What are Renewable Energy Sources?
As the term implies, they are sources that can be renewed and never run out! Non-renewable sources include fossil fuels, e.g. oil, coal, gas and their deposits are limited and can be exhausted. Renewable energy sources include solar, wind, biomass, hydro, geothermal and ocean power.
Solar Energy
With this term we refer to the energy provided by the sun through radiation. The sun is the most powerful source of energy and this energy is free, as long as we exploit it! Technologies are categorized as either active or passive. Active technologies convert solar energy into a form we can use directly either electrical or thermal. Such are photovoltaic cells that convert sunlight directly into electrical energy, like the picture over right, the solar collectors for domestic hot water heating or even solar space heating and cooling, the solar concentrators that use mirrors to focus solar irradiation and generate intense heat, turning water to steam and generating electricity using certain machines and even solar ovens (picture in the left). Passive technologies seek to place buildings in a favorable orientation towards the sun or use special materials and architectural designs to exploit solar energy.