Altitude Control for Optimal Performance of Tethered Wind Energy Systems

系留风能系统用柔性电缆取代了传统的刚性塔架，并且可以利用强大的高空风，所需材料仅为传统涡轮机的10%。系留系统的平准化成本估计为每千瓦时0.05美元至0.25美元，为偏远的离网社区、军事基地和深水离岸地点提供具有成本竞争力的能源解决方案。系留系统可以很容易地改变高度，使它们能够通过找到最佳可用风速来实现最佳性能。初步研究表明，利用这种额外的操作自由度可以使固定高度系留涡轮机的发电量增加50%。该奖项将制定控制法律，改变系绳长度，以测量风速随高度的变化，并利用这些信息来增加能源生产。参与该项目的大学生将通过与位于马萨诸塞州波士顿的系留风能初创公司Altaeros Energies的合作，获得现实生活中的实践经验。与北卡罗来纳州高中生的外联活动将介绍STEM学科在开发新的可再生能源中的作用，并扩大非传统和代表性不足的群体的参与。优化系留风能系统高度的能力取决于风切变剖面的知识和最大化净发电量的稳健优化策略。研究将通过融合信息最大化和极值搜索控制技术来解决风切变廓线绘制和高度优化这一双重问题。虽然这两种工具本身都很强大，但都没有为同时表征风切变廓线和优化高度提供理想的独立框架。在这项研究中，将追求两种机制融合映射和优化目标：一种是隐式机制，使用随机滚动时域控制，另一种是显式方法，估计映射的熵变形的扰动信号的极值搜索算法。这些方法将使用NOAA和NASA的历史风廓线进行验证，并将在Altaeros Energies浮力机载涡轮机（BAT）上进行飞行测试。从这项研究中产生的工具不仅将有利于系留风能组织，而且还将提高对模型不佳和时变环境中性能优化的基本理解。

Tethered wind energy systems replace conventional rigid towers with flexible cables, and can harness strong high-altitude winds using as little as 10 percent of the material required by traditional turbines. Levelized costs for tethered systems are estimated to be from $0.05 to $0.25 per kW-h, providing a cost-competitive energy solution for remote off-grid communities, military bases, and deep-water offshore locations. Tethered systems can easily change altitude, allowing them to achieve optimal performance by finding the best available wind velocity. Preliminary research suggests that exploiting this additional operational freedom can increase energy production by as much as 50 percent over fixed-altitude tethered turbines. This award will develop control laws that vary tether length to measure the change in wind speed with altitude, and use that information to increase energy production. University students working on this project will gain real-life practical experience through collaboration with Altaeros Energies, a tethered wind energy startup based in Boston, Massachusetts. Outreach activities with high school students in North Carolina will introduce the role of STEM disciplines in developing new renewable energy resources, and broaden participation by non-traditional and underrepresented groups.The ability to optimize the altitude of a tethered wind energy system depends both on knowledge of the wind shear profile and robust optimization strategies that maximize net energy generation. The research will attack this dual problem of wind shear profile mapping and altitude optimization through the fusion of information maximization and extremum seeking control techniques. While both tools are powerful in their own right, neither provides an ideal stand-alone framework for the simultaneous characterization of wind shear profile and optimization of altitude. Two mechanisms for fusing the mapping and optimization objectives will be pursued in this research: one is an implicit mechanism, using stochastic receding horizon control, and the other is an explicit method that estimates the map's entropy to morph the perturbation signal for the extremum seeking algorithm. These methods will be validated using historical wind profiles from NOAA and NASA and will be flight tested on the Altaeros Energies Buoyant Airborne Turbine (BAT). The tools arising from this research will not only benefit tethered wind energy organizations but will also improve fundamental understanding of performance optimization in poorly modeled and time-varying environments.