Enabling tall towers in wind energy production

Abstract

<p>Wind energy has already become the second highest renewable energy source that is used to supply electricity in the United States, providing 6.5% of the nation's electricity demand in 2018. With continued technology development, wind turbine towers are designed to be taller with greater wind energy resource, larger turbine blade and bigger turbine size. These efforts help increase wind energy production and reduce the cost of wind energy in the last four decades to an average Levelized Cost of Energy (LCOE) of $ 0.1-0.2 per kWh. Moreover, by increasing the tower height, wind energy production will be increased substantially which enables wind power to be more reliable and cost effective in the wind-rich areas, but also to be accessible for areas where wind resource was previously underestimated at 80 m (262 ft) and wind power was not economically developed, such as the Southeast. However, most current wind turbines built in the U.S. are at the height of 80 m (262 ft) or below, which is constrained by the transportation limits and logistic challenges. To realize the tall tower benefits for both wind-rich and lower wind-speed regions, wind observations from tall meteorological towers and measuring sensors up to 200 m were obtained and used to quantify the potential wind energy production at different sites in terms of annual energy production (AEP), a critical component in LCOE estimation. The calculation model for estimating AEP was validated with a public database and measured power production. Simulated wind data from National Renewable Energy Laboratory (NREL) were also considered in the AEP prediction for areas with limited actual measurements and evaluate the performance of the simulated dataset in wind energy assessment. With the more realistic AEP estimate, cost benefits were estimated for stakeholders if installing tall towers.</p> <p>To increase the hub height of wind towers that are cost competitive over conventional tubular steel towers, Hexcrete Tower was developed to use segmental precast concrete components to assemble wind towers up to 140 m by prestressing strands. Fatigue performance of key tower components and their connections were experimentally evaluated using simulated loads to ensure the corresponding damage would be insignificant. Numerical models were created to support the design process and verified with the test results. Based on the test and finite element analyses, tower system can provide sufficient fatigue strength under the desired number of load cycles and enabling the Hexcrete tower technology to be a cost-effective alternative for tall wind power development.</p>