Thermofluidynamic Model and Comparative Analysis of Parabolic Trough Collectors Using Oil, Water/Steam, or Molten Salt as Heat Transfer Fluids

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
M. J. Montes ◽  
A. Abánades ◽  
J. M. Martínez-Val
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Point Of View ◽  
Heat Transfer Fluid ◽  
Steam Generation ◽  
Parabolic Trough ◽  
Water Steam ◽  
Temperature And Pressure ◽  
Energy Gains ◽  
Gains And Losses

This paper describes the development and use of a thermofluidynamic model for parabolic trough collectors, specifically suited for carrying out systematic calculations on different design options. The model is based on detailed energy balances, and it has been applied to evaluate collector thermal performances with different working fluids: oil, molten salt, or water/steam. For each heat transfer fluid technology, four parameters have been analyzed: collector length, absorber tube diameter, working temperature, and pressure. The influence of these factors has been studied from the point of view of heat loss, pressure drop, energy, and exergy efficiencies. Exergy is considered the suitable magnitude to guide any optimization process in this field, because it accounts for all relevant energy gains and losses, characterized by their corresponding temperature and pressure. Preliminary conclusions point out that direct steam generation is more efficient than oil and molten salt systems.

Assessment of a Molten Salt Heat Transfer Fluid in a Parabolic Trough Solar Field

2003 ◽  
Vol 125 (2) ◽  
pp. 170-176 ◽  
Author(s):  
D. Kearney ◽  
U. Herrmann ◽  
P. Nava ◽  
B. Kelly ◽  
R. Mahoney ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Mojave Desert ◽  
Storage System ◽  
Eutectic Mixture ◽  
Heat Transfer Fluid ◽  
Diphenyl Oxide ◽  
Parabolic Trough ◽  
Electricity Cost ◽  
Solar Field

An evaluation was carried out to investigate the feasibility of utilizing a molten salt as the heat transfer fluid (HTF) and for thermal storage in a parabolic trough solar field to improve system performance and to reduce the levelized electricity cost. The operating SEGS (Solar Electric Generating Systems located in Mojave Desert, California) plants currently use a high temperature synthetic oil consisting of a eutectic mixture of biphenyl/diphenyl oxide. The scope of this investigation included examination of known critical issues, postulating solutions or possible approaches where potential problems exist, and the quantification of performance and electricity cost using preliminary cost inputs. The two leading candidates were the so-called solar salt (a binary salt consisting of 60% NaNO3 and 40% KNO3) and a salt sold commercially as HitecXL (a ternary salt consisting of 48% CaNO32, 7% NaNO3, and 45% KNO3). Assuming a two-tank storage system and a maximum operation temperature of 450°C, the evaluation showed that the levelized electricity cost can be reduced by 14.2% compared to a state-of-the-art parabolic trough plant such as the SEGS plants. If higher temperatures are possible, the improvement may be as high as 17.6%. Thermocline salt storage systems offer even greater benefits.

Enhanced heat transfer in a parabolic trough solar receiver by inserting rods and using molten salt as heat transfer fluid

2018 ◽  
Vol 220 ◽  
pp. 337-350 ◽  
Author(s):  
Chun Chang ◽  
Adriano Sciacovelli ◽  
Zhiyong Wu ◽  
Xin Li ◽  
Yongliang Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Heat Transfer Fluid ◽  
Parabolic Trough ◽  
Enhanced Heat Transfer ◽  
Solar Receiver

Evaluation of a Molten Salt Heat Transfer Fluid in a Parabolic Trough Solar Field

Solar Energy ◽  
2002 ◽  
Author(s):  
D. Kearney ◽  
U. Herrmann ◽  
P. Nava ◽  
B. Kelly ◽  
R. Mahoney ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Eutectic Mixture ◽  
Heat Transfer Fluid ◽  
Diphenyl Oxide ◽  
Parabolic Trough ◽  
Solar Salt ◽  
Electricity Cost ◽  
Critical Issues ◽  
Solar Field

An evaluation was carried out to investigate the feasibility of utilizing a molten salt as the heat transfer fluid (HTF) and for thermal storage in a parabolic trough solar field to improve system performance and to reduce the levelized electricity cost. The operating SEGS plants currently use a high temperature synthetic oil consisting of a eutectic mixture of biphenyl/diphenyl oxide. The scope of this investigation included examination of known critical issues, postulating solutions or possible approaches where potential problems existed, and the quantification of performance and electricity cost using preliminary, but reasonable, cost inputs. The two leading candidates were the so-called solar salt (a binary salt consisting of 60% NaNO3 and 40% KNO3) and a salt sold commercially as HitecXL (a ternary salt consisting of 48% Ca(NO3)2, 7% NaNO3, and 45% KNO3).

scholarly journals Feasibility Study of Freeze Recovery Options in Parabolic Trough Collector Plants Working with Molten Salt as Heat Transfer Fluid

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2340 ◽  
Author(s):  
Cristina Prieto ◽  
Alfonso Rodríguez-Sánchez ◽  
F. Ruiz-Cabañas ◽  
Luisa Cabeza
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Molten Salts ◽  
Heat Transfer Fluid ◽  
Operational Experience ◽  
Parabolic Trough ◽  
Solar Salt ◽  
Parabolic Trough Collector ◽  
Overall Performance ◽  
Solar Field

Parabolic trough collector (PTC) technology is currently the most mature solar technology, which has led to the accumulation of relevant operational experience. The overall performance and efficiency of these plants depends on several components, and the heat transfer fluid (HTF) is one of the most important ones. Using molten salts as HTFs has the advantage of being able to work at higher temperatures, but it also has the disadvantage of the potential freezing of the HTF in pipes and components. This paper models and evaluates two methods of freeze recovery, which is needed for this HTF system design: Heat tracing in pipes and components, and impedance melting in the solar field. The model is used to compare the parasitic consumption in three molten salts mixtures, namely Solar Salt, HiTec, and HiTec XL, and the feasibility of this system in a freezing event. After the investigation of each of these subsystems, it was concluded that freeze recovery for a molten salt plant is possible.

Object-oriented modeling for the transient performance simulation of parabolic trough collectors using molten salt as heat transfer fluid

Solar Energy ◽  
2013 ◽  
Vol 95 ◽  
pp. 192-215 ◽  
Author(s):  
Fritz Zaversky ◽  
Rodrigo Medina ◽  
Javier García-Barberena ◽  
Marcelino Sánchez ◽  
David Astrain
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Object Oriented ◽  
Heat Transfer Fluid ◽  
Transient Performance ◽  
Parabolic Trough ◽  
Performance Simulation

scholarly journals Molten Nitrate Salt Development for Thermal Energy Storage in Parabolic Trough Solar Power Systems

2008 ◽  
Author(s):  
Robert W. Bradshaw ◽  
Nathan P. Siegel
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Power Plants ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Parabolic Trough ◽  
Heat Transfer Fluids

Thermal energy storage can enhance the utility of parabolic trough solar power plants by providing the ability to match electrical output to peak demand periods. An important component of thermal energy storage system optimization is selecting the working fluid used as the storage media and/or heat transfer fluid. Large quantities of the working fluid are required for power plants at the scale of 100-MW, so maximizing heat transfer fluid performance while minimizing material cost is important. This paper reports recent developments of multi-component molten salt formulations consisting of common alkali nitrate and alkaline earth nitrate salts that have advantageous properties for applications as heat transfer fluids in parabolic trough systems. A primary disadvantage of molten salt heat transfer fluids is relatively high freeze-onset temperature compared to organic heat transfer oil. Experimental results are reported for formulations of inorganic molten salt mixtures that display freeze-onset temperatures below 100°C. In addition to phase-change behavior, several properties of these molten salts that significantly affect their suitability as thermal energy storage fluids were evaluated, including chemical stability and viscosity. These alternative molten salts have demonstrated chemical stability in the presence of air up to approximately 500°C in laboratory testing and display chemical equilibrium behavior similar to Solar Salt. The capability to operate at temperatures up to 500°C may allow an increase in maximum temperature operating capability vs. organic fluids in existing trough systems and will enable increased power cycle efficiency. Experimental measurements of viscosity were performed from near the freeze-onset temperature to about 200°C. Viscosities can exceed 100 cP at the lowest temperature but are less than 10 cP in the primary temperature range at which the mixtures would be used in a thermal energy storage system. Quantitative cost figures of constituent salts and blends are not currently available, although, these molten salt mixtures are expected to be inexpensive compared to synthetic organic heat transfer fluids. Experiments are in progress to confirm that the corrosion behavior of readily available alloys is satisfactory for long-term use.

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