Solar Panel: How does it work?

Solar Panel: How does it work?

November 28, 2020 Off By Rob Prosser

A solar panel is a set of solar cells that can convert light directly into electricity. By combining the capacity of several panels, part of a family’s electricity needs can be covered.

At this time,  depending on the type of panel, 5 to 19% of the light energy can be converted into electricity. This is known as the ” exit ” of the panel. As technology is constantly being improved, the output should increase even more.

Using solar you can convert sunlight, which is free and inexhaustible, into electricity. This conversion is achieved thanks to the so-called “semiconductor” material from which each solar cell is manufactured.

Two generations

The most used material for solar cells is silicon. This material can be manufactured in three ways:

  • Monocrystalline silicon
  • Polycrystalline (or multi-crystalline) silicon
  • Thin film

These various forms produce different types of solar panels with different prices, lifetimes, and results:

The converter: the most important element in the installation.

A solar panel generates direct current. To be able to use this current at home or to put the surplus in the network, it must be converted to an alternating current of 230 V. This is done by the  converter , which is integrated into the electrical circuit near the solar panels.

What level of production can we expect?

The capacity of a solar installation is expressed in  peak watts  (Wp). This is the maximum electrical capacity that a solar cell can produce under ideal circumstances: solar collector directed towards the sun in a cloudless sky.

The ideal orientation for the solar is in fact to the south. If the panels are installed between the southeast and southwest, the loss of production amounts to 5%. If the panels are installed outside these limits, the loss increases rapidly. 

Here, a 1,000 Wp installation facing south at a 35 ° angle and without shade generates approximately 850 kWh / year.
 
For a family, in practical terms that means:

  • Assuming that around 10 m² of panels (1,250 Wp) are needed to generate 1,000 kWh / year (depending on the chosen technology)
  • A family of two to three people uses an average of 3,500 kWh / year
  • We can conclude that solar panels covering 10 m2 can provide almost a third of the annual needs of a family.

In the city it is often difficult to use more space for solar panels. But as the output of the panels constantly increases, it will be possible to cover an increasing proportion of the needs with the same surface!

Now we are going to see more in depth the types of solar panels

1. Monocrystalline solar panels

Some think that monocrystalline solar panels are the ‘Rolls Royce’ of solar photovoltaic technology and the best option. Monocrystalline is one of the oldest and most expensive technologies to manufacture, but this type has the highest efficiency.

These panels can generally achieve a conversion efficiency of 15-20% in the real world, that is, converting 15-20% of the sunlight that hits them into electricity. 

They are made from individual crystals of ultrapure silicon the size of a wine bottle and cut like salami to make individual wafers.

These circular wafers have their sides cut into squares, and then they become a monocrystalline “solar cell” that looks like this:

The silver lines are wires that collect the electricity that is created when light hits the cell. The solar panel is made up of an array of these monocrystalline solar cells laid flat, like tiles on your bathroom floor:

Monocrystalline solar cells generally have high performance, but because they waste quite a bit of space between cells when encapsulated in a solar photovoltaic panel (the little white diamonds in the image above) they perform about the same (in terms of efficiency and potency) as polycrystalline.

Some manufacturers use special techniques to make ultra-high performance monocrystalline photovoltaic solar modules, such as “back surface fields”, “laser grooving” and hybrid technologies. 

These super high-performance mono panels get efficiencies of over 20%, which is amazing. But you pay around 30% more compared to conventional monocrystalline solar.

The easy way to spot mono solar on a roof is to look for white diamonds between the cells.

2. Polycrystalline solar panels (also called multicrystalline)

Polycrystalline solar panels are also made of silicon, but the type of silicon used is slightly less pure and they are molded into blocks rather than cut into a single crystal. The fact that the crystals are arranged randomly means that they are individually visible.

Once the polycrystalline ingot is molded, it is cut into square blocks and then cut into square sheets which are processed into solar cells.

Here’s a close-up of a polycrystalline solar cell – you can see that it looks very different from the sleek, uniform appearance of its monocrystalline rival:

Polycrystalline solar cells are very similar to monocrystalline in their performance and degradation, except for multi-crystalline, the resulting cells are typically slightly less efficient. 

However, as you can see here, there is no wasted space between the corners of perfectly square cells:

This means that when they are encapsulated in photovoltaic solar, there is slightly more area available to absorb sunlight. The result is that the performance of polycrystalline solar is almost identical to that of monocrystalline solar. This is what it looks like on a roof:

3. Thin film solar panels 

While mono and polycrystalline solar panels are manufactured very similarly, thin film solar panels use a completely different manufacturing method. 

Instead of creating solar cells by cutting large blocks of silicon, a film containing silicon is “sprayed” onto the surface that will become a solar panel.

Although these processes have been around for a while, modern variations of the thin-film manufacturing process are relatively new technologies, so I would say that the 20-year performance of a modern thin-film photovoltaic solar can only be estimated.

The production processes are generally more energy efficient than any of the other types of solar photovoltaic panels, thus requiring less energy to manufacture than monocrystalline or polycrystalline panels for the same power rating.

Efficiency of thin film solar panels

Although it is improving, thin-film solar panels are usually 8-10% efficient. This means that they are about twice the size of mono or polycrystalline for the same power, and much heavier, so you need a big, sturdy roof and big, strong installers.

Another thing to keep in mind is that thin film solar panels can degrade by up to 20% in the first year on your roof before settling to their specified power output.

You can usually detect thin-film solar panels because they do not have the matrix pattern of crystalline panels, they are just a uniform color, usually blue, black, or brown. 

So to summarize, which solar panels are the best in terms of technology?

When choosing between monocrystalline and polycrystalline solar panels, despite what many sellers will tell you, there is nothing that really distinguishes between the types except their appearance!

Thin-film maybe a little cheaper per kW, but it will be at least twice the area, and no one is 100% sure how much they will degrade in the long run.

Another article on this blog that might interests you:

Solar energy: Everything You Need To Know