Solar Drain-Back System Startup with Sequential Absorber Activation
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Solution Overview
Problem
Solar systems with multiple absorbers and drain-back systems require high initial pump output to start operation, which is inefficient and not necessary in stationary conditions.
Innovation Solution
At startup, all but one shut-off valve upstream of the solar absorbers are closed, allowing the circulating pump to initially only pump fluid against gravity to one absorber, and then subsequent absorbers are gradually or simultaneously activated as needed, with temperature sensors monitoring flow to optimize pump output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all shut-off valves upstream of solar absorbers are opened at startup, then all absorbers can be flooded simultaneously, but the circulating pump requires very high output to overcome gravity for multiple absorbers
Solution Approach 1:
The system divides the solar absorber array into multiple groups controlled by individual shut-off valves. At startup, only one valve is opened to segment the system into a single active circuit, reducing the pump's gravitational head requirement. Additional valves are opened sequentially as fluid reaches each section, enabling progressive system activation without requiring peak power for all absorbers simultaneously.
Solution Approach 2:
The control system pre-establishes a sequential valve opening sequence based on the hydraulic characteristics of the system. By calculating and programming the timing of valve openings, the system ensures that each new absorber group is activated only after fluid has reached the previous section, eliminating the need for high initial pump output while maintaining reliable startup.
2Loss of time
If the circulating pump delivers high capacity to flood multiple absorbers simultaneously, then system startup is faster, but energy consumption increases significantly
Solution Approach 1:
The system employs periodic activation of additional absorber groups through sequential valve opening. Instead of continuous high-power operation, the pump operates at low power for each segment and then transitions to the next segment after a predetermined time interval, creating a periodic activation pattern that reduces overall energy consumption while maintaining acceptable startup speed.
3Power
If shut-off valves are arranged upstream of solar absorbers, then pump output can be reduced for stationary operation, but system complexity increases due to additional valve control mechanisms
Solution Approach 1:
The system uses the fluid's own flow and gravity to automatically trigger valve openings. As fluid reaches each absorber group, the resulting pressure changes or flow detection automatically opens the next valve in sequence without requiring external control signals, making the complex valve system self-regulating and reducing the need for sophisticated external control mechanisms.
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 reduces the initial power requirement of the circulating pump and allows for efficient operation by gradually increasing pump output as additional absorbers are brought online, optimizing energy use and flexibility in power management.
Implementation Method 1
the pump has to build up pressure and deliver at the same time. If the highest point of the solar circuit is overflown by fluid
Implementation Method 2
If the circulating pump is not in operation, the fluid in the solar circuit flows into the collecting tank due to gravity
Implementation Method 3
If a rapid change in temperature is measured at the temperature sensor 6, which in this case serves as a flow monitor, of the solar absorber 1 through which flow occurs
Data Source
Figure 1
Figure 2
AI summary
The plant has two solar absorbers (1) and a drain back module (2) arranged on a connection line (4), and a check valve (5) arranged upstream of one of the solar absorbers. A sensor i.e. temperature sensor (6), is arranged downstream of the solar absorbers, where the sensor acts as a control switch. The check valve is arranged between a circulation pump (3) and the solar absorbers. Another check valve (5) is arranged downstream of the other solar absorber. One of the check valves is closed while starting the solar plant. An independent claim is also included for a method for operating a solar plant.