Evolution of Modern Wind Turbines Part A: 1940 to 1994 - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 153

Foreign Medium- and Large-Scale Wind Turbines
In the late 1970s a resurgence of interest in wind power also reached a high level of
momentum in Europe. Denmark, Germany, and the Netherlands developed broad programs
which included basic technology efforts, the direct and indirect support of the private
development of smaller wind turbines, and government-funded development of medium-
scale or larger systems. Several countries commissioned testing centers: Denmark at Risﾭ,
Germany at Pellworm Island, and the Netherlands at Petten. These centers allowed for the
testing of both experimental and commercial machines as well as setting in place
certiication programs as a requirement for tax or subsidy beneits, which effectively
precluded turbines in Europe from entering the market prematurely.
Since the mid-1970s, some degree of international information exchange has been
accomplished through the International Energy Agency (IEA). The IEA, headquartered in
Paris, was modelled after the International Atomic Energy Agency, and was conceived as
a way for western nations to coordinate and cooperate in energy policy, research, and
development after the shock of the 1973 oil embargo. Two IEA agreements were imple-
mented covering wind energy. One, a general research and development agreement,
initially involved 12 countries (later increased to 16). A second agreement involved the
exchange of information between those countries developing megawatt-class turbines. The
IEA Wind Energy Annual Reports are an excellent source of information on national wind
energy development programs. Table 3-2 is an example of the detailed data in these
reports, listing wind turbines in Europe and the U.S. in 1993 with ratings larger than 500 kW,
together with speciication and performance data [IEA 1993].
IEA cooperative projects have included research activities on comparison of siting
models, wake low, wind low over terrain features, and analysis of system test results.
Development of comparative testing methodology and resource assessment studies are also
undertaken. Of particular interest to the European countries are studies of the potential for
off-shore wind power. With their higher population densities and fewer open areas, this
possibility is of importance even in view of the expected higher cost associated with
shallow water foundations and marinization requirements.
Denmark
For their irst entries into the ield of larger wind turbines, Denmark constructed a pair
of 40-m diameter, 630 kW turbines, placed side by side, at Nibe , near Alborg in northern
Jutland. Conservative in concept, they were a direct outgrowth of the old Gedser machine.
Both had concrete towers, as had been traditional with the larger Danish wind turbines.
Each had an induction generator, a three-bladed rotor upwind of the tower, and steel blade
spars. One of the rotors was tip-controlled with cables for external bracing, while the oth-
er had full-span pitch-controlled cantilevered blades. These were the irst of the new gen-
era-tion of wind turbines in Europe to reach the testing stage. Operating for over 15 years
with various types of blades, they provided some of the irst information on operation
and maintenance costs, reliability, and low interactions between machines, supporting the
expansion of the Danish wind energy industry [Godtfredsen et al. 1993].
Netherlands
The Netherlands government installed a 300 kW, variable-speed experimental machine
at Petten in 1980. It was designed for maximum test lexibility. It still represents one of the
most versatile of test machines and could be rapidly re-conigured and operated in various
modes, with fast turn-around on data reduction.