Wind-to-Hydrogen DC-Link Control for Stable Electrolysis
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Solution Overview
Problem
The challenge of efficiently producing green hydrogen using wind or solar power is hindered by low power availability, leading to issues like hydrogen cross-over and safety concerns due to varying wind conditions, and the internal resistance of the electrolyser increasing significantly at low voltages, which affects generator torque and efficiency.
Innovation Solution
A renewable energy power plant with a hydrogen generating system that includes a control system to balance electrical power differences between wind turbine generators and electrolysis systems, using energy storage and network connections to maintain a stable DC voltage input, and selectively activating electrolysis cells based on available power to optimize hydrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a DC-coupled connection is used to connect the electrolyser directly to the wind turbine generator, then cost is reduced due to omission of grid transformer and switchgear, and electrical efficiency is improved, but the internal resistance of the electrolyser increases significantly at low voltage, causing current and torque to drop drastically
Solution Approach 1:
The system dynamically adjusts the number of active electrolyser stacks based on available wind power. At low wind speeds, fewer stacks are activated to maintain adequate current density and avoid excessive internal resistance. As wind power increases, additional stacks are brought online. This dynamic configuration allows the DC-coupled system to operate efficiently across varying wind conditions without suffering from the low-voltage torque drop problem.
Solution Approach 2:
The invention changes the operational parameters of the electrolyser by adjusting the number of active stacks according to wind power availability. This parameter change ensures that the electrolyser operates within an optimal current density range, preventing the internal resistance from increasing excessively at low voltages, thereby maintaining stable generator torque.
2Productivity
If hydrogen electrolysis is operated at low power availability (below 15% nominal load), then green hydrogen production continues, but hydrogen cross-over into the oxygen stream occurs, reducing efficiency and creating safety issues
Solution Approach 1:
The system dynamically adjusts the number of active electrolyser stacks based on available wind power. When wind power falls below the threshold for efficient operation (15% nominal load), the system reduces the number of active stacks or shuts down electrolysis temporarily, preventing hydrogen cross-over while minimizing interruption to hydrogen production. This dynamic adjustment maintains both safety and productivity.
3Power
If the number of electrolyser stacks is reduced to match low wind power availability, then power balance is maintained, but hydrogen production efficiency decreases due to lower current density
Solution Approach 1:
The system dynamically adjusts the number of active electrolyser stacks to match available wind power while maintaining optimal current density in each active stack. This ensures that power balance is achieved without sacrificing hydrogen production efficiency, as each active stack operates at appropriate current levels rather than forcing all stacks to operate at suboptimal low current.
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 system effectively decouples electrolysis from transient wind variations, preventing voltage drops or rises, reducing hydrogen cross-over, and maintaining efficient hydrogen production by balancing power consumption and generation.
Implementation Method 1
a hydrogen electrolysis system operable to generate hydrogen through electrolysis using power generated by the wind turbine generator
Data Source
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AI summary
Aspects of the present invention relate to a renewable energy power plant for connection to a power network. The renewable energy power plant comprises: a wind turbine generator (WTG); a hydrogen generating system comprising: a hydrogen electrolysis system operable to generate hydrogen through electrolysis using power generated by the WTG; and a DC-link for electrically coupling the WTG to the hydrogen electrolysis system; a connecting network for selectively connecting the power plant to the power network; a power balancing system comprising one or more energy sources and one or more energy loads for balancing electrical power differences between the power generated by the WTG and the power consumed by the hydrogen electrolysis system; and a control system for controlling the WTG, the connecting network, the power balancing system, and the hydrogen electrolysis system to control the voltage on the DC-link to remain within a predetermined range.