Not all of the energy sources that we used here on Earth will be around forever. Sure, oil companies will keep drilling for oil until the Earth is eventually sucked dry of it, but once it's dried up, oil will be scarce and we'll either look for man-made alternatives or search for better energy sources.
Burning oil doesn't exactly make for a great planet either; it creates global warming, which is why we're currently trying to revolutionize the energy market by getting as many organizations to push solar, water, and wind energy as possible.
Wind turbines, also known as wind mills, are a great way to harness energy with just the wind, which is a natural energy source that the Earth almost always provides. Large farms of windmills can produce enough energy to power neighborhoods.
Another form of energy are solar panels, which can be placed on the roofs of buildings to power certain machines and devices that aren't huge on energy draw. These are typically harvested in huge solar energy farms, but can also be tethered to a battery farm that can be used for power even when power goes out.
And lastly, water turbines from dams and other forms of flowing water can be used to generate power. Flowing water occurs when a surface is higher up than another, so gravity does all the work. Then, when it rains, it renews the water, allowing it to continue flowing.
These three forms of energy harvesting are not only clean and good for the planet, but can power a wide variety of machines and devices that we use on a daily basis.