Solar Energy
The Sun is in the origin of all renewable energies. The solar power is the light and the heat radiated by the Sun.
Solar energy technologies use the sun’s energy and light to provide heat, light, hot water, electricity, and cooling. There are two types of energy from the Sun.
Solar Thermal Energy
Solar radiation can be converted into useful energy using different technologies. The solar radiation is captured through collectors (solar panels) that contain fluid (water+ antifreeze mix); this fluid is heated, pumped and then transferred to a hot water cylinder or heating system. The heat-transfer fluid flows through a heat exchanger in a hot water storage tank, heating the water to be used. The circulating fluid never comes into direct contact with the water. A well designed solar water heating system can cover 50 to 60% of a household’s hot water requirements.
There are 2 types of collectors, Flat Plate solar panels and Evacuated Tubes solar panels.
Flat Plate solar panels
The flat plate solar collector consists of a black surface that absorb solar energy, a transparent cover, a heat-transport fluid (often water or glycol solution, sometimes air) flowing through tubes to remove heat from the absorber, and a heat insulating backing. The absorber consists of a thin absorber sheet backed by a grid or coil of fluid tubing placed in an insulated casing with a glass or polycarbonate cover.
Evacuated Tube Solar Panels
An evacuated-tube collector contains several rows of glass tubes connected to a header pipe. Each tube has the air removed from it (evacuated) to eliminate heat loss through convection and radiation. Inside the glass tube, a flat or curved aluminum or copper fin is attached to a metal pipe. The fin is covered with a selective coating that transfers heat to the fluid that is circulating through the pipe. There are two main types of evacuated tube collectors: The vacuum can be excellent thermal insulation. It reduces heat transfer by convection to zero. It is held in a glass container (to let the light through). Since glass is very strong under compression but tends to fail in tension, a tube is a good geometry to use.Vacuum tubes are popular as a retrofit option because the array can be taken up to the roof one tube at a time. The additional insulation of the vacuum means that the efficiency at elevated temperatures (>60C) is higher than for flat plate solar collectors, making them more suitable for industrial process heat applications.
Photovoltaic solar energy
The photovoltaic power is the direct transformation of the solar radiation in electricity by the photovoltaic effect.This transformation takes place in a few devices named photovoltaic panels. In the photovoltaic panels, the solar radiation excites the electrons of a device semiconductor generating a small potential difference. The connection in series of these devices allows obtaining major potential differences.
One of the principal advantages of the photovoltaic technology is his modular aspect, being able to be constructed from enormous photovoltaic plants in soil up to small panels for roofs.
