AUTOMATED CONSTRUCTION OF LIGHTWEIGHT, SIMPLE, FIELD-ERECTED STRUCTURES R. S. Leonard, P.E. Bechtel National, Inc. San Francisco, California Power plants requiring less labor per kilowatt to build will be cheaper, less affected by inflation, and not as constrained by labor shortages, Recent advances in such diverse fields as industrial automation and autonomous planetary rovers indicate that a synthesis of these advanced techniques could result in mobile construction robots. These robots would perform a limited number of very repetitive tasks at relatively benign construction sites. The example demonstrating the feasibility of this proposal is the construction of a large photovoltaic power plant having a peak power output of 100 megawatts. This is similar to the support structures proposed for the Satellite Power System (SPS) rectenna. Preliminary cost estimates show that a limited labor force using construction robots could reduce direct labor costs between 23 to 79 percent. The approach taken in this paper is: to present the reasons to automate the construction process; to define the conventional construction scenario as the reference for evaluation; to list the potential cost benefits by using robots; to demonstrate the technical feasibility of building several possible construction robots; and to show the application to build SPS ground stations. The conclusions in this paper would also apply to underground and surface mining operations, mechanized agriculture, and other industrial situations. Reasons for Automation: Some of the major reasons for considering automating an assembly task are: • shortage or unavailability of labor • low skill level requirements • increased productivity • harsh environments • simple, monotonous, and repetitive tasks • cost savings Recent trends in highway construction costs are shown in the attached figures along with a comparison of the cost of labor to the cost of a robot. In addition, large power plant jobs often see a decline in productivity with respect to small jobs in the same area. This decline is due in part to the size of the job and to the narrow work assignments. Application: The reason to consider using robots to build either photovoltaic power plants or the SPS rectennas is that these two applications involve all the reasons given above for considering automated assembly. Either application involves the placement or assembly of a large number of identical structural elements in a very simple environment. A typical support design for each application is shown in the attached figures. For a 100 megawatt electric photovoltaic power plant, over 250 thousand 4 ft. x 8 ft. panels of cells must be placed on beams. This assembly work will most likely be located in the open desert which provides a fairly simple environment. However, that location is hot, in a remote location, and the work can be considered monotonous.
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