Renewable energy

According to the exact meaning of the term, renewable energy should be produced from sources that are replenished while they are used. In practice, this is impossible, every source will exhaust one day. Thus, it is helpful to consider the lifetime of the source and compare it to the timescale of its use. For example, the sun will shine for another few billion years and provide energy.

This coined the closely related term of sustainable energy which means drawing a certain amount of energy from the source without harming or depleting it.

Fossile energies are hardly renewable because it took millions of years for them to form. Consuming them within a few decades or centuries is by no means a sustainable use.

In contrast, solar, wind, hydro, and geothermal energy make use of very large reservoirs and human requirements will not deplete them in the foreseeable future. Granted, one day the sun will stop shining, the earth will not revolve any more and its core will become cold. But by then mankind will have altogether different problems...

For the time beeing we should try to make use of these renewable or sustainable forms of energy rather than consume fossile reservoirs without taking care of following generations.