MIT Researchers in the opening of the Eni-MIT Solar Frontiers Center (SFC) that was built to promote research in advanced solar technologies has showcased a lightweight and flexible solar cell technology. This new solar cell made by using a process similar to inkjet printers. The paper used is coated paper with organic semiconductor materials.
Solar energy technologies use energy from the sun to produce heat, light, hot water, electricity, and even cooling, for homes, commercial and industrial.
There are a variety of technological applications that have been developed to take advantage of solar energy. Technology can be read further below.
Photovoltaics System
Solar cells work by converting sunlight directly into electricity. The electrons in the semiconductor material, the material used to capture sunlight, will move when the sun’s energy in the form of photons hit it. Solar energy is forcing the electrons to move, occur continuously, and consequently there is also a continuous electricity production. Process, which turns sunlight (photons) into electricity (voltage), called the photovoltaic effect.
Solar Cell Module
Solar cells are usually organized into modules that each module can consist of 40 solar cells. Some modules can be arranged to form a PV line fitted with a fixed angle facing south. Or even could be placed in a sun-tracking device, to get more solar energy throughout the day. Several rows of PV could produce enough power for a house. As for industrial applications or power companies, hundreds of lines of PV can be linked to form one large PV systems and sufficient to meet the electricity needs.
Thin Film Solar Cell
Thin film solar cells use several layers of semiconductor material with a thickness in the micrometer scale. Technology allows to create solar cells integrated into rooftops to the skylights. Even solar cells are designed for applications having the same power with actual roof.
Brooklyn design company SMIT (Sustainable Minded Interactive Technology) has created Tensile Solar, a cool and lightweight shade powered by the sun (through CIGS photovoltaic cells).
From Wikipedia:
Copper indium gallium (di)selenide (CIGS) (CAS NO. 12018-95-0) is a I-III-VI2 compound semiconductor material composed of copper, indium, gallium, and selenium. The material is a solid solution of copper indium selenide (often abbreviated “CIS”) and copper gallium selenide, with a chemical formula of CuInxGa(1-x)Se2, where the value of x can vary from 1 (pure copper indium selenide) to 0 (pure copper gallium selenide). It is a tetrahedrally bonded semiconductor, with the chalcopyrite crystal structure, and a bandgap varying continuously with xfrom about 1.0 eV (for copper indium selenide) to about 1.7 eV (for copper gallium selenide). It is used as light absorber material for thin-film solar cells.
Tensile Solar is come in various designs: saddle, tent, pole mount and the last is intended to a larger architectural structures, such as a party tent.
You may have seen a calculator that has a solar cell? calculator that does not need batteries, and in some cases do not even have the off button. As long as you have enough light, so the calculator can be on at any time and forever. You may have seen larger solar panels, such as in housing or traffic lights, haven’t you? In this article I will review how solar cell work so it can deliver the energy and drive an electronic device.
Today the demand for electricity has become a major requirement in all corners. The presence of power plants sometimes do not solve the need for electricity especially in remote areas where the terrain is always an excuse. Here an alternative energy that can be easily found in nature and can be used as an alternative free energy replacing conventional electricity, because it can turn on household electronics such as televisions, radios and lights.
Solar cells made from pieces of a very small silicon coated with special chemicals to form the basis of solar cells. Solar cells generally have a minimum thickness of 0.3 mm is made from semiconductor materials incision with positive and negative poles. Each solar cell produces usually voltage 0.5 volts. Solar cells is an active element (semiconductor) that utilizes photovoltaic effect to transform solar energy into electrical energy.
Solar cells contain a connection (junction) between two thin layers made of semiconductor materials, each of which is known as a semiconductor type “P” (positive) and semiconductor type “N” (negative).
N-type semiconductor made of silicon crystals and there are also some other materials (typically phosphorus) within the limits that these materials can provide an excess of free electrons.
Electrons are sub atomic particles are negatively charged, so that the silicon alloy in this case known as N-type semiconductor (Negative). P-type semiconductor made of silicon crystal in which there is a small amount of other material (typically boron) which caused the shortage of material free electrons. Lack or loss of electrons is called a hole. Because there is no or lack of electrons electrically negative charged then the silicon alloys in this case as a semiconductor type-P (Positive).
Composition of a solar cell, the same as a diode, consisting of two layers, called PN junction. PN junction obtained by staining a pure semiconductor silicon (valence 4) with the impurity valence 3 on the left side, and one on the right impurity stained with valence 5.
The effect of the electric field in a PV cell
Operation of a PV cell
Basic structure of a generic silicon PV cell
Thus formed on the left side that is not pure silicon again and called P type silicon, while the right side is called silicon type N. In the pure silicon there are two kinds of electrical charge carriers are balanced. Positive electric charge carriers called holes, while the negative are called electrons. After a desecration process, in the P type silicon formed holes (positive charge carriers) in a very large number compared with the electron. Therefore, in the P type silicon holes are majority charge carriers, while the electrons are minority carriers. Conversely, in the N type silicon is formed of electrons in a very large number so-called majority carriers, and holes called minority carriers.
In the silicon rod there was interaction between the P and the N. Therefore called the PN junction. When present, the P associated with the positive pole of a battery, while the negative polar associated with the N, then there is a relationship called “forward bias”.
Under forward bias, electrical currents arise in a series due to both types of charge carriers. So the electric current flowing in the PN junction is caused by the movement of electron and the movement of holes. An electric current is flowing in the direction of holes movement, but opposite direction with the movement of electrons. Just to further explain, electrons moving in the conductor material can lead to electrical energy. And electrical energy is called as an electric current that flows in the opposite direction to the movement of electrons.
But, if the P associated with negative pole of batteries and the N associated with positive pole, then now formed a relationship called “reverse bias”. In these circumstances, the hole (positive charge carriers) can be connected directly to the positive pole, while the electrons are also directly to the positive pole. So, clearly in the PN junction there is no movement of majority charge carriers either the holes or electrons. Meanwhile, the minority charge carriers (electrons) in the part P moves trying to reach the positive pole of the batteries. Similarly, the minority charge carriers (holes) in the N also moved to reach the negative pole. Therefore, in a state of reverse bias, in the PN junction there is also output current even in very small amounts (micro amperes). This current is often called the reverse saturation current or leakage current.
.
Anything interesting in reverse bias. When the temperature of PN junction raised they will be able to enlarge leakage current. Means that if given the energy (heat), the minority charge carriers in the PN junction grows. Because the light is one form of energy, so if there is light that hit a PN junction may also produce enough energy to generate charge carriers. This symptoms are called photoconductive. Based on the photoconductive symptoms made of photodiode electronic components from PN junction.
In reverse bias, with increasing intensity of light that hit photodiode can increase the level of leakage current. Leakage currents can also be enlarged by increasing the battery voltage (reverse voltage), but the addition of leakage currents were not significant. When the batteries in the reverse bias circuit is removed and replaced with a load of resistance, the provision of light that can cause charge carriers both holes and electrons. If the illumination light is increased, current output was greater. Such symptoms are called photovoltaic. Light can provide enough energy to enlarge the number of holes in the P and the number of electrons on the N. Based on the symptoms of this photovoltaic electronic components can be created photovoltaic cell. Because usually the sun as a source of light, the photovoltaic cell is also called the solar cell (solar cells) or a solar energy converter.
So the solar cell is essentially a large photo diode and designed by referring to the photovoltaic symptoms so that could produce the greatest possible power. P type silicon is the very thin surface layer so that light can penetrate directly reach the junction. Part P is given ring-shaped nickel layer, as a positive output terminal. Under the P is the N type that is coated with nickel as well as the negative output terminal.
To obtain a large enough power required much of solar cells. Usually, solar cells arranged form the shape of the panel, and is called the photovoltaic panels (PV). PV as a source of electric power was first used in satellites. Then PV as an energy source for cars, so there are solar electric car. Now, in foreign countries, PV has started to be used as a roof or wall of the house. Sanyo has made even a semi-transparent PV that can be used as a substitute for glass.
After getting the output of the solar cell is a direct electrical current can be used to load utilized. But also the electric current can be used as a charge stored by the battery to be used when needed, especially at night because there was no sun.
If the solar cell is used for storage into the battery, then the resulting voltage magnitude must be above the battery specification. For example the battery used is 12 volts, the voltage produced by solar cell must be above 12 volts in order to perform charging.
We recommend that before carrying out the charging battery should be empty because the incoming flow will be filled with the maximum. The unit capacity of a battery is the Ampere-hour (Ah) and these characteristics are usually found on the label of a battery. For example a battery with 10 Ah capacity will fill up for 10 hours with the solar cell output currents of 1 Ampere.
In general, energy sources are categorized into two parts namely non-renewable energy and renewable energy. Fossil energy sources are among the first group that the bulk of activity in the world using these conventional energy.
It is no doubt that the solar photovoltaic is one source of environmentally friendly energy and is very promising in the future, because there is no pollution produced during the process of energy conversion, and more widely available source of energy in nature, namely the sun.
Fundamental issues in solar cell technology is a very low efficiency in turning solar energy into electrical energy, which to date the highest efficiency can be achieved no more than 20%, and even then in a laboratory scale.
For that in developed countries, research on solar cell is a very big concern, especially with the issue of environmental clean.
From light into electricity
In a simple solar photovoltaic consists of the p-type and n junction semiconductor material (pn junction semiconductor) that if by the sun there will be a flow of electrons, electron flow is well known as the electric current flow. While the structure of the solar cell is as shown in Figure 1.
Figure 1. Structure of a thin layer of solar photovoltaic in general
The main part of the energy changes of sunlight to electricity is the absorber, however, each layer is also very influential on the efficiency of the solar cell. Sunlight consists of various types of electromagnetic waves in a spectrum can be seen in figure 2. Therefore here absorber is expected to absorb as much solar radiation derived from sunlight.
Figure 2. The spectrum of solar radiation
More detail can be explained that the sun consists of a photon-photon, if it happen to solar cell surface material (absorber), will be absorbed, reflected or simply passed (see Figure 3), and only photons with certain energy level that will liberate electrons from atomic bonds, so that electrical current flows. Energy levels is called band-gap energy which is defined as the amount of energy required to discharge electrons out of its covalent bond so that there electric current flow. To free electron from its covalent bond, photon energy (hc/v) must be slightly larger or above than the band-gap energy. If the photon energy is too much of the energy band-gap, then the extra energy will be converted in the form of heat in a solar cell. Therefore it is important to the solar cell to regulate the materials used, namely by modifying the molecular structure of the semiconductor used.
Figure 3. Radiative transition of solar photovoltaic
Of course, that the efficiency of solar cell can be high if the photons from sunlight to be absorbed that as much, then reduce reflection and increase recombination and conductivity of the material.
To be able to make that a photon is absorbed can be as much, then the absorber must have an energy band-gap with a wide range, making it possible to absorb sunlight so energy has a variety of these. One of the many materials being studied are known CuInSe2 is one of the direct semiconductor.
So many advantages of solar photovoltaic as described above was not a polemic and not just stop, saying there was a solar photovoltaic is true when the energy change process there is no pollution produced, but have we calculated how much pollution has been generated in the process manufacturing, small compared to the resulting efficiency. Now the challenge here is indeed how to increase efficiency, which would affect its economic value.
Article You May Be Interested In Reading: Solar Electric
