Thermodynamics investigation of a solar power system integrated oil and molten salt as heat transfer fluids

Abstract In this paper, a new parabolic trough solar power system that incorporates a dual-solar field with oil and molten salt as heat transfer fluids (HTFs) is proposed to effectively utilize the solar energy. The oil is chosen as a HTF in the low temperature solar field to heat the feeding water, and the high temperature solar field uses molten salt to superheat the steam that the temperature is higher than 773 K. The produced superheated steam enters a steam turbine to generate power. Energy analysis and exergy analysis of the system are implemented to evaluate the feasibility of the proposed system. Under considerations of variations of solar irradiation, the on-design and off-design thermodynamic performances of the system and the characteristics are investigated. The annual average solar-to-electric efficiency and the nominal efficiency under the given condition for the proposed solar thermal power generation system reach to 15.86% and 22.80%, which are higher than the reference system with a single HTF. The exergy losses within the solar heat transfer process of the proposed system are reduced by 7.8% and 45.23% compared with the solar power thermal systems using oil and molten salt as HTFs, respectively. The integrated approach with oil and molten salt as HTFs can make full use of the different physical properties of the HTFs, and optimize the heat transfer process between the HTFs and the water/steam. The exergy loss in the water evaporation and superheated process are reduced, the system efficiency and the economic performance are improved. The research findings provide a new approach for the improvement of the performances of solar thermal power plants.

[1]  Fritz Zaversky,et al.  Object-oriented modeling for the transient performance simulation of parabolic trough collectors using molten salt as heat transfer fluid , 2013 .

[2]  Gregory J. Kolb,et al.  Final Test and Evaluation Results from the Solar Two Project , 2002 .

[3]  M. Valdés,et al.  Solar multiple optimization for a solar-only thermal power plant, using oil as heat transfer fluid in the parabolic trough collectors , 2009 .

[4]  Ennio Macchi,et al.  Comparison of different solar plants based on parabolic trough technology , 2012 .

[5]  F. Lippke,et al.  Simulation of the part-load behavior of a 30 MWe SEGS plant , 1995 .

[6]  P. Forster,et al.  Climate change impacts on future photovoltaic and concentrated solar power energy output , 2011 .

[7]  Hongguang Jin,et al.  A three-dimensional simulation of a parabolic trough solar collector system using molten salt as heat transfer fluid , 2014 .

[8]  A. Patnode.  Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants , 2006 .

[9]  M. Ishida,et al.  Energy and exergy analysis of a chemical process system with distributed parameters based on the enthalpy-direction factor diagram , 1982 .

[10]  Justin Raade,et al.  Development of Molten Salt Heat Transfer Fluid With Low Melting Point and High Thermal Stability , 2011 .

[11]  Abdallah Khellaf,et al.  A review of studies on central receiver solar thermal power plants , 2013 .

[12]  Mahmood Yaghoubi,et al.  Transient simulation for developing a combined solar thermal power plant , 2012 .

[13]  Hongguang Jin,et al.  Solar Hydrogen Production Integrating Low-Grade Solar Thermal Energy and Methanol Steam Reforming , 2009 .

[14]  M. J. Montes,et al.  Performance of a direct steam generation solar thermal power plant for electricity production as a function of the solar multiple , 2009 .

[15]  D. Kearney,et al.  Assessment of a Molten Salt Heat Transfer Fluid in a Parabolic Trough Solar Field , 2003 .

[16]  Eduardo Zarza,et al.  Parabolic-trough solar collectors and their applications , 2010 .

[17]  Peiwen Li,et al.  Energy Storage Start-up Strategies for Concentrated Solar Power Plants With a Dual-Media Thermal Storage System , 2015 .

[18]  Eckhard Lüpfert,et al.  Advances in Parabolic Trough Solar Power Technology , 2002 .