Renewable energy sources can be classified into five categories:
solar, wind, water, biomass, and geothermal energy. Apart from geothermal, all these energy sources are caused by the sun. Biomass is any organic substance, which retains the energy created by the sun in the process of photosynthesis. The sun sends a huge amount of energy into space. Approximately one-third of the sun’s energy coming to earth is infrared light (heat rays).
The sun provides the most generous source of energy on Earth. For humanity, the biggest challenge is to catch the sun’s rays and take advantage of their energy to provide electricity. In many countries, governments financially support citizens to use renewable energy sources in their homes, which is just one way to promote and support alternatives and clean energy sources.
The most used are the Solar panels system. Conventional solar energy technologies, such as solar hot water systems, do not require huge investments. These systems generate enough energy to meet the basic needs of the household for hot water throughout the year. Solar cells for electricity production are in progress twentieth century already produced. We’ve all seen solar panels on the roofs or somewhere high but did you ever asked yourself how solar panels work?
Solar systems for electricity production
As it said earlier, solar panels were in production progress since the 20 century, although, in the beginning, their efficiency was
amounting to only 1 to 2%. There is research-documented about solar cells from the 1920s and 1930s. However, the development of new methods in the 1940s and space programs from the 1950s represented significant stages in the development of the solar cell. These are the systems that we have now. Today, the efficiency of standard systems solar cells is about 15%.
As we learned in school, light has dual nature. Sometimes it behaves as a wave and sometimes as a sum of particles. We will consider only second nature, that is, light is consists of photons.
When photons fall on the surface of an absorbing object light, they eject electrons. This process is called the photoelectric effect and occurs on metal surfaces, liquids, and gases. Electrons pass through the material while the rest of the protons (positively charged) flow in the opposite direction. These traveling electrons create the flow of electricity.
The most suitable surface for this process is metal. However, not all metals have a photoelectric effect. The material most proper for creating the photovoltaic effect is silicon. It is the second most common element, after the oxygen in the Earth’s crust. We can make Silicon can from quartz sand.
Besides roofs and solar panel systems, solar cells are vividly used in small appliances. Everyone has probably seen solar calculators or clocks? The price of solar systems is fortunately in constant decline, and theirs use in households, transportation, and the economy is everything more widespread.
How do solar panel systems look inside
Since we only observe one nature of light and that it consists of photons, the conversion is, thus, performed. The materials that are best for this type are semiconductors. Representative examples of semiconductors are germanium and silicon. All materials have cavities and electrons that carry the charge. The change is possible by using two-layer silicon elements.
The first layer is constructed of Si and has an excess of electrons in its structure. We call this layer n-type. The second layer is also made of Si and has a lack of electrons. We call this layer p-type.
The solar photons collide with exposed electrons. How much transmitted energy of solar radiation to these electrons is in the direct connection of the provided conditions for the flow of electricity.
A transverse electric field is created because of the diffusion of electrons into (p) material and cavities into (n) material. The diffusion process stops only when the field reaches a sufficient value. These critical values are called a “potential barrier” for carriers at the p-n union itself.
To obtain electrical power in the solar generator photons must play by three rules:
- The photon energy must be greater than or equal to the gap width. The absorbed photons excite the electrons to a higher energy level.
- Photoabsorption created an electron-cavity pair must be separated by an electric field so that the electrons move towards the (-) terminal and the cavities towards the (+) terminal
- Both charges thus received must reach the p-n coupling without recombination
The working principle of solar panels is the principle of generating electricity. There is a potential difference in the p-n line layer. The electric field is directed towards the layer p. When the n-plate surface is exposed to the Sun photons erupt an overabundance of electrons. Those will accept the forces of the electric field. If an external electrical circuit forms between the ends of these plates, it will move through it.
The current depends on two factors. The first is the power density of the Sun, and the second is the surface of the roofing. However, the current through the external electrical circuit depends only on the surface density of solar radiation. It also remains the same over a wide range of external circuit voltage.
The Sun’s characteristics concerning its position towards the Earth are changeable. For example, the distribution of radiation outside the Earth’s atmosphere is almost constant. It expresses through a characteristic called the solar constant.
The solar constant is the value of solar energy that falls in a unit of time per unit area of the surface. But it has to be perpendicular to the flux of radiation in cosmic space at an Earth-Sun distance. In the real case, the operating temperature range is about 60-80 °C (140-180 F).
Explanation of the operation of solar panels
The image above shows a type of solar panel, named: self-contained photovoltaic systems stand alone. As the name hints, these systems function entirely independently. It means they can work completely autonomously. This is the main reason why they are very useful in places where there is no distribution of electricity. However, in the past two decades, their use is increasing in urban areas.
The reasons why people choose these types of the solar panel are economical. Your life can be easier when there is no monthly electricity bill nor power back down. Such systems can work anywhere and operate independently of the distribution network. For example, a lake house or a mountains house.
The stand-alone photovoltaic system has two main parts. The first one is solar panels, and the second one is batteries. Solar batteries are used to accumulate electricity so that they can use it during the night and days without Sun. The modern design of these systems is practical. They can power the average house with electricity for one to three cloudy days.
First, solar panels collect solar energy. Second, the single-voltage voltage produced in the solar panels passes through the voltage controller. Third, the inverter converts DC voltage to AC. Then the solar battery accumulates electricity. When the battery is fully charged, then the charging stops. After switching from direct current to alternating current, the current is distributed in all electrical devices. Electricity comes either only from the sun, or the sun and batteries, or only from batteries. It depends on the weather and the part of the day.