Advanced Wind Technology: New Challenges for a New Century

Wind Energy demonstrated phenomenal growth and improvement in the later three decades of the 20^th century. From small niche markets for pumping water and charging batteries, wind became an important supplier of grid tied electricity. These improvements saw modern commercial wind electrical generators grow from simple 50-kilowatt (kW) units to sophisticated multimegawatt (MW) machines capable of generating millions of kilowatt-hours (kWh) per year. The technical advances in wind energy in this time frame were not revolutionary. Scaling to larger size was the primary approach used to improve the cost effectiveness; and improved design methods to properly size turbines for their operating wind environment. Advances in generators, gearboxes, blade designs, blade materials, controls, and computers using improved design codes allowed machines to improve in performance and grow in size until the average modern wind turbine is now more than 1 MW in rating. But as with any maturing technology, most of the easier improvements have already been implemented. Now, at the beginning of the 21^st century, wind energy is facing a new set of technical challenges to achieve cost effectiveness in the lower wind speed regimes located closer to large load centers, while avoiding transmission congestion points as much as possible. Success in lower wind regimes and mature turbine design methodologies will require that more technically challenging innovative designs be explored. The application of taller towers to take advantage of higher winds aloft to increase energy capture at the lower wind speed sites is necessitating new research into the turbulent environments at levels of 80 to 150 meter above the ground. At this elevation, the atmospheric boundary layer is much different than near the ground, and new simulation models are needed for this so called mixing layer above Great Plains sites. In addition, new turbine designs of much greater size are being considered for offshore deployment in shallow and even deep waters in both the United States and Europe, where the offshore design environment is quite different than for land-based turbines. Anticipated improvements in technology that will be seen in the next decade in response to these new challenges include: custom designed permanent-magnet (PM) generators; variable-speed power electronic power converters with improved performance characteristics and reliability; unique gearbox designs that are smaller and lighter; improved aerodynamic and structural dynamics codes that accurately predict unsteady loads and aerodynamic stall effects for lighter more flexible turbines under wide ranging atmospheric conditions; improved rotors that utilize aeroelastically tailored blades of advanced materials such as carbon-epoxy composites; higher blade tip speeds with reduced blade chord and lower aeroacoustic emissions; novel new towers employing self erection or advanced composite materials; offshore machines supported on floating platforms; and improved marine electrical collection systems. Any one of these improvements would be considered a major technological advance, but the wind turbine of 2015 will need many, if not all of these innovations to become the low-cost electricity generator of the future.