Dynamic modelling and simulation of linear Fresnel solar field model based on molten salt heat transfer fluid

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.

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

Solar Energy ◽

10.1115/sed2002-1065 ◽

2002 ◽

Cited By ~ 19

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).

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Engineering aspects of a molten salt heat transfer fluid in a trough solar field

Energy ◽

10.1016/s0360-5442(03)00191-9 ◽

2004 ◽

Vol 29 (5-6) ◽

pp. 861-870 ◽

Cited By ~ 162

Author(s):

D. Kearney ◽

B. Kelly ◽

U. Herrmann ◽

R. Cable ◽

J. Pacheco ◽

...

Keyword(s):

Heat Transfer ◽

Molten Salt ◽

Heat Transfer Fluid ◽

Solar Field

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

Energies ◽

10.3390/en12122340 ◽

2019 ◽

Vol 12 (12) ◽

pp. 2340 ◽

Cited By ~ 5

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.

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Conceptual design of porous volumetric solar receiver using molten salt as heat transfer fluid

Applied Energy ◽

10.1016/j.apenergy.2021.117400 ◽

2021 ◽

Vol 301 ◽

pp. 117400

Author(s):

Shen Du ◽

Ming-Jia Li ◽

Ya-Ling He ◽

Sheng Shen

Keyword(s):

Heat Transfer ◽

Molten Salt ◽

Conceptual Design ◽

Heat Transfer Fluid ◽

Solar Receiver

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Central Receiver System Solar Power Plant Using Molten Salt as Heat Transfer Fluid

Journal of Solar Energy Engineering ◽

10.1115/1.2807210 ◽

2008 ◽

Vol 130 (2) ◽

Cited By ~ 71

Author(s):

J. Ignacio Ortega ◽

J. Ignacio Burgaleta ◽

Félix M. Téllez

Keyword(s):

Heat Transfer ◽

Power Generation ◽

Molten Salt ◽

Thermal Power ◽

Solar Thermal ◽

Heat Transfer Fluid ◽

Solar Thermal Power ◽

Central Receiver ◽

Spanish Legislation ◽

Solar Thermal Power Generation

Of all the technologies being developed for solar thermal power generation, central receiver systems (CRSs) are able to work at the highest temperatures and to achieve higher efficiencies in electricity production. The combination of this concept and the choice of molten salts as the heat transfer fluid, in both the receiver and heat storage, enables solar collection to be decoupled from electricity generation better than water∕steam systems, yielding high capacity factors with solar-only or low hybridization ratios. These advantages, along with the benefits of Spanish legislation on solar energy, moved SENER to promote the 17MWe Solar TRES plant. It will be the first commercial CRS plant with molten-salt storage and will help consolidate this technology for future higher-capacity plants. This paper describes the basic concept developed in this demonstration project, reviewing the experience accumulated in the previous Solar TWO project, and present design innovations, as a consequence of the development work performed by SENER and CIEMAT and of the technical conditions imposed by Spanish legislation on solar thermal power generation.

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Comparative Modeling of a Parabolic Trough Collectors Solar Power Plant with MARS Models

Energies ◽

10.3390/en11010037 ◽

2017 ◽

Vol 11 (1) ◽

pp. 37 ◽

Cited By ~ 5

Author(s):

Jose Rogada ◽

Lourdes Barcia ◽

Juan Martinez ◽

Mario Menendez ◽

Francisco de Cos Juez

Keyword(s):

Heat Transfer ◽

Water Vapor ◽

Power Plant ◽

Solar Radiation ◽

Thermal Energy ◽

Power Plants ◽

Solar Power ◽

Rankine Cycle ◽

Heat Transfer Fluid ◽

Solar Field

Power plants producing energy through solar fields use a heat transfer fluid that lends itself to be influenced and changed by different variables. In solar power plants, a heat transfer fluid (HTF) is used to transfer the thermal energy of solar radiation through parabolic collectors to a water vapor Rankine cycle. In this way, a turbine is driven that produces electricity when coupled to an electric generator. These plants have a heat transfer system that converts the solar radiation into heat through a HTF, and transfers that thermal energy to the water vapor heat exchangers. The best possible performance in the Rankine cycle, and therefore in the thermal plant, is obtained when the HTF reaches its maximum temperature when leaving the solar field (SF). In addition, it is necessary that the HTF does not exceed its own maximum operating temperature, above which it degrades. The optimum temperature of the HTF is difficult to obtain, since the working conditions of the plant can change abruptly from moment to moment. Guaranteeing that this HTF operates at its optimal temperature to produce electricity through a Rankine cycle is a priority. The oil flowing through the solar field has the disadvantage of having a thermal limit. Therefore, this research focuses on trying to make sure that this fluid comes out of the solar field with the highest possible temperature. Modeling using data mining is revealed as an important tool for forecasting the performance of this kind of power plant. The purpose of this document is to provide a model that can be used to optimize the temperature control of the fluid without interfering with the normal operation of the plant. The results obtained with this model should be necessarily contrasted with those obtained in a real plant. Initially, we compare the PID (proportional–integral–derivative) models used in previous studies for the optimization of this type of plant with modeling using the multivariate adaptive regression splines (MARS) model.

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Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage

ASME 2010 4th International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2010-90096 ◽

2010 ◽

Cited By ~ 8

Author(s):

Emerson E. John ◽

W. Micah Hale ◽

R. Panneer Selvam

Keyword(s):

Heat Transfer ◽

Energy Storage ◽

Molten Salt ◽

High Temperatures ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Heat Transfer Fluid ◽

Heating Rates ◽

Storage Media ◽

Concrete Mixtures

In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.

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The numerical simulation of enhanced heat transfer on a Linear Fresnel molten salt-type receiver tube filled with porous media

E3S Web of Conferences ◽

10.1051/e3sconf/201911801041 ◽

2019 ◽

Vol 118 ◽

pp. 01041

Author(s):

Chenggang Yang ◽

Yuning Zhang ◽

Fenghe Yan ◽

Wenguang Zhang ◽

Wei Li

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Numerical Simulation ◽

Porous Media ◽

Molten Salt ◽

Temperature Difference ◽

Wall Temperature ◽

Three Dimensional ◽

Heat Transfer Fluid ◽

Filling Rate

In this paper, three-dimensional numerical simulation was taken on a Linear Fresnel solar receiver tube using molten salt as heat transfer fluid (HTF), in which the porous media was filled to enhance the heat transfer efficiency. The simulation was to analyze the influence of the different conditions (filling rate, porosity and thermal conductivity) on heat transfer effect and wall temperature difference. The results revealed that the Nu (Nusselt number) increased firstly and then decreased with the increasing filling rate in both center filling and annular filling types. The optimal thermal performance were obtained when filling rate were 0.8 and 0.2 in center filling and annular filling, respectively. The Nu were about 1.7 and 1.5 times as the clear receiver. The circumferential temperature difference decreased firstly and then increased with filling rate increasing in both center filling and annular filling types. The lowest circumferential temperature differences were achieved at the filling rate 0.8 and 0.4 in center filling and annular filling types, and temperature difference decreased 15.88°C and 22°C compared with clear receiver, respectively. The Nu and PEC both decreased with porosity increasing. However, the thermal conductivity of porous media had little influence to the Nu and circumferential wall temperature.

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Comparison of Two-Tank Indirect Thermal Storage Designs for Solar Parabolic Trough Power Plants

ASME 2009 3rd International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2009-90369 ◽

2009 ◽

Cited By ~ 9

Author(s):

Joseph Kopp ◽

R. F. Boehm

Keyword(s):

Power Generation ◽

Molten Salt ◽

Heat Exchangers ◽

Power Plants ◽

Thermal Storage ◽

Heat Transfer Fluid ◽

Base Case ◽

Parabolic Trough ◽

Trade Offs ◽

Solar Field

The performance of a solar thermal parabolic trough plant with thermal storage is dependent upon the arrangement of the heat exchangers that ultimately transfer energy from the sun into steam. An indirect two-tank molten salt storage system that only transfers heat with the solar field heat transfer fluid is the most commercially acceptable thermal storage design. Annual electricity generation from two differing indirect two-tank molten salt storage designs and a base case with no thermal storage were modeled. Four components were characterized in a quasi-steady state analysis dependent upon key ambient and operational parameters: solar field, storage, heat exchangers, and power block. The parameters for the collector field remained constant for all models and were based on the SEGS VI plant. The results of net power generation favor storage though the design that maximizes annual output depends on whether maximum power generation or power generation during the evening peak demand hours is desired. Additionally, the economic trade offs are discussed for the three arrangements.

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