Summary: Solar panels that you see in rooftops and large solar farms are an assembly of many solar cells.
What is a solar panel? Is it the same as a solar module? And what is the difference between a solar panel and solar cell?
A solar panel is a neat assembly of many solar cells.
A solar cell in itself is too small to generate electric current. A solar panel on the other hand can generate significant amount of electricity – today, solar panels can have capacities up to 300 W, an amount that can produce more than 1 kWh (a unit of power) per day. Arranging cells together in a panel thus makes it possible for a simple placement on rooftop or elsewhere to generate reasonable amounts of electricity.
You might have heard the term “solar module”, and might be wondering how it is related to solar panels. Well, there’s some news for you – they are one and the same! The term solar panel was coined in those days when the solar cells were made only from crystalline silicon. Subsequently, other forms of photovoltaics developed, especially the thin film technology. Owing to the form that it takes, it will be difficult to call an equivalent arrangement of thin film cells as a panel; a better term would be “module”. As a result, today, many prefer to use the term solar module instead of solar panel to refer to an assembly of solar cells.
Parts of a solar panel/module
In a solar panel, or module, it is not enough to place the cells together. A few other components go into the making of a solar module.
The following are the parts of a solar panel, from top to bottom:
- The first layer is glass. A glass covering needs to be provided on top to protect the solar cells from environmental elements.
- Below the glass is a thin plastic sheet, called an encapsulant – Solar cells are sensitive to moisture, oxygen and weather. If not protected, they will degrade with time and loose their ability to produce energy. An encapsulant is used to provide this protection to the solar cells and is placed on the top surface and the rear surface of the cells. The encapsulant material is chosen such that it is stable at elevated temperatures and high UV exposure, and be optically transparent. EVA (ethyl vinyl acetate), a thin transparent film, is the most commonly used encapsulant material.
- Below the EVA encapsulant is the arrangement of solar cells.
- The electrical circuits are built between the cells. This circuit carries the electricity generated by the cells to the outside.
- An encapsulant layer is also present directly below the solar cells, for the same reason as they are present on top.
- A backsheet is provided at the back of the module, under the EVA. The back sheet is needed to protect the solar cells and electrical components from water and hot temperatures. In most modules, a polymer sheet, usually Tedlar, which lowers flammability, is used as the backsheet.
- Finally, a frame is included around the edges of the solar module. This frame is usually made of Aluminium.
Each and every aspect of solar panels needs to be designed with care to increase the efficiency and output. For instance, let’s look at the glass that covers the top of the solar panel. The glass hardly gets a second look, but the type and quality of glass matter a lot. Cheap glass can cloud over time, and clouded glass greatly reduces solar panel efficiency. Glass that breaks easily can allow water to penetrate and create a fire hazard. On the other hand, tempered glass, though not the cheapest in the market, could be the best one to handle the tedious job of serving up 25 long years, rain or shine. Such glass has up to six times the strength of normal plate glass, and could withstand some rather unpleasant accidents that can occur to solar panels.
Questions from the curious cat
- How many cells are there in a module?
There is no standard for this, but typically, you will find 36-40 cells (9 or 10 rows of 4 cells each).
- What is the smallest capacity of a solar panel?
Solar panels can be as small as 2 W. However, when we talk about solar panels typically used on rooftops and in large solar farms, they typically have capacities in the 230-300 W range.
- Is a solar panel the same as solar module?
Yes, solar panel and solar module are one and the same. Either of these two terms can be used.
- Does the solar panel get affected during heavy rains?
Well, no. A high quality solar panel should easily withstand rains for 25 years, and even longer. Some of the components of the solar panel, especially the outer glass and the backsheet, are provided specifically to provide protection from rain and other natural elements.
- How much do solar panels weigh?
The answer depends on the capacity of the solar panel. A 10 W solar panel could weigh about 1.5 Kg, while a large 250 W panel could weigh 18-20 Kg.
- How much area does a solar panel occupy?
The answer depends on the capacity of the solar panel. A 10 W solar panel could measure about 35 cm by 30 cm (about 1000 cm2), while a large 250 W panel could measure 1.5 m in length and 1 m in width (1.5 m2 or about 15 sq.ft.).
- What is the thickness of solar panels?
Thickness of solar panels depend on the capacity and the specific brands, but the thickness of fully assembled solar panels are usually in the range 2.5-4 cm.
Some good videos for you
Learn to make solar panels
A short but good video that shows the various components in a solar panel as well as steps to make a panel
Build your own solar cells at home
Another nice video, with some rather grandstand-like music
Building solar panels – final panel assembly
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