Hydraulic Cold Start Circulation for Wind Turbine Pitch Systems
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Solution Overview
Problem
Hydraulic systems in wind turbines face challenges in cold weather due to increased viscosity of hydraulic fluid, leading to high mechanical and electrical loads, which can result in sluggish shutdowns and increased structural loads, and existing heating solutions are costly and unreliable.
Innovation Solution
A method that uses electronically operated valves to circulate hydraulic fluid through a bypass and pressure lines, leveraging frictional heat to raise the fluid temperature without additional heating devices, allowing the hydraulic system to reach operating temperature safely and efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heater is used to heat the hydraulic fluid in the tank, then the fluid temperature in the tank increases, but the fluid in the pressure lines remains cold and the pump is overloaded
Solution Approach 1:
The hydraulic system is divided into two separate circuits: a cold circuit that operates at ambient temperature and a warm circuit that operates at elevated temperature. The pump is segregated into a cold-start pump and a warm-operating pump. This segmentation allows the heating function to be applied only to the tank and warm circuit without requiring the entire system (including pressure lines) to be heated, thereby avoiding pump overload while still achieving the desired temperature increase in the fluid.
Solution Approach 2:
A heat exchanger is introduced as an intermediary device between the tank and the pressure lines. It transfers thermal energy from the heated fluid in the tank to the cold fluid in the pressure lines without requiring direct heating of the entire system. This intermediary approach allows temperature control to be localized to the tank while still providing warmed fluid to the pressure lines through heat exchange, avoiding the need to overload the pump to heat the entire system.
2Temperature
If a dedicated cold-weather hydraulic fluid with high viscosity index is used, then the fluid remains fluid at extreme low temperatures, but the cost increases significantly and special seals are required
Solution Approach 1:
The system dynamically changes the temperature parameter of the hydraulic fluid by heating it in the tank before it enters the pressure lines. Instead of relying on expensive cold-weather fluid formulations, the invention modifies the fluid's temperature state through active heating, thereby achieving low-viscosity operation at low ambient temperatures using standard hydraulic fluid. This parameter change approach eliminates the need for special fluid compositions and associated high costs.
Solution Approach 2:
The invention converts the harmful effect of cold ambient temperature (which increases fluid viscosity) into a beneficial controlled heating process. By intentionally heating the fluid in the tank and using it to heat the pressure lines through a heat exchanger, the system transforms the cold environment from a problem into an opportunity to implement efficient thermal management, thereby avoiding the need for expensive cold-weather fluid while still achieving the desired fluid flow characteristics.
3Temperature
If the hydraulic system waits for ambient temperature increase before operation, then the fluid viscosity decreases naturally, but the shutdown duration is prolonged and earnings are lost
Solution Approach 1:
The system performs preliminary heating of the hydraulic fluid in the tank before the hydraulic system needs to operate. By pre-heating the fluid during the shutdown period using available auxiliary power, the system ensures that when operation is required, the fluid is already at the appropriate temperature for immediate pump operation. This preliminary action eliminates the need to wait for natural ambient temperature increase, thereby reducing shutdown duration and preventing earnings loss.
Solution Approach 2:
The hydraulic system uses its own auxiliary power supply to heat its own hydraulic fluid, making the heating process self-contained and independent of external environmental conditions. The system serves itself by utilizing available power resources to maintain fluid temperature, rather than passively waiting for ambient temperature changes. This self-service approach enables the system to control its own thermal state and minimize shutdown time regardless of external temperature conditions.
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 method effectively raises the hydraulic fluid temperature without additional heating, reducing component overload and costs, enabling quick and safe system startup in cold conditions, and provides significant cost savings by avoiding the need for expensive cold-weather fluids.
Implementation Method 1
leveraging frictional heat to raise the fluid temperature
Data Source
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AI summary
The invention describes a method of operating a hydraulic system (1) of a plant to resume operation from a minimum operating temperature (Tcold) of the plant, the hydraulic system (1) comprising a plurality of electronically operated valves (Vprop, Vbypass, V1 – V4), the method comprising a first stage (S1) in which the valves (Vprop, Vbypass, V1 – V4) are controlled to cycle fluid from a tank (13) through a bypass valve (Vbypass) and directly back to the tank (13) until the temperature of the fluid in the tank (13) has reached a first interim level (Tint_1); and a second stage (S2) in which the valves (Vprop, Vbypass, V1 – V4) are controlled to cycle fluid from the tank (13) through the pressure lines of the hydraulic system (1) and back to the tank (13) until the temperature of the fluid has reached a desired operating level (Top). The invention further describes a hydraulic system (1) and a wind turbine comprising a rotor blade pitching arrangement with such a hydraulic system (1).