<br />
<br />Reprinted from November 1981, Vol. 103, Journal of Solar Energy Engineering
<br />
<br />~i
<br />i
<br />
<br />One Viewpoint Concerning Unit
<br />Size in the Development of Wind
<br />Turbines1
<br />
<br />W. E. Howell
<br />
<br />C. J. Todd2
<br />
<br />The size of wind machines best adopted for early penetration toward large-scale use
<br />is affected by the size of the national interim windpower goal (/70 GW average
<br />power by 2000 AD) and the experience rate coupling cost of power to number of
<br />machines produced, Windpower mission studies made in 1976 are modified in the
<br />light of various goal-size and experience-rate assumptions, resulting in a rather flat
<br />cost minimum near 0,3-0,6 MW, suggesting that other considerations may be
<br />decisive, Several of these assumptions are discussed, leading to the conclusion that,
<br />although larger machines may prevail in the long run, moderate sizes are best suited
<br />to the early commercialization phase,
<br />
<br />Office of Atmospheric
<br />Resou rces Research,
<br />Bu reau of Reclamation,
<br />Denver, Colo. 80225
<br />
<br />I Introduction
<br />
<br />The Domestic Policy Review of Solar Energy [I] identified
<br />wind as the inexhaustible energy source nearest to practical
<br />application to the nation's electric utility network and
<br />suggested 1,7 quads in the year 2000 (56 GW mean output)2 as
<br />its contribution, Achieving this goal or any other goal of
<br />comparable significance will require building machines with a
<br />total generating capacity of several scores of gigawatts. It will
<br />also require integration of the engineering, operation,
<br />management, and marketing of windpower with utility
<br />networks in an acceptable way,
<br />The size of wind machines proposed for development in-
<br />teracts with these requirements in several important ways,
<br />Economies of scale may be achieved, up to a point, by in-
<br />creasing the size of an individual machine. Other economies
<br />of scale may be achieved by increasing the number of
<br />machines produced, Both are invblved, along with an estimate
<br />of the total generating capacity, Both affect the total cost of
<br />achieving the goal and hence the size range of machines to be
<br />proposed for development.
<br />The purpose of the present contribution is to examine some
<br />implications of machine size as this will affect the advance of
<br />windpower application through the transitional stages that
<br />involve engineering development of the machines, installation
<br />at a variety of sites having different characteristics, operation
<br />under many different conditions, and integration into many
<br />different utility systems. This paper does not attempt a
<br />
<br />1 The views, opinions, and conclusions contained in this material are those of
<br />the authors and do not necessarily represeht those of the U. S, Government or
<br />the Bureau of Reclamation.
<br />
<br />2 Presently a private scientific consultant. 34 Lookout Mountain Circle,
<br />Golden, Colo.. 80401,
<br />
<br />3 The source publication expressed energy as heat flux before conversion to
<br />other forms. Assuming 35 percent conversion efficiency, 1.7 quads per year
<br />would yield 20 GW of electric power. or al?out 3 percent of expected total utility
<br />generation in the year 2000. It implies installation of 50 to 60 GW of wind
<br />turbine capacity.
<br />
<br />Contributed by the Solar Energy Division for publication in the JOURNAL OF
<br />SOLAR ENERGY ENGINEERING. Revised manuscripI received by Ihe Solar Energy
<br />Division September 21, 1981.
<br />
<br />306/Vol.103, NOVEMBER 1981
<br />
<br />prediction of the size of machine, or range of sizes, that may
<br />ultimately dominate the scene at a mature stage of windpower
<br />use several generations hence,
<br />As part of the Federal Wind Energy Program, design
<br />studies of windpowered electric generators were undertaken
<br />early in 1974. The concerned Federal agencies, the National
<br />Aeronautics and Space Administration and the Energy
<br />Research and Development Administration, solicited
<br />proposals from the private sector. Subsequently, the mission
<br />analyses and design studies were performed by General
<br />Electric Company [2], Kaman Aerospace Corporation [3],
<br />and Lockheed-California Company [4]. One purpose of the
<br />design studies was to achieve minimum cost per unit of energy
<br />produced, Each of the companies presented its results in the
<br />form of cents per kilowatt-hour (in 1976 dollars) as a function
<br />of generator capacity for the thousandth (in one case, the ten-
<br />thousandth) machine produced, These results have been
<br />summarized in a report by the .JBF Scientific Corporation [5]
<br />and further presented in graphic form as shown in Fig, I,
<br />Though the results differed in many respects, they agreed that
<br />the optimum machine size exceeded I MW, with two of the
<br />estimates being closer to 5 MW, Subsequently, the Federal
<br />Wind Energy Program proceeded with a single prototype 2-
<br />MW machine and initiated development of a 2,5-MW
<br />machine. Construction of 1000 machines in this category
<br />would create 2.0-2,5 GW of windpower generating capacity,
<br />The question of optimum machine size was addressed also
<br />by Ljungstrom [6] as part of a study of windpower resources
<br />in Sweden. Assuming average distributions of windspeed with
<br />height above ground for the typical Swedish forested terrain
<br />situations, he calculated the ground area and number of
<br />machines that would be required by a lOO-MW windfarm at
<br />an inland location using machines ranging from 1-IO-MW
<br />capacity. He concluded that the wind farm size would decrease
<br />as the machine size increased, the main reason being that the
<br />larger machines would reach up to where the wind was
<br />stronger. He also calculated that, for the smaller machines,
<br />most of the power extracted would have to come from
<br />momentum transported downward over the windfarm area by
<br />
<br />Transactions of the ASM E
<br />
|