The problem with every type of energy supply, from fossil fuels, to nuclear (based on uranium), to geothermal, to hydroelectric, to wind and solar, is diminishing returns. At some point, the cost of producing energy becomes less efficient, and this results in an increase in cost of production.
With oil, the growing cost of extraction comes because the cheap-to-extract oil is extracted first, leaving only the expensive-to-extract oil. This makes the price go up.
Now let’s take Uranium as an example. It experiences the same problem of diminishing returns, similar to oil. After the cheap-to-extract portions are extracted, we must eventually move on to lower-grade and harder to extract ores.
What about hydroelectric? Same problem. When hydroelectric plants are installed, the best locations are utilized first. Gradually, less desirable locations are added. The same holds for wind turbines.
And don’t forget about wood. When it comes to wood, overuse and deforestation are constant problems. Throw in the exponential population growth over that last few decades and the situation is likely to become even worse.
In addition to diminishing returns, there’s another important factor to consider.
Most renewables are still dependent on oil. Oil is required for operating mining equipment and for transporting goods and machinery. Helicopters (requiring oil) are used to maintain wind turbines, especially off shore. Road maintenance even requires oil.
The bottom line is this…
If there is ever a shortage of oil, there will be an enormous drop-off in the production of renewables as well. Thus, renewables are not available in unlimited supply. If oil supply is constrained, you’ll soon discover renewable energy sources will follow shortly thereafter.