Underwater Pump-Turbine Energy Storage With Zero-Flow Start
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Solution Overview
Problem
Existing energy storage systems face inefficiencies and material stress during the start-up phase of the pump mode due to reverse flow and high vibrations, particularly in underwater installations, leading to energy dissipation and potential mechanical failure.
Innovation Solution
An energy storage system with a combination of a shut-off device and non-return device in the connection line, allowing the pump turbine unit to start with zero flow, preventing reverse flow and reducing vibrations, and a configuration minimizing the use of mechanical seals and radial bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the pump turbine unit is started from standstill in pump mode, then the system can begin operating, but reverse flow occurs through the pump turbine unit causing energy dissipation and high vibrations
Solution Approach 1:
The system performs preliminary actions by first accelerating the pump turbine unit to a sufficient rotational speed before opening the connection line to the vessel. This preliminary acceleration ensures that when the connection line is opened, the pump turbine unit can immediately handle the water flow without reverse flow, thereby avoiding energy dissipation and reducing vibrations during start-up.
2Ease of operation
If the pump turbine unit is started from standstill in pump mode, then the system can begin operating, but high vibrations occur causing material stress and potential mechanical failure
Solution Approach 1:
The system performs preliminary actions by first accelerating the pump turbine unit to a sufficient rotational speed before opening the connection line to the vessel. This preliminary acceleration ensures that when the connection line is opened, the pump turbine unit can immediately handle the water flow without reverse flow, thereby avoiding energy dissipation and reducing vibrations during start-up.
3Reliability
If multiple mechanical seals and radial bearings are used in the pump turbine unit, then the system achieves reliable operation, but the device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates unnecessary mechanical seals and radial bearings from the pump turbine unit design. By removing these complex components while maintaining operational reliability through alternative design approaches, the system reduces device complexity and cost without sacrificing performance.
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
Enables efficient and material-friendly starting of the pump mode, reducing energy dissipation and mechanical stress, thereby enhancing the system's efficiency and longevity.
Implementation Method 1
an energy conversion device (3) for selectively converting between potential energy and electric energy
Implementation Method 2
the pump turbine unit (5) is operated in a pump mode and driven by the motor generator unit (6) operated in a motor mode
Implementation Method 3
When the vessel is filled with water, a pump empties the vessel by discharging the water from the vessel against the hydrostatic pressure of the water prevailing at the underwater location of the pump
Implementation Method 4
When there is a higher demand for electricity the water is allowed to flow from the higher reservoir through turbines to the lower reservoir, and the turbines drive generators to produce electric energy
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An energy storage system configured for installation at an underwater location (200) is proposed, comprising a vessel (2) for storing water (W) at a low pressure, an energy conversion device (3) for selectively converting between potential energy and electric energy, and a connection line (4) connecting the vessel (2) with the energy conversion device (3), wherein the energy conversion device (3) comprises a housing (31), a pump turbine unit (5) arranged in the housing (31), and a motor generator unit (6), wherein the housing (31) comprises a low pressure opening (52) for receiving water at the low pressure, and a high pressure opening (53) for discharging water at a high pressure, wherein the pump turbine unit (5) comprises a first shaft (54) for rotating about an axial direction (A), and at least one impeller (55, 55a, 55b) mounted on the first shaft (54) for interacting with the water, wherein the motor generator unit (6) comprises a second shaft (62) for rotating about the axial direction (A), and a rotor (63) provided at the second shaft (62) for rotating relative to a stator (64), wherein the second shaft (62) is coupled to the first shaft (54) for transmitting a torque between the first shaft (54) and the second shaft (62), and wherein the connection line (4) is configured to connect the low pressure opening (52) with an opening (21) provided at the vessel (2) for receiving water from the vessel (2) or discharging water into the vessel (2). The connection line (4) comprises a switching unit (8) with a shut off device (86) and a non-return device (85) connected in parallel, wherein the non-return device (85) is configured to allow a flow of the water only in a first direction, namely from the vessel (2) to the low pressure opening (52). Furthermore, a method of operating an energy storage system is proposed.