Wind power technology - Wind Power Integration: Connection and System Operational Aspects - page 54

construction of several hundred wind generators in the range 5-25 kW in Denmark
in the early 1900s. From the 1920s two- and three-bladed, battery-charging wind
turbines, rated at up to 3 kW, were used for domestic supplies in the United States.
Again, these could not compete with the expanding rural electrification programme
(Johnson, 1985).
Large wind turbine development began with the 30 m diameter, 100 kW tur-
bine erected in the Crimea in 1930, but perhaps the most impressive early machine
was the 53 m diameter, 1,250 kW, Smith Putnam wind turbine erected in 1941
(Putnam, 1948). This remarkable two-bladed, upwind, full span pitch-regulated
machine exhibited many of the features of modern wind turbines and ran success-
fully for around 1,000 hours before shedding a blade. Although considered a
technical success, the project was then abandoned, as the manufacturer could not
see a market for large electricity-generating wind turbines in the face of cheap
fossil fuel. Research continued in Europe and a number of important large wind
turbines were constructed. In 1957, the Gedser three-bladed, 24 m diameter,
200 kW turbine was built in Denmark, while Dr U. Hutter in Germany constructed
an advanced 100 kW lightweight machine. Around this time, individual wind tur-
bines of around 100 kW were also constructed in France and the United Kingdom,
but the low price of oil led to limited commercial interest in wind energy.
However, in the early 1970s the world price of oil tripled, stimulating wind
energy research and development programmes in a number of countries including
the United States, United Kingdom, Germany and Sweden. In general these pro-
grammes supported the development of large, technically advanced wind turbines
by major aerospace manufacturing companies. Typical examples included the Mod
5B (97.5 m diameter, 3.2 MW) machine in the United States, and the LS-1 (60 m
diameter, 3 MW) machine in the United Kingdom, but similar prototypes were
constructed in Germany and Sweden. The technical challenges of building reliable
and cost-effective wind turbines on this scale were underestimated and these pro-
totypes did not lead directly to successful commercial products, although much
useful information was gained.
In a further response to high oil prices, tax and other financial incentives were
put in place to support the deployment of wind turbines, most notably in California.
These measures provided a market for manufacturers to supply much smaller, sim-
pler wind turbines. Initially a wide variety of designs were used, including vertical
axis wind turbines, but over time the so-called 'Danish' concept of a three-bladed,
upwind, stall-regulated, fixed-speed wind turbine became dominant. Initially these
turbines were small, sometimes rated at only 30 kW, but were developed over the
next 15 years to around 40 m diameter, 800-1,000 kW. However, by the mid-1990s
it was becoming clear that for larger wind turbines it would be necessary to move
away from this simple architecture and to use a number of the advanced concepts
(e.g. variable-speed operation, pitch regulation, advanced materials) that had been
investigated in the earlier government funded research programmes. Thus, large
wind turbines (up to 130 m in diameter, rated at 3-5 MW) are now being developed
using the concepts of the large prototypes of the 1980s but building upon the
experience gained from over 20 years commercial operation of smaller machines.