WMOD00380

• Title: One Viewpoint Concerning Unit Sizes in the Development of Wind Turbines
• Date: 11/1/1981
• Weather Modification - Doc Type: Report

spacing of individual machines on a windfarm arises from
interference by the wake of one ~achine with the operation of
another one some distance downwind. So far, estimates of
practicable density of placement have been based on distances
that would allow for near-zero wake interference. The actual
amount of wake interference that would occur, and the actual
tolerance of machines for interference from this source, can
be estimated only very approximately on theoretical grounds,
and the necessity for verification in the field remains. Trying
out many different patterns of machine placement in many
different types of windfarm terrain will be necessary before
full confidence in the principles ,of windfarm design can be
gained. This can be attained far more quickly, at far less cost,
'\ with machines of the 0.5-MW size than with machines of 2
~W or larger. ,
, Respecting alternative strategies for integrating windpower
into existing utility networks, the only mode used so far is
fuel-saving in small nongrid utility settings. The first three
sites where Mod-OA machines were erected (Clayton, New
Mexico, Culebra, Puerto Rico, and Block Island, Rhode
Island) illustrate this mode. Southern California Edison
Company and the Bureau of Reclamation began studying the
possibility of on-grid windfarms about 1977; other studies in
Hawaii and Oregon have since been initiated. One
manufacturer has identified win,dfarms integrated into the
total energy programs of certain large industrial users of
electricity, for which they are now paying point-of-use rates,
as an integration mode likely to have promise.
Those who are potentially the largest users of system-
integrated windpower have shown interest in the largest size
machines because they see these ,as being most suitable for
ultimate large-scale application, We have addressed only the
question of what size machine is most favored to promote the
transfer of technology from the publicly-supported
developmental phase to the phase of private-sector use. The
size of machine that may predominate when windfarms make
significant progress toward the national goals discussed in
section 2 may be governed by other considerations. As with
airplanes and automobiles, the critical element is not the
immediate availability of the ideal product, but of a
demonstrably practical product that can earn a profit and
clear the way toward ultimate full ~cale manufacturing.
Morison [18] has pointed out 'also the tendency for new
technologies to be taken up by users whose interests were not
foreseen by the original developers. As the largest-scale utility
users of wind machines buy larger machines (when they are
perfected), the smaller machines are likely to be in demand for
use in other modes. For instance, windpower has been
identified as a potential for many developing countries
because of their inability to finance continuing purchases of
foreign oil, and machines of the 0.5-MW category displaced
from use in the United States would afford them a way of
getting started.
To recapitulate, wind machines in the medium category,
about 0.3-0.6 MW, present less risk and much greater
flexibility for rapid development of economically feasible
commercial windpower during the immediately forthcoming
stage of refinement. This stage will bridge the gap between
demonstrated technical feasibililty and cost-effective ap-
plication in not just one or a few applications, but in widely
diversified applications. It is a st~ge in which entrepreneurial
experimentation plays a key role, in which the most rapid
progress is likely to be made by many small steps with rapid
feedback of information, rather than by a few giant strides
toward few and insecure steppingstones.

5 Conclusions
The foregoing analysis reemphasizes the importance for a

312/ Vol. 103, NOVEMBER 1981

national wind energy program of encouraging the fastest
possible rate of learning as a contribution to cost reduction
through accumulation of experience, and of establishing a
bold but realistically attainable national goal for windpower
input into the nation's electric utility systems. One may also
conclude from this analysis that emphasis placed on
development and production of windpower generators in the
broad range between 0.3 and O,6-MW capacity, before em-
phasizing production of multimegawatt machines, offers
several distinct advantages for rapid attainment of this goal.
These advantages include a likely rapid cost reduction
through industry-wide accumulation of experience, a
relatively narrower technological gap, an ability to attract a
wider range of inventive, innovative manufacturing and
managerial talent, greater feasibility of a multirack and
multigoal strategy, a broader market base leading to
economies of scale in production, and the earlier establish-
ment of a mature industrial base from which further
refinement may proceed.

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