Currently, the most popular type of solar panel are the crystalline silicon ones. These include monocrystalline and polycrystalline models. As a result, many people think that they are the same, and forget that they actually have quite a number of differences. This page takes you through these, as well as how the panels work and the cost of investment.
How Do Silicon Solar Cells Work?
The main component of a solar cell is silicon, which has been used as a key part of electrical items for decades. They are often referred to as first generation solar panels as the silicon solar cell first started gaining traction in the 190s when the first solar panels were made, resulting in the first form of solar technology. Currently, they make up over 90% of the solar cell market.
Pure crystalline silicon is actually a very poor conductor of electricity. This is because at its core it is a semiconductor. The silicon that is found in a solar cell actually has a number of impurities in it, and this is done so that the other atoms that are added will mix with the silicon ones. This addresses the conduction issue that is presented by the silicon, as the newly mixed atoms work to improve the ability of the silicon to capture energy from the sun and convert it into electricity.
An atom of gallium contains one less electron than an atom of silicon, whereas an arsenic atom possesses one extra electron. When arsenic atoms are placed between silicon ones, there are extra electrons in the structure as a result of the mixture. As a result, an electron-rich layer is formed.
When you use gallium atoms instead, the result is a lack of electrons. What this means is that a poor electron layer will be created. In a solar cell, the layers are placed next to each other, and it is this that creates an electric field. When the sunlight hits the solar cells, the energy stimulates the electrons, and this results in holes being left behind. These then migrate to the electrodes in the cells because of the presence of the electric field. As a result, electricity is created.
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Monocrystalline Solar Cells
Monocrystalline solar cells are also referred to as single crystalline cells, and they are easy to identify thanks to their dark black colour. Monocrystalline cells are also made from an incredibly pure form of silicon, which makes them the most efficient material for the conversion of sunlight into energy.
In addition to this, monocrystalline solar cells are also the most space-efficient form of silicon solar cell. They have the advantage of being the longest lasting silicon-based solar cells as well, with expected lifespans of around 50 years. In fact, you will find that many manufacturers will be willing to offer warranties of up to 25 years on these solar panels, which lasts half of their expected lifetime.
While this system remains the superior one out of all the solar panel types, it does come with quite a large price tag. Monocrystalline cells are the most expensive option out of all the silicon solar cell types. This is primarily due to the fact that the four sides of each cell are cut – resulting in large amounts of waste. Polycrystalline acts as a cheaper alternative to this.
Here are some of the advantages of monocrystalline solar cells:
- They have the highest level of efficiency at 15-20%
- They require less space compared to other types due to their high efficiency
- Manufacturers state that this form of solar cell lasts the longest, with most giving them a 25-year warranty
- They perform better in low levels of sunlight, making them ideal for cloudy areas
Here are some of the disadvantages to monocrystalline solar cells:
- They are the most expensive solar cells on the market, and so not in everyone’s price range
- The performance levels tend to suffer from an increase in temperature. However, it is a small loss when compared to other forms of solar cell
- There is a lot of waste material when the silicon is cut during manufacture
Polycrystalline Solar Cells
Polycrystalline solar cells are also referred to as polysilicon or multi-silicon cells. The interesting thing about them is that they were the first solar cells to be developed when the industry began in the early 1980s. Polycrystalline cells also do not undergo the same cutting method as their monocrystalline counterparts. Instead, the silicon is melted before being poured into a square mould. This is what creates their very specific shape.
One of the benefits that come with the process of creating polycrystalline cells is that they become a lot more affordable. This is because very little silicon is actually wasted during the manufacturing process. However, they are also less efficient than monocrystalline solar cells and require a lot more space. All of this is due to the fact that they have lower levels of purity than the single crystalline cells.
Polycrystalline also has a much lower heat tolerance than the monocrystalline cells. What this means is that they are unable to function as efficiently when operating in high temperatures. In areas with hot climates, this can be a large disadvantage.
Here are some of the advantages of polycrystalline solar cells:
- The manufacturing process is cheaper and easier than the monocrystalline cells
- It avoids silicon waste
Here are some of the disadvantages to polycrystalline solar cells:
- Efficiency is only around 13-16% due to low levels of silicon purity. So they are not the most efficient on the market
- They have lower output rates which make them less space efficient. So more roof space is needed for installation
- High temperatures have more negative effects on efficiency compared with monocrystalline cells. This makes the polycrystalline cells less attractive to people in warmer areas as the price is lower
The Cost of Mono and Poly Solar Cells
It is only a few years ago that silicon solar panels were considered to be expensive to purchase and install. This is because high-quality silicon was used, which was much costlier. The process of purification for the silicon before the addition of gallium and arsenic also added to this cost due to it being both expensive and time-consuming.
However, the further development of new technology means that the use of cheaper and lower quality silicon is possible without affecting the overall quality and efficiency of the solar cells. This means that silicon solar cellsare now more affordable than they were before, and the price is only continuing to fall. In addition to this, government subsidies have also contributed to the lowered cost.
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