How is solar energy produced?
Solar energy is produced from the sunlight received by the photovoltaic panels. This is different from the solar heating system where the sun's energy is used to heat water or air. Solar energy or photovoltaic energy is also known as solar electricity, as it describes the way in which electricity is generated in a solar panel.
If you want to use solar energy to generate heat, solar heating systems are much more efficient than solar electricity, because it requires much smaller panels to generate the same amount of energy.
How is solar energy generated? - The source of solar energy
In the center of the sun an intense nuclear activity is generated which generates large amounts of radiation, which, in turn, generates energy from the light called photons. These photons have no physical mass of their own, but they carry large amounts of energy.
Different photons carry different wavelengths of light. Some photons will carry non-visible light (infrared and ultraviolet), while others will carry visible light (called white light).
Over time, these photons leave the center of the sun, it can take a million years for a photon to leave the nucleus to the surface. Once they reach the surface of the sun, these photons begin to travel through space at a speed of 1.078 million kilometers per hour and then reach the earth in about eight minutes.
On their journey from the sun to the earth, photons can collide or be diverted by other particles and are destroyed by contact with anything that can absorb radiation, generating heat. The human body absorbs photons from the sun, that's why we feel hot on a sunny day.
Our atmosphere absorbs many of these photons before reaching the surface of the earth. That is one of the two reasons why the sun feels much hotter in the middle of the day. When the sun is up the photons have to travel through a thinner layer of the atmosphere to reach us, compared to when the sun is setting the photons have to travel through a much thicker layer of the atmosphere.
This is also one of the two reasons why a sunny day in winter is much colder than a sunny day in summer. In winter, when the location of the earth is far from the sun, photons have to travel through a thicker layer of the atmosphere to reach us.
The other reason why the sun is hotter during the noon than when the sun sets, is because the intensity of the photons is much higher at noon. When the sun is low in the sky, these photons extend a greater distance simply by the angle of their location on the earth in relation to the sun.
The principles of solar energy
A solar panel generates electricity using the photovoltaic effect, a phenomenon discovered in 1839 when Edmon Becquerel, a French physicist, observed that certain materials produced an electric current when exposed to light.
To create this effect, two layers of semi-conductive material are combined. A layer has to have a reduced number of electrons. When exposed to sunlight, the layers of this material absorb the photons, this excites the electrons causing some of them to jump from one layer to another, generating an electric charge.
The semi-conductive material used to build a solar cell is silicon, cut into very thin sheets. Some of these sheets are doped to contaminate them, thus creating an imbalance of electrons in the sheets. Then the sheets line up together to form a solar cell. The metal conductive strips connected to the cells take the electric current.
When a photon reaches the solar cell it can do one of three things, it can be absorbed by the cell, it can be reflected outside the cell or it can pass through the cell.
“ Electric current is generated when a photon is absorbed by silicon.
The more photons (higher light intensity) that are absorbed by the solar cell, the greater the current generated.
Solar cells generate most of their electricity by receiving direct sunlight. However, they also generate electricity on cloudy days and even some systems can generate very small amounts of electricity on full moon nights.
Normally individual solar cells only generate small amounts of electrical energy. To generate useful amounts of electricity, these cells are connected to each other to create a solar module, also known as solar panel, or to be more precise, a photovoltaic module.