18 Steps To Make A Perfect Solar Panels - SKengineers

 

HOW SOLAR PANELS ARE MADE?

We all know by now, that a solar panel is a device that absorbs sunlight and converts this energy into usable electricity. As the price of a solar panel goes down and efficiencies improve, it is attracting masses all over the world to go off the grid. Once you incur the cost of a solar system and its installation, you can practically generate free electricity over the next 25-30 years. But how is this solar panel made, what materials are involved, how different parts are put together to result in a device that is capable of providing you with free electricity?

Are you curious about how a solar panel is made? What processes are involved to get to the final product? Well, for all those who are seeking answers to these questions, you have come to the perfect place. Today we are going to take you inside Loom Solar’s factory at Sonipat, Haryana, where we meet Mr. Anoop - Engineer, who will take us through all these processes in a step by step manner. There are a total of 20-25 machines which involves about 18 steps to finally make a complete solar panel. So let’s see how a solar panel is made. These steps are other than the Incoming Quality Check (IQC) and Final Quality Assurance (FQA).

18 STEPS TO MAKE SOLAR PANELS -

Step 1: Cell Cutting -

Solar Cell cutting process in manufacturing plant -

Using a laser cutting machine, cells are cut out. Depending upon the wattage of the panels you want, the size of a cell is determined. For a full cell size modules, this process is skipped.

Step 2: Stringing Process -

Solar Stringing process in manufacturing plant -

It is a fully automated process. Here at Loom Solar, we are using any cell of size greater than 39 mm. These cells are then assembled or soldered together. The upper Sun facing Side (Blue / Black side) is the negative part while the bottom white side is positive.

Step 3: Solar Glass -

Solar Glass process in manufacturing plant -

Once the cells are stringed together, the machine transfers it to tempered glass, which already having ethylene vinyl acetate (EVA) encapsulation layer over it.

Step 4: Visual Inspection -

Solar Visual Inspection process in manufacturing plant -

The cells are examined by a technician for any fault or error in any string.

Step 5: Taping -

Solar Taping process in manufacturing plant -

In taping, a technician tapes the cells into a matrix alignment.

Step 6: Connection -

Solar Connection process in manufacturing plant -

Connections are then soldered together. Any excess material is cut out.

Step 7: Insulate Module Connection -

Solar Insulate Model Connection in manufacturing plant -

The next step consists of insulating the connections by using a back sheet and EVA encapsulation. This process protects the module from any dust and moisture.

Step 8: Mirror Observation -

Solar Mirror Observation process in manufacturing plant -

The module is visually checked once again for any dust particle, colour mismatch, etc.

Step 9: EI Testing -

Solar EL Testing process in manufacturing plant -

EI Testing or Electroluminescence test is the real testing of the module made so far. It is a testing process, where the module is kind of scanned in an EI machine. We can easily spot any dead or low power cell, short circuit cells, cracks, etc. If any such error is spotted, the module is sent back for fixing the error.

Step 10: Lamination Process -

Solar Lamination process in manufacturing plant -

The module is laminated at 140-degree Celsius. This process takes approximately 20 minutes. After lamination, the modules are left for 10-15 minutes to cool down till it reaches room temperature.

Step 11: Trimming Backsheet -

Solar Trimming Backsheet process in manufacturing plant -

This step involves cutting off the excess material of the back sheet to make perfectly shaped modules.

Step 12: Frame Cutting -

Solar Frame Cutting process in manufacturing plant -

In this step, frames of different sizes are cut out for bordering the panels.

Step 13: Frame Punching -

Solar Frame Punching process in manufacturing plant -

Then holes are punched in the frames for the purpose of mounting and grounding the panels.

Step 14: Sealant Filling / Framing -

 Sealent Filling -

A sealant protects the panels from air, dust, and moisture and helps the module to firmly attach on the frame. After the frame is attached to the module it is again sent to the framing machine, where it is punched to make sure it is permanently attached to the frame.

Step 15: Fixing Junction box -

Solar Fixing Junction Box process in manufacturing plant -

A junction box is attached to the module using the sealant to firmly attach it to the structure. Connections are then soldered and left for 10-12 hours for curing, so that the structures are perfectly dry and attached properly.

Step 16: Clean Module -

Solar Clean Module process in manufacturing plant -

The module is then wiped outside to remove any traces of dust, foreign particles or extra sealant.

Step 17: Module Testing -

Solar Module Testing process in manufacturing plant -

The module is connected to check its output current, voltage, power, etc. A report is generated for each module’s output data. A back label (with all details) is pasted behind the module for the benefit of the users. Finally, the module is sent to the QC lab where it is tested for insulation resistance. A 3000 V DC is passed through it for a minute. If the panel can endure the current, it is passed else failed. Then it is sent to Mechanical Load Test.

Step 18: Packing -

Solar Packing process in manufacturing plant -

After Final Quality Assurance (FQA), this is the last step in the module manufacturing process, where the modules are safely packed into large boxes for transportation and storage.

The Manufacturing -

Process -

Purifying the silicon -

1 The silicon dioxide of either quartzite gravel or crushed quartz is placed into an electric arc furnace. A carbon arc is then applied to release the oxygen. The products are carbon dioxide and molten silicon. This simple process yields silicon with one percent impurity, useful in many industries but not the solar cell industry.

2 The 99 percent pure silicon is purified even further using the floating zone technique. A rod of impure silicon is passed through a heated zone several times in the same direction. This procedure "drags" the impurities toward one end with each pass. At a specific point, the silicon is deemed pure, and the impure end is removed.

Making single crystal silicon

3 Solar cells are made from silicon boules, polycrystalline structures that have the atomic structure of a single crystal. The most commonly used process for creating the boule is called the Czochralski method. In this process, a seed crystal of silicon is dipped into melted polycrystalline silicon. As the seed crystal is withdrawn and rotated, a cylindrical ingot or "boule" of silicon is formed. The ingot withdrawn is unusually pure, because impurities tend to remain in the liquid.

Making silicon wafers -

4 From the boule, silicon wafers are sliced one at a time using a circular saw whose inner diameter cuts into the rod, or many at once with a multiwire saw. (A diamond saw produces cuts that are as wide as the wafer—. 5 milimeter thick.) Only about one-half of the silicon is lost from the boule to the finished circular wafer—more if the wafer is then cut to be rectangular or hexagonal. Rectangular or hexagonal wafers are sometimes used in solar cells because they can be fitted together perfectly, thereby utilizing all available space on the front surface of the solar cell. After the initial purification, the silicon is further refined in a floating zone process. In this process, a silicon rod is passed through a heated zone several times, which serves to 'drag" the impurities toward one end of the rod. The impure end can then be removed. Next, a silicon seed crystal is put into a Czochralski growth apparatus, where it is dipped into melted polycrystalline silicon. The seed crystal rotates as it is withdrawn, forming a cylindrical ingot of very pure silicon. Wafers are then sliced out of the ingot.

After the initial purification, the silicon is further refined in a floating zone process. In this process, a silicon rod is passed through a heated zone several times, which serves to 'drag" the impurities toward one end of the rod. The impure end can then be removed.

Next, a silicon seed crystal is put into a Czochralski growth apparatus, where it is dipped into melted polycrystalline silicon. The seed crystal rotates as it is withdrawn, forming a cylindrical ingot of very pure silicon. Wafers are then sliced out of the ingot.

5 The wafers are then polished to remove saw marks. (It has recently been found that rougher cells absorb light more effectively, therefore some manufacturers have chosen not to polish the wafer.)

Doping -

6 The traditional way of doping (adding impurities to) silicon wafers with boron and phosphorous is to introduce a small amount of boron during the Czochralski process in step #3 above. The wafers are then sealed back to back and placed in a furnace to be heated to slightly below the melting point of silicon (2,570 degrees Fahrenheit or 1,410 degrees Celsius) in the presence of phosphorous gas. The phosphorous atoms "burrow" into the silicon, which is more porous because it is close to becoming a liquid. The temperature and time given to the process is carefully controlled to ensure a uniform junction of proper depth.

A more recent way of doping silicon with phosphorous is to use a small particle accelerator to shoot phosphorous ions into the ingot. By controlling the speed of the ions, it is possible to control their penetrating depth. This new process, however, has generally not been accepted by commercial manufacturers.

 Placing electrical contacts -

7 Electrical contacts connect each solar cell to another and to the receiver of produced current. The contacts must be very thin (at least in the front) so as not to block sunlight to the cell. Metals such as palladium/silver, nickel, or copper are vacuum-evaporated This illustration shows the makeup of a typical solar cell. The cells are encapsulated in ethylene vinyl acetate and placed in a metal frame that has a mylar backsheet and glass cover.

This illustration shows the makeup of a typical solar cell. The cells are encapsulated in ethylene vinyl acetate and placed in a metal frame that has a mylar backsheet and glass cover.

through a photoresist, silkscreened, or merely deposited on the exposed portion of cells that have been partially covered with wax. All three methods involve a system in which the part of the cell on which a contact is not desired is protected, while the rest of the cell is exposed to the metal.

8 After the contacts are in place, thin strips ("fingers") are placed between cells. The most commonly used strips are tin-coated copper.

The anti-reflective coating -

9 Because pure silicon is shiny, it can reflect up to 35 percent of the sunlight. To reduce the amount of sunlight lost, an anti-reflective coating is put on the silicon wafer. The most commonly used coatings are titanium dioxide and silicon oxide, though others are used. The material used for coating is either heated until its molecules boil off and travel to the silicon and condense, or the material undergoes sputtering. In this process, a high voltage knocks molecules off the material and deposits them onto the silicon at the opposite electrode. Yet another method is to allow the silicon itself to react with oxygen- or nitrogen-containing gases to form silicon dioxide or silicon nitride. Commercial solar cell manufacturers use silicon nitride.

Encapsulating the cell -

10 The finished solar cells are then encapsulated; that is, sealed into silicon rubber or ethylene vinyl acetate. The encapsulated solar cells are then placed into an aluminium frame that has a mylar or tedlar backsheet and a glass or plastic cover.

Conclusion -

Its 1 kW Solar AC module is capable of generating enough power to comfortably run one air conditioner (up to 1.5 ton), along with refrigerator, TV, fans and lights during the day for 2-3 bhk house, hospital, office, petrol pump, educational institution, etc.