Classification of solar cells according to generations
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Monocrystalline Silicon Cells
The oldest solar cell technology and still the most popular and efficient are solar cells made from thin wafers of silicon. These are called monocrystalline solar cells because the cells are sliced from large single crystals that have been painstakingly grown under carefully controlled conditions. Typically, the cells are a few inches across, and a number of cells are laid out in a grid to create a panel.
Relative to the other types of cells, they have a higher efficiency (up to 24.2%), meaning you will obtain more electricity from a given area of panel. This is useful if you only have a limited area for mounting your panels, or want to keep the installation small for aesthetic reasons. However, growing large crystals of pure silicon is a difficult and very energy-intensive process, so the production costs for this type of panel have historically are the highest of all the solar panel types.
Production methods have improved though, and prices for raw silicon as well as to build panels from monocrystalline solar cells have fallen a great deal over the years, partly driven by competition as other types of panel have been produced.
Another issue to keep in mind about panels made from monocrystalline silicon cells is that they lose their efficiency as the temperature increases about 25˚C, so they need to be installed in such a way as to permit the air to circulate over and under the panels to improve their efficiency.
For more information about monocrystalline solar cells, a more detailed analysis of their advantages and disadvantages and information about leading panel manufacturers click here.
2. Polycrstalline Silicon Cells
It is cheaper to produce silicon wafers in molds from multiple silicon crystals rather than from a single crystal as the conditions for growth do not need to be as tightly controlled. In this form, a number of interlocking silicon crystals grow together. Panels based on these cells are cheaper per unit area than monocrystalline panels - but they are also slightly less efficient (up to 19.3%).
For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.
Note: Many of the leading firms make both monocrystalline and polycrystalline solar cells for their panels.
3. Amorphous Silicon Cells
You probably never thought about it before, but most solar cells used in calculators and many small electronic devices are made from amorphous silicon cells.
Instead of growing silicon crystals as is done in making the two previous types of solar cells, silicon is deposited in a very thin layer on to a backing substrate – such as metal, glass or even plastic. Sometimes several layers of silicon, doped in slightly different ways to respond to different wavelengths of light, are laid on top of one another to improve the efficiency. The production methods are complex, but less energy intensive than crystalline panels, and prices have been coming down as panels are mass-produced using this process.
One advantage of using very thin layers of silicon is that the panels can be made flexible. The disadvantage of amorphous panels is that they are much less efficient per unit area (up to 10%) and are generally not suitable for roof installations you would typically need nearly double the panel area for the same power output. Having said that, for a given power rating, they do perform better at low light levels than crystalline panels - which is worth having on a dismal winter's day, and are less likely to lose their efficiency as the temperature climbs.
However, there flexibility makes them an excellent choice for use in making building integrated PV (e.g., roofing shingles), for use on curved surfaces, or even attached to a flexible backing sheet so that they can even be rolled up and used when going camping / backpacking, or put away when they are not needed!
For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.
4. Hybrid Silicon Cells
One recent trend in the industry is the emergence of hybrid silicon cells and several companies are now exploring ways of combining different materials to make solar cells with better efficiency, longer life, and at reduced costs.
Recently, Sanyo introduced a hybrid HIT cell whereby a layer of amorphous silicon is deposited on top of single crystal wafers. The result is an efficient solar cell that performs well in terms of indirect light and is much less likely to lose efficiency as the temperature climbs.
The oldest solar cell technology and still the most popular and efficient are solar cells made from thin wafers of silicon. These are called monocrystalline solar cells because the cells are sliced from large single crystals that have been painstakingly grown under carefully controlled conditions. Typically, the cells are a few inches across, and a number of cells are laid out in a grid to create a panel.
Relative to the other types of cells, they have a higher efficiency (up to 24.2%), meaning you will obtain more electricity from a given area of panel. This is useful if you only have a limited area for mounting your panels, or want to keep the installation small for aesthetic reasons. However, growing large crystals of pure silicon is a difficult and very energy-intensive process, so the production costs for this type of panel have historically are the highest of all the solar panel types.
Production methods have improved though, and prices for raw silicon as well as to build panels from monocrystalline solar cells have fallen a great deal over the years, partly driven by competition as other types of panel have been produced.
Another issue to keep in mind about panels made from monocrystalline silicon cells is that they lose their efficiency as the temperature increases about 25˚C, so they need to be installed in such a way as to permit the air to circulate over and under the panels to improve their efficiency.
For more information about monocrystalline solar cells, a more detailed analysis of their advantages and disadvantages and information about leading panel manufacturers click here.
2. Polycrstalline Silicon Cells
It is cheaper to produce silicon wafers in molds from multiple silicon crystals rather than from a single crystal as the conditions for growth do not need to be as tightly controlled. In this form, a number of interlocking silicon crystals grow together. Panels based on these cells are cheaper per unit area than monocrystalline panels - but they are also slightly less efficient (up to 19.3%).
For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.
Note: Many of the leading firms make both monocrystalline and polycrystalline solar cells for their panels.
3. Amorphous Silicon Cells
You probably never thought about it before, but most solar cells used in calculators and many small electronic devices are made from amorphous silicon cells.
Instead of growing silicon crystals as is done in making the two previous types of solar cells, silicon is deposited in a very thin layer on to a backing substrate – such as metal, glass or even plastic. Sometimes several layers of silicon, doped in slightly different ways to respond to different wavelengths of light, are laid on top of one another to improve the efficiency. The production methods are complex, but less energy intensive than crystalline panels, and prices have been coming down as panels are mass-produced using this process.
One advantage of using very thin layers of silicon is that the panels can be made flexible. The disadvantage of amorphous panels is that they are much less efficient per unit area (up to 10%) and are generally not suitable for roof installations you would typically need nearly double the panel area for the same power output. Having said that, for a given power rating, they do perform better at low light levels than crystalline panels - which is worth having on a dismal winter's day, and are less likely to lose their efficiency as the temperature climbs.
However, there flexibility makes them an excellent choice for use in making building integrated PV (e.g., roofing shingles), for use on curved surfaces, or even attached to a flexible backing sheet so that they can even be rolled up and used when going camping / backpacking, or put away when they are not needed!
For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.
4. Hybrid Silicon Cells
One recent trend in the industry is the emergence of hybrid silicon cells and several companies are now exploring ways of combining different materials to make solar cells with better efficiency, longer life, and at reduced costs.
Recently, Sanyo introduced a hybrid HIT cell whereby a layer of amorphous silicon is deposited on top of single crystal wafers. The result is an efficient solar cell that performs well in terms of indirect light and is much less likely to lose efficiency as the temperature climbs.
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