I've been trying to find and assess could ways to harvest energy. Basically, there is only so much energy you can gather, you have to find the best ways to get it.
Energy gives you the capability to do work - the more energy you have, the more work you can use, particularly to gather more energy. There are limits - solar, plants, and so on, are limited by the available space to gather sunlight - a total maximum of one kilowatt (about 1.3 horsepower) per square metre (about 10 square feet). Wind power is very useful, but can be limited... Hydro is great - if you're near a water source that can supply it all year long. I've been wondering about geothermal power - could be useful, but needs you to be in the right spot geologically, needs you to drill a hole, and needs more machinery... Never mind the very high cost of installing such a system.
More machinery means more things that can go wrong.
And more things going wrong means more people needed to keep things going.
On the other hand - do things in a reasonable manner, and there's much more power than the same number of people could produce by themselves...
The flip side is that we forget all the materials we use, and the effort that goes into getting them. Wood is fine for many uses, assuming you don't have lots of termites, but there are limits to what it can go. I have to find a reference I saw many years ago about how some African tribes smelted iron ore to produce usable quantities. Whether there is any iron ore nearby is another question. I have clay in the area, so there's one material; where there's clay, there's also the opportunity for Aluminium, using some novel techniques. I'm several miles from the coast, for better or worse, so no silicon really close to hand...
But copper? Tantalum? Any of the many metals in heavy use...
Energy is one thing, having something to use it on is another.