Solar Collector Pump Control With Adaptive Switch-Off Hysteresis
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Solution Overview
Problem
Existing solar system control methods face inefficiencies due to inaccurate temperature measurements, leading to premature pump switch-off and potential heat reversal from storage tank to collector.
Innovation Solution
Implementing a method where the pump is switched on after a predefined pause time, allowing a test time to determine the maximum temperature difference, which is then used to redefine the switch-off hysteresis temperature value, thereby adapting to actual temperature measurement inaccuracies and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switch-off hysteresis temperature value is selected as small as possible to achieve high system efficiency, then system efficiency is improved, but the pump may be switched off too late due to temperature measurement inaccuracies causing heat reversal
Solution Approach 1:
The patent applies preliminary action by implementing a test phase before the pump is actually switched off. During this test phase, the pump continues to run for a predetermined test time after the switch-off condition is initially met, allowing the system to verify whether heat reversal actually occurs before committing to the switch-off decision. This prevents premature switch-off due to measurement inaccuracies while avoiding unnecessary extended operation.
Solution Approach 2:
The patent implements feedback by monitoring the temperature difference between collector and storage tank during the test phase. The system continuously measures temperatures and compares the actual temperature difference against the expected difference, using this feedback to determine whether to switch the pump off or continue operation. This closed-loop control ensures reliable switch-off timing that adapts to actual system conditions rather than relying solely on predetermined hysteresis values.
2Device complexity
If temperature measurement inaccuracies are not compensated for, then the control system remains simple, but heat may be returned from the storage tank to the collector reducing system performance
Solution Approach 1:
The patent applies partial action by implementing a compensated hysteresis value that is larger than the minimum theoretically required but smaller than the full range of measurement inaccuracies. This compensated value provides sufficient margin to prevent heat reversal while avoiding the complexity of dynamic adjustment mechanisms. The test phase duration is also optimized to be just long enough to detect heat reversal without unnecessary extension.
Solution Approach 2:
The patent changes the hysteresis temperature value parameter from a fixed minimal value to a compensated value that accounts for measurement inaccuracies. This parameter adjustment is calculated based on the specific measurement system characteristics and is applied consistently throughout operation. The compensated parameter values provide a practical solution that prevents heat reversal without requiring complex real-time calculation or adjustment mechanisms.
3Speed
If the pump is switched off immediately when temperature conditions are met, then response time is minimized, but temperature measurement inaccuracies cause premature switch-off and potential heat reversal
Solution Approach 1:
The patent applies preliminary action by introducing a test phase that occurs before the final switch-off decision is executed. When the switch-off temperature condition is initially met, the system enters a test phase where the pump continues to run for a predetermined test time. This preliminary test allows verification of the switch-off condition before actual switch-off, preventing premature termination while maintaining fast response when conditions are genuinely met.
Solution Approach 2:
The patent applies the skipping principle by rapidly transitioning through the test phase when heat reversal is detected, immediately switching the pump off without prolonged delay. The test time is set to the minimum necessary duration to detect heat reversal, and once heat reversal is confirmed during the test phase, the system rushes through to immediate switch-off. This maintains fast response characteristics while adding only the minimal necessary verification step.
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 enhances system efficiency by precisely adjusting the switch-off hysteresis temperature value, reducing heat reversal and improving overall solar system performance.
Implementation Method 1
heat absorbed by a collector can be fed to a storage tank via a solar circuit equipped with a pump and carrying a heat transfer medium
Implementation Method 2
temperature T collector of the heat transfer medium in the collector 1 (to measure this collector temperature, a corresponding, not temperature sensor shown separately)
Data Source
Figure 1
AI summary
The invention relates to a method for operating a solar system, in which the heat absorbed by a collector (1) can be supplied to a store (4) via a solar circuit (3) which is provided with a pump (2) and carries a heat transfer medium, the pump (2nd ) is switched on when a temperature (Tcollector) of the heat transfer medium in the collector (1) minus a predefined switch-on hysteresis temperature value (TEn) is greater than a temperature (Tstorage) of the heat transfer medium in the store (4) and the pump (2) is switched off when the temperature (Tcollector) of the heat transfer medium in the collector (1) minus a predefined switch-off hysteresis temperature value (Toff) is lower than the temperature (Tstorage) of the heat transfer medium in the storage tank (4). According to the invention, it is provided that the pump (2) is switched on within a predefined test time (tTest) after a predefined pause time (tPause) has elapsed after it was switched off, that during the test time (tTest) a maximum amount of a temperature difference value (TMax ) between the temperature (Tcollector) of the heat transfer medium in the collector (1) and the temperature (Tstorage) of the heat transfer medium in the store (4) is determined, and that this temperature difference value (TMax) is used as the basis for redefining the switch-off hysteresis temperature value (TOff).