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Hi everyone welcome back to a solar energy course.
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It is the last lecture.
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We've already discussed the crystalline silicon definition and we take a special type of crystalline
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silicon which is the monocrystalline solar cell.
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Today we are going to take the next type of crystalline silicon solar cell which is polycrystalline
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silicon solar cell their first solar panels based on polycrystalline silicon which also is
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known as the polysilicone and multi crystalline silicon were introduced into the market in 
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1981.
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Unlike monocrystalline  based solar panels, the polycrystalline don't require 
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the
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the czochralski process the row silicone is melted and poured into a square mold.
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Which is cool and cut into perfectly clear waffer but what is the main advantage of this type of crystalline
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silicon solar cells first.
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The process used to make that poly crystalline simpler and the cost is less means the amount
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of waste the silicon is less compared to monocrystalline second polycrystalline solar
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panels tend to have slightly lower heat tolerance than monocrystalline
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solar panels, this technically means they perform slightly worse than the monocrystalline solar panels
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in high temperature means heat can affect the performance of solar panels and shortens the life span.
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However this effect is minor of and the most the home owner don't need to take it into account
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but what is the main disadvantage of this type.
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the efficiency of polycrystalline based solar panels is typically between 13 and 16 percent
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because of lower silicon impurties.
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the polycrystalline solar panels are not quite as efficient as monocrystalline solar panel.
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Second thing is the lower space efficiency you generally need to cover a large surface to output the
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same electrical power as you would with a solar band made of the monocrystalline silicon.
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But this doesn't mean every monocrystalline solar panel performs better than those
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based on poly crystalline
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last thing is that the monocrystalline 
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And thin film tend to be more pleasing since they have a more uniform block compared to the blue color
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of the polycrystalline silicon.
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So we can summarize that the polycrystalline has some efficiencies on the monocrystalline which
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is.
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There is no waste of silicon.
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because they're already shaped in uniform rectangle the second thing the polycrystalline has a slightly lower
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heat tolerance but the efficiency of that poly crystalline is lower than the monocrystalline
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which makes that footprint of polycrystalline solar cells greater than
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footprint of the monocrystalline silicon solar cells.
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polycrystalline solar cell doesn't have a uniform form monocrystalline and thin film tend
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to be more pleasing to eyes unlie the polycrystalline solar.
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cell
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now we already finished their first type of PV module which is crystalline silicon solar cell in
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the next lecture.
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We are going to move on.
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the next is type which is thin film solar cell.
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As we already said it can be module but not panel.
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So we are going to move on the PV module.
see you in the next block