How would a desert arcology be sustainable

An arcology is a self-contained city that is completely closed-off and in control of its ecosystem. arcologies are a method of sustainable living. If you have seen the movie Wall-E then you have seen an arcology. The movie is just an arcology on a spaceship. <br><br>So arcologies are great for preserving ecosystem and minimizing waste, but are they sustainable in the long run. Can they be completely sustainable? I cannot envision a desert arcology having a power source that is sustainable in the long run, i.e. solar panels. I assume that the arcology would be built with a concrete or metal exterior to insulate it. After awhile wouldn't the exterior just heat up and eventually just melt? Or even become weakened to the point where it can't withstand the climate anymore? I just have a hard time figuring out how an arcology in a desert just wouldn't overheat. <br><br>Arcologies just seem like a stopgap measure to me, the goal is to preserve an ecosystem, but they could never fully replace one.