Compressed Air Storage for Wind Energy
Objectives: To develop a localized compressed air system for storing excess energy from off-shore wind turbines.
Approach: In our approach, energy is stored prior to electricity generation in high pressure compressed air vessels, and an efficient compressor/expander with enhanced heat transfer that operates nearly isothermally is used directly for energy storage and extraction. This approach avoids losses associated with multiple conversions and allows the electrical generator and the transmission lines to be substantially down-sized. An open accumulator configuration is used to maintain system pressure so that efficiency and power density can be maintained regardless of how much compressed air is present in the accumulator.
Outcomes: Compressed air energy storage will dramatically alleviate power supply and demand imbalances during the day. This will make wind energy more reliable, predictable and less disruptive to the electrical grid.
For more information on the Compressed Air to Wind Energy Storage Research, please visit: http://www.me.umn.edu/~lixxx099/EFRI_CAES/index.htm
Radar interactions with wind turbines
Objectives: Minimize or eradicate the negative impacts wind farms have on FAA and weather radars.
Approach: Understand the nature of clutter and develop active and/or passive mitigation techniques, including development of new generation of high spectral resolution radar signal processors to provide discrimination against this emerging source of clutter. Study mitigation techniques at a field scale radar facility. Extend results of mitigation techniques to address the needs of the National Oceanic and Atmospheric Administration.
Outcomes: Development and field demonstration of new clutter mitigation techniques and signal processing algorithms for FAA and weather radars.
A Novel Power Electronics based Electrical Generation System for Wind Turbines
Objectives: Develop a novel electrical generation system for wind turbines using power electronics.
Approach: To connect the wind generator to the utility grid, the proposed system will replace the conventional 60-Hz transformer and the conventional converter system with a novel power-electronic-transformer technology, which uses a high-frequency transformer that can be smaller and lighter than a conventional 60-Hz transformer by a factor of 100 or higher. The lab prototype of such a system will be demonstrated at a 5-kVA power level.
Outcomes: Demonstrate that the proposed system results in a nacelle with significantly lighter weight and reduced volume, higher reliability and efficiency. Develop a final report that outlines the results of the sub-scale power electronics package and explains how it can be scaled to a utility scale turbine and the overall benefits.
Multi-scale modeling for wind farm siting
Objectives: Develop and test novel CFD tools for the prediction of high-resolution wind and turbulence in the atmospheric boundary layer, and their interactions with wind turbines and wind farms. Provide a tool for science-based optimization of wind farm design.
Approach: Multi-scale modeling by coupling meso-scale models with atmospheric Large Eddy Simulation (LES) and high-resolved CFD of turbine blades. Integration of wind tunnel experiments with detailed measurements in the field for model validation.
Outcomes: High-resolution Large Eddy Simulation framework for multi-scale simulations and site-specific optimization of wind farms.
Increasing wind turbine output by mitigating blade icing and fouling
Objective: Maximize the recovery of potential energy at a given site by reducing turbine down time and mitigate the reduction in capacity factors caused by ice accumulation on blades. Increase wind plant safety by mitigating ice throws.
Approach: Develop a test system to measure ice-adhesion shear force and evaluate various ice-phobic blade coatings/films via wind tunnel experiments in the SAFL atmospheric wind tunnel.
Outcomes: Develop methods and guidelines for implementing de-icing coating and films at field scale.
High-resolution CFD-FSI code for aeroelastic simulations of turbine blades
Objectives: Develop a high-resolution Fluid-Structure Interaction (FSI) CFD code for aeroelastic calculations at field scale.
Approach: Couple high-resolution, rigid-blade CFD code with an advanced Finite Element model of the turbine blade. Validate the CFD-FSI code with both laboratory experiments and measurements from the field-scale facility.
Outcomes: A high-resolution computer code capable of aeroelastic FSI computations at field-scale that can be used as a tool for wind-turbine blade design.
Active flow control for improving aerodynamic performance and reducing noise
Objectives: Develop open and closed-loop active flow control strategies based on unsteady suction and/or blowing to: delay flow separation and stall in real time; and optimize the overall efficiency and minimize associated noise.
Approach: Carry out a series of wind tunnel experiments to test various active flow control strategies and identify most promising approaches; Use turbulence measurements upwind and downwind of the 2.5MW field turbine to assess the state of the actual flow that needs to be controlled and develop low-dimensional models; Couple this information with CFD modeling and additional wind tunnel experiments to develop guidelines for implementing active flow control strategies in the field.
Outcomes: Develop methods and guidelines to guide future implementation of active flow control on the consortium 2.5 MW field turbine.
Increasing wind turbine output using vortex generators and riblets
Objectives: Develop and test passive flow control techniques based on riblets and vortex generators to maximize the recovery of potential energy at a given site by increasing peak efficiency and broadening the operating envelope of the rotor.
Approach: Perform wind tunnel experiments coupled with computational fluid dynamics (CFD) simulations to determine optimal riblets and vortex generators arrangements. Validate the so-determined optimal solution at the consortium 2.5MW field site by comparing post- and pre-treatment wind turbine output.
Outcomes: Design guidelines and expected performance benefits for riblets and vortex generators and a CFD-based framework for turbine-specific implementation of passive flow control devices.