Recipient Organization
Altaeros Energies, Inc.
42 Charles St
Boston,MA 02141
Performing Department
(N/A)
Non Technical Summary
Hundreds of existing wind power projects have transformed communities by creating jobs, improving economic development, and reducing environmental pollution. However, 85 percent of rural communities cannot utilize wind power today due to community concerns or poor wind resources at ground level that make projects uneconomical. Altaeros Energies is developing an airborne wind turbine that adapts proven aerospace technology to capture winds up to six times higher than tower-based turbines. This enables the harnessing of stronger and more consistent winds, which make wind projects feasible in many new communities by generating clean energy that has both a lower cost and a lower noise and environmental impact. The key enabling technology is a helium-filled support shroud that lifts a horizontal-axis turbine into the air, using a conductive tether to hold the system in place and send electricity down to the ground. The shroud and tether are adapted from decades-old tethered aerostat technology that is mainly used to lift multi-ton radar systems into the air for long periods of time for surveillance or weather monitoring. This project will determine the feasibility of deploying a mid-scale Altaeros airborne wind turbine in rural America. The proposed project will first determine the average and extreme wind speeds for different U.S. regions at the proposed operating height of 500 - 2000 ft above ground. Using this information, a support shroud will be designed and analyzed for its ability to withstand the maximum wind speeds in the most promising regions. Finally, a scale model will be built and tested in a wind turnnel to confirm that the simulation correlates to a real world test under simulated conditions. Taken together, this project will determine the feasibility of the Altaeros airborne wind turbine to operate in real-world wind conditions in rural markets. This feasibility study will be used to justify the development of a commercial-scale airborne wind turbine.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The overall objective of the proposed Phase I work is to quantify the advantages to rural communities of harnessing stronger wind resources at higher altitudes, and to determine the allowable wind speed for the Altaeros airborne wind turbine. The results will determine the feasibility of the development of a commercial-scale airborne wind turbine for rural communities. There are five specific technical objectives that we seek to achieve in Phase I: (1) Calculate the appropriate survival wind speed for each U.S. region. Milestone: Table of regional survival wind speeds, completed by end of month 1. (2) Determine where U.S. rural communities have strong wind resources between 200 and 600 meters but lack Class 4 or higher winds at ground level. Milestone: Analysis of available high altitude wind data, completed by month 3. (3) Determine through analysis the loads, stresses and displacement of the Altaeros airborne wind turbine support shroud under extreme wind conditions. Milestone: CFD analysis and calculations, completed by end of month 5. (4) Ensure stresses of all structural elements of the refined shroud design are below the material limits with a safety margin of at least 50 percent for rigid elements and 100 percent for non-rigid elements. Milestone: Final lifting shroud design, structural dynamics model, and FEA analysis to determine stresses on structural elements, completed by month 6. (5) Validate structural analysis results by measuring strain at key locations on a shroud model in real or simulated extreme wind conditions. Milestone: Collection and analysis of strain measurements on shroud model, completed by end of month 8.
Project Methods
The overall objective of the proposed Phase I work is to quantify the advantages to rural communities of harnessing strong higher-altitude wind resources and to determine the allowable wind speed of the Altaeros airborne wind turbine. In order to meet the first objective, wind speed data from several publically available datasets spanning 0-600m above ground will be collected. The data will be analyzed to calculate the frequency of specified ratios of high altitude wind speed to wind speeds at a specified height above ground, and to highlight regional and local variations in these data. Locations with high quality airborne winds and poor ground winds will be quantified and graphically displayed in order to illustrate the increased potential for cost effective wind energy in rural communities from airborne wind turbines. In order to meet the second objective, Altaeros and its research partners will make significant use of modern numerical modeling methods to calculate the aerodynamic loading on the novel shroud structure and the resulting structural deformation and stress levels. In particular, a viscous flow simulation using commercially available computational fluid dynamic software will be used to calculate the pressure distribution on the shroud. The shroud structure will be modeled with anisotropic composite material properties using a finite element method. The shroud structure model will be loaded using the calculated pressure distribution, and the resulting deformation and stress levels will be analyzed and compared with allowable material stresses. An iterative process will be used to take into account steady state aero-elastic effects. Critical stress areas will be quantified and visually highlighted to guide the design refinement for subsequent shrouds in order to further improve the survivability of aerostat structures in adverse conditions. In addition, critical deformations will be experimentally measured on a model shroud to verify the analysis methodology.