1. As far as non-renewable sources go, we are running out of energy. However, according to these graphs, this will not be in our lifetime or our children’s lifetime. This would be in the distant future, with a few centuries to develop our alternative energies. Renewable energy, depending on the kind, is theoretically infinite, such as solar and tidal. It’s simple enough mathematics. If demand is increasing (due to population increase, or possibly even increase of the need for these resources itself) and supply is decreasing because it is being consumed, it is therefore logical that, in time, the world will run out of energy. However, there are other factors that affect this.
For example, if supply became limited, as discussed further in question 3, then the idea that oil use and production would reach a peak, or possibly even plateau, is possible.

2. Alternative energy, because of this, is a source of energy that should be seriously considered. Since non-renewable energy is steady decreasing and also a pollutant to our environment, not only do the renewable sources of energy offer a cleaner solution to an energy problem, but they offer a source of energy that would not have to be worried about nearly as much for centuries to come because of the nature of that energy. If a source can be renewed, grown, captured, or even something like geothermal to the point that there is so much energy inherent to the Earth already, then this source is not only beneficial to the world, but also more efficient, economical, and even practical in the long run.

3. Since the hunt for oil and other non-renewable resources would eventually become harder, I think the possibility of a war over energy is not just possible, but probable. Richer countries will vie for energy to support their countries. However, poorer or developing countries will not be able to have it. Energy runs our world almost completely, so if it became limited, I can see the possibility of hardship over a dwindling resource quite possible.