Futuristic parabolic trough CSP plant with molten salt flowing through, set against a desert landscape.

Unlock Solar Power's Potential: The Future of Heat Transfer Fluids

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Theo Raines in Climate & Environment August 2025 • 5 min read.

"Optimize energy efficiency in parabolic trough CSP plants with advanced heat transfer fluids like molten salts and cutting-edge technologies."


Concentrated Solar Power (CSP) technology, particularly parabolic trough power plants, stands as a mature and reliable method for harnessing solar energy. Thermal oil has traditionally served as the heat transfer fluid (HTF) in these plants, but the quest for enhanced efficiency and reduced costs has led researchers and engineers to explore alternative HTFs. Molten salts are emerging as a promising solution, offering the potential for higher operating temperatures, improved cycle efficiencies, and more cost-effective thermal energy storage.

The transition to molten salts isn't without its challenges. These materials have higher freezing points and can present operational complexities, particularly in relation to freeze protection systems. However, the potential benefits—including the ability to achieve greater temperature differences within the power cycle and direct thermal energy storage—make them an attractive option for advancing CSP technology.

With various molten salts available, selecting the optimal HTF for a specific location and plant design is crucial. Factors such as solar resource availability, ambient conditions, and financial considerations all play a significant role in determining the most techno-economically viable solution. This article delves into the optimization strategies and analyses that are shaping the future of heat transfer fluids in parabolic trough CSP plants, offering insights into how these advancements can drive down the levelized cost of electricity (LCOE) and make solar power more competitive.

The Science of Salt: Optimizing HTFs for CSP Plants

Futuristic parabolic trough CSP plant with molten salt flowing through, set against a desert landscape.

The core advantage of using molten salts lies in their ability to operate at higher temperatures compared to traditional thermal oils. This increased temperature differential directly translates to improved cycle efficiencies, allowing power plants to generate more electricity from the same amount of solar energy. Furthermore, molten salts facilitate direct thermal energy storage, eliminating the need for additional heat exchangers and reducing storage costs.

Choosing the right molten salt, however, is a complex decision. Several commercially available options exist, each with unique properties and performance characteristics. Key considerations include thermal stability, freezing point, and cost. To navigate this complexity, researchers employ multi-objective optimization techniques, balancing factors such as LCOE and capital expenditure (CAPEX) to identify the most suitable HTF for specific locations and plant designs.

Key parameters in the optimization process include:
  • Storage full load hours: Determining the optimal amount of thermal energy storage to maximize plant output and grid stability.
  • Solar field size: Balancing the size of the solar collector field with the power plant's capacity and storage capabilities.
  • Freeze protection set temperature: Minimizing electricity consumption for freeze protection while ensuring the HTF remains in a usable state.
  • Location-specific conditions: Understanding DNI, Interest Rates and Inflation that effect design process
A study using DYESOPT, a specialized software tool, examined the performance of different HTFs in various locations, including South Africa, Spain, and Chile. The results indicated that Solar Salt generally offers the lowest LCOE, but the optimal choice can vary depending on the specific conditions at each site. For instance, in locations with lower direct normal irradiance (DNI), thermal oil can be competitive with Solar Salt in smaller systems. Conversely, Hitec may be a more cost-effective option in larger systems with high DNI.

The Future is Bright: Towards Sustainable and Efficient Solar Power

The ongoing research and development in heat transfer fluids for parabolic trough CSP plants holds significant promise for the future of solar energy. By optimizing the selection and utilization of HTFs like molten salts, we can unlock greater efficiency, reduce costs, and enhance the overall sustainability of solar power generation. As technology advances and innovative solutions emerge, the potential for CSP to play a critical role in the global energy transition becomes increasingly clear.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1063/1.5067028, Alternate LINK

Title: Identification Of Optimum Molten Salts For Use As Heat Transfer Fluids In Parabolic Trough Csp Plants. A Techno-Economic Comparative Optimization

Journal: AIP Conference Proceedings

Publisher: Author(s)

Authors: Christoph A. Pan, Davide Ferruzza, Rafael Guédez, Frank Dinter, Björn Laumert, Fredrik Haglind

Published: 2018-01-01

Everything You Need To Know

1

Why are molten salts being considered as a replacement for thermal oil in parabolic trough CSP plants?

In parabolic trough CSP plants, the quest for enhanced efficiency and reduced costs has led to exploring alternative heat transfer fluids to thermal oil. Molten salts are emerging as a promising solution because they allow for higher operating temperatures, improved cycle efficiencies, and cost-effective thermal energy storage. The higher temperature differential directly translates to improved cycle efficiencies, allowing power plants to generate more electricity from the same amount of solar energy. Molten salts also facilitate direct thermal energy storage, eliminating the need for additional heat exchangers and reducing storage costs.

2

What challenges are associated with using molten salts as heat transfer fluids?

The transition to molten salts as heat transfer fluids presents certain challenges. These materials have higher freezing points and can present operational complexities, particularly in relation to freeze protection systems. To mitigate the freezing issue, freeze protection systems must be implemented, which consume electricity. Location-specific conditions, such as direct normal irradiance (DNI), interest rates, and inflation, also significantly affect the design process.

3

What key factors are considered when selecting the most suitable molten salt for a CSP plant?

Selecting the optimal heat transfer fluid involves considering factors like solar resource availability, ambient conditions, and financial considerations to achieve a techno-economically viable solution. Researchers employ multi-objective optimization techniques, balancing factors such as LCOE and capital expenditure (CAPEX) to identify the most suitable HTF for specific locations and plant designs. Key parameters in this optimization include storage full load hours, solar field size, and freeze protection set temperature.

4

How does DYESOPT aid in the selection of heat transfer fluids, and what are some key findings from studies using this tool?

DYESOPT is a specialized software tool used to examine the performance of different heat transfer fluids in various locations, including South Africa, Spain, and Chile. Studies using DYESOPT indicate that Solar Salt generally offers the lowest Levelized Cost of Electricity (LCOE), but the optimal choice can vary depending on the specific conditions at each site. For instance, in locations with lower direct normal irradiance (DNI), thermal oil can be competitive with Solar Salt in smaller systems. Conversely, Hitec may be a more cost-effective option in larger systems with high DNI.

5

What is the overall potential of optimized heat transfer fluids, like molten salts, for the future of solar energy?

Optimizing heat transfer fluids like molten salts holds significant promise for the future of solar energy. By carefully selecting and utilizing these fluids, we can unlock greater efficiency, reduce costs, and enhance the overall sustainability of solar power generation. The ongoing research and development in this area can lead to further advancements that enhance the competitiveness of CSP technology in the global energy transition.

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