What does the city of Ember not have in Jeanne DuPrau's novel?
One can say there are many things the city of Ember does not have in Jeanne DuPrau's story. One of the most essential elements the city does not have is a natural source of light; a second is enough knowledge to be able to produce their own goods and make their own major repairs. Without a natural source of light, the people of Ember will be left in total darkness should their power source fail completely, darkness that is impossible to move around in and, thus, impossible to survive in. In addition, the city is not self-sustainable because the people do not have enough knowledge to produce their own goods or fix the generator; therefore, once they've completely lost their power source or all their stored goods run out, the people will perish.
Ember was built as an underground city of refuge to preserve the human population in the case of an apocalyptic event. Since the city is underground, the city is surrounded in complete darkness. The only source of light in the city is electrical, which is powered by a generator. The city of Ember was also populated by ordinary people, however, people who were not knowledgeable in sciences such as electricity or mechanics. As a result, no one in Ember knows how to fix the failing generator, as Doon learns when he asks the old man in charge of the generator how it works and receives the following reply:
Who knows? Our job is just to keep it from breaking down. If a part breaks, we got to put on a new one. If a part freezes up, we got to oil it (Chapter 3).
If the generator fails completely, the citizens will be submerged in complete darkness, which they won't be able to survive in for long.
Equally bad, we can tell the citizens do not have the knowledge to make their own goods because they only rely on what's available in the storerooms. The people have been led to believe that the Builders of the city have stocked the storerooms with enough to ensure the citizens will "always have enough of what they need," which isn't true (Chapter 2). The result is that the citizens' use of their resources without replenishing them will cause them to run out of what is essential for survival soon.