  Luisa F. Cabeza,et al.  Comparative life cycle assessment of thermal energy storage systems for solar power plants , 2012 .

[2]  Mohamed Maaroufi,et al.  Numerical investigations of high temperature packed bed TES systems used in hybrid solar tower power plants , 2015 .

[3]  A. Waked.  Solar energy storage in rocks , 1986 .

[4]  Ibrahim Dincer,et al.  A perspective on thermal energy storage systems for solar energy applications , 1996 .

[5]  A. Hofmeister.  Thermal diffusivity of garnets at high temperature , 2006 .

[6]  D. G. Kröger,et al.  Rock bed storage for solar thermal power plants: Rock characteristics, suitability, and availability , 2014 .

[7]  Jon T. Van Lew,et al.  Analysis of Heat Storage and Delivery of a Thermocline Tank Having Solid Filler Material , 2011 .

[8]  H. T. Ozkahraman,et al.  Determination of the thermal conductivity of rock from P-wave velocity , 2004 .

[9]  C. Clauser,et al.  Thermal Conductivity of Rocks and Minerals , 2013 .

[10]  Elias K. Stefanakos,et al.  Thermal energy storage technologies and systems for concentrating solar power plants , 2013 .

[11]  Andrea Lucchini,et al.  Comparison of Thermocline Molten Salt Storage Performances to Commercial Two-tank Configuration , 2014 .

[12]  D. Fernandes,et al.  Thermal energy storage: “How previous findings determine current research priorities” , 2012 .

[13]  Jeffrey M. Gordon.  Solar Energy : The State of the Art , 2013 .

[14]  A. Steinfeld,et al.  Packed-bed thermal storage for concentrated solar power: Pilot-scale demonstration and industrial-scale design , 2012 .

[15]  S. Chaki,et al.  Influence of thermal damage on physical properties of a granite rock: Porosity, permeability and ultrasonic wave evolutions , 2008 .

[16]  Matthew N. Strasser,et al.  A cost and performance comparison of packed bed and structured thermocline thermal energy storage systems , 2014 .

[17]  Ulf Herrmann,et al.  Engineering aspects of a molten salt heat transfer fluid in a trough solar field , 2004 .

[18]  J. Pacheco,et al.  DEVELOPMENT OF A MOLTEN-SALT THERMOCLINE THERMAL STORAGE SYSTEM FOR PARABOLIC TROUGH PLANTS , 2001 .

[19]  Luisa F. Cabeza,et al.  State of the art on high temperature thermal energy storage for power generation. Part 1—Concepts, materials and modellization , 2010 .

[20]  John J. Burkhardt,et al.  Life Cycle Assessment of Thermal Energy Storage: Two-Tank Indirect and Thermocline , 2009 .

[21]  R. Saini,et al.  A review on packed bed solar energy storage systems , 2010 .

[22]  M. S. Audi.  Experimental study of a solar space heating model using Jordanian rocks for storage , 1992 .

[23]  D. Dewitt,et al.  The thermal diffusivity of eight well-characterized rocks for the temperature range 300–1000 K , 1978 .

[24]  Hans W. Fricker.  High-temperature heat storage using natural rock , 1991 .

[25]  Bhalchandra V. Gokhale,et al.  Rotary Drilling and Blasting in Large Surface Mines , 2010 .

[26]  Esther Rojas,et al.  Study of Thermocline Tank Performance in Dynamic Processes and Stand-by Periods with an Analytical Function , 2014 .

[27]  W. Tao,et al.  The impact of concrete structure on the thermal performance of the dual-media thermocline thermal storage tank using concrete as the solid medium , 2014 .

[28]  K. Ismail,et al.  A parametric study on possible fixed bed models for pcm and sensible heat storage , 1999 .

[29]  S. Garimella,et al.  Molten-salt thermal energy storage in thermoclines under different environmental boundary conditions , 2010 .

[30]  F. Homand-Etienne,et al.  Behaviour of granites and limestones subjected to slow and homogeneous temperature changes , 1984 .

[31]  A. I. El-Sharkawy,et al.  Effect of storage medium on thermal properties of packed beds , 1990 .

[32]  John W. Kelton,et al.  Testing of Thermocline Filler Materials and Molten-Salt Heat Transfer Fluids for Thermal Energy Storage Systems in Parabolic Trough Power Plants , 2004 .

[33]  S. M. Hasnain.  Review on sustainable thermal energy storage technologies, Part I: heat storage materials and techniques , 1998 .

[34]  S. Relloso,et al.  Tower Technology Cost Reduction Approach after Gemasolar Experience , 2015 .

[35]  Steven J. St.Laurent.  Thermocline Thermal Storage Test for Large-Scale Solar Thermal Power Plants , 2000 .

[36]  R. Tamme,et al.  Solid media thermal storage for parabolic trough power plants , 2006 .

[37]  J. Fourmigue,et al.  Experimental and numerical investigation of a pilot-scale thermal oil packed bed thermal storage system for CSP power plant , 2014 .

[38]  Septimus van der Linden,et al.  Bulk energy storage potential in the USA, current developments and future prospects , 2006 .

[39]  Xin Li,et al.  Parametric study and standby behavior of a packed-bed molten salt thermocline thermal storage system , 2012 .

[40]  H. Vosteen,et al.  Influence of temperature on thermal conductivity, thermal capacity and thermal diffusivity for different types of rock , 2003 .

[41]  K. Allen,et al.  Performance characteristics of packed bed thermal energy storage for solar thermal power plants , 2010 .

[42]  Aldo Steinfeld,et al.  High-temperature thermal storage using a packed bed of rocks - Heat transfer analysis and experimental validation , 2011 .

[43]  Zhifeng Wang,et al.  Sensitivity analysis of the numerical study on the thermal performance of a packed-bed molten salt thermocline thermal storage system , 2012 .

[44]  D. Waples,et al.  A Review and Evaluation of Specific Heat Capacities of Rocks, Minerals, and Subsurface Fluids. Part 2: Fluids and Porous Rocks , 2004 .

[45]  B. Troschke,et al.  Thermal conductivity models fro two-phase systems , 1998 .