Evolution of Modern Wind Turbines Part A: 1940 to 1994 - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 164

Advanced Wind Turbine Development
The development of technologically-advanced, higher-eficiency wind turbines continues
to be a high priority of the wind industry worldwide. In the U.S., the Department of
Energy sponsored a range of programs with the goal of developing wind power plants
that can compete with conventional electric generation, producing energy at a cost of
$0.04/kWh by the year 2000 at sites with average wind speeds of 5.8 m/s (at a 10-m
elevation). In the near term, an “Advanced Wind Turbine Program” [Laxson et al. 1992] is
assisting U.S. industry to apply the latest technology to (1) improve existing wind turbine
conigurations, designs, and manufacturing methods, and (2) to initiate conceptual design
studies of advanced wind power systems. Some of the concepts being explored for HAWTs
under this program are
-- increased rotor sizes to take advantage of new airfoils designed to limit maxi-
mum lift coeficients (see Chapter 6);
-- “low-through” rotor structures without bolted joints between blades and hub;
-- aileron control surfaces;
-- integrated gearbox and mainframe structures in the nacelle;
-- aerodynamically-shaped, wood/epoxy rotating towers;
-- totally integrated power trains, mounted directly on tower-top castings;
-- taller towers.
Many of the recent advances in technology and analytical capability have yet to be
applied to commercial wind turbines. This is expected to occur over the next several years,
particularly with the resurgence of interest in alternate sources of energy in the early 2000s.
Passage of the Energy Policy Act of 1992 re-introduced tax credits in the U.S., in the form
of production credits. This is believed by many to be more effective than the earlier tax
credits based on capital investment. Increased emphasis on reducing power-plant emissions
and on global climate changes are also providing a spur to non-polluting energy sources.
Concluding Remarks
Whether commercial machines grow in size to that of the Mod-5B HAWT in the
future, only time, the international marketplace, and the vagaries of energy cost and
availability will determine. Meanwhile, several other advanced medium-scale and large-scale
systems with rated powers from 500 kW to 2 MW and rotor diameters from 30 m to 60 m
are under development in Europe. Commercial development of small- and medium-scale
wind turbines continues, albeit this development was slowed somewhat by the slackening of
the energy market and changes in energy incentives and tax policy. Most of all, research and
advanced technology development continue, in both the private and public sectors, in a quest
for higher-performance coupled with more reliability.
Stepping back from individual details, one can assess the signiicant changes in the
technology of wind turbines over the two decades by examining their overall performance.
Speciic annual energy production (kilowatt-hours per square meter of swept area) has