Sustainability

The challenge of renewable sources

The six main energy sources being used worldwide at present are: oil (35%), coal (25%), natural gas (21%), nuclear power (6.5%), biomass (10%), hydroelectric (2%) and “new” renewable ones (0.5% solar and aeolian). The first thing that we notice when looking at these figures is that 80% of the energy that we use worldwide comes from fossil sources which are very valuable but not renewable. For this very reason it is urgent that we develop and increase renewable sources, but in order to do this we must overcome some thorny issues. First of all, we must succeed in producing energy from renewable sources cheaply and competitively compared to traditional energy sources. Secondly, for an energy source to be convenient, it must be concentrated, storable and conveyable. Energy must be concentrated to be able to fulfill a large demand, it must be storable to make it possible to build up a supply and conveyable so that it may be carried to places where there is a demand for it other than where it is produced. Fossil fuels are popular because they fulfill these three essential requirements, whereas renewable sources still have some drawbacks which hinder their wide scale use. According to the goals set by the European Union, renewable sources should be able to fulfill 20% of the energy demand by 2020 and, in those places where exploitation conditions are particularly favorable, the percentage should be substantially higher. It is obvious that without adequate energy management strategies, the present day electric network will no longer be sufficient to fulfill such an increase in demand. Furthermore, we must not forget that renewable sources are very variable, so our greatest challenge will be to satisfy energy demand at peak times while using sources that are variable and intermittent.