June 26, 2011
June 26, 2011
June 29, 2011
Design in Engineering Education
22.84.1 - 22.84.15
Portability Rubric Applied to the Redesign of a Solar Power Generation SystemPortability is defined as the ability to easily be moved or carried. A key component of manymilitary systems is their ability to be quickly assembled/disassembled, moved to differentlocations, and to use minimum manpower and equipment in order to accomplish their mission.One problem in redesigning systems to increase portability is that there is not currently anestablished rubric for measuring portability. The portability of a system is a function of manyvariables. We have developed a rubric to measure a system’s portability. The rubric includes: Rubric of 17 Portability Measures Weight or mass Moment of inertia in stowed versus deployed state Position of CG Largest dimension in a stowed state Ratio of largest deployed dimension to largest stowed dimension Volume or compactness in stowed state Ratio of volume in deployed state to volume in stowed state Cross sectional area in stowed state Ratio of Cross sectional area in deployed state to cross sectional area in stowed state Largest diagonal in stowed state Ratio of largest diagonal in deployed state to largest diagonal in stowed state Max force to deploy/stow Energy or work expended to deploy/stow Power needed to deploy/stow Energy density with respect to mass/volume/largest dimension Time to deploy/stow Number of steps to deploy/stowIn order to use the rubric, each of the 17 portability measures identified above is quantified forthe system(s) being evaluated. This information can then be used in two different manners. Ifthe rubric is applied to a number of different systems, then the current state of portability forthese systems can be compared. As a second application, the rubric can be used to measure theportability of a current system and to identify redesign opportunities which are specificallytailored to increase portability.In our present work, the rubric is being used in both of these manners. First, we apply it to twopower generation systems currently being used in military operations; a solar system and a dieselgenerator. Next, the output from the rubric, as applied to the solar power generation system, isused to identify avenues for redesign that will enhance the portability of that system.After using the rubric to analyze the Solar Model R10 portable power system and the QuietDiesel Generator (see fig 1) we found that the diesel generator was significantly more portable.Some of the highlights of this analysis are shown in Table1. Table 1: Highlighting Comparison Between Solar and Diesel Systems Model Metric Solar Model R10 Diesel Quiet Generator Weight(lbs) 5200 910 Largest Dimension Stowed(ft) 22 4.5 Volume stowed(ft^3) 2100 34 Largest Cross Sectional Area(ft^2) 270 13 Power Output(KW) 6.0 5.0 Figure 1: Left Solar Model R10, Right Tactical Quiet Diesel Generator Set.From this direct comparison, it is obvious that the larger weight and size of the solar systemmake it inferior, from a portability aspect, to a diesel generator. The next step is to perform aportability focused redesign of the solar system. Specific areas for enhancing portability in theredesigned solar system are identified using the 17 portability measures. These areas includeweight, largest stowed dimension, volume stowed, and cross sectional stowed area. Details areprovided in the paper that show that focusing the redesign effort based on these areas hasallowed the solar system to make significant progress in its portability when compared with thediesel gererator.
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