As large cities in various countries are developing more and more underground space for shops and other usages, the need for moving both people and freight underground intensifies. While the need for transporting people underground can be met with conventional subways, the need for transporting freight underground can best be met by using a network of underground freight pipelines. This paper describes such a proposed freight pipeline system based on pneumatic capsule pipeline (PCP) powered by LIM (linear induction motor) – namely, a LIM-PCP system. The LIM-PCP system for this purpose uses wheeled vehicles (capsules) to carry freight. The capsules run on dual rails similar to freight trains running on railroads, except for the fact that the rails are smaller than that of standard railroads, and each capsule is a small-size boxcar of dimensions 1.475 m ( width ) × 1.719 m (height) × 7.135 m (length). The capsule is sufficiently large to carry most goods that can be placed on pallets, in crates, boxes, bags, or other mini containers. The system is driven by linear induction motor (LIM) pumps placed on the rail track between rails. Each LIM pump stator is 500 mm wide, and 10 to 50m long, made of many segments, each having a length of 500 mm approximately. The PCP tube has a rectangular inner cross-section of approximately 1.6m (width) × 1.8 m (height) in straight sections of the tube, and a larger width in curved sections. The tube is constructed of prefabricated plates supported by steel or aluminum outer frame. The entire tube can be easily assembled and disassembled on site. For any underground city, a network of such PCP tubes will be laid underground along underground streets or corridors. Such network forms a transportation grid, with each node point being a station or terminal. Capsules enter each station to load / unload cargoes, and the cargo may also move vertically via elevator shafts to and from the streets aboveground. Pedestrians can also use such elevators to move between ground level and underground levels. A preliminary engineering analysis has been conducted which shows that with a capsule moving at 15 m / s (54 km / h), the total power needed for the system to serve an area of 1 km2 is about 1 mw (mega watt). The unit cost for freight transport using this system is approximately $ 0.625/ tonne / km, which is reasonable. Less cost is expected with an optimized system.
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