Tag Archives: EVA sheeting

How Do Solar Cells Work?

Power Grid, Solar Energy, , , , , ,
In the last two decades, the contribution of solar energy to the world’s total energy supply has grown significantly. This video will show how a solar cell or photovoltaic cell produces electricity. Energy from the Sun is the most abundant and absolutely freely available energy on planet earth.

In order to utilize this energy, we need help from the second most abundant element on earth sand. The sand has to be converted to 99.999 % pure silicon crystals, to use in solar cells. To achieve this, the sand has to go through a complex purification process as shown.

The raw silicon gets converted into a gaseous silicon compound form. This is then mixed with hydrogen to get highly purified Polycrystalline silicon. These silicon ingots are reshaped and converted into very thin slices called silicon wafers.

The silicon wafer is the heart of a photovoltaic cell. When we analyze the structure of the silicon atoms, you can see they are bonded together. When you are bonded with someone, you lose your freedom.

Similarly, the electrons in the silicon structure also have no freedom of movement. To make the study easier, let’s consider a 2d structure of the silicon crystals. Assume that phosphorus atoms with five valence electrons are injected into it.

Here, one electron is free to move. In this structure. When the electrons get sufficient energy, they will move freely. Let’s try to make a highly simplified solar cell only using this type of material.

When light strikes them, the electrons will gain photon energy and will be free to move.. However, this movement of the electrons is random. It does not result in any current through the load. To make the electron flow unidirectional, a driving force is needed. An easy and practical way to produce the driving force is a PN junction. Let’s see how a PN Junction produces the driving force. Similar to n-type doping, if you inject boron with three valence electrons into pure silicon, there will be one hole for each atom.

This is called p-type doping. If these two kinds of doped materials join together, some electrons from the N side will migrate to the P region and fill the holes available. There. This way, a depletion region is formed where there are no free, electrons and holes.

Due to the electron migration, the N-side boundary becomes slightly positively charged. And the P side becomes negatively charged. An electric field will definitely be formed between these charges.

This electric field produces the necessary driving force. Let’s see it in detail. When the light strikes the PN Junction, something very interesting happens. Light strikes the N region of the PV cell and it penetrates and reaches up to the depletion region. This photon energy is sufficient to generate electron hole pairs in the depletion region. The electric field in the depletion region drives the electrons and holes out of the depletion region.

Here we observe that the concentration of electrons in the N region and holes in the P region become so high that a potential difference will develop between them. As soon as we connect any load between these regions, electrons will start flowing through the load.

The electrons will recombine with the holes in the P region after completing their path.. In this way, a solar cell continuously gives direct current. In a practical solar cell you can see that the top N layer is very thin and heavily doped, whereas the P layer is thick and lightly doped. This is to increase the performance of the cell. Just observe the depletion region formation here. You should note that the thickness of the depletion region is much higher here compared to the previous case.

This means that, due to the light striking the electron hole, pairs are generated in a wider area compared to the previous case. This results in more current generation by the PV cell. The other advantage is that, due to the thin top layer, more light energy can reach the depletion region.

Now, let’s analyze the structure of a solar panel. You can see the solar panel has different layers. One of them is a layer of cells. You will be amazed to see how these PV cells are interconnected. After passing, through the fingers, the electrons get collected in busbars. The top negative side of this cell is connected to the back side of the next cell through copper strips. Here it forms a series connection.

When you connect these series connected cells, parallel to another cell series, you get the solar panel. A single PV cell produces only around 0.5 voltage. The combination of series and parallel connection of the cells increases the current and voltage values to a usable range.

The layer of EVA sheeting on both sides of the cells is to protect them from shocks, vibrations, humidity and dirt. Why are there two different kinds of appearances for the solar panels? This is because of the difference in the internal crystalline lattice structure.

In polycrystalline solar panels, multi crystals are randomly oriented. If the chemical process of silicon crystals is taken one step further, the polycrystalline cells will become monocrystalline cells.

Even though the principles of operation of both are the same. Monocrystalline cells offer higher electrical conductivity. However, monocrystalline cells are costlier and thus not widely used. Even though running costs of PV cells are negligible.

The total global energy contribution of solar voltaic is only 1.3 percent. This is mainly because of the capital costs and the efficiency constraints of solar voltaic panels which do not match conventional energy.

Options. Solar panels on the roofs of homes have the option to store electricity with the help of batteries and solar charge controllers. However, in the case of a solar power plant, the massive amount of storage required is not possible.

So generally, they are connected to the electrical grid system in the same way that other conventional power plant outputs are connected. With the help of power. Inverters DC is converted to AC and fed to the grid.

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Source : Youtube

How Solar Panels Are Made

Clean Energy, Solar Energy, Solar Equipment, , , , , ,
Gigawatts upon gigawatts of clean, green  solar capacity is being churned out by high-tech factories all around the world.  But how are solar panels actually made? Join us now on a sun-seeking sojourn as  we look inside a solar panel factory.

Last month the Indian government announced it had  reached the psychologically important milestone of 100 gigawatts in nationwide renewable energy  capacity. India, eager to develop its renewable infrastructure, may yet reach its ambitious target  of 175 gigawatts on-stream in the year 2022, and 450 GW overall renewable energy  capacity by the close of this decade.

To do that, Indians will need to make solar panels. Lots of them. Vikram Solar is one of a few big players in the field vying for a slice of this lucrative growing market.   And Vikram recently expanded its  own capacity by a not-insignificant 1.3GW through the opening of its new 130,000  square feet plant in Oragadam, Tamil Nadu. So let’s see what goes down inside. Solar panels, also called solar modules, are  made up of a number of individual solar cells.

These cells can trace their origins back to simple silica sand, from which silicon is extracted.   Silicon is the second-most-abundant element  found in the earth’s crust by the way. So we’re not likely to run out any time soon.

Cooked at 2,000 degrees Celsius in a furnace along  with a source of carbon, the raw element is then cooled to create metallurgical grade silicon.  This is usually liquified again in order to   remove remaining impurities.

It’s then blended  with a pinch of boron and a dash of phosphorus, molded into ingots then sliced into  tiny wafers less than 0.2mm thick. These wafers are then coated with silicon nitride  and roughed up a bit to create texture and reduce reflectivity – any light that bounces off a solar panel is wasted, of course.

A silver paste is then applied to the front and rear surface and, pretty much, that’s your solar cell. At Vikram Solar’s new Tamil Nadu facility,  these incoming cells are visually inspected to find any obvious cracks or breakages.

Cracks in the solar cells render them useless for large modular applications like solar panels. But more  often than not, smaller sections of solar cell can be cut away and used for smaller, less intensive  off-grid applications, like solar powered toys.

After this manual visual inspection,  the first of several tests under blasts of artificial sunlight, to  check they work, is undertaken. Then a hydraulic conveyor system  introduces a layer of EVA – that stands for Ethylene-vinyl acetate – to a flat  pane of tempered glass.

This EVA layer serves as an adhesive to hold fast the rows of solar cells that are automatically laid on the pane in a careful tile pattern, by this six-axis  robot arm that can move 12 cells at once.

The cells are connected to each other, and ultimately the grid, via a criss-cross pattern of narrow metal ‘fingers’ and fatter ‘busbars’  . These carry electrons generated from the   activated cells to the tab wires and beyond,  to whatever the panel will ultimately power.

Engineers looking to maximize efficiency of solar cells have debated whether its better having more busbars – conventional wisdom says 5 is a good  upper limit – because resistance is lowered, although the additional hardware inevitably shades parts of the solar cell.

More fingers and busbars can also mitigate the  risk of micro cracks appearing in the cell, or at least prevent cracks  spreading too far across the cell. Once all the cells are in place, another  layer of EVA is laid over the panel and an additional backsheet is added to  encapsulate the cells and internal wiring.

The next stage is called  ‘pre-lamination electroluminescence’.   Exploiting one curious property of photovoltaic cells – that they light up whenever a current is passed through them – inspectors can look  even closer for microcracks that might render the final panel inefficient or at worse useless.

All they need to do is identify the dark spots. These microcracks, incidentally, can  creep in at any stage of the process. Silicon wafers are notoriously brittle, and  mishaps during the manufacturing or transportation phase are common.

Wild fluctuations in ambient  temperature can also cause irreversible damage. After this pre-lamination electroluminescence  phase comes – you guessed it – lamination. An industrial laminator applies heat and vacuum  pressure to the ‘sandwich’ of glass, EVA, solar cells and wires, bonding everything together in a taut, weatherproof panel.

Following this stage, circuit ribbons are attached to the edges,  and an aluminum frame placed around the edge. This aluminum frame offers the panel sturdiness,  which helps prevent nasty cracks.

These frames also make the panels much easier to handle and  store, as well as offering some resistance to the day-to-day mechanical loads the panel will be subjected to, like heavy snow or gale-force winds.

Another electroluminescence test follows, and the installation of a so-called ‘junction box’ on the backside of  the module using strong silicone adhesive. This junction box serves not only as the collector  of electricity, but its diodes ensure power only ever flows in one direction.

This is important,  because solar panels by their very nature generate differing and unpredictable amounts  of electricity throughout their working lives. Final testing looks for weaknesses in the panel’s weatherproofing.

Next, the completed panel is subjected to a final blast of artificial  sunlight. And now our panel is ready to ship. Vikram Solar’s shiny new Tamil Nadu facility is part of a wider drive within India to achieve what prime minister Narendra Modi has  called his ‘Atmanirbhar Bharat’ initiative.

This translates, pretty much,  to ‘self-reliant India’,  the idea being to wean the subcontinent off  of its dependence on foreign expertise and expensive imports. The new plant is all set up  to embrace emerging technologies, for instance using Artificial Intelligence algorithms to spot  microcracks early in the manufacturing process.

As Vikram Solar’s managing director Gyanesh Chaudhary puts it. ‘This is an extension of our  endeavor to provide high quality, reliable, technologically superior products  and timely delivery to our customers.

It will further contribute as an R&D  platform for next-gen module technology’. Talk about sunny optimism. What do you think? Is solar still exciting? Let us know in the comments,   and don’t forget to subscribe for more  utterly illuminating tech content.

Source : Youtube