In this article we will try to explain as simple and didactically as it is photovoltaic solar energy.
Photovoltaic solar energy is the way to generate clean electricity by means of photovoltaic solar panels, this allows saving money and protecting the environment.
What is solar photovoltaic energy?
Photovoltaic solar energy is a source of clean and renewable energy that uses solar radiation to produce electricity.
It is based on the so-called photoelectric effect, by which certain materials are capable of absorbing photons (light particles) and releasing electrons, generating an electric current.
For this, a semiconductor device called a cell or photovoltaic cell is used, which can be monocrystalline, polycrystalline or amorphous silicon, or other thin-film semiconductor materials.
The cell of monocrystalline silicon is obtained from a single crystal pure silicon and reach maximum efficiency, between 18% and 20% on average. Those of polycrystalline silicon are made in block from several crystals, so they are cheaper and have an average efficiency of between 16% and 17.5%.
Finally, the amorphous silicon have a disordered crystalline network, which leads to worse performance (average efficiency of between 8% and 9%) but also a lower price.
Photovoltaic energy is the direct transformation of solar radiation into electricity . This transformation occurs in devices called photovoltaic panels .
In photovoltaic panels, solar radiation excites the electrons of a semiconductor device generating a small potential difference. The series connection of these devices allows to obtain greater potential differences.
Although the photovoltaic effect was known since the nineteenth century, it was in the 50s, in full space race , when the photovoltaic panels began to experience an important development. Initially used to supply electricity to geostationary communications satellites, they are now a renewable generation technology .
One of the main virtues of photovoltaic technology is its modular aspect , being able to build from huge photovoltaic plants in soil to small panels for roofs.
How is photovoltaic solar energy generated?
As we say, photovoltaic solar energy is one that transforms the sun’s energy into electrical energy. But how does this transformation take place? How is photovoltaic solar energy really generated?
The photovoltaic solar energy is based on the principle that the energy contained in the particles of light (the photon ) can be converted into electricity . This is achieved through the so-called photovoltaic conversion process .
The direct conversion of solar energy into electricity is done through a semiconductor material (silicon, for example). It does not require moving parts, fuel or noise.
The basic element is the photovoltaic cell: exposed to light, it absorbs the energy of photons of light. These set in motion electrons that are trapped by an internal electric field. The electrons collected on the surface of the cell generate a continuous electric current
The output voltage of a photovoltaic cell is low (0.6 V). This is why the cells are placed in electrical arrays, then they are encapsulated between a glass plate in the front and another moisture-proof material in the back.
Therefore, they form a photovoltaic module (product that is commercially available). According to the technologies and the type of use that is made of it, this module has a surface area of 0.1 m² (10 W) to 1 m² (100 W), average indicative values, and declines voltages of 12 V, 24 V or 48 V depending on the application.
In broad strokes we can summarize that what happens is that, by using a device specially designed for this purpose, electricity is obtained thanks to the photoelectric effect of sunlight . Generally these devices consist of a semiconductor metal sheet that is called a photovoltaic cell .
Another variant is a deposition of certain metals on a substrate or thin layer. Recently, it has also experienced great advances in the development of organic devices.
As a result of this process photovoltaic conversion is obtained energy at low voltages (between 380 and 800 V) and DC. Later an inverter is used to transform it into alternating current .
The devices where these photovoltaic cells are located are called solar panels and, for personal or family use, they usually have a price of around 7,000 euros.
In addition, these facilities have the advantage that they do not need much maintenance. Of course, they must be installed in the right place (where there are many hours of sunshine) and with the proper placement and orientation.
The electricity produced is available in the form of direct electricity or stored in batteries (decentralized electric power) or electricity injected into the network.
The performance of a photovoltaic installation depends on the orientation of the solar panels and the sun areas in which it is located.
But yes, the degree of use of photovoltaic solar energy is much less than that provided by resources such as oil or natural gas, and is more or less at the same level of use as wind energy (depending on the geographical area, Of course).
However, its uses are increasing and today it is already used in very different areas, as we can see in the following section.
Types of photovoltaic plants
There are two types of photovoltaic plants: those that are connected to the network and those that are not. Within the first there are, in turn, two other classes:
- Photovoltaic power station: all the energy produced by the panels is poured into the electricity grid.
- Generator with self-consumption: part of the electricity generated is consumed by the producer (in a house, for example) and the rest is poured into the network. At the same time, the producer takes the necessary energy from the grid to cover his demand when the unit does not supply enough.
These installations with connection to the network have three basic elements:
- Photovoltaic panels: these are groups of photovoltaic cells mounted between layers of silicon that capture solar radiation and transform light (photons) into electrical energy (electrons).
- Investors: convert the continuous electrical current produced by the panels into alternating current, suitable for consumption.
- Transformers: the alternating current generated by the inverters is low voltage (380-800 V), so a transformer is used to raise it at medium voltage (up to 36 kV).
On the other hand, facilities not connected to the network operate on an island and are usually found in remote places and farms to meet lighting demands, support telecommunications and pump irrigation systems. These isolated plants require two additional elements to function:
- Batteries: responsible for storing the energy produced by the panels and not demanded at that moment when necessary.
- Regulators: protect the battery against overloads and prevent inefficient use of it.
Uses of photovoltaic solr energy
Photovoltaic solar energy can be used for different applications:
Applications in photovoltaic systems connected to the network
Photovoltaic systems connected to the grid are one of the newest and most innovative applications of photovoltaic systems.
This application includes the installation of a photovoltaic sensor and an inverter capable of transforming the energy supplied by the photovoltaic panels and being injected into the network.
The investor in this type of installation is the core. The UPS must have some protection for situations that may occur in the electrical network (for example, phase shift network, network failure, voltage out of range).
The cost per kWh produced is generally higher than the energy produced by other power generation systems. Therefore, to guarantee the economic viability of these systems, the country in which it is applied must have legal regulations and financial aid lines to offset the higher cost per kWh produced.
On the other hand, in isolated systems, that is, systems that are not connected to the diversity of PV array applications, the applications seem endless. However, we highlight some examples:
Photovoltaic systems for lighting
Lighting using photovoltaic systems is one of the most economical solutions for illuminating entrances to towns, intersections, rest areas, etc.
This type of photovoltaic applications can also be found in billboards, bus stops, street lighting and tunnel lighting, among other examples.
Implementation of signage with photovoltaic energy
The solar fotovoltaicapermite automation of lighthouses.
For the use of air, they are used for electrical beacon signals and traffic signals on the tracks.
Lighthouses and buoys for marine purposes.
Another great application of roundabouts, curves, signs, barriers, etc. using high brightness LED. The low power consumption of the light emitting diodes allows a small photovoltaic installation in these systems.
In this sense, we also find examples of time and temperature indicators on public roads, at railway crossings or on oil platforms.
Another great application that has recently been incorporated is very important in road safety, roundabouts, curves, traffic signs, doors, etc. using high brightness LED, low power consumption that allows a small photovoltaic installation.
Photovoltaic systems related to telecommunications
In the field of photovoltaic solar energy, telecommunications are used in the field of mobile telephony, radio and television repeaters. On the way, the SOS poles work with renewable energies, as the work saves network cables in operation.
The radar, radio stations in general and military surveillance or rural satellite telephony are other examples in which solar energy is used to operate.
Rural photovoltaic electrification
Rural electrification with solar panels has all the conveniences you can have in conventional electrification. This parity is due to the incorporation of new sinusoidal wave inverters. This system allows the use of any device.
Thus, it becomes one of the most important applications is the electrification of small towns with a centralized system.
To manage the power supply, the equipment is installed in each power limiter of the house’s electronic equipment, which must be delivered by a user on a daily basis, however, the equipment must be intelligent enough to increase the assigned power if the Battery status is not good, or else if it is bad.
The second major disadvantage is the inverter power and efficiency compared to small loads, but this is solved by installing several inverters in parallel.
This is all about photovoltaic solar energy, an energy that, surely, will be very important in the not too distant future, when the human being has finished with all the fossil resources of the planet, something that will happen sooner or later as it It deals with non-renewable resources (not at least at the rate at which they are consumed).
Application of photovoltaic solar energy in farms and livestock
In agricultural applications, photovoltaic solar energy is used to power pumps to provide water for livestock irrigation.
Light energy is also used in farms. Often, the farms are far from the power distribution lines. Photovoltaic panels allow these cases to be electrical (lighting engines, scissors, etc.).
On some farms, photovoltaic energy is used for milking and milk cooling systems. Even these systems are practical for the electrification of fences.
Directly operated water pumps are one of the most important applications in agriculture. This application highlights its ease of installation, without maintenance and full automation.
These systems consist of a field of photovoltaic panels, an electronic device and the entire system of sensors and pumping control.
Another important application in agriculture has been the control of electrification and solenoid valves for irrigation. This electrification has allowed a better distribution and saving of water, mainly on the basis of drip irrigation or low pressure systems.