Everything, if allowed, will sag (insert old age joke here). If it's flexible enough, it will sag into the catenary shape. To keep a mirror flat, it will take a great deal of supporting structure to resist the forces of natutre. To keep a catenary reflector in its preferred shape, all you need to do is "let it hang." I joke to my friends that this concept is very Zen like. if the wind blows, it will deform the mirror temporarily, but when the wind stops, it returns to it original shape. By conforming instead of resisting external forces, its simplicity is its elegance.
I feel that the concept is very scalable from personal use to industrial scale for manufacturing or residential purposes. The smallest reflector, using a few square meters of a tarp-like sheet for cooking and boiling water in developing regions can be made with local resources, packed and moved in minutes. On the other scale of the spectrum, the larger reflectors made by hanging sheets of stainless steel can focus solar energy to drive hot-air motors or heat exchanger for providing industrial heating or electricity.
Because this concept is a reflector that can concentrate sun light, it can raise the temperature of the target to a high level, making use of the fact that Carnot efficiency (the theoretical limit of heat engines) is much higher when the top temperature of the device is higher with respect to the bottom temperature, i.e., large delta T. Perhaps the only cheaper method of using solar energy would be limited to the low-grade heat uses such as home water heating, but because of the inability to focus energy, their utitilty is limited to low level heating applications.
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