Of course, renewable energy is a very important topic. Current energy sources are running out, such as petroleum, some metals (copper, iron, gold...) and even water (althought is still considered renewable), because some water is polluted, and hydraulic energy is being used in excess. Fossil fuel is a potencial pollutant too, so, also running out of energy, we are going to live in a polluted world.

There are many clean and renewable energy sources, like: solar energy, geothermic energy, wind energy, and others. These sources, besides give us lasting energy, will help us with another serious problem, the environmental care.

The difficult point in theese situation is that theese energies are not as "powerful" as the fossil fuel, therefore, the gathering machinery used in the extraction is quite expensive. For example, photoelectric cells are very expensive, and if you want a lot of energy (for a building) you will need more than one.

Anyway, as soon as we seriously start using renewable energy, we will get lasting energy and a clean environment.