An on-site test method for thermal and optical performances of parabolic-trough loop for utility-scale concentrating solar power plant

Abstract An on-site test method for thermal and optical performances of parabolic-trough (PT) loop for utility-scale concentrating solar power (CSP) plant is proposed. This method is comprised of sequentially off-focus and in-focus tests. The off-focus test is first conducted for thermal performance as that in a complete PT loop, the front (upstream) collectors are used to heat up the heat transfer fluid (HTF) flowing through the rear (downstream) off-focus ones (the test section) while being cooled by the ambient. The front-rear order is reversible to test all the collectors. The correlation between the heat loss and the absorber (outer surface)-ambient temperature difference of the collectors is obtained by fourth-order polynomial data-fitting. Then, the in-focus test is carried out for optical performance, which is achieved based on the energy balance. The heat loss is calculated based on the correlation acquired in the off-focus test. The incident solar radiation, heat gain, cosine loss and end loss are calculated based on the meteorological data, experimental data, local time and astronomical conditions, respectively. Therefore, the optical performance, i.e. the optical efficiency, is readily achievable. The proposed test method was implemented on the 300 kWt experimental rig located in Langfang, Hebei, China. The optical efficiency is evaluated to be (70.77 ± 1.08)%, which lies within the published range. On the other hand, a thermohydraulic model for the parabolic-trough collector (PTC) loop of the 300 kWt experimental rig was developed for system-level use. This model was incorporated with the optical efficiency obtained on the experimental rig. The good agreement between the simulation results and experimental data leads to the reciprocal verifications between the proposed on-site test method and the thermohydraulic model.

[1]  W. Beckman,et al.  Solar Engineering of Thermal Processes , 1985 .

[2]  W. Beckman,et al.  Evaluation of hourly tilted surface radiation models , 1990 .

[3]  Hongguang Jin,et al.  A new rotatable-axis tracking solar parabolic-trough collector for solar-hybrid coal-fired power plants , 2013 .

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

[5]  Eduardo Zarza,et al.  Optical and thermal performance of large-size parabolic-trough solar collectors from outdoor experiments: A test method and a case study , 2014 .

[6]  Richard Bannerot,et al.  Determination of error tolerances for the optical design of parabolic troughs for developing countries , 1986 .

[7]  Eckhard Lüpfert,et al.  Slope Error Measurements of Parabolic Troughs Using the Reflected Image of the Absorber Tube , 2009 .

[8]  Eckhard Lüpfert,et al.  Ensuring performance by geometric quality control and specifications for parabolic trough solar fields , 2014 .

[9]  Stuart W. Churchill,et al.  Correlating equations for laminar and turbulent free convection from a horizontal cylinder , 1975 .

[10]  Charles F. Kutscher,et al.  Generation of a Parabolic Trough Collector Efficiency Curve From Separate Measurements of Outdoor Optical Efficiency and Indoor Receiver Heat Loss , 2012 .

[11]  R. Forristall,et al.  Heat Transfer Analysis and Modeling of a Parabolic Trough Solar Receiver Implemented in Engineering Equation Solver , 2003 .

[12]  Robert J. Moffat,et al.  Describing the Uncertainties in Experimental Results , 1988 .

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

[14]  Robert Pitz-Paal,et al.  Validation of Optical Modeling of Parabolic Trough Collectors by Flux Measurement , 2007 .

[15]  W. Beckman,et al.  Solar Engineering of Thermal Processes: Duffie/Solar Engineering 4e , 2013 .

[16]  Hui Hong,et al.  An optimized tracking strategy for small-scale double-axis parabolic trough collector , 2017 .

[17]  Eckhard Lüpfert,et al.  Parabolic Trough Optical Performance Analysis Techniques , 2007 .

[18]  Study of the Optical Impact of Receiver Position Error on Parabolic Trough Collectors , 2013 .

[19]  Jan Fabian Feldhoff,et al.  THERMAL MODELLING AND SIMULATION OF PARABOLIC TROUGH RECEIVER TUBES , 2010 .

[20]  Robert Pitz-Paal,et al.  QUASI-DYNAMIC ANALYSIS OF THERMAL PERFORMANCE OF PARABOLIC TROUGH COLLECTORS , 2009 .

[21]  Robert Pitz-Paal,et al.  Influence of Measurement Equipment on the Uncertainty of Performance Data from Test Loops for Concentrating Solar Collectors , 2010 .

[22]  Charles F. Kutscher,et al.  A Method for Measuring the Optical Efficiency of Evacuated Receivers , 2014 .

[23]  Y. Çengel.  Heat and Mass Transfer: A Practical Approach , 2006 .