Molten Salt Tower Receiver Recirculation for Thermal Gradient Control
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Solution Overview
Problem
Molten salt receivers in solar central tower systems face issues such as material resistance, corrosion, and structural damage due to high thermal gradients and non-uniform flow distribution, leading to short operating periods and increased thermal losses.
Innovation Solution
A cavity-type receiver design with recirculation of a portion of the exit flow of hot molten salts is implemented, reducing temperature gradients and thermal tensions by mixing cold and hot salts before entering the vertical pipes, and using control valves for uniform flow distribution based on incident radiation power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If molten salt is used as heat transfer fluid to reach high working temperatures, then the efficiency of the thermodynamic cycle increases, but thermal gradients and thermal tensions cause material resistance and structural damage
Solution Approach 1:
The receiver is divided into multiple independent panels (24 panels in 4 sections), each handling a portion of the thermal load. This segmentation distributes thermal stresses across multiple smaller units, preventing catastrophic failure and allowing individual panel replacement without shutting down the entire system.
Solution Approach 2:
Different regions of the receiver are designed with locally optimized properties - panels are configured with specific pipe arrangements (32 vertical pipes per panel) and flow distribution systems tailored to their position and radiation exposure, allowing each local region to handle thermal loads optimally while maintaining overall structural integrity.
2Power
If direct solar radiation is concentrated in the receiver, then high thermal energy is achieved, but thermal losses through radiation and convection increase
Solution Approach 1:
The receiver employs a cavity design with curved surfaces that trap and redirect thermal radiation back into the heat transfer fluid. The cavity geometry creates multiple internal reflections, increasing the path length of thermal radiation and reducing net radiative losses to the environment while maintaining high energy concentration.
3Productivity
If cold heat transfer fluid is supplied to the receiver panels, then heating efficiency is improved, but thermal gradients cause cracks in welded sections and pipe damage
Solution Approach 1:
The system pre-heats the molten salt before it enters the receiver panels using waste heat from the heat exchanger outlet. This preliminary heating action reduces the temperature differential between the salt and receiver walls, preventing thermal shock and cracking while maintaining efficient heat transfer during operation.
Solution Approach 2:
The heat transfer fluid circulates continuously through the receiver panels in a closed loop, ensuring constant heat absorption and preventing localized overheating. The continuous flow maintains uniform temperature distribution across all panels, reducing thermal gradients that would otherwise cause material failure.
4Ease of operation
If the receiver is designed with multiple panels and sections, then flow distribution can be optimized, but device complexity and manufacturing difficulty increase
Solution Approach 1:
All 24 panels are designed with identical internal structures (32 vertical pipes each) and standardized connections, allowing them to perform the same function universally. This modularity simplifies manufacturing and assembly while enabling flexible flow distribution control through the standardized panel interfaces and section configurations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the durability and efficiency of the receiver, reducing the risk of structural damage and thermal losses, while maintaining high working temperatures, thus extending the receiver's lifespan and improving the thermodynamic cycle efficiency.
Implementation Method 1
The receiver is the system where all the solar radiation coming from the solar field concentrates. This solar energy transforms into the thermal energy of the heat transfer fluid
Implementation Method 2
The configuration must allow the incident power to exceed the losses caused by radiation and convection
Implementation Method 3
A mixture of molten salts are used in the receiver as a heat transfer fluid which allows high working temperatures to be reached
Implementation Method 4
using control valves for uniform flow distribution based on incident radiation power
Implementation Method 5
direct solar radiation is reflected by a field of heliostats towards the receiver, situated on the upper part of the tower (optical system focus)
Data Source
Figure 1
Figure 2~3
AI summary
Molten salt solar receiver and procedure to reduce the temperature gradient in said receiver. The receiver consists of at least one panel of semi cylindrical geometry, formed by a combination of vertical pipes. The receiver (10) is supplied with a heat transfer fluid made up of molten salts which originate from a recirculation system which is composed of a mixture deposit (6), a hot salt storage tank (9) and a cold salt storage tank (8); the mixture tank (6) which is supplied by a part of the hot heat transfer fluid (4) which exits the receiver (10) and the cold heat transfer fluid (5) which exits the cold salt storage tank (8); the hot salt storage tank is connected to the exit of the receiver (10) so that a part of the heat transfer fluid which does not recirculate is stored (3).