renewable energies are all the energy forms whose tax of use is inferior to its tax of renewal; the energy source can have terrestrial origin (geothermal energy), gravitational (tides), energy of solar radiation, hydraulical energy and kinetic energy of the wind;
	it's also considered renewable energy source the agricultural, urban and industrial residues (biomass energy); in Portugal, the energy dependence of the exterior is very high, in the decade of 90 it was imported more than 80% of the consumed primary energy.