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A solar panel is an element of solar installations. Its function is to take advantage of solar energy. It can also be called a solar module.

There are solar panels for photovoltaic energy and for thermal energy. In this way, we distinguish:

In both cases, its objective is the production of energy using renewable energies.

Photovoltaic panels

The photovoltaic panel is designed for the production of electricity. They are used for photovoltaic installations. The panels convert the Sun's radiation into electrical energy thanks to the photovoltaic effect.

Panel solar

Normally, this type of solar panel is made of silicon. It uses the energy of the photons present in the light to blow up an electron from the silicon. The sum of several electrons causes an electric current.

These solar panels generate electricity in the form of direct current. They can go with current converters to get alternating current.

How does a photovoltaic panel work?

A photovoltaic panel works thanks to the photovoltaic effect. When a photovoltaic cell receives sunlight it causes an electron to jump. The sum of these electrons generate an electric current. Electricity.

Used materials

In general, solar cells are composed of crystalline silicon or gallium arsenide. Gallium arsenide crystals are created for these uses. Silicon crystals are also produced for consumption by the microelectronics industry. 

According to the silicon configuration, the photovoltaic plates can be:

  • Polycrystalline solar panels. Polycrystalline silicon has a lower conversion rate, but at a reduced cost.
  • Monocrystalline panels.
  • Thin-film solar panels.

Construction technique of a solar panel

A 6 cm silicon cell exposed to direct 1 AU light can produce a current of 0.5 amps at 0.5 volts. Gallium arsenide is even more efficient than silicon.

Solar panel kits can produce electricity for isolated places with good lighting.

The glass is cut into small discs. It is polished to eliminate the danger of cutting. Dopants are inserted into the discs. Metal drivers are deposited on each surface: a small connector on the sun-facing surface and a connector on the other side.

Solar panels are built with these cells cut into appropriate shapes. They are protected against radiation and other damages by applying a layer of glass and cemented on a substrate (either a rigid or flexible panel).

Electric connections

Electrical connections are made in series-parallel to determine the total output voltage.

The protective layer must be a thermal conductor. The cell enters when it absorbs infrared energy from the sun that is not converted into electrical energy. Since cell heat reduces operating efficiency, it is desirable to reduce this heat.

How many photovoltaic cells does a solar panel have?

A solar panel is a set of photovoltaic cells. Although each photovoltaic cell provides little energy, a set of solar cells can generate enough energy to be useful.

To receive the most energy, solar panels should be aimed directly at the sun.

The most common solar cell configurations are as follows

  • 36 cell solar panels: This type of panel is the most compact on the market. Connect 36 solar cells to obtain an output voltage of 12V. Recommended in small isolated installations.
  • 60 cell solar panels. It uses 60 solar cells to obtain an output voltage greater than 24 V.
  • 72 cell solar panels. This type of photovoltaic module connects 72 solar cells to obtain a voltage greater than 24V. They are mainly used in electrical grid connection installations.

Solar collectors

Panel solarSolar collectors are part of thermal solar energy installations. 

Its function is to take advantage of the heat energy of the sun to heat a liquid. For this, the laws of thermodynamics are applied.

The main applications are:

  • Get sanitary hot water.
  • Provide heat for a heating system.
  • Thermal power stations. Electricity production.

This type of solar panel works by circulating a fluid inside it. The panel captures the heat energy from the sun. This fluid is heated as it circulates inside the collector.

Types of solar collectors

There are different types of solar collectors. Its use depends on the application where it is going to be used:

  • Low temperature collectors: Flat solar collector, Vacuum tube collector.
  • High temperature collectors: Parabolic mirror solar concentrators, flat mirrors (or linear Fresnel lenses).
  • Very high temperature collectors. Sometimes solar oven. Currently it is made with fields of adjustable flat mirrors.

Factors that affect the efficiency of photocells 

The structural characteristics of solar cells cause a decrease in the performance of the panels with increasing temperature.

Partial dimming of the panel causes a drop in the output voltage. This attenuation is due to losses in the switched off element, which begins to act as a parasitic load. This problem can be eliminated by installing a bypass in each photocell of the panel.

In cloudy weather, in the absence of direct sunlight, panels that use lenses to concentrate radiation become ineffective. In these cases, the effect of the lens wears off.

From the operational characteristics of the photovoltaic panel it can be seen that to achieve maximum efficiency. For this, the correct selection of the load resistance is required.

For this reason, photovoltaic solar panels are not directly connected to the load. They use a controller to control photovoltaic systems. The controller ensures optimal operation of the panels.

What is the lifespan of solar panels?

The general rule indicates that the useful life of a solar panel is 25 years. 

As a general rule, the power of a photovoltaic panel is reduced by less than 1% each year due to the degradation of its photovoltaic cells. Therefore, the power of a panel 25 years later will be over 75%.

Today's solar modules, with better technology and better manufacturing techniques, have even better resistance.

For monocrystalline silicon the degradation rate is less than 0.5%. For panels manufactured before 2000, and less than 0.4% for panels manufactured after 2000.

That means that a panel manufactured today should produce 92% of its original power after 20 years.

However, with proper maintenance, these numbers can be improved.

Why do solar panels degrade?

The life of a solar panel depends on its degradation. The main cause of degradation of a solar panel is the weather.

Crystalline silicon modules located in extreme climates show higher rates of degradation. For very cold climates, panels subjected to strong winds and snow loads are the ones that suffer the most.

On the other hand, panels in similar climates installed on a facade, eliminating the snow load, have very low degradation rates.

At the other extreme, solar panels in desert climates exhibited large declines in production over time. This decrease is close to 1% per year, mainly due to high levels of exposure to ultraviolet rays.

Panels in more moderate climates (such as the northern United States) had degradation rates as low as 0.2% per year. Those panels could retain 96% of their production capacities after 20 years.

Are you thinking of buying solar panels?

Before making a solar panel installation you should ask yourself the following questions:

Do you have a roof that can support solar panels?

You may have a shady roof for most of the day all year. In this case, you may not have a "solar window" favorable enough to justify the costs of the panels.

If you have a roof with adequate sunlight to work the structure should be fine.

Finally, imagine the future of your garden. If the roof is not obstructed now, but you just planted a battalion of leafy oaks, you could run into trouble a few years later.

Have you done everything possible to improve efficiency?

The amount of solar energy you need to produce depends on the amount you use. Start with an energy audit. Also, look for efficiency data before making plans.

What kind of solar energy makes sense?

The two dominant solar technologies to choose from are photovoltaics and thermal solar energy.

A solar thermal investment may be suitable for:

  • Homes with a high consumption of heating.
  • Homes where heating fuel is expensive.

How do you connect to the network?

Details vary depending on where you live.

Every time you connect with a utility company, there is a lot of logistics to solve. Do you have to pay a fee? How long does the utility take to get hooked? Once connected, how and when will you be credited for the electricity you generate?

Is your installer reliable?

This applies every time you hire someone. Solar energy combines the logistics of a home improvement project with the risks of electrical work. Credentials and references are important.

Examples of use of solar panels

  • Portable electronics. To provide electricity and / or recharge batteries of various consumer electronic products.
  • Electric cars. To recharge electric cars.
  • Energy for buildings. Large solar panels, such as solar collectors, are widely used in tropical and subtropical regions with a large number of sunny days.
  • Use in space. Solar batteries are one of the main ways of generating electrical energy in spacecraft. These batteries work for a long time without consuming any materials. At the same time they are ecological, unlike nuclear and radioisotope energy sources.

Summary

A solar panel is an element of a solar installation. Its function is to capture solar radiation and convert it into:

  1. Electric power. Photovoltaic panels.
  2. Thermal energy. Solar collectors.

Photovoltaic panels can be connected to the grid or to a battery. Installations connected to a battery are isolated installations.

The useful life of solar panels is about 25 years. This depends above all on maintenance and the weather.

References

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Published: July 16, 2015
Last review: May 17, 2020