1. What is photovoltaic solar energy?
Photovoltaic solar energy is that obtained through the direct transformation of the sun’s energy into electrical energy. It seems simple, but how is that done? And, in addition, the energy that is obtained, can be used directly?
2. How is photovoltaic solar energy generated?
When we think of this type of energy, one of the first images that comes to us is that of a solar panel. These plates are formed by modules and these in turn by photovoltaic cells . Its cells are formed by one or more sheets of semiconductor material and covered with a transparent glass that allows solar radiation to pass through and minimizes heat losses.
Conventional photovoltaic solar cells are made of silicon . Those manufactured with this material are quite efficient, with average yields of 14-17%, but also more expensive to produce due to the high dependence on the availability of silicon.
They have begun to use other cheaper materials, these cells being called “second generation”, although their yields are lower (10-12%).
For the concentration systems materials that form ” multi-joints ” are used, greatly increasing the yield and reaching values of 25-30%.
Research continues to reduce production costs and further increase the versatility of the modules, as well as the possibility of using more abundant materials on the planet.
In this way you can choose between different types of photovoltaic cells for the specific characteristics of each installation.
The process of obtaining energy from the sun is simple.
Sunlight (which is composed of photons) affects the photovoltaic cells of the plate, creating a field of electricity between the layers. This is how an electrical circuit is generated.
The more intense the light, the greater the flow of electricity. In addition, it is not necessary to have direct light, since on cloudy days it also works.
The solar cells convert solar energy into electricity as DC , and this tends to transform alternating current to use electronic equipment that we usually have in our homes.
The device that is responsible for this transformation is called the inverter . The inverter transforms the direct current into alternating current with the same characteristics as that of the electrical network to which it is going to be poured, controlling the uniformity and quality of the signal.
This generated alternating current finally passes through a counter (that quantifies it) and from there it is injected into the general network.
How can photovoltaic solar energy be used?
How is photovoltaic solar energy used? Solar photovoltaic technology can be used by:
• An isolated installation , without access to the electricity network. This is very useful in populations where it is difficult to make this type of connections. The electricity generated is used for self-consumption.
In this case it will be necessary to install batteries to the system in order to accumulate this generated energy and thus be able to consume it during the night;
• an installation connected to the network . In this case the electric current generated by a photovoltaic installation can be poured into the electricity grid as if it were a power plant. The producer continues to buy the consumed electrical energy and separately will sell the produced product.
This type of facilities have meters to measure the energy produced and sent to the network.
With the new Royal Decree for small power installations, procedures will be streamlined to connect to the electricity grid and in the future self-consumption can be reached when economic conditions are favorable.
In this way, the sunlight is transformed into electricity in a clean and safe way. In addition, the life of photovoltaic systems guarantees a long period of operation.
It is estimated that the life of a module is about 30 years, and its performance after 25 years of use is above 80%. And they can even be recycled since the materials used (silicon, glass, aluminum, etc.) can be reused!
How does a photovoltaic system work?
Photovoltaic solar energy consists of the transformation of light energy from the sun into electrical energy.
This conversion process occurs as soon as sunlight hits the photovoltaic cells . The solar panel uses semiconductor materials and captures the photons transmitted in sunlight to transform them into a continuous stream of electrons, that is, electricity.
The electricity generated by the renewable energy systems has the capacity to supply systems in direct current (12v / 24v / 48v) or in alternating current (220v and 380v).
With this technology it is possible to generate clean, constant, silent and renewable electric power, in addition to reducing the monthly cost of your electricity bill.
With the generation of electrical energy from renewable sources, it helps to reduce the impact generated by traditional energies (fossil fuels) to our environment.
Operation of renewable systems
There are several connection alternatives in renewable systems:
Isolated from the public network: These are systems associated with batteries that feed electrical consumption 24 hours a day. The systems are usually dimensioned in order to have 3 days of autonomy without sun, providing security 365 days a year.
Systems associated with batteries and the public network: They are similar to the isolated systems of the public network. However, in case of reaching the maximum discharge stipulated for the batteries (after 3 days of consumption and minimum generation), the system has the possibility of connecting (automatically) to the electricity grid or to a generator.
Hybrid systems: Systems designed to reduce electricity consumption. Circuits are fed only during daytime hours (solar radiation). However, there is an accumulation bank in order to face and provide stability of tension and autonomy (usually 24 hours) in the event of power outages.
Synchronous systems: Systems designed to reduce your electricity bill. Electric consumption is only fed during daytime hours (solar radiation). In this case, there is no battery bank, and therefore, in case of possible light cuts, the power supply is completely cut off.
What are the applications of photovoltaic solar energy?
- Provision of private homes, country clubs, country clubs
- Rural facilities, agricultural, livestock and industrial activities
- Institutions, governments, municipalities
Difference between photovoltaic and thermal solar energy
Although the two energies use solar radiation, the thermal uses the heat of the sun while the photovoltaic converts the light into electricity. Solar thermal energy is mainly used to heat a fluid, which in turn serves for the production of domestic hot water (or industrial), heating or for the air conditioning of pools.
Benefits of renewable energies
Renewable energies are those that produce electricity from the sun, wind or water. They are inexhaustible or practically inexhaustible sources.
- They generate independence from public services.
- No unwanted light cuts are suffered.
- Renewable energies do not produce CO 2 e emissions throughout their useful life, so the environmental impact of energy sources decreases.
- The resources are practically inexhaustible.
- They require minimal maintenance.
- The investment is recovered in a few years (depending on the technology).
- Renewable energy does not generate waste during its entire useful life.
What are the components of a photovoltaic system?
- Photovoltaic solar panel: generator of electricity (direct current)
- Inverter (optional): DC voltage converter in alternating current (220v or 380v)
- Battery bank (optional): energy storage system.
- Charge regulator: protects batteries from overloads and over discharges, thus extending the life of the batteries.
How many kinds of current inverters are there?
- Isolated from the public network : These are systems associated completely with batteries in order to accumulate electricity for periods of constant consumption and variable generation.
- Systems associated with batteries and the public network (or generators): These systems are similar to the previous ones, however, in case of reaching the minimum reserve of the batteries, the system automatically takes the surplus from the electric network or generator, in order to guarantee the electricity supply.
- Hybrid systems: Systems designed to reduce the electricity consumption of the network. Additionally, they have a battery bank (smaller), in order to guarantee the power supply in case of power outage.
- Synchronous systems: these are systems exclusively for the purpose of reducing consumption of the public network. In case of power outage, the system does not have an energy reserve
Applications of photovoltaic solar energy
To understand the importance of this possibility, it is convenient to bear in mind that approximately a quarter of the world population still does not have access to electric power.
- Electrification of homes, businesses and industries.
- Electric current for homes isolated from the electricity grid (rural electrification).
- Emergency communications systems.
- Microwave and radio repeater stations.
- Beacons, buoys and maritime navigation beacons.
- Pumping for irrigation systems and drinking water in rural and isolated areas.
- Loading systems for ship accumulators.
- Weather stations.
- Repeaters of communications.
The system can incorporate current inverters. Its function is to transform the output current of the panel to a single-phase (220 volts) or three-phase (380v) alternating voltage, equivalent to that provided by the national electric power network, allowing the connection of any electrical device without the need for intermediate equipment.
What are the benefits of photovoltaic solar energy?
Between 2001 and 2015 there was an exponential growth in the generation of photovoltaic energy, doubling approximately every two years.
Thanks to technological advances, sophistication and economy of scale, the cost of photovoltaic solar energy has been reduced steadily since the first commercial solar cells were manufactured, increasing efficiency, and achieving that its average cost of electric generation is already competitive with conventional energy sources.
The rate of energy return of this technology, meanwhile, is decreasing. With current technology, photovoltaic panels recover the energy necessary for their manufacture in a period of approximately 1 year and a half (depending on the area where they are installed).
How is the electricity generated stored and maintained?
The energy collected, later transformed into electricity, is stored in a battery bank in order to be available for the desired consumption moment.
The charge regulator electronically controls the voltages, and the charge and discharge current of the same.
How are they installed?
The installation is relatively simple and fast. The panels can be installed on floors, ceilings and also on any surface resistant and wide enough to support the weight of the same.
It is very important that its location has a north orientation, since in this way a greater efficiency is achieved in terms of the absorption of energy coming from the sun.
On the other hand, it is recommended that they be installed with a slope between 35 ° and 40 ° which on average will allow them to produce the required energy in the worst month of the year, without compromising production too much in the other months.
Do they need maintenance?
The maintenance of photovoltaic energy systems is practically nil. It is necessary to keep the panels clean, if rain does not do it naturally, and it must be ensured that they are not affected by shadows of trees, plants or other structures that can block the radiation incident on them.
Do the systems have guarantees?
Photovoltaic solar panels have a factory warranty, which guarantees an efficiency greater than 90% after the first 10 years and 80% even after 25 years. However, facilities from the 70s have been registered and still have efficiencies of over 85%. It must be taken into account that the useful life of solar panels is greater than 30 years.