Energy is what keeps us going
For everything we do, we need energy. If you don't know what hunger is, then realising that the first step is energy for the body might be casual. But it's not. We could only develop as a human race when we found out how to generate enough energy so that not all members of the community need to supply food. When that was established we needed even more energy to fuel the activities of those that develop new technology. Simply put, energy is what keeps us going.
Oil made energy cheap
The technological leaps in the past few centuries are all linked to the knowledge to use oil. Oil is a wonderfull product, maybe too underappreciated. It is cheap to obtain, it is safe to handle, it contains the building blocks of life (any carbo structure) and it packs a smackload of energy. For the moment there is not a single alternative that tops oil in all these fields. Maybe coal can measure up, but it's drawback is that it's much more poluting than oil.
We know oil is limited. What are the alternatives?
Since oil is such a wonderfull product, it is a shame we use it just to burn. Because that is essesialy what combustion engines do. Burn oil to get energy. We could use the oil for far more interesting products like drugs, plastics, paint, etc... the list is endless. All these products cannot be as simple produced without oil. So it is essential that we for our need of energy, other means are necessary. Alternatives are natural gas, hydrogen and nuclear power.
Electricity
Electricity for example is a common source of energy. But unfortunatly electricity is merely a carrier of energy, and not a source of energy. Electricity can be obtained from all sorts of renewable sources (wind, water, sun) but as of today, a large proportion is still gained from just burning oil. Electricty is cheap to obtain, relatively safe to handle, can be transformed in all sorts of energy, but cannot be stored. We're not talking about a simple battery here. We're talking about large strategic reserves. Electricity cannot be transported over large distances. So all good things about electricity are valid as long as it can be produced hic et nunc. Production should be done by renewable sources, but for now we rely on other means.
Natural Gas
It is still abundant and can be simply burned to obtain electricity where needed. It is more dificult to handle, more difficult to store and more difficult to produce with, but it packs a lot of energy. It's emission from burning is not as poluting, but still much more than should be acceptable. All in all, I'd say that natural gas will remain a dominant source of energy for the next 100 years. But it too has it's limited sources.
Hydrogen
The gas has some serious advantages coupled with disadvantages. It can be obtained from plain water (for now it is produced from natural gas), so it's supply is endless. It packs a lot of energy and is absolutly not poluting because burning hydrogen with oxigen given plain water. The downside is that it too is difficult to store long term and difficult to handle.
Nuclear power
Nuclear fission, splitting atoms, provides around 25% of the global energy. It is cheap, easy to store, no green house gas emission, and packs tons of energy. But as we all know, it is dangerous to handle and it's waste products remain a long term hazard. Nonetheless, nuclear fission is still a reliable source of energy for the comming 100 years.
Nuclear fusion on the other hand, is a promissing technology. Unfortunatly, it's been promission for over 50 years now. Joining 2 hydrogen cores yields an enormous amount of energy. But today it requires more energy to initiate than energy released. A negative yield. If we could turn this around and produce more energy than that is consumed, there would be an endless source of energy that is not poluting, that packs a lot of energy, but lacks the versatility from oil as it suffers the same drawbacks because the energy carrier would be electricity.
Have we reached the pinnacle?
With no other sources that can replace oil, and oil is limited, does this mean we will soon face a downfall in the develeopment degree of our society? Yes and No. We have about 50 years time to turn the oil dependency into something else. And most probably it will be a mixture of all alternatives explained above. Is there any hope for a source of infite clean energy? Yes, that's the good thing.
The Future on Green Energy?
Personally I don't believe the future belongs to the renewable energy source, because simply put, we've already evolved beyond that. Our energy needs will only rise and cannot be matched by green energy alone. It would be fantastic if we pull it of, but I doubt that poorer developed countries will have the capacity to invest in these types of energy sources.
The Future on Technology?
We have been spoiled with all sort of technological advancements that we rely on the scientist to solve every problem. This naieve thinking is a bubble that has already bursted. When the first nuclear plants were erected, there was no plan for the nuclear waste. Yet everyone was confident that in the near future, a good solution would be found. Well, 50 years later, there is still nothing. The russians dump it in the deepests gorges in the ocean, other try to cover it with tons of earth. The problem remains, it is only replaced.
I do have hope!
Yet, there is one breakthrough that will give us the ideal world with renewable unlimited energy: superconductors. A superconductor material is a material where electricity flows freely without resistance. It creates flawless magnetic fields and can make electricity storage devices. In other words, it can overcome all the drawbacks from electricy. But it gets better. Who cares about a perfect carrier if you don't have the perfect source? Well, the perfect magnetic field of a superconductor can help in overcomming the nuclear fission yield problem. And thus we'll have unlimited source and carrier of energy. And the world population will explode, but that's another story.