Research and development of photovoltaic solar energy

In this article we will analyze the photovoltaic solar energy development and current research , we will see the technological advances in solar energy for the benefit of the human being.

Research and development of photovoltaic solar energy

Solar energy is a concept that we have pursued in recent years, if only to try to find a better way to address the problem of global energy supply   without harming the environment  .

 For those who know very little about this source of energy, it is fundamentally that obtained from the sun and that can be converted into energy that we can use, that is, electricity or thermal energy  for heating or cooling environments  .

Solar energy is simply the energy that comes from the sun. The mother star of our solar system is a powerful source of energy. Without it, no life on Earth would have existed. 

It is a  renewable source  , we are all free to use it, it is widely available and clean. Currently it is already used to satisfy the energy demand of homes and offices, but it also has other purposes, such as heating the domestic hot water that we all use to wash or feed the electricity grid in small countries.

How does solar energy work?

Now let’s take a closer look and see how solar energy works and, in particular, let’s see what solar panels are and how they can help us achieve our goals when it comes to using solar energy efficiently. . As one of  the cleanest and safest renewable technologies  , it is time for the general public to recognize the effectiveness of this type of solution.

Useful energy is derived from the conversion of energy from the sun. There are three main ways in which this transformation can be carried out:

Solar photovoltaic:

• Photovoltaic processes take place with photovoltaic panels, which take sunlight and transform it into electricity. The elementary component of the generator is the  photovoltaic cell  in which the conversion of solar radiation into electric current takes place. It consists of a thin slice of semiconductor material, usually silicon. We will discuss this in more detail below.
• Solar panels are made predominantly of   materials that naturally convert sunlight into electricity  . These materials are known in the scientific field as semiconductors. When sunlight strikes these semiconductors, they release free-moving electrons, which are channeled through the device and produce an electrical current.
• Photovoltaic devices undergo constant technological development in this period because some wavelengths of sunlight, including UV rays and infrared rays, can not be converted by these devices. This can be problematic when the sun does not shine and, consequently, UV and infrared rays are the main rays that reach the surface of the earth.

Solar thermal:

• The energy that the sun creates is transformed into energy that  can be used to heat or cool the devices that work  . There are processes that can help in almost any imaginable context, from commercial buildings to homes, but also for pool heating.
• This time the fundamental element for energy conversion is the solar collector. It is very different from a solar panel, since its purpose is not to convert the sun’s energy into electrical energy, but rather to heat a fluid that passes inside its pipes. A collector is mainly formed by a heat transfer fluid that is inside the tubes, a transparent cover that allows the rays of the sun to pass through it, an absorbent plate that captures them and an insulator to avoid the most delicate components of the collector. Overheat too much
• The main reason why solar heating and cooling devices are needed is because  we must reduce our dependence on natural gas and other fossil fuels  . Heating systems, such as traditional boilers, mainly use natural gas or methane to feed. Air conditioning systems are a big problem, since conditioners use a lot of electricity to cool the rooms, and this is often produced with fossil fuels.
• Even in the thermal sector, technology is constantly evolving and adapting. The progress made in this area of ​​science is significant and not a day goes by without discoveries on how to best use this type of energy.

Solar thermodynamics:

Concentrated solar systems, generally called CSP (Concentrated Solar Energy), are one of the most recent technologies to exploit solar energy. The CSP technology is not yet fully developed, but it has its strength in the possibility of supplying electricity independently of the resource.

They are plants used to produce electricity by supplying high temperature heat to a plant based on a thermodynamic cycle. The process is called “indirect conversion of solar energy” as opposed to the direct transformation of solar energy into electricity (photovoltaic systems).

Mirrors are the main elements of a CSP system; They concentrate all the solar energy in a single point so that the whole system works more effectively. Without the mirrors, CSP systems would have no reason to exist. For this reason, the implants can have a point shape (they use a parabolic mirror to channel all the rays in the center of the parabola), with a central tower (the mirrors placed on the ground direct the sun’s rays to a point located in the upper part of a special tower) and for linear Parabolas (they are formed by parabolic tubes, that is to say, without upper cover, which heat a fluid contained inside the pipes).

The energy accumulated by the fluid is then made to expand in the steam turbines that ensure that electricity can be produced and stored. This makes CSP systems different from other types of solar energy exploitation because the energy storage system is much more advanced than those found in other types currently in use. By 2020, it is expected that there will be more than 5,000 concentration plant projects around the world, already in operation or under construction.

How do solar panels work?

Now that we have examined all the different types of solar energy conversion to useful energy, how they work and which are the basic components for transformation, let’s look at one of the most common devices used to obtain energy from the sun: solar panels.

• In short, the sun’s energy, which can be described as a specific amount of energy, composed of multiple particles called photons, passes through semiconductors, which in turn  generate electricity and develop it so that it can be used effectively  .
• The solar panels are capable of exploiting different types of solar radiation and not only from the sun, but also the light reflected from the roofs of houses, from snow and ice, which is called albedo.
• As mentioned above, solar panels are composed of a certain amount of solar cells. A single cell can not do much, but a group of cells can help create enough energy to power the most diverse devices. Solar cells are small discs, composed of semiconductor materials, among which the best known is silicon. Solar cells are capable of producing energy  only when hit by solar radiation . Within these structures an electric field is created that opposes the propagation of free electric charges. This electric field gives the cell a structure called “diode”, in which the passage of the current, constituted by free charge carriers, for example electrons, is hindered in one direction and facilitated in the opposite direction.
• Photovoltaic panels are sold  with a guarantee of 80% initial performance after 25 years  . They have been developed as aerospace technology (satellite power supply) and for security applications (light signaling), where reliability is one of the priorities. The tests are carried out exposing the modules to thermal cycles (from -40 to + 80 ° C), exposure to humidity and electrical tests. The rate of degradation of efficiency is estimated between  0.5% and 1% per year  .
• As mentioned, solar panels are the main way for a space station, along with other astronomical technologies, to obtain the electricity needed by astronauts. A curiosity: sometimes, solar panels in space are damaged by small meteorites or other elements called “space junk”; this requires that the astronauts leave the cabin where they are and make the  appropriate repairs if necessary

How to check the performance of a photovoltaic panel?

An interesting thing to do to verify the real efficiency of a photovoltaic panel is the energy balance of a single cell, since it describes the percentage of incident solar energy that is not converted into electricity. As an example, if you consider that the incident solar energy is equal to 100%, there are the following typical losses:

• Of the  20%  to maintain in position the electric field in the transition region of the cell;
• Of  8.5%  in carrier recombination free charge (electrons do not follow the flow direction);
• Of  23%  for photons with high wavelength, with insufficient energy to release electrons;
• Of  3%  for reflection losses and shading of contacts placed between the environment and the cell (eg protective glass);
• Of  0.5%  for electrical transmission losses (due to circuit resistance);
• Of  45%  of the photons with a short wavelength that are absorbed, but whose 32% is excess energy (heat production);

In the end, in this example,  only the remaining 13% of solar energy is absorbed and transformed into electricity  , which means that the yields of solar panels are currently too low to be competitive with traditional forms of energy production.