Tethered Airfoil Wind Energy System with Hydraulic Buffer
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Solution Overview
Problem
Pumping kite generators face challenges in efficiently converting linear mechanical input into electricity, maintaining consistent power output, and meeting electrical utility requirements due to variable wind energy and high costs associated with power electronics.
Innovation Solution
A system using a tethered airfoil with a winching device and accumulator to store wind energy hydraulically, allowing for electricity generation during both traction and retraction phases without expensive power electronics, and incorporating a control system to manage energy storage and dispatchability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pumping kite generators use power electronics for load following and voltage stability, then power output stability is improved, but system cost and complexity increase
Solution Approach 1:
The patent employs a hydraulic transmission system with a hydraulic motor connected to the generator shaft, using hydraulic fluid under pressure to drive the generator. This hydraulic mechanism provides mechanical smoothing of power fluctuations, enabling stable power output without requiring complex power electronics. The hydraulic system acts as a mechanical buffer that absorbs and releases energy to maintain consistent generator rotation speed.
Solution Approach 2:
The patent introduces a hydraulic transmission intermediary between the kite tether and the generator. This hydraulic intermediary decouples the direct mechanical connection, allowing the system to absorb wind variability through hydraulic fluid compression and expansion while maintaining stable generator operation. The hydraulic medium serves as a buffer that mediates between irregular wind input and steady power generation requirements.
2Device complexity
If pumping kite generators directly convert linear oscillating mechanical input to electricity, then conversion simplicity is improved, but power consistency deteriorates
Solution Approach 1:
The patent uses a hydraulic transmission system that converts the linear oscillating motion of the tether into rotational motion of the hydraulic motor, which then drives the generator. This hydraulic conversion mechanism smooths out the oscillating input by utilizing the compressibility and flow characteristics of hydraulic fluid, transforming irregular mechanical input into consistent rotational output for electricity generation.
Solution Approach 2:
The patent replaces direct mechanical coupling with a hydraulic transmission system. Instead of directly converting linear oscillating motion to electrical energy through simple mechanical means, the system uses hydraulic fluid as an intermediary medium to transform and smooth the mechanical input before generation, improving power consistency while maintaining relatively simple overall system architecture.
3Extent of automation
If the system uses stored energy to retract the tether, then autonomy is improved, but energy storage requirement increases
Solution Approach 1:
The patent implements a self-service energy management system where the hydraulic accumulator stores energy during high-wind periods when the kite generates excess power, and automatically releases this stored energy during low-wind periods or during tether retraction phases. The system autonomously manages its own energy requirements without external utility connection, using the hydraulic-fluid-storage system to provide both energy storage and power smoothing functions.
Solution Approach 2:
The patent utilizes changes in hydraulic fluid pressure and volume parameters to store and release energy. The hydraulic accumulator modifies the physical state of the hydraulic fluid (pressure and volume) to store energy during traction phases and release it during retraction phases, enabling autonomous operation while managing energy storage requirements through parameter variations rather than large physical storage volumes.
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
The system provides stable, constant electricity generation and load-following capabilities, reducing reliance on utility electricity during retraction and minimizing costs by using stored wind energy, while maintaining grid stability and efficiency.
Implementation Method 1
A tethered airfoil system using hydraulic transmission to store wind energy during traction phases and generate electricity during retraction phases
Implementation Method 2
during a traction phase, allowing wind to extend a kite tether
Data Source
AI summary
The present disclosure is directed at a method and system for harnessing wind energy using a tethered airfoil. During a traction phase, wind is allowed to extend a kite tether. Wind energy that is harnessed through extension of the kite tether is mechanically stored prior to using the wind energy that is stored to generate electricity. During a retraction phase, the wind energy that is mechanically stored during the traction phase is used to retract the kite tether. Beneficially, the mechanical storage allows the kite tether to be retracted without relying on electricity from an electrical grid.