Method for operating a solar thermal array
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Solution Overview
Problem
Solar thermal systems face challenges in reliably starting and operating during the initial phase due to rapid temperature fluctuations, leading to premature pump shutdown or failure to start, as existing control methods do not adequately account for the dynamic temperature differences and gradients during system initialization.
Innovation Solution
A method that uses temperature sensors to calculate and manage temperature gradients between the collector and storage, adjusting the pump operation based on predefined setpoints and limit values, ensuring reliable start-up by switching the pump on when a sufficient temperature difference is reached and switching it off after stabilizing temperature maxima are detected, without relying on waiting times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple temperature difference controller is used to control pump operation, then the control system is simple and easy to operate, but the system fails to start reliably or switches off too early during the starting phase due to rapid temperature fluctuations
Solution Approach 1:
The system performs preliminary actions by detecting temperature maxima before making control decisions. The controller monitors temperature fluctuations and identifies when a defined number of maxima have occurred, indicating that the system has reached a quasi-stationary state. This preliminary detection prevents premature pump shutdown by ensuring the temperature has stabilized before switching off the pump.
Solution Approach 2:
The controller continuously monitors temperature differences and fluctuations, using this feedback to adjust pump operation. By detecting temperature maxima and measuring the temperature difference between collector and storage tank, the system adapts its control strategy in real-time, switching the pump off only when stable temperature conditions are confirmed through multiple maxima detection.
2Reliability
If the pump continues to run during temperature fluctuations, then the system eventually reaches a quasi-stationary state, but the pump operates unnecessarily during transient phases causing energy waste
Solution Approach 1:
The control system dynamically adapts its operation based on real-time temperature conditions. During transient phases with rapid temperature fluctuations, the pump continues running to establish stable conditions. Once a defined number of temperature maxima are detected, indicating the system has dynamically stabilized into a quasi-stationary state, the pump is switched off, optimizing energy consumption while ensuring reliable operation.
3Loss of energy
If the pump is switched off early based on temperature difference thresholds, then energy consumption is reduced, but the system shuts down prematurely before reaching stable operation
Solution Approach 1:
The system replaces simple mechanical temperature threshold switching with an intelligent detection mechanism that monitors temperature maxima. Instead of using a fixed temperature difference threshold that may trigger premature shutdown, the controller detects the pattern of temperature maxima to determine when the system has truly stabilized. This substitution ensures reliable operation by confirming quasi-stationary conditions before pump shutdown.
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 approach ensures a stable and reliable operation of the solar thermal system by maintaining the pump in operation until a quasi-stationary state is achieved, preventing premature shutdown and ensuring consistent energy transfer, thus enhancing the system's efficiency and reliability during the starting phase.
Implementation Method 1
the temperature gradient at the collector (1) is calculated, the temperature difference ΔT between the measured temperature T1 at the collector (1) and the measured temperature T2 in the storage (2) is calculated
Implementation Method 2
the heat transfer medium to be heated by means of a pump (3) in a circuit between a storage device (2) and at least one collector (1) is conveyed
Implementation Method 3
The brine is heated by solar radiation in the collector
Implementation Method 4
The heat is transferred to the coolant, among other things, by the liquid flowing directly through the absorber
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Method for operating a solar system, in which the liquid to be heated is conveyed by means of a pump in a circuit between a storage device and at least one collector, with which a reliable pump start and operation of the solar system in the initial phase is ensured.