Types and efficiency of solar panels

Sep 9, 2017   //   by admin   //   Knowledge Base  //  No Comments

Solar panels can be differentiated in to following types on the basis of material used-

 

  • Thin Film Modules
  • Silicon Modules
  • Polymer Modules

 

Thin Film Modules –

They connect Thin Film solar cells (TFSC) together to generate electricity. They are third generation solar cells with high productivity with low costs. TFSC is a solar cell that is made by depositing one or more thin layers (thin film) of PV material on a substrate. It is also called a thin film photovoltaic cell (TFPV). They have easy installation process and can be installed on to the roofs either finished or integrated roof covering. These have less weighted in comparison to traditional solar panels. These are usually categorized according to the PV material used:-

 

  1. Thin Film Silicon
  2. Cadmium telluride (CdTe)
  3. Copper indium gallium selenide (CIS or CIGS)
  4. Dye-sensitized solar cell (DSC)

 

They are two types of Thin film modules: –

 

1) Rigid thin modules:-

 

In rigid thin film modules the cell is created over a glass or substrate and the electrical connections are created in a “monolithic integration”. It is then laminated with a transparent sheet or a glass sheet.

 

2) Flexible Thin film modules:-

 

These are produced in the same production line by depositing a layer of photoactive materials on a flexible substrate.

The cells are then assembled into modules and are laminated with a transparent colourless fluoropolymer and polymer suitable for bonding on the back side.

 

 

Crystalline Silicon: –

In these types of cells the core material is crystalline silicon (c-Si). This is later on separated on is separated into numerous categories according to crystallinity and crystal. The advantage of cystalline silicon modules is that their individual parts can be recycled for e.g. glass, plastics and metals by various recycling processes. There are two types of crystalline silicon:-

 

1) Mono crystalline silicon (c-Si): – They are single crystal wafer cells. They aren’t completely square in shape and leave a little gap in the cell. These are more expensive then Polycrystalline Silicon solar cells as they have high silicon levels.

 

2) Polycrystalline Silicon (poly-Si): – They are made up of square ignots (molten silicon). Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient. But the overall construction overcomes the efficiency so they are good for roof mounting.

 

 

Polymer Solar Cell –

It is made up of polymers i.e. large molecules with repeating structural units that produce electricity from sunlight by the PV effect. These include organic solar cells also called plastic solar cells. This technology is comparatively new and is currently being very actively researched by universities, national laboratories, and companies around the world. Compared to silicon-based devices, polymer solar cells are lightweight, disposable and inexpensive to fabricate, flexible, and customizable on the molecular level. They also have lower potential for negative environmental impact. Organic PV’s are made of electron donor and electron acceptor materials instead of semiconductor p-n junctions. The molecules forming the electron donor region of organic PV cells, where excited electron-hole pairs are generated, are conjugated polymers possessed with delocalized π electrons.

 

There are various factors effecting the efficiency of a solar panel:-

 

1) Temperature: –

Though heat is good for solar panel but like other semi-conductors excess of heat can harm the solar panels. For every 1% variation in silicon PV modules the efficiency can reduced up to 0.5% and 0.25% in amorphous cells.

 

2) Mounting and positioning: –

The mounting and positioning of solar panels is an important factor which decides the efficiency of solar panels. An open location always has much access to sunlight then a place with shade.

 

3) Partial Shading: –

The panels are obvious to produce less power when are placed under shade. When the panels are in series even if only one panel is under shade the system will get affected. So, In situations where shading is unavoidable it is advised not to connect the panels in series.

 

4) Materials used: –

The efficiency of solar panels largely depends upon the material used. The silicon modules are efficient then Thin film modules.

 

A solar panel with minimum voltage of 24 V would normally have around 72 consituent solar cells, resulting into current upto 28.8 volts. If the voltage exceeds this limit current drops off rapidly , resulting in Maximum power output.

When the panel is connected to the battery with charge controller, the battery will attract the volatge. It results into low efficiency of panels until the battery is fully charged. To reduce these defects the panels use MPPT technology which maintains optimum voltage supply in the system.

 

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