The development and investigation of renewable energies is nowadays becoming more and more important. They have a lower environmental impact as they come from natural resources such as water, sunlight and wind and have been used by man since the early ages. This issue is devoted to biomass, tidal power and wave power.
Three quarters of our planet's surface is covered by seas and oceans in continuous movement both at the surface as in the depths and they are energy filled deposits in development by means of wind and tidal energies.
Tidal energy is generated by the relative motion of sea water due to the gravitational attraction by the Sun and Moon. Tidal generators and turbines use this phenomenon to generate electricity. The stamp design features some of the symbolic elements used to produce this type of energy such as the sea and the water motion, the influence of the moon and the technical mechanisms.
Wave energy is produced from the surface motion of ocean waves or from pressure fluctuations below the surface. Wave power devices are generally categorized by the method used to capture the energy of the waves. They can be floating devices or underwater ones anchored to the sea ground and connected to a buoy moving a generator. The stamp design represents the energy captured by the movement of the waves generated by the wind, with a shinning sun and the floating device needed to produce energy.
Biomass is organic matter used as a fuel, especially in the generation of electricity. There are various types of biomass depending on where it comes from: Natural biomass, produced by nature with no human interference; residual biomass generated by agriculture, stockbreeding, the agro alimentary and wood industries and purpose-grown biomass for fuel. The stamp features a crop transformed into fuel.