Researchers from the University of Michigan managed to achieve complete transparency of solar panels. This achievement makes it possible to convert any window or screen surfaces (like your smartphone) into a solar PV cell. Unlike previous designs that were previously reported, this battery option is almost completely transparent, as can be seen from the photo above.
Research leader Richard Lunt said that there is confidence that such solar panels can actually be used in a very wide range: from high-rise windows to screens of mobile devices such as a telephone or an e-book.
Scientifically, a transparent solar panel is a bit of an oxymoron. Solar cells, which operate on the principle of the photoelectric effect, absorb photons (sunlight), then convert them into electrons (electricity). But if the material you see is transparent, it means that the sunlight was not absorbed, but passed through it, reaching the retina of your eye. It was this moment that the developers could not get around before, trying to create completely transparent solar panels. They (the batteries) were partially transparent, and on top of that, they usually had rainbow stains.
To solve this problem, researchers at the University of Michigan used a slightly different technology for "collecting" the sun's rays.
Having abandoned attempts to create a completely transparent photovoltaic cell (which is almost impossible), they used a so-called transparent luminescent solar concentrator (TLSC)
TLSC is a material consisting of organic salts that absorbs ultraviolet and infrared radiation invisible to the eye, which then converts into infrared waves of a certain length (also invisible to the eyes). The received infrared radiation is directed to the edges of the plate, where thin strips of photovoltaic solar cells, already of normal operation, convert it into electricity.
If you look closely, you will see black stripes on the cut of the plastic sheet. Thus, due to the organic material making up the majority of the solar panel, it is highly transparent.
Today, the efficiency of Michigan TLSC plastic is 1%. However, according to scientists, it is likely that it can be increased to 5%.
Similar opaque fluorescent concentrators (which fill the room with rainbow light) have a maximum efficiency of 7%. By themselves, these numbers are not huge or impressive, but on a large scale - for example, when used in every window of a home or office, the number increases rapidly.
In addition, until a technology is created that supports the uninterrupted operation of your smartphone or phone for an indefinite period, replacing the device display with a screen made from TLSC can increase its battery life by several minutes or hours without recharging.
The developers are confident that the technology can be widely used: from global industrial scale to consumer household level. Until now, one of the biggest obstacles to the widespread use of solar panels has been their bulkiness and unaestheticness. Obviously, if it becomes possible to convert sunlight into electricity using sheets of glass or plastic, no different from ordinary ones, the use of such solar panels will be versatile.
Windows let light into the house, and with it the sun's heat. There are many technologies for passively dimming windows to reduce or increase the amount of heat supplied. But this is heat, in fact, energy that can theoretically be converted into electricity. Scientists at the US Department of Energy have developed a transparent solar film that will turn windows into green electricity generators.
It is clear that for the most efficient use of solar energy, the collectors should be located in places of direct contact with the sun's rays. Until now, only the roofs of houses were considered as such. The new development will expand the use of solar technologies also on the surface of windows.
A joint development by scientists at Brookhaven National Laboratory and Los Alamos National Laboratory, it is a transparent thin film that can absorb light and generate an electrical charge. The material, described in Chemistry of Materials, could be used to create transparent solar panels or even windows that absorb solar energy and generate electricity.
The new material consists of semiconducting polymers with the addition of fullerenes - molecules consisting of six carbon atoms. With exact observance of the conditions of the technological process, the material is independently structured, creating a repeating pattern of micron-sized hexagonal cells on a relatively large (several millimeters) area (a structure originally characteristic of fullerenes).
“Such thin honeycomb films have already been created from common polymers like polystyrene, but our material combines semiconductors and fullerenes for the first time, which enables it to absorb light and efficiently generate and separate electrical charges,” said Mircea Cutlet, a physicist at the Brookhaven Center. functional nanomaterials (CFN).
In addition, the material remains practically transparent, since when fullerenes are added, the polymer chains line up along the edge of micron hexagons, and their layer in the center remains loose and very thin. As Cutlet explains, the denser edges of the hexagons absorb light more strongly and can facilitate conduction of electricity, while their central part is relatively transparent and therefore absorbs very little light.
"The combination of these features to achieve large-scale structuring will enable practical applications of the technology, for example, to create energy-generating solar windows, transparent solar panels or new types of displays," said Zhihua Xu, a materials scientist at CFN.
To obtain a solar honeycomb film, scientists passed a stream of tiny (micron) water droplets through a thin layer of a mixed solution of polymer and fullerene. In the polymer solution, these water droplets self-assembled into large matrices. After complete evaporation of the solvent, the polymer took the form of a hexagonal honeycomb lattice of a rather large area. According to the developers, this method is effective enough to be applied not only in laboratory conditions, but also on an industrial scale.
Scientists have tested the uniformity of the honeycomb structure using various scanning methods and electron microscopy, and also tested the optical properties and charge formation efficiency on different parts of the honeycomb structure (at the edges, in the center of the cells, at the intersection of individual cells) using time-controlled confocal fluorescence microscopy ...
It turned out that the degree of compaction of the polymer is determined by the rate of evaporation of the solvent, which, in turn, affects the rate of charge transfer through the material. The slower the solvent evaporates, the denser the polymer is and the better the charge transfer.
“Our work has allowed a deeper understanding of the optical properties of the honeycomb structure. The next step is to use these thin honeycomb films to make transparent, flexible and environmentally friendly solar cells and other devices, ”concluded Mircea Cutlet.
Researchers from Michigan State University, which in doing so converts sunlight into electricity. Compared to previous conventionally transparent materials, this one really looks like glass. In the future, it will be possible to put it instead of glass in the window of a residential building and receive additional free energy, or turn it into a smartphone / tablet screen so that it recharges on its own.
Of course, a solar panel needs to capture photons to generate electricity, which will generate energy. This means that it cannot be completely transparent. Therefore, previous versions of such materials were translucent. What's the catch?
The new material uses "solar concentrator" technology. The organic salts it contains absorb invisible (ultraviolet and infrared) radiation. Once inside the panel, all radiation goes into the infrared range. This radiation, reflected from the planes of the panel from the inside, penetrates to its edges. There he is met by narrow strips of ordinary photovoltaic panels, which absorb light and release energy.
So far, the energy harvesting efficiency of the test panels is 1%. Scientists believe that this figure can be increased to 5%. The maximum efficiency for opaque solar concentrators is 7%. Of course, this is very small in comparison with modern solar panels, in which the efficiency of serial samples reaches 25%, and in laboratories it reaches 50%. But transparent energy converters can be installed in homes instead of conventional glass. If you imagine a whole skyscraper, in which the entire surface processes energy, then the resulting number will already be quite impressive.
More recently, innovative developments have begun to appear on the solar energy market, which involve the use of window panes as solar panels. This is a very promising technology that can find application not only in urban high-rises, but also in many other industries. That said, many companies are working on the ability to convert windows to battery windows.
Some suggest installing thin strips of silicon photocells directly between glass panes in double-glazed windows. In appearance, such battery windows resemble open blinds, as a result they do not block the view from the window. Others suggest using glass with a special translucent coating for windows. Such a layer is active, it converts light radiation into electrical energy, accumulating in special semitransparent conductors. Others suggest sticking a film on glass that has the properties .
Device
Battery windows are currently available in two types: flexible substrates and glass substrates. But there are other developments as well.
- Flexible options resemble tint film, they are glued to transparent structures (facade glazing panels, windows, and so on). Their light transmittance is about 70%, which actually does not reduce the level of illumination of the room. They are made from a flexible composite material that is similar to plastic.
- The second option for transparent panels involves applying a two-layer film to tempered glass. A thin film of amorphous silicon is applied to a tempered glass substrate (in some cases, triplex). A transparent silicon microfilm is deposited on top of it. Microfilm converts infrared rays, while amorphous silicon converts the visible spectrum.
- A number of companies have decided not to create a fully transparent photovoltaic cell. Instead, they decided to take TLSC, which is a transparent fluorescent solar concentrator. TLSC-material consists of organic salts, it absorbs infrared and ultraviolet radiation invisible to the eye, as a result it is converted into infrared waves of a certain length (they are also invisible). This infrared radiation goes to the edges of the plate where thin strips of photovoltaic solar cells are installed.
- The latest development of scientists is a completely transparent material that, when absorbed by sunlight, can generate its electricity. The material is a semiconducting polymer film saturated with fullerene carbon "balls". The uniqueness of this material is that under certain conditions it forms an ordered structure that resembles a honeycomb when zooming in multiple times.
Operating principle
- Window transparencies contain an active luminescent layer. Small organic molecules absorb specific wavelengths of sunlight. At the same time, it is possible to customize the structure for certain wavelengths. So these materials can only absorb ultraviolet and near-infrared rays, in order to subsequently "highlight" a different wavelength in the infrared range.
- "Glowing" infrared light can be converted into electricity using thin strips of photovoltaic solar cells. Due to the fact that these materials do not emit or absorb light in the visible spectrum, they look absolutely transparent to the human eye.
- A completely new approach to creating a battery window is demonstrated by the technology of creating a material that creates an electric current when it is irradiated. It happens like this:
Microscopic water droplets are directed through a thin layer of material that is in a liquid state.
As the polymer cools, the droplets are evenly distributed over the surface and evaporate.
As a result, a texture of hexagons is created, their density is determined by the rate of evaporation and determines the efficiency of charge transfer. In other words, the tighter the packaging, the more efficient the material.
The polymer strands are spread over the faces of the hexagons. At the same time, they remain empty, and the material itself looks almost completely transparent. However, the tightly packed filaments along the edges are excellent at absorbing sunlight and also conducting electrical current, which is also generated when the material is exposed to sunlight.
Features:
- The main feature of the already created panels is the use of the invisible spectrum of the sun's rays, that is, its ultraviolet and infrared parts.
- Absorption and "processing" of infrared radiation allows to achieve an important advantage - minimization of thermal effects. This is extremely important for countries with hot climates. It is the IR spectrum of the rays that leads to heating of surfaces and the need to cool them. The transparent solar panels absorb infrared rays without heating up. As a result, you can minimize the cost of cooling systems.
- At the moment, the mastered technologies of transparent solar cells demonstrate low efficiency. But with the improvement of technology, efficiency will increase. Even low productivity will pay off with the absence of the need to find an installation site and ease of installation. A significant area of \u200b\u200bglass structures that are virtually of no practical use will generate a significant amount of electricity.
Advantages and disadvantages
The advantages include:
- Ease of use, there is no need to look for additional space for deploying batteries, because they themselves are placed in the glass. They don't take up space.
- Ease of installation.
- Environmental friendliness.
- "Electric glass" takes away part of the light energy, as a result of which buildings heat up less. This reduces the cost of ventilation and air conditioning. This is especially true in countries with sunny and hot climates.
- Possibility of wide application.
The disadvantages include:
- Battery windows are imperfect and many of them take away some of the light that must enter the room.
- Low efficiency.
- Low prevalence.
- Lack of sophistication of technologies.
Prospects and application
Battery windows in the near future may well replace conventional glass in:
- Houses and other buildings.
- Electronic devices.
- Cars.
Several companies already produce glass in small quantities for installation in buildings, such as the Japanese corporation Sharp and a number of others. The possibilities of using such an invention are quite extensive, but the effectiveness of the technology at the moment is limited by the imperfection of the technology. Already proven technologies provide only 1%, and more advanced ones - 5-7%.
However, the prospects for transparent solar cells are vast. So, replacing the display of a smartphone or laptop with a new "solar" screen will significantly increase its life without recharging. Cities of the future will be able to turn into green power plants without installing additional equipment - buildings can supply themselves with energy.
As you know, classic solar panels are dark in color, either blue or almost black. Because of this, they often stand out very strongly against the background of the building, introducing a tangible dissonance in its architectural style. In addition, designers have to take into account color features when developing modern energy efficient buildings and small architectural forms. The solution to this problem was found not so long ago: scientists have developed transparent solar panels for facades and glazing systems.
The scope of application of transparent panels is very extensive:
- Glazing of facades;
- Construction of winter gardens;
- Construction of greenhouses and livestock complexes;
- Glazing of pavilions;
- Creation of glass roofs and patios (atriums);
- Glazing of attics and penthouses;
- Creation of various kinds of sun protection systems (over recreation areas, swimming pools, etc.).
The main feature of such panels is the use of the invisible spectrum of the sun's rays, its infrared and ultraviolet parts. At the same time, the absorption and "processing" of infrared radiation has another advantage - the minimization of the thermal effect. The fact is that the overheating of the photo panels, due to which they need additional cooling, is precisely the IR spectrum. Transparent models absorb infrared rays, and they do not heat up the panels themselves. This means that it becomes possible to dispense with cooling systems and reduce the total cost of installing the solar field.
Design nuances
Currently, there are two types of transparent panels: on glass substrates and on flexible substrates. Flexible options resemble tint film and are designed to be glued to transparent structures (windows, facade glazing panels, etc.). Their light transmittance reaches 70%, which does not actually affect the level of illumination of the room. They are made from a flexible composite material similar to plastic. The use of modern developments makes it possible to minimize the costs of producing such films and to make their production cost-effective.
The second option for transparent panels is the application of a two-layer film on a tempered glass base. Such panels are used for the construction of facades. A thin film of the latest generation of amorphous silicon is applied to a tempered glass substrate (often triplex). A transparent silicon microfilm is deposited on top of it. Amorphous silicon converts the visible spectrum, while microfilm converts infrared rays.
Moreover, thanks to the use of special dyes, scientists were able to give transparent facade panels almost any shade. This means that with the help of such batteries, you can create any facade compositions. In addition, developers are actively using organic dyes with photoelectric properties in transparent panels.
This technology allows you to increase the efficiency of the product, while giving it the desired color. The organic dye is supplemented with nanocomponents, placed between two glass substrates, and the joints are filled with glass powder. Then the resulting "sandwich" is baked at temperatures of about 600 ° C. The result is a silicon-free photo panel with an efficiency of about 4%. True, the cost of such products so far exceeds the economic benefit from their mass production.
Performance of transparent panels
Despite a lot of advantages, transparent facade panels also have some disadvantages, which so far prevent their widespread distribution. The main limitation is low productivity. The efficiency of such products is still only slightly more than 1%. However, scientists are actively working to improve power generation and expect to bring the efficiency up to 5% in the near future. This will be enough to start industrial production and the introduction of transparent facade panels.
Low productivity will pay off with ease of installation and the absence of the need to find an additional installation site. Ultimately, the cost of installing such panels will not exceed the cost of placing conventional silicon photocells. A significant area of \u200b\u200bglass structures (which in their usual form, in fact, do not bring any practical benefit) will allow them to generate quite a tangible amount of electricity.
Another promising direction, possible with an increase in efficiency, is the use of such "photo glasses" in the screens of laptops, tablets, smartphones, etc.
