Integrated Energy Storage for Next-Generation Wind Turbines

Author: ORCID icon
Simpson, Juliet, Mechanical and Aerospace Engineering - School of Engineering and Applied Science, University of Virginia
Loth, Eric, EN-Mech & Aero Engr Dept, University of Virginia

To reduce the impacts of climate change, the US must shift to a carbon-free electrical grid, requiring increasing renewable energy generation. The implementation of a carbon-free electrical grid is investigated from multiple different aspects within this work, including wind turbine modeling, energy storage modeling, and techno-economic analysis of renewable energy and energy storage systems.

To meet increasing wind energy generation goals, wind turbines may shift to downwind turbines, where the wind first hits the tower and then the rotor plane. The downwind turbine “tower shadow” effect, whereby blades experience a change in loading when they pass behind the tower, has not previously been studied with experimental field test data. Herein, a method was developed for simulating turbulent wind field conditions and used to compare wind turbine simulations to field test data. The tower shadow effect was simulated using the conventional Powles model and a new Eames model (developed herein).

With increasing generation of variable renewable energy, the ability to provide energy when demanded by the grid is critical. The standard design metric for renewable energy systems, Levelized Cost of Energy, does not consider the value of energy when it is produced. Herein, a new metric is proposed, the Cost of Valued Energy (COVE), to better account for the time-varying value of energy generation. Energy storage can also be used to meet electrical demand, but further analysis is needed on how to pair energy storage with renewable energy. A techno-economic analysis of Liquid Metal Battery storage located with an offshore wind turbine was completed and found that adding storage can increase the relative value of the combined system.

A low-cost, long-duration energy storage option, such as compressed air energy storage (CAES), is needed to provide sufficient energy stability for a fully renewable electrical grid. Increasing heat transfer during the compression and expansion processes through a method like droplet spray injection can increase the overall system efficiency of CAES. The key nondimensional parameters which control isothermal efficiency of CAES with spray injection are characterized herein, and paired compression and expansion 1-D numerical simulations are used to investigate roundtrip efficiency. A theory-based equation for polytropic index was derived using a new nondimensional number, the Crowe number. High-efficiency direct spray injection designs were identified, and pre-mixed cases were also considered with 1-D and 2-D simulations. Future work is suggested to further improve spray injection CAES modeling and test high-efficiency cases with experiments.

PHD (Doctor of Philosophy)
energy storage, compressed air energy storage, wind energy
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