CSP Receiver Flow Control for Stable HTF Outlet Temperature
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Solution Overview
Problem
Concentrated solar power (CSP) systems face challenges in maintaining stable outlet temperatures due to rapid variations in heat input from solar radiation, leading to unstable control of heat transfer fluid flow rates, especially with traditional control methods that struggle with low radiation conditions and variable heat inputs.
Innovation Solution
A CSP system incorporating an array of heliostats, a solar receiver with flow control, radiation sensors, temperature sensors, and a controller that uses feedforward control and thermal imaging to regulate the flow of heat transfer fluid, along with a high turn-down ratio valve arrangement to maintain consistent outlet temperatures, even under varying solar radiation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed loop control using feedback from outlet temperature is used, then control of flow rate to regulate output temperature is achieved, but the control becomes unstable due to significant time delay in the effect of receiver heat input variations on outlet temperature
Solution Approach 1:
The control system uses thermal imagery to measure temperatures across the receiver in real-time, obtaining advance information about heat distribution before it propagates to the outlet. This preliminary measurement allows the controller to anticipate temperature changes and adjust flow rate proactively, compensating for the inherent time delay in the thermal response chain.
Solution Approach 2:
The system implements closed-loop feedback control by continuously monitoring outlet temperature and comparing it to the desired setpoint. The controller adjusts the flow rate based on the temperature deviation, creating a self-correcting system that maintains stable output temperature despite variations in receiver heat input.
2Loss of time
If thermal imagery is used to measure temperatures across the receiver, then the time delay in feedback is reduced, but the control remains relatively unstable
Solution Approach 1:
The system replaces traditional mechanical temperature measurement methods with optical thermal imaging technology. This substitution enables non-contact, real-time measurement of temperature distribution across the receiver surface, providing faster feedback without the mechanical delays associated with physical sensors.
Solution Approach 2:
Instead of measuring temperature at a single point (outlet temperature), the system measures temperature across the entire receiver surface simultaneously. This spatial dimensionality provides comprehensive information about heat distribution patterns, enabling more informed control decisions that account for localized thermal variations.
3Adaptability or versatility
If the heat input from CSP plant varies rapidly from full to zero power, then the system can respond to atmospheric disturbances and control adjustments, but the control of flow rate to regulate output temperature becomes fundamentally difficult
Solution Approach 1:
The control system is designed to be highly dynamic, with the ability to rapidly adjust flow rate in response to changing heat input conditions. The system continuously monitors thermal imagery and outlet temperature, making real-time adjustments to maintain stability despite rapid variations in solar radiation and atmospheric conditions.
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
The system achieves stable outlet temperatures with improved control stability and adjustability, allowing for efficient operation during low radiation conditions, reducing temperature fluctuations and extending the lifespan of mechanical components.
Implementation Method 1
at least one radiation sensor for sensing values representative of the aggregate solar radiation falling on the solar receiver via the heliostats
Implementation Method 2
an external surface of the tubes receiving solar radiation reflected from the array of heliostats for heating the heat transfer fluid
Implementation Method 3
the use of the sun's reflections as a heat source is applied to heating a heat transfer fluid (HTF) by focusing the sun onto a tower-based receiver
Implementation Method 4
at least one temperature sensor for measuring input temperature of the HTF at or near the inlet
Data Source
AI summary
A concentrated solar energy collection system includes an array of heliostats and a solar receiver that further includes a plurality of tubes having at least one inlet and at least one outlet for carrying a heat transfer fluid (HTF). A flow control arrangement is provided for controlling the flow of HTF through the tubes. This includes at least one radiation sensor such as a pyranometer for sensing values representative of the aggregate solar radiation falling on the solar receiver via the heliostats. At least one temperature sensor measures input temperature of the HTF at or near the inlet. A controller coupled to the radiation and temperature sensors regulates the outlet temperature of the HTF by controlling the flow of HTF through the tubes via the flow control arrangement. A pressure differential sensor arrangement measures pressure differential across the flow control arrangement, providing an input to the controller.