Sustainability

Solar energy

Earth receives from the Sun the equivalent of a whole year’s worldwide energy demand in less than an hour. As opposed to other energy sources, solar energy is available everywhere on our planet (in spite of differences depending on latitude), and it is a source which we will continue to have for billions of years. Therefore, in addition to being renewable, solar energy is readily available in adequate amounts everywhere on our planet. These characteristics would make the Sun our primary source of choice if it were not that it is low power and locally intermittent energy. In fact, the flow of solar energy depends on the alternation of night and day and on weather conditions. Smaller power for greater energy A very useful parameter to determine what energy is “worth” is its power density, also known as radiation, which indicates the amount of radiation per surface unit of measure. The amount of solar power that reaches Earth’s surface, minus the reflection and absorbance effects it undergoes in the atmosphere, is equal to 85,000 billion W. Knowing that Earth’s surface measures 5.1 billion square kilometers, we also know that each square meter receives approximately 170 W/sqm, and this value becomes substantially lower when converted to usable power. Present day lifestyles in the most advanced countries require a power density in the range of 20 – 100 W/sqm for a home and 300 – 900 W/sqm for a steel factory. Obviously, present day solar technology cannot fulfill the demand of high energy structures such as factories and hospitals. The main technological challenge nowadays is to find the way to store the huge amount of energy produced by the sun and make it readily available with adequate intensity wherever there is a demand for it.